REPORT NO. FRA/ORD-79/51 PB so / 63 g&L MEASUREMENT AND CORRELATION ANALYSIS PLAN FOR CONCRETE TIE AND FASTENER PERFORMANCE ANALYSIS A *TES OV N NOVEMBER 1979 INTERIM REPORT Document is available to the public through the National Technical Information Service, Springfield, Virginia 22161. Prepared for U.S. DEPARTMENT OF TRANSPORTATION FEDERAL RAILROAD ADMINISTRATION Office of Research and Development Washington, D.C. 20590 NOTICE This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Govern- ment assumes no liability for its contents or use thereof. NOTICE The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this report. Technical Report Documentation P; 1. Report No. FRA/ORD- 79/51 2. Government Accession Nc 3. Recipient's Cotolog No. 4. Title and Subtitle MEASUREMENT AND CORRELATION ANALYSIS PLAN FOR CONCRETE TIE AND FASTENER PERFORMANCE EVALUATION 5. Report Dote November 1979 6. Performing Organization Code 7. Author's) 8. Performing Organization Report No. F.E. Dean* H.I}. Harrison* R.H. Prause,* E.T. Selig** and D. McMahon** 9. Performing Organization Nome and Address 10. Work Unit No. (TRAIS) "Battelle Columbus Laboratories 505 King Avenue Columbus, OH 43201 'Dept. of Civil Engineering University of Massachusetts Amherst, Mass. 01003 11. Contract or Gront No. DOT-FR-8164 12. Sponsoring Agency Name and Address U.S. Department of Transportation Federal Railroad Administration Office of Research and Development Washington DC 20590 13. Type of Report and Period Covered Interim Report October - December 1979 14. Sponsoring Agency Code RRD-32 15. Supplementary Notes 16. Abstract This report was prepared as part of the Improved Track Structures Research Program sponsored by the Office of Rail Safety Research of the Federal Railroad Administration. The report presents an experiment plan and a correlation methodology through which the long-term performance of concrete tie track will be evaluated. The experiment plan defines test segments, instrumentation and measure- ment procedures for a comprehensive evaluation, over a two-year period, of three concrete tie test sections and one wood tie control section, all of which are installed on revenue service track. This evaluation is to be correlated with similar track performance data from the Facility for Accelerated Service Testing (FAST) . Formats for FAST data to be requested from the Transportation Test Center are summarized. Finally, the methods of direct comparison, regression and analytical simulation, by which track performance at FAST and on the revenue service will be compared, are defined. 17. Key Words Concrete Cross Ties, Track Performance, Ties and Fasteners, Track Testing 19. Security Classif. (of this report) Unclassified 18. Distribution Stotement Document is available to the U.S. public through the National Technical Information Service, Springfield, VA 22161 20. Security Classif. (of this page) Unclassified 21. No. of Pages 22. Price Form DOT F 1700.7 (8-72) Reproduction of completed page authorized i Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/measurementcorre7951dean PREFACE This interim technical report presents an experiment plan and a corre- lation methodology through which the long-term performance of concrete tie track will be evaluated. The report was prepared by Battelle's Columbus Laboratories and the University of Massachusetts in fulfillment of the first major require- ment of the performance study, which is called the Concrete Tie and Fastener Performance and Correlation Analysis. The study is sponsored by the Federal Railroad Administration, Office of Rail Safety Research, as part of a larger program to improve the economics and safety of track structures in U.S. ser- vice, called the Improved Track Structures Research Program. The prime contractor for this work is Battelle's Columbus Labora- tories. Mr. Robert Prause of Battelle is the project manager. The University of Massachusetts is a subcontractor for investigations of ballast and subgrade, and this work is under the direction of Dr. Ernest Selig. Mr. John Weber, a private consultant, will assist in conducting inspections of the concrete ties at the various test segments. Mr. Howard Moody of the FRA is the Contracting Officer's Technical Representative. His support and suggestions in the preparation of this plan are gratefully acknowledged. This work was performed under Letter Contract No. DOT-FR-8164. Ill ■ • , t f ec o u < oc o u o oc iVi III ill III 5 >- m ■ - e a -> 3 « fl r « W o o fi *• o OC ? i - • » IlssS I 5 I I 5 1-58 I * is * i * ? sill I 6 E fc 5 VeI • 3 f ..I ill iff it V«t - r - till S - 8 « - O IS •* O u> % 1 1 ~ ft ff M U U = .5 = 5 a a is SI ; n M 8o CZ tt II M 61 II M '• «l ►! tl tl II 01 6 J I 9 « I » e t i lllllllll lllllllll lllllllll Itllilll lllllllll Hllllll! Ilillllll lilllllll lllllll lllllilll lllllllll lllllllll lllllllll lliiillll lllllllll llllllllliliilllillillllllill llllliiillllllllill Hlliillllillffi l!!ii!!i .|.|. ( . .|.|.|. .|.|. ( . . ( .|.|. T | T T |.|. T |.|. >|.|.|. •I'l'l'l'l'l'l' 'I'm- >|>p> •m>|> •mi|> -m-|- -|-|i|< i|.|'|' >mi|> 1 incttet 5™E~E J 2 6 E E E E is ; Hi! ■ 9 - u o fc .a * r Sill. • i • • t « < K f J it s t 1 i £ n « ® r> a HI! .M O* s » -> • 5 * «9 V) < X • J 1 . 1 5 1*1" * '" £ s * o o 1 • o • -n a • C 5 - »f i I S _ £** v«Y 3 S til i.a&'cX IV CONTENTS P age 1. INTRODUCTION 1 2. CORRELATION ANALYSIS METHODOLOGY AND PERFORMANCE EVALUATION CRITERIA 3 2.1 Correlation of Component Degradation 6 2.1.1 Data Reductions 6 2.2 Correlation of Geometry Retention 9 3. MEASUREMENT AND DATA REQUIREMENTS 16 3.1 Maintenance and Traffic Data 16 3.2 Track Response 17 3.2.1 Wheel/Rail Loads 17 3.2.2 Tie Strain 19 3.2.3 Rail/Tie Accelerations 19 3.2.4 Rail Fastener Strain 19 3.2.5 Wheel Detection and Train Speed 20 3.3 Track Parameters 20 3.3.1 Vertical Track Modulus 20 3.3.2 Ballast Characterization 21 3.3.3 Subgrade Characterization 22 3.3.4 Track Lateral Restraint 24 3.4 Geometry 25 3.4.1 Track Geometry Car Measurements 25 3.4.2 Survey-to-Benchmark 26 3.4.3 Average Tie Spacing 28 3.4.4 Tie Movement and Rail Creep 28 3.5 Component Inspections 29 3.5.1 Tie/Fastener/Pad/Insulator Inspections 29 3.5.2 Gage Face Wear 30 3.6 Summary of Measurement and Data Requirements 30 4. TEST SITE DESCRIPTION AND INSTRUMENTATION PLAN 36 4.1 Test Sites 36 4.1.1 Chessie Site at Lorraine, Virginia 36 4.1.2 Norfolk & Western Site at Roanoke, Virginia 36 4.1.3 Sante Fe Site at Streator, Illinois 39 4.1.4 Northeast Corridor Site at Aberdeen, Maryland 39 4.2 Collection of Dynamic Data 42 5. INSTRUMENTATION SELECTION, EVALUATION, CALIBRATION, INSTALLATION AND OPERATION 45 5.1 Wheel/Rail Loads . . 45 5.2 Tie Bending Strains 48 5.3 Rail and Tie Accelerations 54 5.4 Fastener Strain 55 5.5 Wheel Detection and Train Speed 56 5.6 Vertical Track Modulus 59 CONTENTS (Continued) Page 5.7 Field Inspection of Ballast and Subgrade Conditions 60 5.7.1 Introduction 60 5.7.2 Scope 60 5.7.3 Information Needed 60 5.8 Ballast Physical State Tests 62 5.8.1 Introduction 62 5.8.2 Scope of Tests 63 5.8.3 Test Layout 69 5.8.4 Test Procedures and Apparatus 69 5.8.5 Test Schedule 72 5.8.6 Additional Sampling 72 5.8.7 Railroad Assistance 73 5.9 Ballast Index Property Tests 73 5.9.1 Introduction 73 5.9.2 Scope of Tests 75 5.9.3 Test Procedures 75 5.9.4 RR Assistance 77 5.10 Subsurface Investigations 77 5.10.1 Objectives and Scope ' 77 5.10.2 Test Equipment 79 5.10.3 Test Schedule 80 5.10.4 Undisturbed Sampling 81 5.10.5 Laboratory Tests (Disturbed Samples) 82 5.10.6 Expected Results (Disturbed and Undisturbed Samples) . . 82 5.10.7 Railroad Assistance 82 5.11 Laboratory Stress-Strain and Strength Testing 83 5.11.1 Purpose 83 5.11.2 Methods and Scope 83 5.12 Moisture Monitoring and Sampling 84 5.12.1 Introduction 84 5.12.2 Oven Samples 84 5.12.3 Moisture Sensor Instrumentation 84 5.12.4 Moisture Sensor Installation 87 5.12.5 Moisture Sensor Calibration 87 5.12.6 Railroad Assistance 90 5.13 Weather Information 90 5.14 Survey-to-Benchmark Measurements 91 5.14.1 Initial Installation 91 5.14.2 Vertical Elevation Measurements 91 5.14.3 Horizontal Distance Measurements 91 5.14.4 Longitudinal Rail Movement Measurements 95 5.15 Tie Movement Measurements 96 5.15.1 Equipment 96 5.15.2 Measurement Procedure 96 5.16 Rail Creep Measurements 96 5.16.1 Markings 96 5.16.2 Measurements 97 5.17 Tie/Fastener/Pad/lnsulator Inspection 97 5.17.1 General .; 97 5.17.2 Inspection Procedure 99 vi CONTENTS (Continued) Page 5.18 Gage Face Wear 100 5.18.1 Measurement Locations 100 5.18.2 Equipment 100 5.18.3 Measurement Procedure 101 6. RAILROAD SUPPORT REQUIREMENTS 102 6.1 Surface-and-Line Maintenance 102 6.2 Track Geometry Measurements 102 6.3 Locomotive and Car 103 6.4 Maintenance and Traffic Data 103 6.5 General Assistance 104 6.6 Track Time 105 7. DATA ACQUISITION AND RECORDING 106 8. DATA ANALYSIS PROCEDURES 108 8.1 Data Formats 108 8.2 Acceleration Data Requirements Ill 9. FAST TRACK PERFORMANCE DATA 113 REFERENCES 120 ILLUSTRATIONS Figure 2-1. Track Model 11 2-2. Procedure for Exercise of Vertical Response Models 14 2-3. Measurements to Establish Substructure Definition for Vertical Response Analysis 15 4-1. Layout of Measurements on Concrete Tie Test Section at Lorraine, Virginia 37 4-2. Layout of Measurements on Concrete Tie Test Section at Roanoke, Virginia 38 4-3. Layout of Measurements on Concrete Tie Test Section at Streator, Illinois 40 4-4. Layout of Measurements on Wood Tie Control Section at Streator, Illinois 41 4-5. Distribution of Data Channels to Multiplex Units and Tape Recorder 43 vii ILLUSTRATIONS (Continued) Figure Page 5.1-1. Strain Gage Circuits to Measure Lateral and Vertical Wheel/Rail Loads, for Long-Term Installation on Concrete Ties. . 46 5.2-1. Fixture for In-Situ Calibration of Tie Bending Strain 49 5.2-2. Strain Gage Coupon for Installation on Concrete Ties 51 5.2-3. Strain Coupon Installation 52 5.5-1. Example of Use of Wheel Detector Transducer to Provide Wayside Data Peak Detection and A/D Conversion in Data Processing 57 5.5-2. Wheel Detector Transducer Signal Conditioning 58 5.8-1. Schematic Illustration of In-Situ Ballast Density Apparatus . . 64 5.8-2. Schematic Illustration of Plate Load Test Apparatus 65 5.8-3. Schematic Illustration of Lateral Tie Push Test Apparatus. ... 66 5.8-4. Typical Layout of Physical State Tests in Ballast 70 5.8-5. Typical Cross Section of Ballast Physical State Tests 74 5.8-6. Sample Processing Flow Chart for Ballast and Subballast Index Tests 76 5.12-1. Cylindrical Sensor 86 5.12-2. Typical Calibration Curves (Type A Sensor) 89 5.14-1. Typical Benchmark Construction 92 5.14-2. Placement of Benchmarks in a Typical 400-Foot Test Section ... 93 5.14-3. Survey-to-Benchmark Measurement Schemes 94 5.17-1. Tie/Fastener/Pad/Insulator Inspection Form 98 7-1. Block Diagram of BCL Field Data Acquisition System 107 8-1. Peak Lateral W/R Load Statistics for All Traffic, All Speeds, All Measurement Sites (0.6 Kip Load interval) 110 Vlll LIST OF TABLES Table Page 2-1. Summary of Performance Measures and Track Characteristics . . 5 3-1. Assumed Axle Population Statistics for Each Test Site Involving Dynamic Measurements 18 3-2. Predicted Duration of Tests to Achieve Specified Statistical Limits (Days) 18 3-3. Summary of Required Data and Data Reductions 31 4-1. Dynamic Track Response Measurements 44 5.8-2. Required Test Apparatus and Equipment 71 8-1. Statistical Data Processing Range and Increment Requirements 109 8-2. Summary of Track Dynamic Response Measurement Data Format Requirements 112 8-3. Data Processing and Formats for Track Vertical Accelerations . 114 9-1. Summary of Fast Track Performance Data Requirements 116 IX 1. INTRODUCTION The study for which this plan was developed will compare the long- term performance of selected concrete tie segments in U.S. revenue service, and of one wood tie control section, with similar performance data from the Facility for Accelerated Service Testing (FAST) . A knowledge of long-term track performance is critically important in the development of new track systems. FAST was designed to accumulate long-term performance data by acceleration of the service life of both the 5-mile track loop and its 76- car test train. For more than two years, tonnage has been accumulated on a variety of track systems, including many combinations of concrete ties and fasteners, at rates 7 to 10 times higher than average revenue service. However, FAST represents only one among many service environments, which fall in broad ranges of traffic and climatic conditions and track structure configurations. This raises the question of: "How can FAST data be extrapolated to represent the 'real world' of revenue service?" The Tie/ Fastener Performance and Correlation Analysis was designed to answer this question by using data for a limited number of concrete tie test segments in revenue service and thereby to develop a methodology by which track performance can be related between track segments of dissimilar construction, contour, service loads and climate. This report describes the methodology to be applied to the task of correlation, and provides a detailed experiment plan for com- pletion of the measurement program. The data required for this correlation analysis will be collected through the following activities: a. Revenue Service Performance Measurements . Three concrete tie test segments and one wood tie control segment, all on revenue service track, will be subjected to periodic assessments of track performance by measurements on the rails, fasteners, ties, ballast and subgrade. A total of 5 data sets will be collected during 4 visits to each site over a period of approximately 2 years. During the first site visit, instrumentation will be installed and data will be collected both before and after surf ace-and-line maintenance. The locations of the test sites are: (1) Lorraine, Va . (Chessie Svstem) - concrete ties (2) Kumis , Va . (Norfolk & Western) - concrete ties 1 (3) Streator, Illinois (Santa Fe) - concrete and wood ties. An Additional program of visual inspection and track geometry measurements will be conducted on a segment of the newly installed concrete tie track of the Northeast Corridor near Aberdeen, Maryland. b. FAST Data . A request for performance data from selected concrete and wood tie segments at FAST will be submitted through the Federal Railroad Administration to the Transportation Test Center or the AAR. Following the acquisition and reduction of the required track perfor- mance data, a correlation analysis will be conducted. Two basic approaches will be applied: a. Correlation by Comparison and Regression . Direct comparisons of performance indices will be meaningful to indicate the effect of differences in traffic, construction and environment. Regression analysis will be applied to identify correlation coefficients which, when calculated from the results of two or more track segments, can be verified by correlation with results from an additional track segment. b. Correlation by Analytical Simulation . Vertical track response analytical models, plus input data collected from laboratory measurements of ballast and subgrade materials, will be used to correlate both short-term and long-term measured performance. 2. CORRELATION ANALYSIS METHODOLOGY AND PERFORMANCE EVALUATION CRITERIA The purpose of the correlation analysis is to determine the depend- ence of track degradation on the characteristics of track structure, traffic and climate. An ultimate objective is to develop the ability to analytically predict long-term performance. However, the current state-of-the-art in analytical prediction is limited, even for simulation of very short-term phenomena, and can be applied to long-term performance only in relative terms for a few performance measures. The correlation effort is required if data from FAST are to be extrapolated to the conditions of typical revenue service. For some or all of the selected revenue service test segments, differences with FAST condi- tions include: a. Rail size b. Types of fasteners and pads c. Track contour d. Track class e. Maintenance frequency for vehicles and track f. Traffic - average axle load, speed and unbalance in curves g. Subgrade material h. Environmental factors - subgrade moisture content, tempera- ture range, freeze-thaw cycles. The dissimilarities in construction, traffic and environment make it imperative that the fundamental causes or governing factors of long-term track perfor- mance be identified. To achieve this correlation, or understanding of cause and effect, the following general plan will be followed: a. The track performance data from the revenue service test segments and from FAST will be collected and reduced. The data reductions will be generally classified into three groups: 1. Primary performance measures - measures of geometry retention and component degradation. Representative values will be plotted vs. accumulated tonnage (MGT) . 2. Governing structural characteristics - vertical and lateral stiffness, fastener stiffness and toe load, 3 transfer function of tie pads, subgrade moisture content, subgrade elastic and plastic limits, ballast gradation and general ballast condition 3. Loading and load response - wheel/rail loads, tie and fastener strains, rail deflection. b. A search for the dependence of performance measures on governing structural characteristics and loads will be undertaken by the simple ap- proaches of comparison and regression. c. Analytical simulation of vertical elastic track response and of a relative measure of vertical track settlement will be performed. The simula- tion of elastic response will provide confidence that the track character- istics are understood and have been adequately measured. A correlation of measured vertical settlement with an analytical estimation based on the predicted elastic response represents a major advance in the understanding of this important track performance measure. Table 2-1 lists the planned measurements which fall under each of the three previously discussed categories. The objective of the correlation analysis is to define the dependence of the variables in the first category (performance measures) on the remaining two (structural characteristics and traffic/climate conditions). The following sections describe the correlation methods planned for analysis of each of the two major subdivisions of performance measures: component degradation and geometry retention. TABLE 2-1. SUMMARY OF PERFORMANCE MEASURES AND TRACK CHARACTERISTICS PERFORMANCE MEASURES Component Degradation 1. Rail Creep ht/c 2. Gage Face Wear (\J/C 3. Tie Skew and Spacing Deviations AJ/c 4. Tie Cracks and Damage i/^ 5. Fastener/Pad Insulator: a . Movement ^ b. Wear and Damage ^ Geometry Retention 1. Deviations from Average Contour a. Profile WUmfrflM b. Alinement -s^a; c. Crosslevel ^^c d . Gage tJ , L 2. Track Shift from Fixed Reference a. Vertical settlement P^irmerM b. Lateral S£**/. c. Longitudinal Uil. TRAFFIC/CLIMATE CONDITIONS Wheel/Rail Loads a. Vertical i/ b. Lateral • Tonnage Accumulation <^' Consist Definitions f/iix Train Speed <^ Moisture History */ Weather Conditions ^ — 10. TRACK CHARACTERISTICS Tie Strain Rail/Tie Accelerations Fastener Characteristics (Measurements only at FAST) Toe Load Stiffness Vertical Track Modulus Ballast Density Plate Load Resistance Lateral Tie Push Resistance Ballast Gradation ^ Ballast Material Properties a. Liquid & Plastic Limits b. Specific Gravity c. Chemical Composition d. Angularity, Sphericity, e. Hardness Subgrade Penetration Resistance Dutch Cone Standard 11. Subgrade Material Properties a. Shear Strength b. Resilient Modulus c. Permanent Strain 12. Subgrade Classification a. Material Identification b. Stratification c. Moisture d. Density pZOrfr*, 0ft _ rM0 ^ r i or mm ,. 2. 1 Correlation of Component Degradation 2.1.1 Data Reductions Results of the component inspections will be reduced to a set of comparable performance indicators, plotted vs. MGT. In some cases several alternatives are listed. The final selection of formats will depend on the range and variability found in the data. The formats selected will be those which show, with greatest statistical reliability, performance changes leading to maintenance requirements. In each case, a curve fit of the basic data reduction will yield an average rate of change of the measurement over the test period. The measurements and data reductions are: MEASUREMENT Rail Creep 2. Gage Face Wear 3. Tie cracks 4. Tie chips 5. Fastener Clip Movement 6 . Pad Movement 7. Pad Deterioration 8. Insulators DATA REDUCTION (PLOT VS. MGT) Mean creep ///c_ Percent of ties with creep exceeding selected threshold cj -_ Creep value exceeded by 5% of ties/^ Mean and standard deviation of wear K>l (_ Percent of ties in test section with cracks exceeding 2 inches Percent of ties in test section with chips exceeding 1 inch in depth (Sufficient to cause further deterioration) Percent of clips in test section with displacement greater than half way to fall-out Percent of fall-outs Percent with movement above 2 inches vk- Percent of pads in test section which are torn, cracked or delaminated Percent seriously displaced or missing Percent cracked or broken It must be anticipated that many of the component inspections will yield very little variation over the period of the test. For example, the past several six-month inspections at the Chessie site have shown little or no change in such indicators as fastener component movement or tie cracking. Although the lack of degradation is itself a meaningful performance measure, it will provide little opportunity to examine the sensitivities of component degradation to track structural and climate conditions. It will be possible to document the characteristics of structure, traffic and climate for which the components in question appear to provide a "successful" design. For those performance indicators which display variation with respect to MGT as well as variation among test sections, a search for depend- ence of performance on the conditions of structure, traffic and climate will be carried out. The indicators of track condition will include the following list, as well as any additional indicators whose utility is revealed by examination of the data: 1. Traffic: mean or 5% exceedance level of vertical and lateral wheel/rail load, 5% exceedance level of tie strain oJ~ 3oofe 2. Track geometry a. Curvature b. Indices of vertical and lateral roughness - 5% exceedance values of profile and alinement 3. Ballast a. Average gradation b. Average density c. Average lateral tie push loads d. Average vertical track modulus 4. Subgrade a. Stress defining elastic limit b. Moisture content 5. Fasteners (Measurements only at FAST) a. Toe load b. Stiffness The correlation analysis by comparison and regression will then be carried out on the following three levels: a. Direct Comparison . Either of the following two situations would consitute a significant addition to the data bank on concrete ties: 1. Consistent performance among all test segments, indicating the independence of performance from the governing factors which differ among the test segments. 