5 Cop 5 G-3 BULLETIN OF ILLINOIS COAL MINING INVESTIGATIONS COOPERATIVE AGREEMENT Issued bi-monthly VOL. I July, 1914 No. 2 State Geological Survey Department of Mining Engineering, University of Illinois U. S. Bureau of Mines BULLETIN 5 Coal Mining Practice IN District I (Longwall) BY S. O. ANDROS Field Work by S. O. Andros and J. J. Rutledge Published by University of Illinois Urbana, Illinois (Application for entry as second-class matter at the postoflice, at Urbana, 111-, pend/np:) The Forty -seventh General Assembly of the State of Illi- nois, with a view of conserving the lives of the mine workers and the mineral resources of the State, authorized an investiga- tion of the coal resources and mining practices of Illinois by the Department of Mining Engineering of the University of Illinois and the State Geological Survey in cooperation with the United States Bureau of Mines. A cooperative agreement was approved by the Secretary of the Interior and by repre- sentatives of the State of Illinois. The direction of this investigation, is vested in the Director of the United States Bureau of Mines, the Director of the State Geological Survey, and the Head of the Department of Mining Engineering, University of Illinois, who jointly determine the methods to be employed in the conduct of the work and exercise general editorial supervision over the publication of the results, but each party to the agreement directs the work of its agents in carrying on the investigation thus mutually agreed on. The reports of the investigations are issued in the form of bulletins, either by the State Geological Survey, the Depart- ment of Mining Engineering, University of Illinois, or the United States Bureau of Mines. For copies of the bulletins issued by the State and for information about the work, address Coal Mining Investigations, University of Illinois, Urbana, 111. For bulletins issued by the United States Bureau of Mines, address Director, United States Bureau of Mines, Washington, D.C. 3 3051 00006 3739 ILLINOIS COAL MINING INVESTIGATIONS COOPERATIVE AGREEMENT State Geological Survey Department of Mining Engineering, University of Illinois U. S. Bureau of Mines BULLETIN 5 Mining Practice IN District I (Longwall) BY S. O. ANDROS Field Work by S. O. Andros and J. J. Rutledge Urbana University of Illinois 19 14 19 14 CONTENTS PAUE Introduction 7 Description of bed 10 System of mining 12 Work at the face 22 Ventilation 27 Timbering 32 Haulage 36 Hoisting 38 Preparation of coal 40 —2 G ILLUSTRATIONS NO. PAGE 1. Map showing area of District I Frontispiece 2. Plan of longwall mine 12 3. Entries in shaft pillar 13 4. Pack walls around shaft pillar 14 5. Elliptical shaft pillar 16 6. Entry in mine with no shaft pillar 17 7. Plan of mine with auxiliary permanent entries 18 8. Method of working panel longwall 19 9. Roof breaks 20 10. Diversion of face around a closed place 21 11. Location of march props 22 12. Mining in fireclay 23 13. Props at working face 23 14. Plan showing direction of ventilating current 27 15. An entry closely timbered 30 16. Cog built of props 31 17. Sketch of branch cog 32 18. A typical lye 33 19. Circular hoisting shaft 34 20. Amount of "company brushing" necessary after subsidence 35 21. Typical shaft bottom 36 22. Receiving hopper at shaft bottom 37 23. Skip adjusted to hoist men 38 24. Tandem cage 39 25. Typical surface plant 41 TABLES No. PAGE 1. General data by counties 8 2. Comparative statistics for the State and for District I for the year ended, June 30, 1912 8 3. Physicial characteristics of bed 11 4. Dimensions of workings 19 5. Blasting 25 6. Comparison of accidents in District I and in all other districts combined 26 7. Per capita production of employees 27 8. Comparative mine temperatures 28 9. Temperature readings near gob fire 29 10. Comparison of longwall and room-and-pillar rib dust of haulage ways 30 11. Ventilating equipment 31 12. Cost of mine timbers 35 13. Underground haulage 37 14. Hoisting equipment 39 15. Tipple equipment 40 16. Power plant equipment 42 Fig. 1. Map showing area of District I. (Shaded portion). Drawn by F. H. Kay BULLETIN OF ILLINOIS COAL MINING INVESTIGATIONS COOPERATIVE AGREEMENT