2. Consistently different performance between com- parable segments of concrete and wood tie track. At Streator and at FAST, such segments can be obtained with the same contour, traffic and ballast/subgrade support conditions. b. Plots of Performance Indices . (Rates of track roughness varia- tion) vs. indices of the governing characteristics (load, stiffness, subgrade plastic limit, subgrade moisture content, etc). Performance differences may be explainable in these simple terms. c. Multiple Linear Regression Analysis . This procedure will attempt to establish the possible dependence of performance indices on two or more governing characteristics. For example, the rate of increase in the 5-percent exceedance level of profile roughness error (PE) might be assumed to be a function of average axle load (V) and vertical track modulus (k-,) • Then an estimate of PE would be postulated in the form n n PE = C V x + C 2 K^. From data gathered at the three track segments, the constants C, , C„, n.. and n„ could be estimated by regression analysis. The validity of the pro- cedure (the selection of parameters and the assumed linear relationship) would be checked by using the derived coefficients to verify the measured degradation rates of other track segments. 2 . 2 Correlation of Geometry Retention The correlation of the track geometry performance measures listed in Table 2-1 with the characteristics of track structure, traffic and climate will begin in a manner similar to the effort for correlation of component degradation rates. Indicators of performance and of track conditions will be compiled and, as a first step, will be examined for obvious connections between performance and track conditions. Where possible dependencies are identified, the methods of comparison and regression described in the previous section will be carried out for the geometry retention performance measures. In the case of vertical track settlement, an analysis will be carried out which uses a combination of field measurements, laboratory mea- surements and analytical simulation of elastic response to produce a relative measure of vertical track response, or a track settlement index. The current state of the art regarding track settlement indicates that only a relatively simplified performance index is justified. However, this index should include the fundamental ballast and subgrade parameters needed for evaluating the effects of variations in track design parameters. This requires identifying the relative contributions from the ballast and subgrade to the total settle- ment. One possible format for a Track Settlement Index (TSI) is based on total vertical settlement per MGT of a defined traffic. This could be represented as ? 3. N. TSI = X X X N P ' Eli i where N.P. gives the tonnage for N. number of axles at mean axle load P., and ii i i B. is the track settlement rate for those N. axles. i i The track settlement rate is a result of the cumulative settlement in each of j layers representing the ballast and subgrade, a. 3. = E C. a. 3 . i . l d . . h. . The settlement in each layer depends on the permanent strain per cycle given by C . o , and the layer thickness h., where ij a, = deviatoric stress in the j layer for the traffic of P., N. d . . 11 ij C. and a. = empirical parameters for the particular material and stress condition of layer j . The critical parameters which a track analysis model must provide are the average deviatoric stress in a layered representation of the roadbed for the statistical loading description of the railroad traffic. Other operating parameters which affect dynamic wheel loads, such as train speed, track roughness, etc., would be included by using a probability density description for wheel/rail loads to calculate the resulting roadbed stresses. The TSI representing the rate of uniform vertical settlement can be used as the basis for estimating differential vertical settlement as a function of wavelength by using available soil settlement data and empirical results from the track tests. A separate relationship for rail profile and track cross level would permit a prediction of surface deterioration to be compared with the maximum allowable deviations under a 62-ft chord that are currently the basis for track safety standards and maintenance decisions. In the initial stage of implementing a track surface deterioration model of this type, the traffic response is obtained using the track analysing model MULTA for static wheel/rail loads to evaluate a range of track design configurations. These track response parameters in terms of stresses and strains at any point in the layered roadbed can then be used as input to a set of transfer functions for ballast and subgrade settlement. The Battelle-developed model of vertical elastic behavior of the track structure (MULTA) has been refined by UMASS into a program which includes an iterative procedure to handle stress-dependent properties of the subgrade material and improves computational efficiency. The result is a 3-dimensional model for which the basic components and input data are illu- strated in Figure 2-1. This refinement of the MULTA model is called GEOTRACK. A detailed description of the solution process accomplished by the track analysis appears in Appendix G. 10 Wheel load Wheel load Ballast FIGURE 2-1. TRACK MODEL 11 This model predicts resilient behavior in terms of a complete set of stresses, strains and deformations in the track substructure, as well as rail and tie response. The results have been checked with FAST data in the ballast, subballast and subgrade on both wood and concrete tie sections. The agreement is considered good. The stress-state dependency of the elastic modulus was found to be an important feature of the model. With this feature, the model correctly predicted the nonlinear relationship between the track response parameters and the wheel load. The present approach to permanent deformation prediction is to use the stresses from the MULTA model together with repeated load triaxial data representing the inelastic behavior of the ballast, subballast and subgrade materials. This approach predicts uniform settlement, which is in turn assumed to be a relative measure of differential settlement. The loading data for this analysis of settlement will be an approxi- mation of the cumulative probability distribution of vertical load for some increment of tonnage, such as 1 MGT. That is, from the measured probability distribution and the total number of load cycles involved in the tonnage increment, a set of force levels V. and associated numbers of cycles N. will 1 1 be supplied as input to the routine. It is probable that a relatively small number of high-load cycles will account for most of the settlement. The MULTA model permits consideration of the magnitude and fre- quency of train load, the type and spacing of ties, the rail stiffness, the ballast thickness and properties, the subballast thickness and properties, and the subgrade properties. However, the model assumes that each layer of mate- rial is homogeneous. Therefore, it is intended that the model predictions will be supplemented by selected analysis with the PSA model to determine the influence of variation in properties along the length of the tie. The PSA model is a three-dimensional finite-element roadbed model that analyzes a prismatic solid which is loaded by vertical forces spaced periodically along the longitudinal track direction. The PSA model assumes the prismatic body is infinite in length with constant cross sectional and material properties in the longitudinal direction. Material properties can vary from point to point in the cross section and the geometry of the ballast section can be represented accurately. This model would be applied to represent elastic vertical force-deflection behavior in cases where measured plate-load bearing tests showed substantial variation along the length of the tie. io The planned simulation procedure is further illustrated in Figure 2-2. Figure 2-3 shows the relationship of all the information required to properly characterize the ballast, subballast and subgrade layers. 13 WHEEL LOADS TRAFFIC RECORDS TIE CHARACTERISTICS RAIL CHARACTERISTICS TIE SPACING LAYER THICKNESSES BALLAST, SUBBALLAST £ SUBGRADE PROPERTIES TRACK LOADING DEFINITION *- TRACK STRUCTURE DEFINITION >■ SUBSTRUCTURE DEFINITION VERTICAL TRACK RESPONSE MODEL RESIDUAL STRAIN PREDICTION RESIDUAL SETTLEMENT RAIL/TIE RESPONSE 1 ' — — ELASTIC LAYER RESPONSE FIGURE 2-2. PROCEDURE FOR EXERCISE OF VERTICAL RESPONSE MODELS 14 STANDARD PENETRATION TEST CO z O ■—1 h- < > ■ < ct u LU CO CO i — i en > O 1 CO LU CO n LU 2 Z O CJ cu I— < z> r CO i— V OL h- LU co >- 5!i _l 3 Q Z y DQ < o ' ) 1— 1 CO CO h- •\ LU ^ h- t— 1 — 1 co 5 Qi LU D. LU _l O h- £ C* a. LU Pi o Pn z o fa w Q w Pi :=> H U § H CO DQ En CO CO H H CO CO H >H hJ < H CO w w co o fa CO CO H W z Pi w Pi CJ !=> H co H I CM w u H fa 15 3. MEASUREMENT AND DATA REQUIREMENTS 3. 1 Maintenance and Traffic Data Descriptions of all maintenance performed on the test section are needed for the. available history of the test section. Maintenance records should include: a. Type of work performed b. Crew size c. Machines used d. Man-hours required e. Components replaced. These records will be used to compile plots of maintenance activity as a function of tonnage in million gross tons (MGT) and to record rates of com- ponent replacements. The following descriptions of traffic over the test site should be provided by the railroads to Battelle within one month after each site visit: a. Consist Descriptions . Detailed consist descriptions for a two- week period of traffic spanning each site visit should include: 1. date and time of train passage 2. the type of each car 3. the gross weight of each car 4. the overall gross weight of the train 5. direction of travel over the test site. b. Cumulative Tonnage . Overall train tonnage should be accumul- ated, beginning with the first test interval and continuing for all traffic over the test section through the full 18-month to two-year period of the tests. Data "points" should be provided in the form of the date and total accumulated tonnage at intervals no greater than one month. In addition, any available record of tonnage accumulation since the installation of the concrete ties is desired. This long-range record should be defined at intervals no greater than three months. At the double-track sites, care should be taken that the data pro- vided includes only the traffic passing over the test section and not over the adjacent track. 16 3. 2 Track Response The primary requirement for dynamic track response is to determine the characteristic loads and stresses within the track structure without dis- turbing the tie/ballast consolidation. An evaluation of the statistics from the field tests performed under DOT-TSC-1051 provide a basis for estimating the population which can be expected at the three dynamic test sites. Listed in Table 3-1 are some of the assumed values using the statistics from the Union Pacific data and adjusting these where different traffic mixes are anticipated. From Table 3-2 it can be seen that the Lorraine and Streator sites may require five days to achieve the minimum required population while the Roanoke site may need less than three days to obtain comparable statistics, It should be noted that these figures are based on annual average tonnage and do not account for seasonal or weekly variations. The one week cycle reflects the reduced work force making up trains on the weekends. At any point on the railroad the lull in traffic will depend on the travel time from main yards and the lull in traffic in opposite directions may or may not coincide. This tends to make the timing of the specific days of dynamic data collection critical. If delays are encountered in setting up the test site for dynamic runs, one or two additional days of data collection may be necessary. 3.2.1 Wheel/Rail Loads Documenting the wheel/rail loads at each of the test sites provides a direct means of characterizing the load environment (traffic mix) for com- parisons between test sites. It has been shown in previous test programs that spatial variations in wheel/rail loads on Class 5 or better track are on the same order as changes in traffic mix, so minimum gains would be made in measuring wheel/rail loads in more than one location at each test site. In other words, the scatter in loads (say + 10 percent) measured under a certain percentile vehicle (say 20th percentile) due to spatial variations in the track will be comparable to the load variations caused by a fluctua- tion in traffic mix from one week to the next that will change the character- istics of that 20th percentile vehicle. 17 TABLE 3-1. ASSUMED AXLE POPULATION STATISTICS FOR EACH TEST SITE INVOLVING DYNAMIC MEASUREMENTS Annual Tonnage - MGT Total Axles/Day Locomotive Axles/Day Cars > HOT GVW Axles/Day Flat Wheels/Day* Chessie N&W Sante Fe Lorraine Roanoke Streator 35 45 20 5200 6700 3000 200 500 240 1000 1200 550 100 130 60 * Measured at a 10 inch zone, TABLE 3-2. PREDICTED DURATION OF TESTS TO ACHIEVE SPECIFIED STATISTICAL LIMITS (DAYS) Load Exceedance = .01 percent (All Cars, All Speeds - One Count) Locomotive + 3a Load Limits (2400 lb Load Interval - 5 Counts) Chessie Lorraine 1.9 5.5 N&W Roanoke 1.5 2.2 Sante Fe Streator 3.3 4.6 18 3.2.2 Tie Strain Tie strains and the corresponding bending moments induced by the wheel/rail loads vary widely due to variations in the support conditions. Therefore, tie strains must be measured in several locations to provide a statistically significant description of the tie loading environment. Five randomly selected tie locations including one location with three adjacent ties (a total of 7 ties) should be instrumented to provide documentation of short and long wavelength variations in tie support conditions. 3.2.3 Rail/Tie Accelerations Time histories of rail and tie accelerations can provide a descrip- tion of several dynamic properties of the track structure and the dynamic loading during train passage. Transfer functions of the fastener/pad assembly can be made from simultaneous measurement of acceleration on the rail base and the top of the tie adjacent to the rail. Spectrum analysis of these accel- erations will help define the tie vibration environment, thereby improving the understanding of possible fatigue related failures. The effects of rail corrugations on the track loading is of particular interest. 3.2.4 Rail Fastener Strain The failure experience of rail fasteners at FAST demonstrate the importance of further investigations of fastener performance. Statistical samplings of insertion and dynamic strain levels, including the effects of dimensional tolerances and stiffness properties of the fastener assemblies, are needed to characterize the fastener load environment. This information will be determined at FAST under a test program planned for April 1979. However, the results will be of direct value to the revenue service tests since the rail fastener being instrumented is used at all sites. 19 3.2.5 Wheel Detection and Train Speed It will be necessary to provide wheel detectors adjacent to each instrumented tie to assist in the data reduction process. The wheel detector must provide a non ambiguous pulse for each wheel passing an instrumented location so that a discrete sample from each data channel at that location will be processed for each wheel. By measuring the distance between two wheel detectors, train speed can be determined. Speed must be calculated and logged for the beginning and end of each train. 3. 3 Track Parameters 3.3.1 Vertical Track Modulus Vertical track modulus is required to help characterize each test site. This parameter will be used to compare the characteristics of different track and is a primary input to many track models. Because track modulus can vary widely due to local support conditions under individual ties, a statisti- cal sampling of the force/deflection measurements used to determine modulus will be required. As a minimum, static defection measurements should be made under known loads at a random sampling of tie locations throughout the entire test site on the first field trip to identify both long and short wavelength variations in modulus. This would include the five instrumented tie locations in that section of the track and a minimum of three locations in each additional section of track where tie type or spacing is varied. Spot measurements at three or four load levels will also help determine the variation between tangent and secant modulus due to local slack or free play within the track structure. After the initial site visit a minimum of seven locations in one section of track will be measured on each successive trip to monitor variations due to commulative tonnage and seasonal variations. This number of measure- ments was used for recent tests in Nevada [3-1], which produced standard deviations of approximately 40 percent of the mean in each test section. This level of consistency is considered the minimum necessary to characterize differences between test sites. The wood tie section at Streator will also be measured at seven random locations on each site visit. 20 3.3.2 Ballast Characterization Ballast and subballast are key components of the track structure. The characterization of these materials is grouped into two categories. The first category is the classification or index properties identifying the com- position and properties of the components making up these materials. The second category is the physical state or structure of the material in-situ. Both categories are essential to document in order to completely define the ballast and subballast material and conditions. The index properties will be determined in the laboratory from samples gathered on the first site visit. At present, knowledge is lacking on which index properties best identify the influence of these materials on track per- formance. Therefore, it is planned that all of the commonly measured index properties will be determined. The specific tests required in each case will depend upon the samples obtained, but they will include gradation, Los Angeles abrasion, particle shape, composition, specific gravity, and liquid and plastic limits of the fines. The number and type of tests in each case can remain flexible because this decision does not affect the field costs or require railroad assistance, except for providing information which might be available from their suppliers. The physical state of the ballast in-situ will be determined directly during the site visit by field ballast density tests, plate load tests, moisture contenc determination, and visual observations. The physical state, particularly changes, is also affected by maintenance, weather and traffic history. Important weather information includes precipitation and tempera- ture. The physical state information is needed to define the conditions for the laboratory stress-strain and strength tests. The information is also needed to estimate the range of property values to be considered in the analytical models. In the case of the GEOTRACK model, the variations with horizontal position and with time as a result of traffic and weather, must be considered in determining the proper average properties for each layer. The physical state information from the field will also be used to estimate varia- tions along the tie for use with PSA model. 21 Maintenance and traffic are primary factors influencing ballast physical state. Information on maintenance and traffic will help to estab- lish the initial conditions and the number of cycles of what stress levels to apply to ballast samples in the laboratory tests which measure the resilient modulus and the permanent strain development. However, maintenance and traffic history will also be used as a measure of track performance for eval- uating the permanent deformation predictions. 