Issued bi-monthly Vol. I July, 1914 No. 2 MINING PRACTICE IN DISTRICT I (LONGWALL) BY S. O. ANDROS Field work by S. O. Andros and J. J. Rutledge INTRODUCTION This is the only field in the United States where longwall mining produces any considerable tonnage of coal, although in a few states this method is practiced to a limited extent. The Longwall District, as shown in fig. 1, includes all longwall mines, thirty-six in number, work- ing bed No. 2 of the Illinois Geological Survey correlation in Will, Woodford, Putnam, Marshall, LaSalle, Grundy, and Bureau counties, and is District I of the Illinois Coal Mining Investigations. A detailed description of the districts into which the State has been divided and of the method of collecting data from which this bulletin was written is contained in Bulletin I, A Preliminary Report on Organization and Method. The coal produced by the longwall mines during the fiscal year ended June 30, 1912, totaled 5,032,346 tons, 1 or s.1 per cent of the total coal production of Illinois. Xo undercutting machines are used in these mines. The coal mines of the district have 11,631 employees, 14.7 per cent of the total number in the coal mines of the State. Bureau County with 1,664,092 tons produced in longwall mines leads l he counties of the district. On account of the initial expense of opening a mine to be operated on the longwall system only two local mines are found in the district, all others being shipping mines. These longwall mines had an average of 20!) days of active; opera- tion during the year ended June 30, L912, as compared with an average of 160 days for all mines in the State. The average daily production of the district is 24,078 tons. Table 1 gives general data tabulated by comities on the longwall mines of the district. Table 2 shows comparative statistics for the dis- trict and for the State, representing the year ended June 30, 1912. 1 Thirty-first Annual Coal Report of Illinois. 3 G COAL MINING INVESTIGATIONS Table 1. — General Data by Counties 1 County Num- ber of mines 8 I C b3 a> .a >- OS 3 A g 9 o "3. CD 0) o o 39 ^ >> X on ■gg c3 T3 fe.8 d 03 S3 11 >*> a a to 42 (), 1912, the average number of tons of coal produced per employee per day was 2.1 for District I, as compared with 4.0 for all the other districts combined. 26 COAL MINING INVESTIGATIONS The number of employees consequently is out of proportion to the amount of coal gained, the number employed in the district being 14.7 per cent of all employees in coal mines of Illinois. The number of days of active operation for the district averaged 209, as compared with 160 for the State. With an average of 11,631 employees working 209 days there were 2,430,897 days of labor performed. This number is 19.1 per cent of the total for the State as a whole. It is seen, therefore, that its 24.5 per cent of non-fatal injuries shows careless mining. Table 6. — Comparison of accidents for the year which ended June 30, 1912 District I All other districts com- bined Number fatal accidents Per cent from falling coal or rock Per cent from pit cars Per cent from explosives Number deaths per one thousand employees. Number tons mined for each life lost Number non-fatal accidents ^^ Per cent from falling coal or rock Per cent from pit cars ' Per cent from explosives Number injuries per one thousand employees Number tons mined to each man injured 168 54.2 19.1 6.6 2.5 313, 124 604 38.2 27.7 3.1 8.9 86, 827 Table 2 compares fatal and non-fatal accidents for the State and the district. A comparison of this district with all the other districts of the State combined, as given in Table 6, shows that District I has fewer fatalities per ton of coal mined or per 1,000 employees, but has almost twice as many non-fatal injuries per 1,000 employees, and produces less than one-third as many tons of coal per non-fatal injury. Including both fatal and non-fatal accidents the district has 17.8 per 1,000 em- ployees as compared with 11.4 for all other districts combined. In both fatal and non-fatal accidents the percentage caused by falling rock or coal greatly exceeds the percentage from this cause in the remainder of the State; and in non-fatal accidents this