3.3.3 Subgrade Characterization The layers beneath the ballast and subballast, designated the sub- grade, are usually the existing natural ground at the site. Hence, the prop- erties of the subgrade can vary widely with depth and with distance along the track. The subgrade plays an important role in track performance because it affects such behavior as drainage, pumping, settlement under repeated traffic load, settlement from subgrade penetration into ballast, and dynamic track displacement. A combination of field and laboratory investigations is needed to characterize the subgrade for use in the methodology. Available geological information will be obtained first to determine the expected materials and strata. Field subsurface penetration tests to a depth of 10 to 25 ft are required to give a measure of the soil conditions at enough points along the track section to determine the variation of subgrade properties. The cone test has been selected for this purpose because it is rapid, it is not expected to disturb the roadbed significantly, and it is the simplest test that has the potential for correlation with values of soil properties required by the meth- odology. Based on the results of the geological evaluation and the cone pene- tration tests, several representative locations will be selected for soil bor- ings to get visual samples for identification. The Standard Penetration Test has been selected for this purpose because it is an efficient means to get suitable visual samples, and at the same time it provides values of blow count which are commonly used as a rough index of soil properties. 22 If the subgrade is cohesive enough, additional borings will be done to obtain undisturbed tube samples which will be taken to the laboratory for repeated load tests. If the soil cannot be obtained without disturbance, the samples will be taken anyway, and then reconstituted in the laboratory as close as possible to the field conditions before disturbance. Results from tests using reconstituted samples are much less certain, but they are better than estimations from the field investigations. The results from the three types of field investigation will be used to define the layers for the analytical track model. As done for the ballast and subballast, repeated load triaxial tests will be performed on the subgrade samples to determine the resilient modulus and permanent strain character- istics of these materials. The results will be correlated with the field cone data to provide an assessment of the range and average of values for the entire test section. A successful correlation between the repeated load tests in the laboratory and the cone soundings in the field will have an important benefit to the railroads, because the cone method provides a rapid and economical means of obtaining property data from other sites. Samples obtained from the Standard Penetration Test and unused portions of the tube samples will be used in the laboratory to obtain index properties on the subgrade materials which will identify the material composi- tion. Moisture and density measurements on portions of these samples will also be used to define the physical state. Additional physical state information will be obtained in the field at the top of the subgrade using the plate load test and density test, and by obtaining samples for moisture content measure- ment. Moisture sensors will be implanted in the subgrade during the first site visit to provide a means of indicating changes in properties during the period of field observations. 23 3.3.4 Track. Lateral Restraint Track lateral restraint is of interest for both the loaded and the unloaded states. The first provides a measure of resistance to lateral train forces while the track is loaded by the train weight. The second is a measure of resistance to buckling from thermally-induced rail stresses. Experi- mental determination of lateral restraint under train load is difficult and will not be done in this program. Lateral restraint on vertically unloaded track will be measured using lateral tie push or pull tests (LTPT) . There are two types of LTPT's. One measures the resistance of an individual tie, while the other measures the resistance of panel sections con- necting more than one tie. In the single tie test, the rail fasteners or spikes and tie plates are removed from the test tie, and force is applied in the lateral direction. Load levels are measured by pressure gages or load cells, while deformations are recorded by displacement transducers. In the panel tests the ties remain attached to one or both rails. The displacement of each tie is usually measured, as is load applied to the entire panel through the rail. The panel test requires a much greater reaction force and a much more elaborate instrumentation package than does a single tie push test. The panel test also causes some disruption of train traffic, in part because of the necessity for cutting the rails. However, the panel test is more representative, because it tests the integrated system of ballast, ties, fasteners and rails. Details of the test procedures and apparatus for both types of LTPT's are discussed in reports prepared in the State University of New York at Buffalo (SUNYAB) ballast compaction study. Almost all previous experience has been on wood tie track. Only the LTPT on the single, unfastened tie is proposed for this concrete tie correlation study. At present, little information exists to establish a correlation between these test results and lateral track restraint, particularly on a train-loaded track. More information is available to correlate the single tie LTPT to the panel test on vertically-unloaded track. Compared to the development of track structure models for vertically-loaded track, little work has been done on laterally-loaded track. Thus suitable methodology for predicting lateral track restraint still needs to be established. 24 The approach planned in this study is to use available information to empirically relate the single tie LTPT results measured at the test sites to lateral track stability. The single tie LTPT will be performed in accordance with procedures developed at SUNYAB for the ballast compaction study. 3.4 Geometry 3.4.1 Track Geometry Car Measurements Track geometry measurements of gage, alinement, profile and cross- level are to be made with the track geometry cars belonging to the railroads. The measurements should coincide as nearly as possible with the site visits. However, it is recognized that the scheduling of the track geometry cars for a specific place and time is difficult. Therefore, the only requirement for this measurement is that the runs should correspond in frequency with the interval of approximately six months planned between site visits. To the extent possible, the railroad should adhere to the following target: a. measurements within two weeks before and after the first site visit visits. measurements within two weeks before or after all remaining site The major requirements for track geometry car measurements and data are as follows: a. Automatic location detectors should identify the beginning and end of each test segment. b. The data reductions normally performed by the railroads should be submitted to Battelle within 2 weeks after the completion of a run. c. Strip chart records of each track geometry run should be supplied to Battelle immediately after the completion of each run. The data should clearly indicate the scales of each measurement and the point of passage over each automatic location detector. In addition to using the track geometry cars owned by the railroads, it is planned that the DOT/FRA T-6 geometry car will be operated over each of the concrete tie test sites one or more times. This will provide track geometry data which are directly comparable for the different sites and eli- minate differences in track geometry measurement systems. 25 3.4.2 Survey- to-Benchmark The track geometry measurements made by survey to benchmark (STB) will be used as a track performance indicator. The required measurements are vertical, longitudinal, and transverse movements of the rails and ties relative to fixed references. All of these measurements will be made on an unloaded track. The first set of measurements will be made before maintenance on the first visit as a basis for evaluating the maintenance operation. The second set of measurements will be made immediately after track maintenance prior to traffic. The measurements will again be repeated at the end of the first site visit and once on each subsequent site visit. Permanent ballast strain data from FAST will give an indication of the rate at which track adjustments take place after maintenance operations, and thus this FAST data can provide a guideline for the frequency of STB measurements. The vertical track measurements will give an average and range of track settlement to compare with the permanent deformation prediction. The measurement of vertical movement is relatively easy and is the most important of the three geometry measurements. The longitudinal measurement will indicate the movement of 'ties and rails resulting from such effects as thermal stress, and braking and accelera- tion train forces. Of interest are movements of one inch or longer, and these can be easily determined by taping from a fixed reference. However, the establishment of a stable horizontal reference is more difficult than a vertical reference. The transverse deformation is a measure of the average and range of lateral movement from lateral track forces and from rail stresses. This mea- surement is the most difficult to do with sufficient accuracy, but it is of particular interest for the curve site. Survey-to-benchmark measurements will be made at a sufficient number of sites in each test section to permit an adequate statistical description of movement trends as functions of tonnage. Ties at extreme ends of the sections will be avoided because movement in this case could be affected by the tie transition. The remaining section length will be sampled at the following rates: a. Chessie site (curved site) - every tenth tie . b. All other sites - every twentieth tie. 26 These rates will provide about 22 measurement locations at the Chessie site and about 40 at the remaining sites. Independent surveys will be made on each side of the grade crossing at the N & W site. This sampling rate will be sufficient to identify any long-wavelength trends or variations within the test sections. The planned measurements are summarized as follows: a. Vertical . Elevations of the rail base and the tie surface on both sides of the track b. Lateral . The lateral position of the rail base, relative to the fixed lines established by the benchmarks, for the rail nearest the bench- marks c. Longitudinal . The longitudinal positions of both rails, relative to fixed transverse lines established by the benchmarks. There will be three such lines in each test section. The major requirements of these measurements are: a. Benchmarks . It is planned to install three benchmarks adjacent to each test section. For this purpose, the N & W site will be divided into two sections on either side of the grade crossing. Thus, for the three con- crete tie sites and the one wood tie control section, a total of fifteen benchmarks will be required. This number of benchmarks is required to limit the maximum sight distance- between benchmarks to 300 feet, which is about the upper limit for the establishment of sight lines and for shooting elevations. The benchmark installation will involve drilling and casing of a hole approximately 10 inches in diameter and five feet deep. The hole be- neath the casing will then be cleaned, concrete will be poured and a steel tube approximately four inches in diameter will be inserted into the concrete base and partially grouted with concrete. UMASS will assume responsibility for benchmark installation, which will be done during the preliminary site visit to obtain subsurface characterization samples. This installation will take place several weeks in advance of the "first" site visit, during which instrumentation will be installed and initial performance measurements will be taken. 27 b. Equipment . All lines and levels will be established with a theodolite, to be provided by Battelle. In addition, a surveyor's chain, temporary markers and other normal surveying accessories will be required. c. Skills . An engineer with surveying experience will supervise the first survey and train selected staff, who will complete all subsequent measurements. In Section 5.14, the construction and placement of benchmarks are illustrated and detailed procedures for the completion of vertical, lateral and longitudinal survey-to-benchmark measurements are provided. 3.4.3 Average Tie Spacing As a check on the nominal design spacing of each test section, the length of the section centerline will be chained and the number of ties will be counted. Average tie spacing will be calculated from these measurements for each subsection where tie type changes. 3.4.4 Tie Movement and Rail Creep All occurrences of significant spacing deviation and skew will be identified by the following procedure. A spacing bar will be prepared to indicate deviations in spacing in increments of 4 inches. A similar protractor-type device will indicate skew in the angular increments, which are equivalent to a difference in spacing, between the two ends of the tie, of 4 inches (2.25 degrees for an 8.5-foot tie). The observer will count all exceedances of the designated movement levels which fall in each section of the same tie/fastener combination. The relative longitudinal movement between rails and ties (rail creep) will be measured at all ties where vertical and lateral STB measurements are to be made. Rail creep measurements will assess the capability of the tie/ fastener/ballast system to restrain the rails. Creep markings will be painted on each field side rail base and on the adjacent tie surface. Tie movement and rail creep measurement procedures are provided in Sections 5.15 and 5.16. 28 3. 5 Component Inspections 3.5.1 Tie/Fastener /Fad /Insula tor Inspections Visual inspection of ties and fastener components will be made to determine the extent of tie cracking and chipping and of damage and disloca- tion of fastener clips, insulators and pads. The inspections will combine FAST inspection codes with the procedures used in semiannual inspections of the concrete ties at the Chessie site in Lorraine, Virginia. It is planned to inspect the top surfaces of at least 50 ties in each concrete tie subsection of the same tie/fastener combination. The one exception to this plan will be made at the Chessie site, where top inspections of all 224 ties have been made at six-month intervals for several years. This inspection will be continued. For the remaining sites, the selection of ties within each segment of the same tie/fastener combination will be made randomly. Tie face inspections, which require opening of cribs, will be made for at least twenty ties of each type in each test section, but only at the first and last site visits. The selection of crib locations will be made randomly except at the Chessie site, where the present scheme of crib migra- tion will be continued. For the remaining test sections, the sites should be separated by at least three cribs. In addition, any previously identified major cracks will be inspected on each successive visit to monitor crack growth. A major crack is defined as a crack which is visible on at least two surfaces. The major support requirement of the inspections will be for railroad labor to open and then restore the designated tie cribs. No interruption of traffic is required, since trains can operate over isolated open cribs without danger. The top surfaces will be inspected for tie cracking, tie chipping, and damage or dislocation of the fastener clips, insulators, fastener shoulders and tie pads. Tie face cracking and damage will be recorded for the faces adjacent to the opened cribs. The inspection form and procedures are described in Section 5.17. 29 3.5.2 Gage Face Wear Gage face wear, or the lateral position of the gage face relative to the rail web, will be measured with a snap gage of the type planned for use in the Phase II experiments at FAST. Measurement locations will be the same as for vertical and lateral STB measurements, but gage face wear will be measured only on the first and last visits. Battelle will investigate the purchase or construction of a snap gage device. Measurement procedures are provided in Section 5.19. 3. 6 Summary of Measurement and Data Requirements A summary of required data and data reductions, for each experiment to be conducted or set of records to be obtained during this program, is provided in Table 3-3. 30 r X X M ■ •-( CM en <• rH cn en -a- rH CM CO -4* CO rH CM CT1 o TJ 3 H C CO CO X im -H X E to c O C ^H J= X) 4J •H cm CO -H CO Z co G X O iH CJ 01 Li CO Ll M .H 00 O o -o 4J3 CO 01 o 4-1 Ll u • 4-1 oi c M CO •H 111 • ■ > <4-l 01 J= B CD 4J • CO 01 CD > -H H u 4J E CO CJ CM 4-1 •H CD CD •H 01 TJ O 3 U l-i > •H O • C Ll -T3 CM 01 oj a TJ h a 3 O 01 o CM CO T-i CD O -H •H O 01 Q x ID U-l CO >M CO > 1-t 1M X Li 4-i a. >. 01 X W l u 4-1 <0 01 60 U 10 O ID 4J CJ 1 3 c ■4-1 0) c Ll 60 CO C C 01 •H 01 00 • 0) -H c « O CL 01 4-1 CO) -H O rH rH -H 01 CO Ll rH CO CO < e 6 CO -H rH ■H jQ •H 4J 11 > -H TJ > H X A! 01 14-1 Ll 4-1 rH 4J CO CD X -H CO Cl X 01 1 < 4-1 Li o o C. 91 01 CO 1-1 4-1 CO CD CJ 01 -H CO 01 01 O CO 60 O co rH e c > rH Ll o X c CJ rH X CJ CJ > C 3 i-H c 10 01 -H CO 3 CO rH O 01 4J Li CJ o X Ll 01 CL o Ll CO Ll E > a. 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U-l o •H rH -H M O C C co CO CO 13 cfl co c 4J IH 1j o- Oi tH c cu s ■h -a -a CU 4-1 jr. 4J CO CO Cfl CJ CO 4J a a a. u >, •-< MH o 0) rM J3 o « « 4J a c 01 co M M o a u c to cu oi a> o CO o o T3 C C i-t i-H CO C4H 4H *H U 01 11 4-1 4J 4J O 4-1 4-1 O iH CU - CO CJ CO CO O 3 rH OS o H CO z M ^ 1 5 a, I 0? g a w co z z 5 p W O w m H H c/3 H r^ -~- Ph W (DO H Z H M CN 9 o CM a E CO CO CU T> CO M 60 J3 3 C/3 CO tl CU -1 4J c) CU O CJ C CJ >H 01 CO c c_) r-i C CO •-t CU B H o 4_l ^3 CO CD 4-1 4-1 r< I>4 CO ■ i n * ■ 35 TEST SITE DESCRIPTION AND INSTRUMENTATION PLAN 4.1 Test Sites Layouts of the four revenue service test sites are provided in Figures 4-1 through 4-4. Each layout shows the track segments selected for installation of instrumentation and for measurements of track geometry, com- ponent condition and ballast/subballast/subgrade properties. In the three concrete tie sites, the instrumentation will be placed either on CC244 ties (Lorraine) or on CC224C ties (Roanoke and Streator). This is required to insure the greatest possible uniformity among the test sections and the best correlation of laboratory and field measurements. Further discussion of each test section, including the Northeast Corridor site, follows. 4.1.1 Chessie Site at Lorraine, Virginia This is the shortest of the test sections, containing 224 ties at 25-inch spacing on a curve of approximately 3 degrees (Figure 4-1). The instrumentation will be installed on a 100-tie segment of CC244 ties. All other measurements will generally span the entire section, which includes 118 RT-7S ties. 4.1.2 N orfolk & Western Site at Roanoke, Virginia This tangent site contains 1666 feet of CC244C and RT-72 concrete ties at 24-inch and 26-inch spacings . The site is bisected by a grade crossing which exerts a considerable effect on track geometry. Long- wavelength undulations in surface have been observed emanating from the crossing in the eastbound direction of predominant traffic flow. It would be desirable to isolate the instrumentation from the crossing to the extent possible. But since the CC244C ties are located next to the crossing, the only alternative is to concentrate the instrumentation in the eastern end of the section, perhaps within the last 50 ties. Surfacing maintenance would reduce the effect of surface irregularities initially, but N&W is not planning to perform any maintenance during the test program-. Ballast and 36 w H W Pi C_> o o O an H Pi en Pn O H o I w Pi 37 n o pq H en < w £ J CO Pi Pi u co En Q En X! H o 1 o i-J O Pi > z o H i-H s En 1 CO H CO w H En 1 H U z o z o CO H Z E=> CO En o H !=> o H Q O W M H ^1 Hi W o 1 H & fa o O Pi CM X 53 CJ n p_j - H 1 s l-l J 1 1 r' "1 r => L- — — J (_ -1 r 1 c 1 r~ 3 J c 77777 L _ — J J J c =r :t L j c 7J c: unci 3 r — "1 C" 777.7 J c; 77777 3 C" 7777. 5 c- ~ i 3 c . 71 c ; 3 l: ; J r. Si ' 3 [ u < Of 1 1 L y- J c ■ 3 c. ID ) c (- I I ) c, n 3 c . o 1 C o J r 1 c .. 71 r. T c 777: ) C — 3 r ' ~z~ 3 C 777". "7. c _ J c 777 .) r. 37 3 c "ZU" .3 c 777 :j c "ttt i c 77."" i C _. 1 co M O H Pi o H <: H CO H < O H H U W CO § o o w H H n o § 53 O CO H 53 53 CO fa o H 57> o < s H fa bangent site. An adjancent section of tangent track will be identified for comparison of failure rates and geometry degradation. It is planned to define an 800-foot section of the curve as a control section. Component inspections will be made on this segment at the same frequency as the site visits to the revenue service test sections. If possible, the FRA track geometry car should make passes over the track section at the planned measurement frequency. 4. 