discrepancy is marked, the ratio being as 67.8 to 38.2. This high percentage of accidents for the district is due principally to inability to enforce proper spragging of the coal and propping of the roof at the face. Unless compelled to mine properly the miner will pull the coal down with a pick, or will wedge it down after he has undermined 2 to 8 inches. He does not consider it necessary to sprag the coal for this short undermining, and is often injured when the unsupported coal falls away suddenly. A comparison of production per employee is given in Table 7 for each of the 11 mines examined, for District I and for all the other districts of the State combined. MINING PRACTICE 27 Table -Per capita production of employers Number Employees O c3 3 * n >»p 1 2 3 4 5 6 7 8 9 10 11 All mines in District I All other districts combined l 33 40 33 10 9 10 11 26 17 40 25 902 5,576 570 400 279 216 160 375 376 300 121 400 510 10, 632 59, 297 518 320 225 200 150 340 I 291 260 104 325 448 8,510 44, 808 603 1,450 17.3 6.1 43.9 2.5 440 900 10.0 2.7 22.5 2.3 312 750 8.5 2.6 22.7 2.7 226 550 21.6 i . i 55.0 2.5 169 400 17.7 7.9 44.4 2.5 385 900 37.5 (. o 90.0 2.4 387 800 34.2 3.0 72.8 2.1 326 700 11.5 3.9 26.9 2.3 138 200 7.1 3.1 11.7 1.6 440 1,000 10.0 2.8 25.0 2.5 535 1,200 20.4 5.2 48.0 2.3 ,534 24, 299 10.7 2.8 26.9 2.4 ,873 301, 845 10.6 2.2 54.1 5.1 2.8 2.8 3.3 2.8 2.7 2.7 2.8 2.7 1.9 3.1 2.7 2.8 2.4 2.2 2.4 2.4 2.4 2.3 2.0 2.1 1.4 2.3 2.2 2.1 1 Shipping mines only during the year ending June 30, 1912. VENTILATION The ventilation of mines operated on the longwall system presents few difficulties, and the problem of supplying air to the men at the Overcasts shown thus: X Curtains shown thus.- — Fig. 14. Plan showing direction of ventilating current. (After Swift) 28 COAL MINING INVESTIGATIONS working face is easy of solution. In room-and-pillar mining, the faces of the rooms, that is, the working places of the miner, are outside the direct flow of the air current except when the face of a room is at the point where a cross-cut is driven through the room-pillar. In longwall mines the air-current always flows along the working face, as shown by fig. 14. More physical discomfort is suffered by the longwall miners, however, because the temperature at the face of longwall mines is greater than at the face of room-and-pillar mines. This is shown in Table 8 which gives return air temperature for mines worked under both systems. Table 8. — Comparative temperatures Average Average Number tempera- tempera- Degrees weeks ture at ture at of heating in Location Mining svstem of daily bottom of bottom of passage readings intake return through air shaft — air shaft — mine degrees F degrees F Oglesby Longwall 39 52.2 74.0 21.8 LaSalle ..do .... 47 40 58.3 53.9 76.9 64.9 18.6 Benton Room-and-pillar 11.0 Glen Carbon... ..do .. 44 43 56.9 55.3 68.0 75.5 11.1 Average for longwall Average for room-and-pillar. 20.2 Room-and-pillar 42 55.4 66.5 11.1 This table shows that during passage through the workings of a long- wall mine of average size the ventilating current undergoes an average rise in temperature of 20.2 degrees above that at the bottom of the downcast shaft. In a room-and-pillar mine of ordinary extent of work- ings the air current has its average temperature raised 11.1 degrees F. while passing through the mine. This average difference throughout the year of 9.1 degrees between the temperatures of longwall and room- and-pillar mines is largely because in the former a much smaller quantity of air with lower velocity passes over more men and lamps. Sometimes the gob fires in longwall mines increase the temperature. When mining is done in the clay under the coal few gob fires occur because then not much coal finds its way into the gob. Gob fires are more frequent where undermining is done in the coal. Every condition necessary for spontaneous combustion is then found in the gob about 15 feet from the face : Fine particles of coal. Finely divided ircn pryites. Moisture. Air confined in the interstices of the gob. Initial heat produced perhaps by roof pressure on the gob. Where the gob is not heated to the point of combustion its temperature may be raised