2 Collection of Dynamic Data Figure 4-5 shows the distribution of wheel detectors, instrumented ties and vertical and lateral load circuits in a typical instrumented sec- tion. Additional channels are allotted to clip strain (4) and rail/tie acceleration (2). Six wheel detector sensors will be used independently for each direction of traffic (W or W ), but the recording of wheel detection is the same for either direction. The figure shows the distribution of channels to each of the two multiplex units and to the tape recorder directly. Table 4-1 summarizes the transducer characteristics and required data channels for the dvnamic data set. 42 c c o o •H •H 4J 4-1 U CJ QJ OJ 4-1 5-4 5-J 4-1 •H •H •H •H 3 P p 3 CJ a u ». m 5-1 •H CO CO •H u 5-1 5-1 u O T) 4J 4-1 -a cfl 5-1 CJ u co o QJ QJ QJ o hJ c 4J 4J 4-1 h-i ■H (13 QJ QJ rH 03 R « p H cO 5-i O co a 4J 5-1 H 1-1 5-i •H en QJ 0) 0) QJ 4-1 H a) ai 4-1 5-i QJ (U ^ g cO QJ > ■H H CJ o < ii ii II II II II hJ > o 4 tz n jOl XX * K sTtf aTtfc fj zj zi en c (/) o C -H •H 4-1 d) cfl 5-i 5-i 4-J QJ CO H QJ QJ O •H CJ H < CO CN1 • e pq c o •H 4-1 CJ QJ 5-1 C O •H 4-1 u QJ 5-i •H a 5-1 QJ 4-1 CO 5-1 O 4-1 CJ QJ 4-) QJ P CO H >H QJ QJ C QJ C rC CO 5 CJ ^D O • Pi o u w o H H CJ co c o •H 4J cO 5-i QJ H QJ O CJ PJ P Pi O CJ w Pi pa Ph < H P co H M 25 P X w ►J Ph M H O H CO .J w 2 < H cd a o N PS cd 4-i 4-) -d 03 -H Q 12 3 cd PQ toO 3 03 Pi u a) a 3 CO 3 n) 5-i H T3 3 cd 5-i 3 CO cd 0) 4-1 3 3 (U CU 3 PQ 3 cd cd ■H ■H rH rH •H H 1 aj rH Cu H a cd cd cu CU cd CU O O •H •H 5-i 5-i CJ a 5-i a) H CO cd 4-1 4J CJ o 4-1 r; Pi Pi Pi co 4-1 cn cu < -J H H Pi H P-i s H T3 OJ 3 •H 6 U CU 4-1 CU -3 CU o H 44 5. INSTRUMENTATION SELECTION, EVALUATION, CALIBRATION, INSTALLATION AND OPERATION Dynamic track response will be determined by measuring the input wheel/ rail loads and those track response parameters which can be measured with minimum influence on track performance: tie strain, rail/tie accelerations, and fastener strain. 5.1 Wheel/Rail Loads (a) Purpose . Vertical and lateral wheel/rail loads will charac- terize the dynamic loading environment generated by revenue traffic through the test site. (b) Principle . Strain gage patterns measuring the principal strains in the rail web and rail base will be used to measure vertical and lateral W/R loads, respectively. These gage patterns have been verified from laboratory and field experimental results under Contract No. DOT-TSC-1051. Appropriate gage patterns are illustrated in Figure 5-1. (c) Accuracy . The desired measurement accuracy is + 1.5 kips lateral, + 2.0 kips vertical, including system noise, linearity, hysteresis, and cross talk contributions to error. (d) Equipment . Weldable strain gages, 1-inch length (Ailtech Type SG-129/30 or equivalent) will be used in a quantity of 12 per vertical/lateral measurement site. Due to the required 2 year circuit life, the survival of the Ailtech gage is in question and alternate gages including the Micro- Measurements and Hitec weldables are being considered. The known performance history of the Ailtech gage may still provide a better approach even at the extreme case of replacing all gages prior to each new field data collection period. Equipment for installation includes a capacitive-discharge welder (30 to 100 watt-second range), a rough grinder, a small die grainder, a gage layout marking fixture, a wire stripper, and a terminal crimping tool. (e) Measurement Locations . See Section 4. (f) Preparation . Weldable strain gages will be applied according to the manufacturer's recommendations in the User's Manual supplied with the 45 / hJ f < w Z u M j^r s <3 o P5 Z <3 UJ J J CN cj \ / cj PS M o o z M PS :=> CO < I Q < O .J ►J < M & > !3 O PS M u o M CO < w s I o < o H 3 w H I O Z o PS o w H H hJ P W CJ CJ w CO CO O W 5 megohm from shield to rail) before they are terminated in the bridges of Figure 5.1-1. Two strain relief straps will be used to secure the integral lead strain relief structure. After completion of the gage checkout, a heavy bead of clear , bathtub seal (RTV rubber) will be run over the length of the gage and the strain relief to reduce the effects of rail vibration and to provide some mechanical protection. Gage leads will be terminated within the rail web region or routed through a pro- tective housing to the end of the tie to prevent damage from tampers and dragging equipment. (g) Instrumentation . Signal conditioning amplifiers will provide 'a 5-volt excitation to each strain gage bridge. Appropriate cabling and connectors and/or terminal strips will be provided for rapid connection of the instrumentation and recording system for each site visit. (h) Calibration . A physical, end-to-end calibration is required from each wheel/rail load transducer to the output of the signal conditioning ampli- fier (SCA) . A physical calibration is necessary at the time of installation, at the beginning of each subsequent site visit, and after any repairs are made to the transducer. The calibration is done by applying known lateral and ver- tical loads to the rail head using laboratory-calibrated load cells, cycling these loads through some reasonable range (0 to 20 kips minimum, lateral, to 30 kips minimum, vertical) while reading the outputs of both the load cell and the gage pattern on an X-Y plotter. Lateral load calibration cycles will be run while under vertical load (15 to 25 kips) , with care taken to avoid trans- verse load paths through the vertical load fixture. After the calibration X-Y plot is run, a bridge shunt calibration (precision resistors across the opposite, active arms of the bridge) will be recorded. The slope of the X-Y plot then provides a determination of SCA output (lb/volt) , and the equivalent 47 value of the shunt calibration. Suggested resistor sizes to achieve a double shunt step approximately 50 percent of the desired full range are as follows: W/R Load Resistor Full Range Vertical 301K ohm 75,000 lb Lateral 200K ohm 25,000 lb SCA gain will then be adjusted so that full-scale output voltage is roughly twice the shunt calibration step voltage, set to some convenient value of volts per kips, or lb per volt. 5.2 Tie Bending Strains (a) Purpose . Strains along the tie longitudinal axis will be used to determine tie bending moments and stresses in response to vertical and lateral wheel/rail loading. (b) Principle . Longitudinal strain gage coupons will be bonded to one side of the tie at two locations: beneath the rail seat, and at the tie center. From an analytical evaluation of the CC244 tie and from practical considerations of tie damange on the bottom edges, the rail seat gage coupons will be located directly beneath the rail centerline and centered 1.5 inch up form the lower edge of the tie. This will leave about one inch of space to accommodate broken edges. This also coincides with the height of the bottom strands of prestress wire. Resulting strain measurements will be related to tie bending moments by in-situ calibration using the fixture shown in Figure 5.2-1. A series of laboratory tests will be performed to determine the difference in sensitivity indicated using the rail as the center load path and the sensitivity using the AREA recommended loading fixture. Variations in material properties from one batch to another preclude the use of a single sample of ties to determine Young's Modulus. Different amounts of air entrainment from one installation to another is especially significant . The webbing straps will produce minimal disturbance to the tie support but as an additional precaution, the calibration will be performed just prior to the surface and lining on the Chessie and Sante Fe sites. 48 FRAME JACK STRAP FIGURE 5.2-1. FIXTURE FOR IN-SITU CALIBRATION OF TIE BENDING STRAIN 49 (c) A ccuracy . The desired measurement accuracy is + 10 micro- strain (ue) due to contributions from circuit noise, gage placement dimen- sional tolerances, etc. (d) Equipment . Preassembled, hermetically-sealed strain gage coupons will be used on the concrete ties. These strain coupons, as sketched in Figure 5.2-2, consist of a 4-arm bridge with integral leads, with two parallel 2-inch active gages wired into opposite arms of the bridge, and two shorter temperature-compensating gages completing the bridge. Final configuration of the strain coupon will be determined during laboratory evaluations. The effects of apparent strain on the bridge comple- tion gages will be determined by comparing the performance of two coupons- one with the completion gages bonded to the base shim where they will respond to the apparent strain (due to temperature) of the concrete while also responding to vertical compression and Poisson strains, and the other coupon will contain completion gages on an isolated wafer as shown in Figure 5.2-2 which will not track the apparent strain in the concrete tie but will also not respond to the compression and Poisson strains. A template is needed for accurate and repeatable location of strain coupons on the tie, and a bonding fixture is needed to apply adequate pressure to the coupon during the curing of the cement. A calibration fixture as shown in Figure 5. 2-1 will be required to perform in-site calibrations. (e) Measurement Locations . See Section 4.0. (f) Preparation . The pressembled strain coupons will be installed on the tie in situ to avoid disturbing the tie seating in the ballast. The surface of the concrete will first be prepared by tapping away any obviously loose or protruding materals , and a careful examination then made for hairline cracks in the concrete greater than about 1/2 inch in length (if such cracks are present, an alternate tie location will be chosen for the site). Strain gage coupons will be applied at the locations sketched below in Figure 5.2-3: An application of AE-10 strain gage epoxy will be made as a preliminary seal to fill all voids. After curing and sanding the epoxied surface flat, a second application of AE-10 will be made to bond the coupon to the tie. A bonding fixture will be used to assure sufficient bonding pressure during the 50 Strain Relief Strap Temperature Compensation Gage Resilient Cement Output Cable Strain Reli R' 4 Active Gage Strain Gage Backing Plate FIGURE 5.2-2. STRAIN GAGE COUPON FOR INSTALLATION ON CONCRETE TIES 51 TIE CENTER 1, RAIL SEAT FIGURE 5.2-3. STRAIN COUPON INSTALLATION 52 cure, and heat lamps will be used to speed the curing if ambient temperatures are below 70°F. Protection of the strain coupon from ballast will be provided by a suitable cover bonded to the tie with a resilient adhesive, such as a bead of RTV rubber. Gage leads will be routed so that track and ballast movement will not cause damage, and additional protection will be provided as necessary to avoid damage from traffic and track maintenance operations . Durability of this installation technique will be verified by installing two gage coupons at FAST so that they can be subjected to a substantial amount of traffic. The installation at FAST should verify its abrasion resistance as well as any fatigue problems. (g) Instrumentation . Signal conditioning amplifiers will provide a 5 volt excitation to each strain gage bridge. Appropriate cabling and connectors and/or terminal strips will be provided for rapid connection of the instrumentation and recording system. (h) Calibration . Resistor shunt calibration across the two active arms of the bridge will be used in the field to determine strain gage output in microstrain per volt at the signal conditioning amplifier. Precision resistor sizes will be determined for the strain coupons based on laboratory tests to provide a step change in output roughly 50 percent of full scale. The strain gage bridge output is based on the relationship: /„ / j- . s (active arms) . . e/V = (gage factor) x -. (e) where so that e = voltage out V = excitation voltage e = strain (in/in) 2 x Ae (SCA Gain) x (gage factor) x V , calibration step equivalent strain where Ae = change in output voltage by shunt calibration, (SCA Gain) = amplifier gain setting. The effects of long cable lengths between the gages and the SCA (greater than about 50 ft) will be determined by means of a precision calibrator, and the strain equivalent of the shunt calibration step adjusted accordingly. 53 5.3 Rail and Tie Accel erations (a) Purpose . Measurements of vertical accelerations of the rail and the tie in the vicinity of the rail seat will characterize the transfer function between rail and tie through the pad/fastener combination, as well as define the vibrational environment of these two track components under revenue traffic. The effect of rail corrugations, if present, is of particular interest . (b) Principle . Accelerometers for measuring vertical accelera- tions will be mounted to the rail base and to the tie top surface as close as possible to the rail seat area. These two simultaneous signals will be analyzed by Fast Fourier Transform (FFT) techniques to determine the transfer function between rail and tie, as well as the power spectral density, amplit- tude and phase spectra of the individual signals. (c) Accuracy . The desired measurement accuracy is + 5 g on the rail acceleration, and + 1 g on the tie accelerations, based on the following range and bandwith: Measurement Full-Scale Range Minimum Data Bandwidth, Hz 2000 Channels Per Site Rail Vertical Acceleration + 500 g 1 Tie Vertical + 50 g 2000 3 (d) Equipment . Accelerometers with the required amplitude and frequency range given above will be required, plus appropriate signal condi- tioning amplifiers and special leads or cabling as required. As a minimum, a 4-channel FM magnetic tape recorder is recommended for permanent recording, and an oscilloscope and/or light-beam oscillograph for on-site data quality control. (e) Measurement Locations . See Section 4.0. However, in addition to general location requirements, specific tie locations will be chosen to be as near as possible to any kind of rail running surface anomaly (rail joint, dipped weld, wheel burn, corrugation, etc.) to provide the highest W/R load input for a good "signal to noise" ratio. Locations will be marked and logged by tie number. 54 (f) Preparation . Small phenolic blocks (about 1" square) will be used for mounting the particular accelerometers to the tie or rail. A number of these can be made up in the shop and mounted at the chosen tie locations. Blocks for the rail base will be tapered on the bottom surface to the angle of the base so that the accelerometer , when mounted, will be perpendicular to the plane of the track. On the rail base, a patch will be ground to remove dirt and mill scale, as close as practical on the gage side to the centerline intersections of rail and tie. The block will be mounted with quick-setting epoxy cement and held by c-clamp until cured. For installa- tion on the top of the tie, a patch will be cleaned as close as practical to the tie centerline and the edge of the rail base on the gage side, and a layer of epoxy cement load down as a surface filler. After this has cured, the block will be mounted with additional quick-setting expoxy cement and held under pressure until cured. (g) Calibration . Accelerometers and associated amplifiers will be calibrated prior to each day of measurements using a standard laboratory cali- brator, such as the General Radio Model 1557A calibrator, which provides an excitation of 1 g rms at 100 Hz. 5 . 4 Fastener Strain Fastener strain will be evaluated in depth at FAST under contract DOT-TSC-1595 . It is anticipated that little or no additional information will be required during the field testing for this program. However, strain gaged clips may be available from the other test program to provide correla- tion with FAST results with a minimum of additional effort on this program. Data system capacity will not be affected by this measurement because it can be used alternately ("time shared") with the acceleration measurements. It is likely that the major interest will be in comparison of dynamic clip strains when installed on pads with different stiffnesses. 55 5.5 Wheel Detection and Train Speed (a) Purpose . Wheel detector pulses from each independent measure- ment location will be required for statistical processing of data and deter- mination of train speed. An example of the wheel detector pulse with relation to typical W/R load measurements is shown in Figure 5.5-1. (b) Principle . Standard electromagnetic wheel detector transducers positioned at the measurement locations will provide an electrical pulse that will be used in the data processing sequence. Each wheel passing the trans- ducer will generate the raw pulse which is then conditioned for recording by the circuit of Figure 5.5-2. The recorded pulse will later be used to generate a timed pulse to enclose the data generated by that wheel through the measure- ment zone. (c) Accuracy. The pulse accuracy desired is defined by a zero crossing (change in polarity) within + 1 inch of the center-line of the trans- ducer body. (d) Equipment . Twelve wheel detector transducers (Servo Corporation Model 400022-16) and wheel detector clamps (Model 200114-01), or equivalent are required, along with six conditioning circuits (Figure 5.5-2) and assoc- iated cabling, in each of the two test sections. (e) Measurement Locations . The transducers will be placed on the rail in the crib area on either side of each single instrumented tie and in all 4 cribs at the 3-tie primary location as shown in Figure 4-5. (f) Preparation . Wheel detector transducers will be attached at the locations noted in (e) using the associated clamps. No preparation of the rail is required, other than cleaning off excess dirt and grease. (h) Calibration . Transducers will be checked out at the condition- ing circuit output by passing a hammer or spike maul over the transducer to determi if a sufficiently high voltage pulse for recording purposes is generated. 56 peak — peak VERTICAL W/R LOAD — peak LATERAL W/R LOAD peak WHEEL DETEC- TOR PULSE J\ U V TIMED LOGIC PULSE (PEAK DETECTION) FIGURE 5.5-1. EXAMPLE OF USE OF WHEEL DETECTOR TRANSDUCER TO PROVIDE WAYSIDE DATA PEAK DETECTION AND A/D CONVERSION IN DATA PROCESSING 57 WD zx xz 12 on FM Tape Channel FIGURE 5.5-2. WHEEL DETECTOR TRANSDUCER SIGNAL CONDITIONING 58 5.6 Vertical Track Modulus Because concrete tie track has a relatively high modulus, it is recommended that an optical instrument such as a surveyor's theodolite be mounted at least twenty feet from the rail to resolve the relatively small vertical deflection of the rail under load. A point load of known magnitude will be applied simultaneously to both rails using vertical hydraulic jacks reacting against a loaded freight car. Deflection readings will be made at a minimum of three loads (e.g., 10, 20, 30 kips) at each of the tie locations discussed in Section 3.3.1. Track modulus will be calculated using the expression: where u = track modulus - lb/in/in, k = AP/AY from the measurements, 59 5 . 7 Field Inspection of Ballast and Subgrade Condition s 5.7.1 Introduction As a part of the overall field inspection of track conditions, ballast and subgrade conditions will be inspected visually during each site visit. The objectives of this visual inspection are to document the general condition of the ballast and subgrade layers and their changes with track history, and to identify any significant problems in the ballast and subgrade layers that may influence behavior of other track components and track performance. Care- fully executed visual inspection will aid in accurate characterization of in-situ ballast and subgrade conditions, in proper interpretation of various proposed measurements, and in meaningful correlation between the measurements and track performance. 5.7.2 Scope A total of 4 series of visual inspections will be made at each test site, at an interval of approximately six months. The first and fourth inspec- tions will be made simultaneously with the ballast physical state tests. These visual field inspections will be performed by an experienced University of Massachusetts geotechnical staff member. Emphasis will be given to the description of the ballast profile, ballast degradation and fouling, drainage, and subgrade conditions. However, general information on the site conditions, the relevant area geology, and seasonal variation of climate condi- tions will also be gathered. Photographic documentation of ballast conditions will be made during each site visit, so that a continuous and systematic com- parison of the ballast condition changes can be made with track history. The results from the field site inspection will be compiled into a series of field inspection reports. 5.7.3 Information Needed The following lists the information to be gathered during the visual inspection of ballast conditions: 60 1 . Ballast Conditions. a. Profile: mean and variation of ballast depth and shoulder dimension over the test section. b. Displacement and/or dislocation: caused by traffic induced loads, track maintenance work, and lateral, longitudinal, and/or vertical dislocation of tie. c. Degradation of ballast particles: caused by wear, abrasion, or crushing. d. Ballast fouling: 1) Infiltration of fines from outside the track 2) Pumping from subgrade 3) Abraded fines 4) Spillage 5) Coal dust 6) Vegetation. e. Drainage conditions: presence of moisture and/or water pockets . f. Degree of ballast densif ication. 