considerably by the oxidation of coal and pyrites. Because the presence of air is necessary for this process gob fires do not occur much further than twenty feet behind the face as beyond this point the settling of the roof has packed the gob so tightly that air is excluded. That sufficient heat is developed by a few gob fires to bring about the increased temperature at the longwall face is shown by readings in Table 9 taken at the face 10 feet from a gob fire after the air current MINING PRACTICE 29 has passed the sealed-off fire, and also by readings taken at the face 100 feet distant from the fire before the current has passed over it. Table 9. — Temperature readings near gob fire Location Temperature degrees F. Face one hundred feet towards intake from fire 73 Ten feet beyond fire 84 The cost of removing sulphur from the mine varies from % to 1% cents per ton of coal mined. Fires in the gob of longwall mines are easily sealed off. The usual method is to build around three sides of a fire a solid wall of roof rock leaving the gob which has been packed by roof settling as the fourth side. A lining of fine sand is placed inside of the wall. The sand is usually brought into the mine for this purpose and stored underground to be ready for immediate use when needed. In- cluding cost of sand the expense of sealing off a small gob fire approx- imates $25. In some mines road dust instead of sand is used for sealing off fires and serves the purpose as well because road dust consists prin- cipally of inert shale pulverized by car wheels on the track and by the feet of men and animals on the roadways. If a fire occurs from 5 to 20 feet from the face between two rooms, it is reached in some mines by digging through the burning gob which is then loaded oul if possible be- fore sealing off is begun. This method of walling off is regarded as very efficient because the sand or road dust packs remain effective for ;it least two months; and before the end of this period the fires are ex- tinguished. Very little marsh gas is found in longwall mines, although occa- sional pockets are discovered in small sand deposits immediately above the shale roof. Whenever it thus occurs it is quickly diffused in the air and become- so dilute that no cap is shown by a testing lamp. Eoof falls caused by the expansion and contraction of roof material on account of temperature change- are numerous, because cracks extend several feet into the immediate roof. Two of the mines examined beal the intake air in winter to keep the temperature more constant and also to prevent the formation of ice in the intake shaft. The amount of roof fall is in this way lessened. In one of these mines the exhaust steam from the fan engine is put into the downcast air shaft through a 1-inch pipe; and as ;i precautionary measure againsl a temperature so low thai exhaust steam could not keep the shaft free from ice. a l'/.-inch pipe for live steam also runs int.. the -haft. It is seldom necessary, however, to use this live steam. In the other mine the live steam is sent down the intake shaft through a 3-inch pipe, which leads to a cylindrical radia- tor 7 feet in diameter placed at the bottom. The necessity for artificial humidification to prevent coal-dust ex- plosions has not been apparent in longwall mines. Inasmuch as nil the coal is removed from the seam as the face advances ami as the excava- tion is tilled with waste rock the only sources of supply for coa] are the daily working face of fresh coal and the spillings from the pit r;\v*. 30 COAL MINING INVESTIGATIONS In room-and-pillar mines the ribs of the entire workings and sometimes also the roof and floor are of coal ; and the spalling of this coal furnishes a cumulative supply of dust that becomes constantly drier and more explosive. The coal dust from mining at the face in the longwall mines is covered with shale and clay within a few days after it is made so that Fig. 15. An entry closely timbered. (Photo by J. J. Rutledge) there is no accumulation of it. The dust brushed from the ribs of long- wall mines is not inflammable. The analyses of samples thus taken show that the dust consists principally of shale or other inert matter. Table 10 gives the average of analyses and of pressures developed in the explosibility apparatus for 14 samples of longwall rib dust collected in the haulage ways. Table 10. — Comparison of longwall and room-and-pillar rib dust on haulage ivays Mining system Number samples Proximate analysis of coal — First: " As received" with total moisture. Second: •'Dry" or moisture free Pressure in pounds per square inch developed in explosi- bility flask at 2192° F. Moisture Volatile matter Fixed carbon Ash Average longwall 14 3 / 3.45 I Dry f 5. 