2 . Subgrade Conditions a. Drainage b . Pumping c. Instability d. Ballast intermingling. The following information will be provided by the subcontracting railroad 1. General Site Conditions . This information will be gathered prior to or during the first site visit. Items a, b, c and d are needed for correlation with ballast and subgrade conditions and will be the responsibility of BCL. (a) Name of subcontracting railroad (b) Geographical site location including mile post or appro- priate test section number (c) Track description including track type, FRA classification, type and magnitude of traffic, and train speed 61 (d) Track super structure: rail weight and type, joints, fastener type, rail anchorage, tie type, and dimension, including manufacturer's name and model number 2 . Track History . (a) Maintenance work: type and scope of maintenance done prior to and/or between site visits, type of machine used, maintenance procedures used (b) Traffic history: type, tonnage, etc. (c) Climate record: weather, precipitation, temperature, etc. (d) Other significant events that have occurred at the test site prior to and/or between site visits (e) Ballast and subballast: type, specified characteristics including gradation, shape, relative hardness, origin and supplier, specified ballast depth and shoulder width (f) Subgrade: soil type and conditions 5.8 Ballast Physical State Tests 5.8.1 Introduction The objectives of this series of tests are to determine the ballast physical states at the beginning of the testing program, and to evaluate sub- sequent changes from maintenance operations and traffic. Determination of in-situ ballast physical states with track history, along with visual inspec- tion of field track conditions, will provide basic information needed for identifying important track parameters influencing track responses and their correlation to track performance. The measurements planned for the ballast physical state determina- tion include (a) in-situ ballast density, (b) plate load resistance, and (c) lateral tie push resistance. In-situ ballast density is measured by determining the volume and weight of ballast samples, carefully excavated with- out disturbing in-place structure of ballast and subgrade layers. A special method for measuring in-situ ballast density has recently been developed, 62 and this is described schematically in Figure 5.8-1 (Reference 1). The basic concept is that of the water replacement method, which has been widely used in the highway and embankment constructions. The plate load test measures vertical ballast and/or subgrade stiff- ness under applied load. The test will be accomplished by applying static loads to a small size (5-inch diameter) plate and measuring the resulting deflec- tion. Often, the measurements are also taken during subsequent unloading to determine the rebound characteristics. The test is a direct measure of ballast physical state and load-deformation characteristics. Figure 5.8-2 shows a schematic illustration of the plate load test apparatus. The lateral tie push test is a common field method of measure- ment related to track performance used in the railroad industry. It measures lateral tie resistance to displacement under unloaded rail conditions. The test is only an indirect measure of ballast physical state, but it is directly relevant to the lateral track restraint. Figure 5.8-3 describes a device for measuring the resistance of a single tie to lateral force. Detailed description of these tests can be found in Reference 1. 5.8.2 Scope of Tests The ballast physical state tests will consist of three series of measurements at four test sections, including the wood tie control section. The first and second series will be conducted before and after tamping during the first site visit. The third series will be done during the last (fourth) visit after the accumulation of about 2 years of traffic. During each series, each test section will be subjected to 18 ballast density tests (BDT) , 22 plate load tests (PLT), and 6 lateral tie push tests (LTPT). Six or more ties per test section are needed to be unfastened for the lateral tie push tests. Among the 6 randomly selected, nonconsecutive ties used for the LTPT's, 4 ties will be completely removed for the under-tie ballast density and plate load tests, i.e., two ties each. Two cribs near the removed ties will also be involved in each of the tests. 63 TOP SECTION BOTTOM SECTION BASE PLATE MICROMETER POINT GAGE CLAM UNDISTURBI BALLAST RUBBER LINER FIGURE 5.8-1. SCHEMATIC ILLUSTRATION OF IN-SITU BALLAST DENSITY APPARATUS 64 o < o _J < Q >- X 1 < LJ O h- O < en V CO 5! H CO w H Q u QL _l o o Z> _) _l h- 1— co LL h- h- ■ — , 1- _l Q O _l 1 Q_ 1 CO 1 1 J Q H CO < CO H CO w H W H < H CO i-J < £L Q co EC O, Pn O H ^> O >-■ < |3^1L CJ 0. 0. ZK CO LU h- O LU LU CO >- o Q Z < >- _J s: c* O LU Q CO < =5 Z < O => < a o LU I— < an 2 X o -J Q < CL LU LU h- LU LU i- -j a QUJZ CO CO z> E-i I oo o l-H LU I- o TABLE 5.8-2. REQUIRED TEST APPARATUS AND EQUIPMENT 1. Ballast density devices and accessories. 2. Reference density test device and accessories. 3. Plate load test apparatus and accessories. 4. Lateral tie push test apparatus and accessories. 5. X-Y recorder for items 3 and 4. 6. Power generator. 7. Track carts. 8. One set of heavy-duty balance with weights, 20 kg. capacity, 1 gm. sensitivity. 9. One set of 12-in. -diameter sieves: 2 in., 1-1/2 in., 1-in. , 3/4-in. , 1/2 in., 3/8 in., #4, #10, #20, #40, #60 (or #70), #100, #200, pan and #200 washing sieve. 10. Sieve shaker for item 9. 11. Drying oven. 12. Two to four mixing pans, 2 ft x 2 ft size. 13. Two to three water containers, at least 5 gal. capacity. 14. 200 to 400 lb plaster of Paris. 15. Sample bags, plastic lined cloth, medium size. 16. Miscellaneous soils lab tools. 17. Tools to remove and replace ties and ballast. 18. Sand cone density apparatus. 71 test procedures are contained in Appendices A to D. Data reduction proced- ures are also briefly described in the test procedures in the appendices. For general description of test site conditions to be obtained during the tests, general guidelines for visual inspection should be followed. 5.8.5 Test Schedule Field crew for the ballast physical tests will consist of 1 supervi- sor, 2 persons for BDT, and 2 persons for LTPT/PLT. With this level of staff- ing, the track time required to perform the tests is about 3 days for each track condition, assuming that the track would be accessible and closed to train traffic for two separate five hour intervals. One to two additional days are also needed for on-site preparation, sample collection, and other related activities . Since so many activities are scheduled during the first site visit, careful scheduling and coordination are mandatory among various groups of persons involved. The sequence of various tests is also important because of usually limited track time and space. A detailed schedule will be arranged in advance, with consultation among BCL, the subcontracting railroads, and the University of Massachusetts . 5.8.6 Additional Sampling In addition to sampling for gradation and moisture content at the BDT locations and moisture sensor locations, a quantity of ballast samples is needed for ballast reference density test, index property tests, and repeated load triaxial tests. Sampling for these tests will be done after the first series of ballast physical state tests and prior to the track maintenance during the first site visit. To minimize disturbance to the track, the additional material sampling will be done as much as possible at those ties assigned for the ballast physical state tests. Additional samples will be taken under the plate load tests at both elevations to insure an adequate supply to perform the laboratory tests. When excavating for the subballast tests, a continuous log will be kept and samples will be taken down to the depth where the sampling from the subsurface investigation began. This will provide a continuous characterization of the supporting soil. 72 Figure 5.8-5 shows a representative cross section of track with typical measure- ments and samples to be taken. A total of 4 ties and 2 cribs is involved in the sampling. The sampling plan will provide 36 ballast and 12 subgrade samples. About 20 lb of samples will be taken at each sampling location, totaling about 720 lb ballast and 240 lb subgrade materials per test section. The ballast samples will be used for the index property tests and the triaxial tests. The sub- grade samples will mainly be used for the index property tests, and classifi- cation tests including moisture content and gradation, supplementing to the boring samples. Care will be excercised to ensure representative and quality sampling throughout the test sections. All the samples will be carefully bagged in plastic-lined cloth sample bags with proper identification, and will be shipped to the University of Massachusetts for required tests. They will be weighed at the site and upon arrival in the laboratory as well. 5.8.7 Railroad Assistance The following assistance from the subcontracting railroads will be needed for the ballast physical state tests: (1) Shut down the test section during test period. (2) Ensure safety of test crews at the site. (3) Provide 2 to 3 man track gang to unfasten, remove, and replace ties as needed, and to replace ballast removed for various tests . (4) Restore track to original conditions existing prior to tests. (5) Provide track maintenance and traffic history prior to tests, and information on any significant environmental changes which have occurred. 5 .9 Ballast Index Property Tests 5.9.1 Introduction The objective of the proposed ballast index property tests are to pro- vide fundamental information needed for classification of ballast materials and for 73 0\/ SUBGRADE P= PLATE LOAD TEST D= BALLAST DENSITY TEST "UNLESS SUBGRADE IS WITHIN 18 INCHES OF TIE BOTTOM FIGURE 5.8-5. TYPICAL CROSS SECTION OF BALLAST PHYSICAL STATE TESTS 74 relating ballast properties to observed track performance. Many index property tests have been developed for characterizing both physical and chemical proper- ties of ballasts. However, they serve as only indirect indicators of potential in-service behavior. At present, no acceptable method of relating the index properties to suitability of ballast exists, simply because the index property tests quite often evaluate characteristics of the individual particles making up the ballast materials, and proven methods or criteria for rating ballast in terms of its effects on track performance are not available. Rather, the index properties are currently used as a basis for establishing some minimum specifications or guidelines for selecting ballast. 5.9.2 Scope of Tests Since this study concerns existing ballasts, only important and signi- ficant tests should be included in the testing program. Based on the literature review (References 2, and 3), the following tests have been selected on the ballast materials: (1) Gradation test. (2) Liquid and plastic limit tests on material finer than No. 40 sieve. (3) Specific gravity tests on material both coarser and finer than No. 4 sieve. (4) Water absorption test on material coarser than #4 sieve. (5) Chemical soundness on material coarser than #4 sieve. (6) Los Angeles abrasion test on material coarser than #4 sieve. (7) Composition analysis on three separate fractions, such as material larger than #4 sieve, between No. 4 and No. 40 sieves, and smaller than No. 40 sieve. (8) Descriptive tests on material coarser than #4 sieve, such as visual estimation of angularity and sphericity, and hardness. 5.9.3 Test Procedures Figure 5.8-6 illustrates the proposed sample preparation and test sequences for the index property tests. Detailed procedures for the sample processing and tests are described in Appendix E. 75 VOID RATIO BALLAST DENSITY TEST SAMPLE WATER CONTENT DRY DENSITY GRADATION >#4 SIEVE >i i +0 BUT < #<4 SIEVE H O Xi 4-1 (-1 C o cu 4-1 6 cu CU CxO CO c cC cd u M u H cd cd ■H A! o M CU CD D. e CO JZ u td d 0) CO PQ •H .. w H o z 2 O M H w CO H CO w H H O O Pm I o o ■ H w Pi O H 93 MEASUREMENTS EVERY TENTH TIE, ON TIE AND KAIL BASE INSTRUMENT SETUP ~2_ BM-1 ^ [a] Vojitlnal Me.aAuAem2.nt!> BM-3 b) laX.QA.at M2.aMVi2.m2.nt6 INSTRUMENT SETUP (OVER ANY BENCHMARK) riE To^r *~>Jl [c] Longitudinal. M2.aAuA2m2.nt!> FIGURE 5.14-3. SURVEY-TO-BENCHMARK MEASUREMENT SCHEMES 94 for this purpose. The theodolite should be centered over the benchmark within + 0.01 ft. (2) At each designated tie, measure the perpendicular distance from the nearest field side rail base to the sight line. This distance is found by moving the chain back and forth along the sight line until a minimum distance is read through the theodolite. Record readings to the nearest 0.01 ft. 5.14.4 Longitudinal Rail Movement Measurements (1) Use the theodolite to establish the locations of the transverse reference lines illustrated in Figures 5-14-2 and 5. 14-3 (c) . read angles to the limit of accuracy of the instrument, which should be + 1 second of arc. (2) For the first measurement, place permanent markings on the base of each rail to define the original position of the rail under the transverse reference line at each STB site. (3) For all subsequent measurements, place a temporary mark on each rail base to define the current position of the rail under the transverse line. Measure the distance from the current mark to the original mark, to the nearest 0.01 inch. Record movement as positive if the original mark has moved in the direction of increasing tie numbers relative to the transverse reference line. 95 5.15 Tie Movement Measurements > . I ') . ] Kqu i pnii'iit (1) A spacer bar is required to indicate deviations in longi- tudinal tie spacing of + 4". (2) A large protractor should be constructed of clear plastic to indicate tie skew deviations of + 2.25 degrees. This skewing angle would be caused by a difference in longi- tudinal position of opposite ends of the tie of 4". 5.15.2 Measurement Procedure (1) Record data separately for each section of track where the tie/fastener combination remains the same. The data will consist simply of numbers of exceedances. (2) Walk the track and inspect all ties for spacing deviations (> 4- 4") and skew (> + 2.25 degrees). Where exceedances are suspected, measure: a. longitudinal spacing along the centerline of the track b. skew of the ties with respect to one rail base. Use the following signs: a. Spacing deviation is positive for spacing greater than nominal b. Skew is positive counterclockwise looking down on the track. Thus, the exceedances will fall in one of the following categories : TIE SPACING (INCHES TIE SKEW (DEGREES) + 4" - 4" + 2.25 deg. -2.25 deg. 5.16 Rail Creep Measurement s 5.16.1 Markings Rail creep will be measured at all ties where vertical and lateral Survey-to-Benchmark measurements are made. Place creep markings during the first site visit, after the surf ace-and-line maintenance. Paint lateral 96 strips, in-line with each other, on each field side rail base and on the adjacent top tie surface. 5.16.2 Measurements Measure creep at the end of the first site visit and once during each subsequent site visit. Sign convention: if the rail has moved relative to the tie in the direction of increasing tie numbers, this is positive creep, 5 . 17 Tie/Fastener /Pad /Insulator Inspection 5.17.1 General The inspection form is illustrated in Figure 5.17-1. All ties in the designated test section (all concrete ties) should be inspected for all items on the form except tie face cracking. Center cracking visible from the top of the tie will be inspected on all ties. Tie face cracking will be inspected for ten percent of the ties at the Chessie site and for five percent of the ties at all other sites, during the first and last site visits only. The first inspection should be made before surface-and-line maintenance. The crib locations should be selected randomly, except that they should be separated by at least three cribs. If locations are selected with less separation, make additional selections. Inspect the faces of the two ties adjacent to each crib. In addition, all previously identified major face cracks (those appearing on two or more surfaces) should be examined on all inspections . There is ONE EXCEPTION to this plan for opening cribs: avoid the locations of ballast density and plate bearing tests. Do not open a crib if it is either the location of one of these tests or is adjacent to a test location. Lateral tie push tests must be performed before opening cribs. Only one inspection will be made during the first site visit. This should be completed before the surface-and-line maintenance. 97 PQ o H U w PL, CO H < o i— i E-f CJ W CO H CO w H in 4 o x> so or o h- = \ -T \ cr: oc LU z _j o ~ - ro vj- LO -9 r^- 03 o CM 2000 Hz) will be recorded on remaining FM record tracks at DC-20 KHz bandwidth. Data quality will be verified by monitoring on a fibre optic oscillograph at the same bandwidth as the data will be reduced. 106 cO u CJ u d) rH CO § •H rH X m tfl H u C_) pH CD Pi r-l 00 r"! rl O u o u cO U O cO hJ c e u 4-1 to c M •H ,£) O ►J CJ pq to 1 CJ o <: a >-. > > o r^ CN I rH i 3 XI O X 60 C •H c o X> C O CJ CO c o E CD M 12 O pd pq CJ M CJ > O M 13 O »J w u W CJ > XI CD CO CO 12 CO XI CD 4-1 • -i •H ^-\ XI CJ •H CO fn o 4_) 4-1 CD M •H (0 to O 00 Q co CJ •H nJ CD Q O pi c U o CD •H e O 4-1 cO 4J CD Vj 3 4J a 4J O a- cO 3 co •H R « X> >> *u o CJ CD Pi CO rH CO cO C ■ IYb 4-J -H «H IP co e Q r-l (D H pa CD CD "S*^ O B x> rH -H O Pi H U M O CD U rH 4-J 3 a x> o o cj S CJ p > CN CJ < >- > c r^ 3 XJ O c •rH c c CJ CJ < > o r^ CN CD X S 53 o rH ^ O Pi pq CJ H U > ^ o pq O a > x> CD 4-J • in to co xi CD 4J oo co co CNI rH • =»= O co O M S O Pi pq CJ H U> I Pi CJ M Cn X> CD CO CO rH • O P-. CJ •o 4-J CU CD u • • CO co CJ H • 4-1 O P-, 0) CO • < •H O u *^, • co *» co u =* TJ • X X cj 4-1 UJ LlQ^LjJOZDLxIZ:0>- lH(nh^OOC^ CDD) cor-CDLO^rnru *-« lo nj CD CD (7) CD CD CD D_LUCt:OUJZ:H- —JLUI>LiJ-3 LUXOLdUJQLUQ CO q w w p., CO ►J H-l <5 „ u H Pn |X| /*~N t H <3 H > Di hJ w J H <1 X M i H P5 23 W hJ a t pi W ;_j H w <1 ^ 3 cu CO w •H bO ►J 3 M bC bO 50 G w CT CU O O O O •H o CU -a hJ hh hJ rJ CO c_> Pi 3 CO < 4-1 * •* *v #» cu •H ^ M M V4 CJ -1 rH CO cO CO CO o -a W ,-s u a i— 1 •H 2 '— ' o o CM N o o o O o o o •H H co K vO o o O vO o o a ■H 1-1 , jr. o o o O o o O co Ph ^ 4-> cO x) u CO C -H o o o O o o o o H < & o o o o o o o MH <3^ T3 > Ph CO o o o o o o o u O W CO Ph CO CO g cu G 3 cO H S-i > ro o ■H 4-1 cu CO e CO 4-1 CO •H n rC cfl ai H cu 4J W S-i -u CO ■^^^ 4-) T3 h4 CU c ^~s ^— v •rl pq rH CU 4-1 rH 4-1 cu > 25 CU e cO •H cO u T3 H a cu CU CO cu c a u CO Pi CO cu cO < 3 S-i •H Xi CO cu rH cu rH H iH Cfl CO •H 4-1 CU •H CO Cfl CU CO cO T) d •H cO T3 •H t) s pq Pi C 0) H Pi C CO •H N ' W u — ^ W >^ 4-1 Pi H H H Pi H H CL, < O CO o o H a 1- o co X < h- _i LU _j ^ < CO or LU > O o LU 1- 3 I « Cd !=> O B-3 B.2 Test P rocedures for Uncompacted Samples L. Select a representative sample of about 1 cu ft. Then oven-dry the sample and let it cool. 2. Thoroughly mix the prepared sample, using a scoop. 3. Loosely place the ballast into the sample container in a uniform manner by gently pouring the ballast from the scoop with a minimum height of fall. Move the scoop in a spiral motion from the outside of the container toward the center to form a uniform density without particle segregation. Continue this process until the container is approximately 80% full. 4. Level the surface of the ballast in the container by filling any large voids and by removing any particles which project out too much. 5. Measure the volume of the ballast sample in the container, using the volume determination procedures described in part B.4 of this appendix. 6. Remove and weigh the ballast in the container. 7. Repeat this test at least once more. The average of all of the tests run is used as the bulk density of the uncompacted sample. B . 3 T e st Procedures for Compacted Samples 1. Re-use the sample from part B.2. Thoroughly mix the sample, using a scoop. 2. Loosely place the ballast into the sample container in a uniform layer of approximately 4 in. thick, by gently pouring the ballast from a scoop with a minimum drop height. Move the scoop in a spiral motion from the out- side of the container toward the center to form a uniform layer without particle segregation. 3. Compact the loose layer of ballast by delivering a specified number of blows from the impact hammer. For each blow, allow the rammer to fall freely from a height of 17 in., and evenly distribute the blows over the surface of the sample. The suggested number of compaction blows are either 10, 20, or 40 per layer. 4. Repeat steps 2 and 3 for the next two layers. When completed, the sample should fill about 80% of the container depth. 5. Level the surface of the ballast in the container by filling any large voids and by removing any large particles which project out too much. 6. Measure the volume of the ballast sample in the container, using B-4 volume determination procedures described in part B.4. 7. Remove and weigh the ballast sample in the container. 8. At least two tests should be made for each compactive effort. The average of the tests performed is taken as the bulk density of the compacted ballast for the particular compactive effort. B .4 Sample Volume Determination Three alternative methods are provided to measure the volume of the ballast sample in the container when the container is filled to about 80% of its volume. These are designated the plate cover method, the probe method, and the water replacement method (Fig. B-2) . 1. Plate Cover Method a. A cover plate is placed on the top surface of the sample in the mold, and the distance from the top edge to the plate cover is measured in at least four positions equally spaced apart along the circumference of the mold . b. The average height of the ballast sample in the mold is obtained by subtracting the average distance measured in step a. plus the plate thick- ness from the inside depth of the mold. c. The volume of the ballast sample is calculated as the average height of the sample times the inside cross-sectional area of the mold. 2. Probe Method a. A probe plate with guide holes is firmly set on the top of the mold. b. The distance from the bottom surface of the plate to the ballast particle surface directly beneath the hole location is measured by inserting the probe through each probe hole. c. The average height of the sample in the mold is obtained by sub- tracting the average distance determined in step b. from the inside depth of the mold . d. The volume of the sample is equal to the average height of the sample times the cross-sectional area of the mold. 3. Water Replacement Method a. A plastic membrane is laid loosely over the top surface of the ballast sample so that it is in as close contact as possible with the inside of the mold and the ballast surface. B-5 b. The depression in the membrane is filled with water to within 1 or 2 in. from the top of the mold. c. The volume of water added and the distance from the top edge of the mold to the water surface are measured in at least four positions equally spaced apart along the circumference of the mold. d. The unfilled volume between the top edge of the container and the ballast surface is determined from step c, and then the volume of the ballast sample in the container is obtained by subtracting this volume from the container volume. B.5 Calculations 1. Compactive Effort and Density Calculate the compaction effort and bulk density of the compacted ballast sample for each trial as follows: 3W DN E = -4— , (B-l) V c and = W s V V cpr y ' pc = W s V cpc y ' wr = W s V cwr (B-2a) (B-2b) (B-2c) where E = compacting effort (ft-lb/cu ft), V , y , V = bulk density of a ballast sample obtained from using ' pr ' pc ' wr J * & the probe method, the plate cover method, or the water replacement method, respectively (lb/cu ft), V" ,. V _ > V = Volume of a ballast sample determined from using the probe cpr, cpc cwr ^ ° r method, the plate cover method, or the water replacement method, respectively (cu ft), W = weight of sample (lb), W = weight of hammer (lb) , B-6 D = free fall distance of hammer (ft) , N = number of blows per layer, V = ballast sample volume in container corrected for c container boundary effects (cu ft) . 2. Ultimate Density The sets of values of bulk density and compactive effort from the refer- ence density test are plotted in the form given by Fig. B-3. The data are assumed to fit the hyperbolic form of Fig. B-3a which may be plotted in linear form using the coordinates of Fig. B-3b. A straight line is fit through the points in Fig. B-3b, either by eye or least squares curve-fitting methods. The ultimate density is calculated by the relationship v . = I + y n » (b-3) 'ult b ° where 1 b = slope of the line in Fig. B-3b, y = uncompacted density when E = 0. B-7 Z w o H CO •J CO w ti S o g w a u 2 2 M M H c < M 0- C/} 8 2 o Q COMPACTIVE EFFORT, E a) Hyperbolic Plot COMPACTIVE EFFORT, E b) Transformed Plot FIGURE 3.5. REPRESENTATION OF RELATIONSHIP BETWEEN DENSITY AND COMPACTIVE EFFORT B-8 APPENDIX C. APPARATUS AMD RECOMMENDED PROCEDURES FOR FIELD PLATE LOAD TEST (R e f. 1) C.l Apparatus 1. Load System The assembled apparatus for the plate load test is shown in Fig. C-l. Each component will be described in detail and its function will be explained in this appendix. The presentation is subdivided into the two categories representing the two main components: 1) the load system in- cluding the reaction frame, hydraulic jack and electrical load cell, and 2) the deformation system including a mechanical dial gage, electronic dis- placement transducer and supporting apparatus. a. Load Bearing Plate A circular steel bearing plate (Fig- C-2) having a 1-in. (2.54 cm) thickness and a 5-in. (12.7 cm) diameter is used to apply the load to the ballast. The plate is seated on a thin layer of plaster of paris covering the ballast surface at the test spot. The plaster ensures a level plate and distributes the load more uniformly over the ballast surface. The bear- ing plate has a hole recessed in the center that is 1-9/16 in. (4.0 cm) in diameter and 3/16 in. (0.48 cm) deep to receive the displacement reference block. b. Displacement Reference Block A displacement reference block, seated in the recessed hole on the load bearing plate, establishes a reference point for measuring the average plate vertical displacement. The displacement reference block is a partially slotted steel cylinder of 1-1/2-in. (3.8 cm) diameter and 2-3/8-in. (6.0 cm) height (Fig. C-3) . The lower section which is 1-1/2-in. (3.8 cm) high, contains a 5/16-in. (0.8 cm) wide slot 1 in. (2.54 cm) deep. At midheight of this section, a 1/8 in. (0.32 cm) diameter and 1-1/2-in. (3.8 cm) long brass rod is press fit through a hole, which is perpendicular to the slot and traverses through the exact center point of this lower section. The brass rod is called the de- formation reference pivot. The upper section, which is 7/8 in. (2.2 cm) high,, is firmly fastened to the lower section by four 1/8-in. (9.32 cm) dia- meter countersunk flat head screws. The top surface of the upper section is C-l machined to a concave shape for seating the load cell. c. Load Cell An electrical load cell gives a continuous reading of the load applied to the ballast during cycles of loading and unloading. The load cell must have sufficient capacity for measuring the maximum expected applied load (10,000 lb or 4500 kg). Input voltage to the load cell is supplied by an appropriate power source and the output signals are recorded on the Y-axis of a compatible X-Y recorder. The load cell is rigidly fixed to the moving piston of the hydraulic load jack in coaxial alignment. The length and diameter of the load cell must be such that the unit will not interfere with free movement within the load jack assembly support frame. The load cell used with this apparatus is shown in Fig. C-4. d. Hydraulic Load Jack The hydraulic load jack is used to apply a vertical load to the bear- ing plate. The piston and moving head may be advanced or retracted at the proper deformation rate by either a manually or an electrically operated hydraulic pump. The hydraulic pump is equipped with a calibrated fluid pressure gage to visually indicate the magnitude of the applied load and also to serve as a check on the load response of the load cell. The load jack, hydraulic pump and the attached hoses and connections must have suffi- cient capacity for applying the maximum desired load to the ballast. The load jack used with this apparatus is shown in Fig. C-5. The upper fixed end of the load jack is fitted with an appropriately sized steel base plate with a hemispherical ly shaped bearing tip protruding from the free end of the base plate and located at the center of this plate. This bearing tip allows small rotations of the hydraulic load jack during testing or small misalignments during the assembly of the components. The bearing tip is fastened by a screw and set into a counter sunk hole in the bottom of a thrust plate (Fig. C-7) which is a portion of the load instru- mentation support and reaction frame. e. Spacer Cylinder A spacer cylinder (Fig. C-6) is inserted between the load cell and the moving head of the hydraulic jack in order to lengthen the assembly to reach the ballast at the bottom of a tie. The spacer is composed of a 6-in. C-2 CO a H 2 < O- a. < a: E- o co UJ E- < o Q < O _) UJ < < o -J Cu o Q z UJ < -J CO •£. h- UJ Q CO 00 O < u UJ OS 3-3 to CO »- 0. < or £ to Q UJ < Ui CO _l UJ UJ Q His Be CD "0. 2 O h- < ce it 1- > liJ > UJ cc o < CL 2: UJ ;0 X UJ > f- 0- UJ CL O CO o ro >- _J _l 00 / Q / < / O lO|C0 UJ (O u. CO UJ UJ cc _J- ■ V 1 _l _ CO III CD < 10 s y UJ a: u. UJ ■v w\r a •*■* 00 a. cc cc / 1-1 cm. ro UJ > r- O CD w fn 00 H a CO I 8 M ft, UJ > o I- =5 > UJ a CO B o H PCS < cS I o o M fn C-4 3/8" .4 BEARING TIP I 1/4" LONG, 1/2" DEEP INTERNAL THREAD FOR 1/4" 4 SCREW 3 /g 6 HOLE DEEP HOLE FOR 3/8 4 COUNTER SUNK HEAD SCREW TOP VIEW, PLATE ATTACHMENT SAME SIZE AS SPACER CYLINDER END (FIG. C-6) TO X-Y RECORDER PISTON STROKE ' •4 3/4" JACK HEAD TO HYDRAULIC HAND PUMP 10' t i 2" T TOP PLATE, SAME SIZE AS END OF SPACER CYLINDER, FIG. C-6 BOLT OR WELD TO JACK HEAD FIGURE C-4. LOAD CELL FIGURE C-5. HYDRAULIC LOAD JACK C-5 32 * H0LE 2 1 1 2 r 2 "-i i!! Z in TOP AND BOTTOM VIEW PIPE, 2 t O.D. 3" | WALL THICKNESS SIDE VIEW WELD FIGURE C-6. SPACER CYLINDER C-6 o to UJ O »— t u < UJ CO I tu a: CJ5 tolco H CO i o o M C-7 (15.2 cm) -long steel pipe section with a 2-3/4-in. (7.0 cm) diameter and 3/8-in. (0.95 cm) wall thickness. At each end is welded a 1/2-in. (1.7 cm) - thick steel bearing plate having a shape compatible with the connection between the load cell and the moving head of the hydraulic jack. The spacer cylinder is rigidly fastened to both units. The end bearing plates also must be parallel with each other and perpendicular to the load jack piston axis. The length of the pipe section depends upon the stroke of the load jack, the lengths of the load jack and load cell and the needed vertical spacing. f . Load Jack Support Frame The load jack support frame (Fig. C-9) serves the dual purpose both of holding the hydraulic load jack and load cell assembly and also of trans- ferring the applied load from the bearing plate to the structural load frame. This support frame must have a structural capacity equivalent to the maxi- mum loads expected for the load jack and load cell. Four 1/2-in. (1.27 cm) -diameter threaded steel rods in a rectangular array, connect the thrust plate (Fig. C-7) and a jack support plate (Fig. C-10). The rods must have a minimum length of 6 in. (15.2 cm) plus the depth of the structural section of the structural load frame. In this apparatus the rods were 13-1/2 in. (34.3 cm) -long. The thrust plate is secured by 8 nuts at one end of the four rods. Slotted holes in this plate make the frame assembly easier. A 1/4-in. (0.64 cm) -diameter bolt through the center of the thrust plate into the bearing tip supports the weight of the hydraulic jack when the jack is not loaded. g. Reaction Plates The reaction plates (Fig. C-8) are held together by a pair of springs to prevent slippage from the rods in the frame. The location of the re- action plates is set so that the distance to the roller bearings on the support plate is equal to the depth of the structural load frame. The re- action plates are completely adjustable in the field once the entire hydraulic load jack assembly is inserted between the structural sections of the structural load frame. h. Jack Support Plate The jack support plate (Fig. C-10), located immediately below the thrust plate, performs the following functions: a) for vertical adjustment of the hydraulic load jack assembly to the proper height above the displacement C-8 -CX ft i ! | i* Ml '1*1 "J I' TO i iffl J" ■THRUST PLATE (FIG. C-7) ■BEARING TIP JACK SUPPORT PLATE (FIG. C-IO) VERTICAL ADJUSTING PLATES (FIG. D-3) REACTION PLATES (FIG. C- 8) 1 " > 2 NUT LATERAL JACK SUPPORT PLATE (FIG. D- ■4) HYDRAULIC LOAD JACK (FIG. C-5) FULL THREADED ROD, ^-13 SPACER CYLINDER, IF USED GOES HERE (FIG. C-6) LOAD CELL (FIG. C-4) FIGURE C-9. LOAD JACK SUPPORT FPJUE C-9 WASHERS FOR j: fi ROD 4 r f CHANNEL 7 \ LONG 3 |" ■7 O.D. 8 - !.D. 4 4 AXLE= -7 ALLEN 4 BOLT l" LONG 7 iSil WASHER l" FOR - BOLT 4 SQUARE NO THREADED RODS SHOWN BAR STOCK BRAISED ONTO - 4 THREDED 4 FIGURE C-10. JACK SUPPORT PLATE C-10 reference block, b) as a partial lateral brace for the load jack, c) to make the load instrumentation support and reaction frame a rigid unit, and d) with the four roller bearings, the entire assembly can easily by moved along the length of the structural load frame to allow for proper positioning of the load cell over the displacement reference block (Fig. C-3) . The support plate is all steel construction and essentially consists of two halves of a square plate 1/2-in. (1.27 cm) thick connected by two 3/8-in. (0.95 cm) - diameter and 7-in. (17.0 cm) long bolts. When the two halves are joined, the plate has a hole in the center 1/16 in. (0.16 cm) larger than the out- side diameter of the load jack and four holes set to the proper spacing for the threaded rods of the load support frame. Also mounted at the edges and near the corners of the plate are four 3/4-in. (1.9 cm) -diameter roller bearings, with a track width equal to the center-to-center distance between the two structural members of the structural load frame. i. Structural Load Frame The structural load frame provides the mechanism through which a suffi- cient dead weight will produce the desired reaction for the plate load applied to the ballast surface. The dead weight reaction is supplied by the weight of the track structure in the vicinity of the test zone. However, in addition, a track vehicle should be located as close as possible to the test location to provide additional dead weight reaction to the track. High upward forces applied to the track by the PLT apparatus might otherwise cause track buckling. The frame must have sufficient capacity to resist the expected applied maximum loads. The two basic components which comprise the frame are steel structural sections (Fig. C-ll) and rail clamps (Fig. C-12) . The two structural sections should have a length of 8 ft (244 cm) and be spaced apart at a distance of 3/4 to 1 in. (1.91 to 2.54 cm) greater than the distance to the outsides of two threaded rods in the jack support frame. This later feature allows for proper positioning of the load cell over the displacement reference block in the direction parallel to the rails. Two rail clamps are attached to the structural sections by 1/2-in. (1.27 cra)-diameter threaded steel rods passing through the rail clamp pressure plates. The separation of the rail clamps is equal to the distance between the centerlines of the two rails. The threaded rods are fastened to the structural sections. The length of the pressure plate is equal to the C-ll ro|co _L roK Mco e> z o or < m Q UJ Q < UJ cc X X UJ _l _i »- o: UJ o UJ Q u. 1- «d to UJ to X — ~9. o 1 < _ -Ic\j UJ — ICM CO 2 O t— i H OJ CO a Q < O < OS H U a: H i u UJ © B HCM ^ 4 T C-12 rf THREADED — hr 3 1^ LONG 1" PIN, ^ * ^ WIDE , | DEEP ROD 4^ LONG 17 Sz * HOLE Itil I SQUARE BAR STOCK WELDED TO CLAMP PLATES 5" if 1 I 8 7 8 3 8. »r Fn@M i — I*- ■i ti ^7 h! CLAMPS CLOSED k3 4 1 3 li rt 8 4- — T3"" 2 "* PRESSURE PLATE a) Clamp a rara 8 3 3- °4 'i ■ ;i 4 2 5 1 MACHINED TO if * P1N b) Thrust Plate FIGURE C-12. RAIL CLAMPS C-13 distance between the structural sections, while the rail clamps are 1/8-in. (0.32 cm) smaller in total width. A rail clamp is forced against the under- side of the rail heads by tightening the pivotal adjusting screw. This will restrict vertical and horizontal movements of the frame relative to the rails. The frame is designed for standard track gage and can be used on standard rails. Difficulty will arise in using these rail clamps at joints in bolted track. 2. Deformation System The deformation support system ensures proper support and alignment of the displacement instrumentation with the deformation reference pivot in the displacement reference block. The following are the components of the de- formation support system. a. Deformation Reference Beam The deformation reference beam and support pivot arm are the key elements of this system (Fig. C-13) . The 7-5/8-in. (19.4 cm) -long, 3/8-in. (0.95 cm) -deep and 1/4-in. (0.64 cm) -wide aluminum reference beam is notched at one end. This notch is inserted the full distance of the slot underneath the deformation reference pivot in the displacement reference block. Thus, the center point of the reference pivot is located 1/4-in. (0.64 cm) from this end of the beam. Fastened at the other end of the reference beam is an aluminum reference plate with a recessed seating hole to accommodate the piston of the displacement gage. In the center of the beam is a 1/8-in. (0.32 cm) diameter pivot pin, which is press fit into a notched magnesium (option aluminum) pivot arm. The beam rotates freely about the pivot pin, but is restricted from movement in any other direction. The exact distance from the center of the pivot pin to the center of the seating hole is 3-1/2-in. (8.89 cm) and equal to the distance from the center of the pivot pin to the center of the deformation reference pivot in the reference dis- placement block. Thus, a direct measurement of displacement is obtained. The length of the reference beam was determined to be the minimum acceptable length such that the deformation system would not interfere with the load system. The notch in this beam always maintains contact with the reference pivot since added weight is applied at the other end by the seating plate and force from the spring in the displacement gage. Measured displacement read- ings are acceptable if the load bearing plate does not rotate more than 5 deg during testing. C-14 1_ r lol^r c ro UJ UJ rj \ _i \ a. \ UJ UJ CO UJ _J to or . * ?E o 2 "ml"*- CD -*+* — *■ -rr 1 ~f UJ CO O a, a. to < 2 U4 ca UJ u oi UJ u, UJ 0£ o I— I O UJ a ro i U UJ a: UJ o I— I H o U- UJ a i <_> UJ to UJ UJ *_ to C-15 b. Deformation Support Beam The deformation support beam (Fig. C-14) both supports and correctly aligns the displacement gages with the deformation reference beam. The pivot arm must be perpendicular to the support beam. The support beam consists of 1-in. (2.54 cm) square steel telescopic tubing 22-1/4-in. (56.5 cm) long with a 1/4-in. (0.64 cm) steel plug at one end, which has a threaded hole for the support pivot arm bolt. On the top of the tube section at 3-1/2-in. (8.89 cm) from the plugged end is a 1/2-in. (1.72 cm) -diameter hole for the displacement gage piston to pass through. A steel slide plate, which is 1/8-in. (0.32 cm) thick by 3/4-in. (1.91 cm) wide and 8-in. (20.3 cm) long, is welded 1/16-in. (0.16 cm) from the edge and perpendicular to the top of the tubing. The plate is mounted 2-in. (5.1 cm) from the plugged end and is used to adjust the displacement gages on the support track for the proper vertical height. c) Support Beam Slide and Level The support beam slide and level (Fig. C-15a) is fastened to the bottom of a camera tripod by a single bolt and is used for lateral adjustment of the deformation support beam with respect to the displacement reference block. The slide is a steel tube 1-in. (2.54 cm) square on the inside. This permits free movement of the support beam, which has the same dimensions. Once the support beam is in position, a thumb screw lock secures the beam to the beam slide. A 2-in. (5.1 cm) by 3-in. (7.6 cm) steel plate is welded to the top of the beam slide to hold bubble level in order to insure that the deformation system is level. The distance from the camera tripod connecting bolt to the load area of the plate is roughly 8 to 10-in. (20.3 to 25.4 cm). The lateral or vertical movements of the ballast particles at this distance during loading of the bearing plate are not expected to be significant. d. Support Beam Counter Weight The support beam counter weight (Fig. C-15b) is used to keep the center of gravity of the deformation system near the camera tripod connecting bolt. A piece of solid steel bar stock is welded to a 3-in. (7.6 cm) -long piece of steel tube the same as the bar slide. This 2.6 lb (1.18 kg) weight slides on the support beam on the opposite side of the support pivot arm and displacement gage. Once equilibrium is reached, the weight is secured in place by a thumb screw. e. Camera Tripod A camera tripod used to support the entire deformation system is equipped C-16 Id £C O CO X. o o V 0€ --Icvi- -KM ro ,,«K CM to hr — |. X a o a. cc UJ x o < UJ _l o X -|CO :\j 00 H f— '• 2 o UJ 2: UJ O = cc ro uj o h- u 2 3 5 O UJ o CQ " BJ o o- a. :z> to LO ■— ( u UJ ct rs CJ (—4 _j u- UJ > UJ _J o 2 < UJ a CO C-17 with adjustments for aligning and leveling the system. The tripod stands approximately 8-in. (20.3 cm) high when the three legs are fully opened. In the center of the tripod is a notched rod 8-in. (20.3 cm) long, which is connected to the support beam slide. A small hand crank moves the rod vertically. The camera tripod must be of the type that the camera mount pivot may be remounted at the bottom of the vertical adjustment rod for attachment to the support beam slide. When the proper height is reached, i.e., when reference beam is at the same elevation as the bottom of the reference pivot, the rod can be secured by a lock screw. At the bottom of the rod and fastened directly to the beam slide is a ball bearing connected to another lock screw. This feature allows for small rotations of the de- formation system in the plane nearly perpendicular to the vertical adjust- ing rod such that the system can be leveled. The vertical and rotational adjustments should be performed together in order to position the reference beam nearly level, but preferably 0.15 in. (0.38 cm) downward from horizontal at the seating plate. This condition is desirable since it will optimize the rotation of the reference arm by allowing the minimum horizontal displacement at either end of the reference beam due to rotation. f . Support Beam C-Clamp Lock The support beam c-clamp lock (Fig. C-15c) clamps the deformation support beam to one leg of the camera tripod. This provides for a more stable and rigid deformation system and prevents possible rotations due to fasteners or connections not tightened securely. g. Displacement Transducers An electronic displacement transducer provides a continuous displacement response of the plate during loading and unloading. The transducer must have sufficient travel (preferably 1-in. (2.54 cm). Input voltage to the transducer is supplied by an appropriate power source and the output signals are recorded by a compatible X-Y recorder. The proper attachments should be fabricated to suitably connect and align the displacement transducer with the dial indicator piston. A dial indicator is used to provide a means of calibrating the electronic transducer and also provide a visual check on the displacement during the plate loading. The indicator is graduated in units of 0.001 in. (0.00254 cm) and is capable of recording a maximum deflection of 1-in. (2.54 cm). The mechanical spring loaded piston should move freely and be C-18 suitably connected to the electronic displacement transducer. The piston should also have attached a brass displacement calibration lever (Fig- C-16) , which has a lever length of 3/4-in. (1.91 cm). h. Displacement Gage Support Track The displacement gage support track rigidly attaches and aligns the displacement gages such that their pistons freely move (Fig. C-16). The dial indicator is bolted and the displacement transducer is securely fitted with a retainer clamp conforming to the shape of the transducer. The track is a 1-in. (2.54 C m) magnesium angle section with one leg notched 1/8-in. (0.32 cm) -wide and 1/2-in. (1.27 cm) -deep for the full length of the section. The length should be sufficient to accommodate the sizes of displacement gages used. The dial indicator should be positioned on the gage support track such that reading can easily be recorded. The deforma- tion system is placed between the structural sections of the structural load frame, which may interfere with obtaining the readings. The notched leg fits tightly to the slide plate of the deformation support beam and the track can be vertically positioned to align and set the gage piston within the seating hole in the reference beam. Lock screws secure the track to the slide plate once positioning is completed. 