54 I Dry 14.68 15.19 34. 89 39. 94 6.77 7.01 39.21 41.51 75.12 77.80 20. 37 21. 56 0.175 Typical room-and-pillar mine in southern 111 inois 4.760 MINING PRACTICE 31 The high average temperature of the air in longwall mines de- creases the relative humidity and considerable moisture is absorbed from the dust of ribs and roads so that, unless additional moisture is supplied by seepage water or by sprinkling, the dust of the roadways becomes very dry. In a few mines of this district the haulage roads are sprinkled at intervals varying from one week to three months. Fig. It3. Cog built of props The work performed by the ventilating fan was determined by a water gage at 5 of the mines examined. The readings varied from 1.7 to 2.5 inches. By a provision of the State law effective /Inly 1, 1913, water gages must be installed in all mines. Table 11 gives data covering ventilating equipment at the mines examined in this district. Table 11. — Ventilating equipment No. mine Depth of air shaft in feet Clear dimensions of air shaft in feet Number compart- ments Fan Diameter in feet Length in feel Material of fan house Water gage read- ings iu inches 1 413 2 Slope 3 398 4 546 5 135 6 100 7 200 8 300 *9 Slope 10 480 li 530 9 x 12 2 14 8 8 x 12 2 10 4 5 x 9 2 8 4 X x 10 2 20 10 6 x 12 2 20 6 10 feet diameter 1 16 4 8 x 10 2 2 1 1 (i X () 10 } » / ") X f) i 0x7 4 8 x 12 2 16 6 :» x 9 2 20 6 Brick Frame Corrugated iron Concrete Frame Brick and concrete Brick, steel and concrete. Frame Brick and concrete. Brick 2.0 No gage No gage No gage 2. 5 No gage 1.9 1.7 No gage No gage * Two air shafts. 32 COAL MIXING INVESTIGATIONS TIMBERING The continual subsidence of the strata overlying the coal in longwall mines makes timbering of roadways difficult and expensive. Permanent timbering can be extended only to that point where the first rapid and violent subsidence has ceased, and it is not usual to extend permanent timbering to any point until the face has been advanced beyond it for at least two years. Roof breaks destroy the cohesion of the shale and large masses of rock must be supported by timber so that the collars of the three-piece gangway set must be heavier than those ordinarily used in room^and-pillar entries. For usual timbering with ordinary roof con- ditions an 8-inch cross bar is supported by 6-inch legs. These are bat- Fig. 17. Sketch of branch cog tered iy 2 inches for each vertical foot between rail and cross bar. Under bad roof the entry is usually closely timbered as shown in fig. 15. The frames in this photograph have white oak legs 8 inches in diameter, and 10-inch white oak cross bars. These frames are spaced on 6-foot centers, and the top and sides of the entry are lagged with split and round props 4 to 5 inches in diameter. When it is necessary to support the increased area of roof resulting from turning off a cross entry from the main entry, or from turning rooms from a cross entry, cogs are' built with props as shown in fig. 16. A sketch showing details of these cogs, called "branch cogs," is given MINING PRACTICE 33 in fig. 17. These cogs are filled two-thirds full of waste rock and mining dirt. It is necessary to allow for subsidence of the overlying strata which crushes the cog, as the weight comes on it. A cog built 4 feet high above the floor will in 18 months be crushed to a height of but 18 inches above the floor. If cogs were entirely filled with waste rock and dirt they would offer too much resistance to roof subsidence and the roof would "cut" at the cog. This roof caving would increase the danger of acci- dents from roof falls and would add to clean-up expense. Article V of the