3. Other Equipment The following other essential material and equipment is needed: a. Plaster of paris and appropriate mixing pans and tools. b. Bubble level to adjust plate orientation. c. X-Y recorder for load and displacement. d. Suitable power supply for instrumentation. e. Track car to carry apparatus and instrumentation box. C.2 Field Test Procedures The following steps are involved to measure the in-situ ballast plate load resistance using apparatus described in section C.l: 1. For tests on the tie bearing area, carefully remove all the ballast in both adjacent cribs for the full depth and length of the tie. Carefully remove the spikes, tie plates and rail anchors such that minimal disturbance to the tie occurs. Rail jacks may be placed in the next adjacent full crib C-19 MAGNESIUM TRACK DIAL INDICATOR O.OOI IN. /DIVISION,- l" TRAVEL CALIBRATION LEVER WIRES FROM BOTH EXTERNAL POV/ER SOURCE AND X- Y RECORDER TRACK LOCK SCREW D.C.D.T. — T BRASS DEFORMATION PISTON FOR D.C.D.T. 1 AND DIAL INDICATOR ALUMINUM D.CD.T. RETAINER CLAMP FRONT SIDE FIGURE C-16. DISPLACEMENT INSTRUMENTATION MOUNTED ON DISPLACEMENT GAGE SUPPORT TRACK C-20 not to be tested to raise the rail. Carefully remove the test tie with tongs such that minimal disturbance occurs to the ballast bed under the tie and to the crib selected for testing. No removal of track components is necessary for tests in the crib providing that the deformation system is positioned in the crib. If the deformation system is position on an adjacent tie, then the rail spikes must be removed from both ties adjacent to the crib designated for testing. 2. Select the center of spots to be tested in the crib and under the tie. These might be the center of the track and 5 to 8-in. from the rail base on the inside and outside of the rail. Mark the location on a drawing. Identify each test plate with a number from the data sheet. 3. In the crib remove any high ballast particles in the plate seat- ing area in order to achieve as level a surface as possible. Under the tie, removal of particles is not necessary. 4. Mix one pound of plaster of paris with two pounds of water and spread thinly over the plate seating area. 5. Place the 5-in. -diameter load bearing plate on the plaster of paris and level the plate with a bubble level. Trim and remove the excess plaster of paris from around the circumference of the plate. Wait 15 to 20 minutes for the plaster to set. The resulting thickness of the plaster of paris between plate and ballast particles should be approximately 1/8-in. 6. Place PLT structural load frame on the rails in a position straddling the plate. 7. Record the position coordinates of the test plate with reference to the rails and adjacent ties. All measurements should be made within 1/8-in. CO* 32 cm). The load frame may be used as a reference datum for elevation measurements. 8. Insert the hydraulic load jack assembly in the PLT frame over the test plate. In the case of PLT tests under the tie, a 7-in. spacer disc is first inserted between the load jack and load cell. 9. Place the displacement reference block on the load bearing plate. 10. Use the hand pump to move the load cell such that contact is nearly made with the concave seat in the displacement reference block. 11. Adjust the structural load frame and the hydraulic load jack frame so the loading piston is above the center of the reference block. Tighten the nuts for the reaction plates; also, the rail clamps on the structural load frame . C-21 12. Set up the camera tripod with the deformation system on level ballast or on a tie plate placed on the ballast to give a firm foundation. 13. The displacement instrumentation mounted on the gage support track can then be aligned and attached to the slide plate on the deformation support beam. Temporarily seat the piston in the hole on the reference plate. Level the deformation system by using the adjusting lock screws on the camera tripod. Adjust the deformation system until the reference beam can be inserted properly in the slot and under the deformation reference pivot in the displacement reference block. The displacement gages should be positioned such that there is approximately 3/4-in. (1.91 cm) of travel available. 14. Attach the related cables for the load and deformation systems to the appropriate input lines on the recorder and to the appropriate external power sources. 15. Inscribe X and Y reference axes on the graph paper, when it is properly positioned and attached to the recorder. Record the date, air temperature and test number on the graph paper and on the data sheet. 16. Record several calibration traces for each load and displacement on the X-Y plotter. For displacement calibration, first set the dial indicator on a zero reading. Use the displacement calibration lever on the dial indicator piston and move the lever upward to the full displace- ment calibration distance. A value of 0.2-in. (0.51 cm) is suggested. Record the calibration displacement value on the graph paper. Load cali- bration can best be done electrically. 17. The recorder pen may now be conveniently positioned on the graph paper to record the load-displacement curve. Mark the origin point on the graph paper. 18. Use the hydraulic hand pump to move the load jack and also the load cell until the loading piston is nearly in contact with the seating hole in the displacement reference block. 19. Record initial hydraulic jack system pressure, initial deformation dial reading, and the cycle number. 20. With the hydraulic hand pump, displace the piston at a constant deformation rate of about 0.25 in./min. until 0.3-in. of displacement is reached. At this point, simultaneously record peak hydraulic jack pressure, and displacement reading from the dial indicator. C-22 21. At the instant peak displacement is reached, unload the plate at approximately the same rate as in loading. When the plate is completely unloaded, but with the loading piston nearly in contact with the plate, record the dial indicator reading. 22. Perform additional cycles of plate loading to the same peak pressure as in the 1st cycle. Use the same test procedure and record the same load and deformation values. The rebound displacement point of the previous cycle on the graph paper may be used as the origin point for the next loading cycle plot. 23. Record any unusual test condition such as excessive plate rotation, particle degradation, amount of fine ballast material, degree of satura- tion of the ballast, or problems encountered during testing. 24. Use the load and displacement calibration signals to properly scale the axes of the recorded load-displacement curve. Then compute all desired strength indices for the first cycle of loading only, such as: Ballast Bearing Index (BBI) , Modified Ballast Bearing Index (BBL) , Modified Resilient Modulus (E ) , Modified Modulus of Deformation (E ) , and rm m the percent Elastic Recovery (E ) as E r =( JLL\ ioo f (c _i) where K and /v. are recoverable and total deformation, respectively, per cycle (in.). For each additional cycle, compute only E , E and E . C-23 APPENDIX D. APPARATUS AND RECOMMENDED PROCEDURES FOR FIELD LATERAL TIE PUSH TEST (Ref . 1) D.l Apparatus The assembled apparatus for the lateral tie push test is shown in Fig. D-l. Each component will be described in detail and its function will be explained in this appendix. The presentation is subdivided into two categories: 1) the load system, and 2) the deformation system. 1. Load System a. Serrated Seating Plate Assembly The serrated seating plate assembly (Fig. D-2) insures good seating, uniform load distribution and prevention of load cell slippage during test- ing at the tie end. The assembly fits over the load cell and is fastened to the load cell attachments on the moving head of the hydraulic load jack. The plate also serves as a vertical adjusting guide for centering the hydraulic load jack assembly at the tie end. The key component is a 1/2-in. (1.27 cm) -thick aluminum serrated seating plate 5 in. (12.7 cm) square. The plate area covers a sufficient portion of the end area of most standard ties. The non-serrated side of the plate has a centered seating hole of the same shape as that of the PLT displacement reference block to fit the load bearing piston of the load cell. The serrated plate is connected at the edges by four springs, which are fastened to 1-1/2-in. (3.21 cm) -long eyebolts in a 1/4-in. (0.63S cm)- thick aluminum annulus 6 in. (15.24 cm) in diameter. The annulus has an internal radius to fit the load cell radius and the mating connector. The springs should have a low stiffness and the length is a function of the load cell height. This length is flexible since the eyebolts are used for adjustment to provide a 10-lb (4.54 Kg) force necessary to maintain contact between the serrated plate and the load cell bearing piston. b. Load Cell The load cell is the same as described for the PLT in Appendix C. c. Hydraulic Load Jack Assembly The hydraulic load jack assembly is the same as described for the PLT in D-l FIGURE D-2. SCHEMATIC ILLUSTRATION OF LATERAL TIE PUSH TEST APPARATUS D-2 Appendix C. However, the lateral jack support plate and the vertical adjusting plates in Fig. C-6 are described below rather than in Appendix C because they are used just for the LTPT. The lateral jack support plate (Fig. D-4) ensures that the hydraulic load jack assembly maintains a horizontal position parallel with the structural load frame. This plate is necessary, since the load instru- mentation is fully supported at one end by thrust and pressure plates and partially supported by the reaction plates near the midpoint of the load jack. The lateral jack support plate is placed on the two bottom threaded rods of the hydraulic load jack assembly and positioned under the outer load jack cylinder nearest to the moving head. This plate consists of a 1-in. (2.54 cm) -wide aluminum bar stock with length and thickness dependent upon the dimensions of the load jack and the load instrumentation support and reaction frame. The top of the plate is inscribed with a seat having a radius equal to the outer load jack cylinder radius. On the opposite face are two seating grooves spaced to fit onto the threaded rods. The vertical adjusting plates provide the means for raising or lower- ing the hydraulic load jack assembly so that this unit may be aligned parallel with the tie centerline. These plates are located midway between the pressure and reaction plates and opposite the two threaded rods with the lateral jack support plate. Two 3/8-in. (0.95 cm) -thick steel plates are required (Fig. D-3) . The length and width of the plates are again dependent upon the size and spacing of the threaded rods. Allen set screws secure the adjusting plates to the threaded rods at a 1/2-in. (1.27 cm) spacing. The center of each plate has a 1/2-in. (1.27 cm) diameter hole in order to accommodate the connecting bolt for the vertical adjusting screw mounted in the L- frame. d. Structural Load Frame The structural load frame is the same as described for the PLT in Appendix C, except for the L-frame attachment (Fig. D-5) . The L-frame pro- vides support and reaction for the hydraulic load jack assembly, utilizing the track structure as an anchor. The L-frame consists of two 15-in. (38.1 cm)-long structural steel sections similar to those of the structural load frame and spaced at the same distance. The load jack assembly is as mobile in the L-frame as in the structural load r rame. Transfer of the assembly is easily accomplished by removing the two steel reaction plates. D-3 1 4 ± 3 1/2" 01 IT HOLES gg • FIGURE D-3. VERTICAL ADJUSTING PLATE RADIUS OF LOAD JACK FIGURE D-4. LATERAL JACK SUPPORT PLATE D-4 £ * 6 LONG RODS | X l"BAR-^/ STOCK ^A FULL — ' PENETRATION WELDS ^ PLATE WING -7 NUT WELDED TO 4 T PLATE 4- STD. THREADED ROD , ll" LONG a. JACK SUPPORT SYSTEM VERTICAL JACK SUPPORT PLATE W C 5X9 SECTION VERTICAL ADJUSTING PLATE (FIG. D-4) FIGURE D-5. L- FRAME ATTACHMENT TO STRUCTURAL LOAD FRAME D-5 The steel sections are welded at the top and bottom to 1/4-in. (0.635 cm) - thick steel plates. In order to securely fix this attachment with the load frame, steel support plates welded to the top of the structural sections are located and dimensioned so that the L-frame may be snuggly inserted between the flanges and perpendicular to one end of the structural load frame. Also, two 1/2-in. (1.27 cm) -diameter steel rods with a length equal to the width of the load frame are inserted through closely fitting holes bored in the same locations in the support plates at the end of the load frame. These rods provide the shear and bending resistance for the antici- pated lateral tie loads so that the hydraulic load jack remains parallel to the tie center line under load. The L-frame should adequately accommodate the hydraulic load jack assembly with adjustments so that the system can easily be adapted to track systems having various rail heights, tie plate thicknesses, and tie depths. The frame is also designed for standard 8-1/2-ft (259 cm) -long ties, but the load jack assembly is flexible enough so that tie lengths from 8 ft to 9 ft (244 cm to 274 cm) can be handled easily. A 12-in. (30.5 cm)-long and 1/4-in. (0.635)-diameter threaded steel rod with a wingnut adjusting screw is inserted through the top plate of the L-frame and fastened to the vertical adjusting plates of the load jack assembly. This provides a reliable method to vertically adjust the load jack parallel to the centerline of the tie. 2. Deformation System a. Deformation Support System The deformation support system is attached to the top of the tie at the end. It supports the displacement gages in order to accurately monitor tie displacement during loading (Fig. D-6) . A 37-in. (94 cm)-long, 1-in. (2.54 cm) by 1-in. (2.54 cm) magnesium T-section is bolted to plates hold- ing the horizontal and vertical adjusting screws. The displacement gage support track is capable of sliding into the correct position with respect to the reference stand on any of the legs of this deformation reference arm. This arm has the same thickness as the slide plate in the PLT deformation support system. Therefore, the two deformation systems can be interchanged easily. Also, the reference arm length just extends beyond the L-frame attach- ment. This setup provides for the most accurate measurement of displacement D-6 HNW* -*■"— ICVJ o -lev/ o oc •» £ n UJ hi en n o I— I m D-7 readings since 1) the deformation reference stand and displacement gage instrumentation would interfere with the structural load frame at any closer distance, and 2) the tie displacement reference point is far enough away from the loaded tie to be stable. The deformation reference arm can be visually aligned parallel to the centerline of the tie by the steel vertical and horizontal adjusting screws. The horizontal adjusting screw aligns the reference arm parallel with the side of the tie and is capable of adjusting to different tie widths. The vertical screw aligns the reference arm parallel to the top of the tie, and is used to support the weight of the displacement gage support track, and instrumentation at the end of the reference arm. b. Displacement Transducers The displacement transducers are the same as described for the PLT in Appendix C. c. Displacement Gage Support Track The displacement gage support track is the same as described for the PLT in Appendix C. d. Displacement Reference Stand The displacement reference stand (tripod) is firmly seated on the ballast shoulder and away from the test area to provide a reference datum by which the tie horizontal displacement can be recorded accurately. The stand essentially consists of a steel base with three telescopic aluminum legs, adjustable by wingnuts to any angle, and a vertical telescopic tube with an attached 6-in. (15.2 cm) -square steel deformation reference plate 1/4-in. (0.635 cm)-thick (Fig. D-7) . The base and reference plate have telescopic structural tubing the same as the PLT deformation guide support and reference beam, respectively, with lengths of 7-in. (17.8 cm) and 10-in. (25.4 cm). The reference plate is secured at a fixed elevation by a vertical adjusting screw mounted on the steel base. Each telescopic leg is a 1-in. (2.54 cm) channel section 6-1/2-in. (16.5 cm) -long fastened to a semi- slotted 5-in. (12.7 cm)-long by 1/4-in, (0.635 cm)-thick aluminum bar stock. The stand can be adjusted for heights of 15 to 22-in. (38.1 to 55.9 cm). The reference plate is positioned such that the displacement instru- mentation mounted on the displacement gage track support is perpendicular to the plate. The reference plate is heavy and stable enough such that mild winds do not affect the displacement reference. D-8 LOCK SCREW AND HANDLE 5" X 5" PLATE, /4 STEEL PLATE BRAZED TO VERTICAL TUBING WELD SQUARE STEEL TUBING , 8" LONG ^ SQUARE STEEL TUBING, REFERENCE 5~ LONG 4 STEEL CHANNELS 5^ LONG ALUMINUM TELESCOPING LEGS, Z X I BAR, LONG FIGURE D-7. DISPLACENENT REFERENCE STAND (TRIPOD) D-9 3. Other equipment The following other essential equipment is needed: a. X-Y recorder for load and displacement. b. Suitable power supply for instrumentation. c. Track car to carry apparatus and instrumentation box. D.2 Field Test Procedure The following steps are followed to measure the lateral tie resist- ance using the apparatus described in Section D.l: 1. Carefully remove the ballast at the end of the selected tie from the shoulder for the full depth of the tie and the entire width of the shoulder to accommodate the structural load frame with L-frame attachment and the hydraulic load jack assembly. 2. Carefully remove the rail fasteners on five adjacent ties and the pads on the middle selected tie. The use of rail jacks should be avoided. 3. Note and record tie condition and dimensions. 4. Place the structural load frame on the adjacent ties as shown in Figure D-l. 5. Attach the serrated seating plate assembly to the hydraulic load jack assembly and insert the entire unit into the L-frame. Bolt the vertical adjusting screw to the vertical adjusting plates connected to the threaded rods of the hydraulic load jack assembly. Adjust the horizontal position of the load jack assembly to provide for at least 1/2 to 1-in. (1.27 to 2.54 cm) clearance between the serrated plate and the tie end. This is accomplished by adjusting the relative position of the load jack reaction and pressure plates on the load jack assembly. An option to accomplish this would be to insert and fasten a 4-in. (10.2 cm) -long spacer cylinder between the load cell and load jack. 6. Insert the lateral jack support plate on the two bottom threaded rods of the hydraulic load jack assembly and under the load jack. 7. The load frame with the entire hydraulic load jack assembly should be positioned over and parallel to the centerline of the tie. Both rail clamps then should be tightened to secure the frame to the track and D-10 subsequently restrict horizontal and vertical movement of the frame during testing. 8. Use the vertical adjusting screw, mounted on the top of the L-frame, to adjust the vertical position of the hydraulic load jack assembly such that the point of load application is at the center of the tie end and the jack is parallel to the centerline of the tie. The square serrated seating plate may be used as a guide for centering the assembly. At this point the serrated plate should not be in contact with the tie. 9. Remove a small quantity of ballast from the crib near the loaded end of the tie to accommodate the horizontal clamp of the deformation support system. Clamp the support system to the top of the tie end. Adjust the horizontal and vertical clamps to ensure the deformation refer- ence arm is parallel to the centerline of the tie. The reference arm should extend past the end of the structural load frame. 10. The deformation system reference stand (a tripod) is firmly seated on the ballast shoulder. The stand is about three inches (7.6 cm) from the reference arm and also has the reference plate perpendicular to this arm. Use the vertical height adjustment screw to position the reference plate, such that the reference arm is near the center point of the plate. 11. The gage support track which contains the displacement gages, is attached to the reference arm. This track is moved on the reference arm to the reference plate until the dial indicator stem is depressed for approximately 3/4-in. (1.90 cm) travel and is then tightened. The dial stem should be depressed and released to insure free movement of the stem. 12. Attach the related cables for the load and deformation systems to the appropriate input lines on the recorder and to the appropriate external power sources. 13. Inscribe X and Y reference axes on the graph paper, when it is properly positioned and attached to the recorder. Record the date, air temperature and test number on the graph paper and on the data sheet. 14. Record several calibration traces for each load and displacement on the X-Y plotter. For displacement calibration, first set the dial indicator on a zero reading. Use the displacement calibration lever on the dial indicator piston and move the lever upward to the full displace- ment calibration distance. A value of 0.2-in. (0.51 cm) is suggested. Record the calibration displacement value on the graph paper. Load D-ll calibration can best be done electrically. 15. The recorder pen may now be conveniently positioned on the graph paper to record the load-displacement curve. Mark the origin point on the graph paper. 16. Use the hydraulic hand pump to move the hydraulic load jack assembly until the serrated plate is nearly in contact with the tie end. Record the initial hydraulic jack system pressure and the initial dial indicator readings. 17. The test may commence by displacing the hydraulic load jack piston with the hydraulic hand pump at a constant deformation rate of 0. 25-in./min. (0.635 cm/min.) until a maximum deformation of 0.25-in. (0.635 cm) is reached. Simultaneously record the peak hydraulic jack pressure and the peak displacement reading. 18. At the instant peak displacement is reached, unload the tie at approximately the same rate as for loading. When the tie is completely unloaded, i.e., when the serrated plate is not in contact with the tie end, record the tie horizontal rebound displacement reading from the dial indicator. 19. Record any unusual test conditions, i.e., deficient crib ballast and amount, different shoulder width or slope, non-square tie end, skewed ties, degree of saturation of ballast, tie popping, or problems encountered during testing. 20. A second cycle of loading may be performed using steps 16 to 18. 21. The structural load frame and hydraulic jack assembly can be moved to the next test tie and the same test procedure can then be uti- lized. 22. Use the load and displacement calibration signals to properly scale the axes for each of the recorded load-displacement curve. 23. Compute the load at the following displacement levels for all cycles: 0.0-in. (0.0 cm), 0.039-in. (1 mm), 0.079-in. (2 mm), 0.157-in. (4 mm), and 0.25-in. (6.35 mm). 24. Compute the percent elastic recovery (E ) as CD-I) D-12 APPENDIX E. PROCEDURES FOR BALLAST INDEX TEST 1. Oven dry and then sieve the sample on sieves used for coarse ag- gregate. Use the entire sample if 50 lb or less. If the sample is heavier than 50 lb, then reduce it down to 44 lb (20,000 g) using a sample splitter, and save and label the portion in excess of 44 lb. The maximum sieve size must be 2 1/2 inch and the minimum must be #4. The choice of intermediate sieves should be made to provide approximately equal distribution of the sample among the sieves. 2. Reduce to 500 g by sample splitting or quartering the quantity of material from Step 1 that passes the #4 sieve. Carefully break up lumps with rubber hammer or with rubber rollers in ball mill. Weigh the sample, wash through #200 sieve, and then oven dry and weigh the material remaining on #200 sieve to determine the percent finer than #200. Dry sieve the sample larger than #200 size using the following suggested sieve sizes: 4, 8, 16, 40, 60, 100, 140 and 200. 3. Take the portion of the sample passing the #4 sieve remaining from Step 2 after removing the 500 g sample. Carefully break up lumps as in Step 2 and dry sieve through #40 sieve. Perform liquid limit and plastic limit tests on the material passing the #40 sieve. Save all portions of sample that are required for chemical tests. 4. Perform petrographic analysis to determine the mineral composition of the portion of the sample from Step 3 smaller than the //40 sieve, and the portion larger than the #40 sieve. The method of selection and prepara- tion of the samples for the analysis is quite important and must be specified with the test results. For example, at least the sample larger than //40 should be crushed to pulverize it before conducting the petrographic analysis. Procedures must be employed to ensure that the sample tested is representa- tive of the entire portion. 5. Split the sample > #4 from Step 1 as required to perform the fol- lowing tests: specific gravity, water absorption, magnesium sulfate soundness, Los Angeles abrasion, petrographic analysis, and descriptive tests such as visual inspection of angularity and sphericity, and hardness. If total sample is not enough to use separate portions for all of these tests, the specific gravity and absorption test portion may be recombined with the remainder of > #4 before conducting the other tests. E-l 6. Determine bulk specific gravity and percent absorption on a portion of sample prepared in Step 5 according to ASTM Procedure C127. 7. Perform the petrographic analysis to determine the mineral composition of the portion of the sample from Step 5 that was larger than #4 size. Pulverize a representative portion of this sample for the analysis and specify the procedures used for preparation and test. Save the unused portion of this sample. 8. Conduct a Los Angeles abrasion test on a portion of material larger than #4 sieve from Step 5. To permit a comparison between samples, the same sample weight, grading, number of spheres and number of revolutions must be used for all samples. The requested procedure will use a 5000 g sample, Grading A, 12 spheres and 500 revolutions (ASTM C131). 9. Conduct a test on aggregate soundness using a portion of material larger than the #4 sieve from Step 5 (ASTM C88) . Use 5 cycles with magnesium sulfate solution. 10. Conduct descriptive tests on a portion of material larger than #4 sieve from Step 5. For visual inspection of angularity and sphericity, take at least 50 particles of a range of sizes. For hardness, follow ASTM-C235. 11. Tabulate test results with appropriate comments. Indicate any neces- sary deviations from the specified procedures. If these deviations are expected to change the results substantially they must be approved in advance. The samples should be saved until all results have been evaluated so that any required additional tests can be performed if needed. E-2 APPENDIX F METHODS AND APPARATUS FOR CYCLIC TRIAXIAL TESTING The main requirement of the triaxial equipment is to subject cylindrical samples of ballast, subballast or subgrade, or composites of these materials, to cyclic or repeated stresses imposed by the passing trains in the field. These stresses are predicted by a multi-layer computer model that takes into consideration the effect of the ties and rails in distributing the wheel loads. The complete state of strain, volume change and pore pressure as a function of time resulting from the applied stresses is to be measured. An extensive amount of time was devoted to a literature review and discussions with experienced persons concerning the requirements of the cyclic triaxial system. The design of the system was specified based on the results of this effort. Because a suitable triaxial cell was not available commercially, a special cell was fabricated. The cell control system and the instrumentation were also designed and assembled. Because it is necessary to characterize the behavior of the roadbed materials under time varying load, an important requirement of the cyclic system is a testing machine to produce and maintain the applied cyclic stress or strain over a large number of load applications. A summary of different systems for applying the load in stress controlled tests has F-l been presented by 3rown (Ref. F-l) . The principal systems are pneumatic (Ref. F-2) , mechanical (Refs. F-3, F-4 and F-5) , electrical (Ref. F-6) , and hydraulic (Ref. F-7) . These systems have been used for the testing of soils under repeated loading conditions and are usually purpose-built machines. Many of the existing systems have an uncertainty of loading over long duration tests and a lack of flexibility in application. The drawbacks of these systems are overcome by adopting servo-controlled hydraulic type of machines for soil testing. The most important feature is that programmed stress changes with time can be applied without being affected by changes in sample behavior during the test. In addition to this, any type of complex wave form of loading can be readily applied. Among the important requirements selected for the triaxial cell were: 1) Sample size of at least 6 in. diameter. 2) Loading in extension and compression. 3) Controlled cell pressure and back pressure. 4) Pore pressure, volume change, lateral strain, axial strain and axial load monitoring. 5) Pore water flow for saturating samples. 6) Low friction resistance between oscillating load piston and cell chamber. 7) Provision for accurate alignment of specimen with top cap and actuator piston. F-2 The resulting cyclic triaxial cell (Fig. F-l) consists of a 12-in. OD , 1/2-in. thick and 2 4- in. long cylindrical acrylic chamber which is sealed to 2-in. thick anodized aluminum cell top and base plates by means of rubber O-rings. The cell was designed for a maximum internal pressure of 160 psi and for 6- in. and 8-in. diameter soil samples with a H/D ratio of 2 to 2.5. Six 3/4-in. diameter stainless steel tension rods are used to compress the O-rings between the acrylic chamber and the plates. The tension rods are built inside the acrylic chamber to facilitate top cap alignment during sample preparation. The top of the cell is divided into two parts: 1) a top plate connected to the tension rods, and 2) a top collar for the acrylic chamber that is fixed to the top plate by means of screws. The specimen base pedestal and top cap are made of stainless steel. The cell pressure and back pressure applied to the sample during testing are obtained from an air compressor by means of air-water interfaces created in reservoirs specifically designed and built for this purpose. The reservoirs have been designed for a maximum pressure of 160 psi. The air pressure cannot be applied directly to the sample because the rubber membranes in which the samples are enclosed are about ten thousand times more permeable to gases than to water. With the use of reservoirs it is possible to pressurize the cell very quickly with water. The pressure may be maintained accurately for any desired period of time using air pressure regulators that maintain the desired pressures regardless of fluctuations in line pressure, provided that this does not fall too low. The air pressure regulators used have a maximum value of 160 psi and will maintain the pressure constant to within 0.01 psi. F-3 pn TOP COLLAR TOP PLATE TENSION RODS BASE PLATE CELL PRESSURE VB - BACK PRESSURE VB-: PISTON ROD ■PISTON CLAMP •BALL BUSHING ASSEMBLY VT-I TO AIR PRESSURE SUPPLY VT-2 TO BLEED OFF AIR ACRYLIC CHAMBER LATEX MEMBRANi BASE PEDESTAL VB-4 TOP DRAINAGE VB-2 MEASURE PORE PRESSURE Fig. F-l. Ballast Cyclic Triaxial Cell F-4 At the present time the UMASS cyclic testing facility is equipped with a static volume change device. An investigation has been made into the possibilities in the future of adding an automatic volume change de- vice to the facility for cyclic loading (Ref. F-8) . The present volume change device is intended to be used in the consoli- dation stage of saturated samples of ballast, subballast or subgrade. During the cyclic or repeated loading stage it will not be possible to automatically record volume change in a drained test. For this purpose a different system is sought (Ref. F-8). At the present moment, a decision has not been made in relation to the fabrication or acquisition of an auto- matic volume change device for the purpose of cyclic testing of materials in a drained condition. Meanwhile, during the drained cyclic tests, it is planned to measure volume change by means of measuring the axial deformation with an LVDT and 'the lateral deformation either with soil strain gauges, (Ref. F-9) , or by constructing a circumferential measuring device. There is also the alternative of using the static volume change device as a back-up system by stopping the test periodically and measuring the cumu- lative volume change. F-5 LU -J LlI CD d \ < or < 1 LU cc > w. 1 o > «BM* rj> <\ ^ LU NOIlVPNHOdBa -3- I 5N £ 50 0) -a 53 O V •u aj a 01 05 30 'm 3 a 5 o Vi_l o a o 50 > F-6 •H The sample deformations will have two components: one irrecoverable or permanent, and the other of much smaller magnitude which is recoverable. This situation is depicted in Fig. 2-9 from Brown and Snaith(.Ref. 2-24). The expected test duration is long (up to 100,000 cycles) and for this reason, together with the need to determine the dynamic, recoverable deformation component, measurements must be capable of automatic recording. The simplest method of obtaining a measurement of the vertical sample deformation is by an external displacement transducer or dial gauge moni- toring the movement of the piston relative to the triaxial cell. The hydraulic actuator provides an LVDT signal that can be recorded for this purpose. In addition to the LVDT, a dial gauge is attached between the piston and top plate to monitor the axial deformation during sample setup and during consolidation, and permanent deformation at the end of the test. The LVDT system of measurement is subjected to error due to deformation in the loading frame that may be of the same order of magnitude as a typical resilient sample deformation. The dial gauge will help to indicate when these errors become significant. The main purpose of the recording system is to have time plots of the outputs from the actuator load cell and LVDT through the servo-control panel, and also the time plots of the lateral strain and either the pore pressure or volume change depending upon whether the test is undrained or drained. A schematic of the instrumentation and recording system is presented in Figure F-3. F-7 tu §1 -J UJ z 2 _l O cr H Z O o en 1 o —J UJ Jl oo co o o CO cr UJ >H i K xo _i CL o < h- o < o -J Z> < Q > X _1 _l UJ > UJ o o CD O ce UJ Q cc o o co > h- _J UJ < X o _J co%uj m C0_1 cr uj uj o EZ a: _i CL 05 CD Z> o CO cc UJ o CL o UJ < cc u_ Q < o _l e 4-1 en >^ CO oo c •H t3 U o a v a: c CO c o •H U CO 4-1 S = 5 u 4-1 en c O C3 e ai -= o I CO •H fa is F-8 REFERENCES (F-l) Brown, S. F. , "Laboratory Testing for Use in the Prediction of Rutting in Asphalt Pavements," Transportation Research Record, 616 , TRB, National Academy of Sciences, 1976. (F-2) Seed, H. G. , and McNeill, R. , "Soil Deformations Under Repeated Stress Applications," ASTM, STP No. 232., pp. 177-196, 1958. (F-3) Grainger, G. D., and Lister, N. W. , "A Laboratory Apparatus for Studying the Behavior of Soils Under Repeated Loading," Geotechnique, 12, 1_, pp. 3-14, 1962. (F-4) Castro, Gonalo, "Liquefaction of Sands," Ph.D. Thesis, Harvard University, Cambridge, Mass., 1969. (F-5) Silva-Tulla, Francisco, "Predicting Settlement of Clay Foundations Subjected to Cyclic Loading," D. Sc. Thesis, MIT, Cambridge, Mass., 1977. (F-6) Weissmann, G. R. , and Hart, R. R. , "The Damping Capcity of Some Granular Soils," ASTM, STP No. 305, pp. 45-54, 1961. (F-7) Dunlap, Wayne A., "Deformation Characteristics of Granular Materials Subjected to Rapid, Repetitive Loading," Texas Transportation Institute, Texas A & M University, College Station, Texas, 1967. (F-8) Alva-Hurtado, Jorge E. , "Automatic Volume Change Devices for SUNYAB Cyclic Triaxial Cell," SUNY at Buffalo, January, 1978. (F-9) Selig, E. T. , "Soil Compaction Evaluation With Strain Measurement," Civil Engineering Department, SUNY at Buffalo, December, 1971. (F-10) Brown, S. F., and Snaith, M. S., "The Measurement of Recoverable and Irrecoverable Deformations in the Repeated Load Triaxial Test," Technical NOtes, Geotechnique 24, pp. 255-259, 1974. F-9 APPENDIX G DESCRIPTION OF MULTA/GEOTR ACK Based on an evaluation of PSA, ILLITRACK and MULTA, a new model, GEOTRACK, which accounts for the stress-dependent nature of roadbed materials, has been developed. The model emphasizes the geotechnical aspects of track behavior. In addition to the more fundamental question of material modelling, certain other deficiencies were eliminated from the MULTA model. In order to obtain a more efficient and practical model, the following additional modifications were made: 1. The MULTA model presently repeats calculations of influence coeffi- cients generated by loading on the 2nd to 5th tie segment. A study of the axisymmetric nature of the multilayer roadbed model shows that the same influence coefficients are generated for similar axisymmetric locations relative to each loaded segment. This repetition is eliminated in GEOTRACK by generating the influence coefficients for the 2nd to 5th segment loading from those of the 1st segment loading. This modification has reduced the input data by four-fifths. 2. The MULTA model computes parameters for only three depth locations with linear layers. GEOTRACK can compute results for six depth loca- tions with five non-linear layers. 3. Truck loading (i.e., a pair of axles) constitutes the dominant cyclic frequency. Therefore, automatic superposition of adjacent axle loads is incorporated into the GEOTRACK model. The combined stress state is employed in the determination of the magnitude and directions of the principal stresses of the roadbed elements. G-l A. The BURMISTER and LAC codes are combined in GEOTRACX to form a single model, thus eliminating the need for two separate runs which for MULTA required an external computer tape. 5. Based on the track geometry information which is specified by the length of tie, tie spacing and number of ties, the radii locations of the points of interest where stress and displacement information are desired are computed automatically in GEOTRACK, thus eliminating the need for manual computation and reducing the input data require- ments appreciably. The resilient modulus of roadbed materials has been related to the stress state as follows: E r = f (a 3 , a d , 0) where a = the confining pressure, a = the deviator stress a - a , 9 = a + a + a = sum of the principal stresses. Due to the different effects of 3 and a, the resilient modulus of soils a may increase or decrease with stresses depending on the type of soil. It has been found experimentally that for granular materials, has a greater effect than a , and the modulus increases with according to: d E = K.0 K 2 , r 1 where E = resilient modulus, r 9 = the bulk stress = a.. + a ? + o , a , a , a = the major, intermediate and minor principal stress, respec- tively, K , K = experimentally determined constants. On the other hand, for fine-grained materials, a has a greater effect than and the modulus generally decreases with increase in a,. d G-2 The GEOTRACK model incorporates realistic non-linear characteristics of the roadbed materials. The general logic of modelling is the same as for MULTA. Figure 1 shows the geometrical representation of the track structure in the GEOTRACK model. The roadbed is represented as a number of layers of finite thickness, the last layer being semi-infinite. The rails are assumed to be supported over a finite number of ties, say, eleven. If the track section is symmetric about the center tie and symmetry of loading on both rails is assumed, only one-quarter of the total track section, as shown in Fig. 1, need be specified. The BURMISTER Code based on Burmister's three-dimensional elasticity solution of multilayer system is employed in determining the influence coefficients for the desired points of interest in the roadbed. Usually points along the ties at the centers of each tie segment, and midway between ties (forming a grid as shown in Fig. 2) and at some depth locations directly under the surface points are taken as the desired points of interest. Each point of interest is identified by coordinate (r, 9, Z) . The influence coefficients are obtained by loading each of the tie segment equivalent circular areas with a unit load, with no load on the other segment areas. A study of Fig. 2 reveals the axisymmetric nature of the problem — at a particular depth level in the roadbed, all points which are at the same relative radii locations to the loaded segment would have the same stress and displacement influence coefficients. Therefore, in the GEOTRACK model, the influence coefficients for loading on the 2nd to 5th segment are generated from those of the first. The influence coefficients are first calculated in cylindrical coordinates and then transformed into Cartesian coordinates for use with the LOAD and COMBINATION code. Figure 3 shows the transformation from cylindrical (R, 0, Z) , to the Cartesian (X, Y, Z) system. G-3 >- X G-4 11 POINTS IN LONGITUDINAL DIRECTION PER SEGMENT BETWEEN TIES UNIT LOAD-' INFLUENCE COEFFICIENTS FOR ALL POINTS GENERATED BY LOADING EACH SEGMENT WITH A UNIT LOAD WHILE LOADS ON ALL OTHER SEGMENTS = Fig. 2. Illustration of Supporting Ties, Loaded Segments, and Points of Interest 6-5 GIVEN STRESS TENSOR 9 < TRANSFORMED STRESS TENSOR >- X X Y Z 4 2l '31 e u 22 u 23 Q 32 a 33 => R e Z X cos 8 -sin8 Y sine cos9 Z 1 Fig. 3. Transformation of Stress Tensor From Cylindrical to Carzesian System G-6 The components of the stress tensor are input into an eigen vector routine to determine the magnitude and directions of the principal stresses. Since, as established earlier, the resilient moduli of roadbed materials are stress dependent and the stresses themselves are functions of the moduli, a compatible solution requires successive iterations. The iterative procedure. which is one of the methods of approximating nonlinear material properties, is employed in the GEOTRACK model. It con- sists of solving the same problem repeatedly under the full load, choosing for successive solutions a value of resilient modulus for each layer corres- ponding to an average effective state of stress calculated for the layer in the preceding cycle. Thus in each iteration,