Third Vein District Agreement states : "The price for turning a room where the company does the brushing and builds the cog shall be $5, and where the miner does the brushing and builds the cog the price shall be $8,747, the company to have the option of method/' Besides the branches at entry and room junctions two other wide roof areas must be supported, that is, the shaft bottom and the lyes called FIG. 18. A typical lye partings in room-and-pillar mines. In this district the timbering of the bottoms does not generally differ from the timbering of bottoms in room- and-pillar mines. The roof is supported by props alone, by timber-sets, by masonry, or by steel I-beams. In one mine in which pillar coal was removed, after roof and floor met the bottom was widened and timbered with 10 by 12-inch frames spaced on 4-foot centers and lagged with 3 by 12-inch planks. No trouble from root' cutting has ever beer experienced in this mine. In a few mines the inner lyes are in abandoned rooms but generally the lye is formed by widening the entry at the desired location. The usual width of a lye, as shown in fig. IS, is 11 feel ; ten-inch collars and legs are used for the timber sets which are spaced 6 feel apart. This lye is 75 feet long and provides storage for 13 cars on cacli track. 34 COAL MIXING INVESTIGATIONS The high temperature of the return air current in this district is very favorable to fungus growth; the heavy and expensive entry timbers on the return fail through decay in from 2 to 4 years. In one mine of the district preservative treatment is given to the timber used on the main roads. At this mine the life of an untreated white oak collar averages two years on the intake and less than one year on the return. Treated timbers have already been in service on the return for three years without sign of decay. The timbers to be treated are peeled and sun-seasoned. Before taking them underground they are painted with a heavy coat of carbolineum. The cost of labor and carbolineum for treating two legs 7 feet long and 6 inches in diameter, and one collar 6 feet long and 7 inches in diameter, is 16 cents. The cost of the un- treated timbers is 45 cents. Where a soft wet fire clay several feet thick underlies the coal it is sometimes necessary to build short cogs as a foundation for the legs Fig. 19. Circular hoisting shaft of the frames in the lyes. A cog of 4-inch props is usually constructed 3 feet high and 4 feet square. On the top of this cog, a 3 by 12-inch plank 4 feet long is placed. The bottom of the leg rests in a notch cut in this plank. As the roof weight settles on the frames the cog is pushed into the clay and the settling is gradual and continuous. The cost of timbering in a district where conditions of roof and floor are so widely different varies with each mine. Total cost of timbering at the 11 mines examined varied from 5 to 8 cents per ton of coal mined. At that mine in which the total cost of timbering was 8 cents, the cost of face props was 6 cents per ton of coal mined. A mine producing 1,450 tons a day employed 8 day-timbermen and used daily 1,500 props; 70 cross bars, 7 feet in length; 50 bars, 8 feet in length; and 2 bars, 10 MINING PRACTICE 35 feet in length. Props 3y 2 or 4 inches in diameter are usually bought. From .5 to 1 cent per linear foot is paid for props; the number used per ton of coal mined varies from iy 2 to 3. The expense of cross bars in- creases rapidly with increased diameter and length of span. Table 12 gives average cost in the district of mine timbers of various diameters and lengths. These figures do not include the cost of placing in posi- tion but refer only to the timbers as piled on the surface. Table 12. — Cost of mine timbers Length Diameter Average cost Feet 6 Inches 8 8 10 10 12 Cents 15 7 16 7 80 10 125 14 fc 190 Shaft linings are generally of timber, but concrete is also used. One of the earliest concrete-lined shafts built in the countrv is at the Xo. 6 ; 9 >.,' * *'■ -j y ,. .», ' Hi JKe^aEKB *»4 -V -,'■ '.:■'■! 'Np-'- ■■IP •'» JH| R B ■PL' ■• ' 5t» , 4i r «Bra \ r • |i p/M 20^^ V9s^v ^SO Amount of "company brushing" necessary after subsidence mine of the Big Four Wilmington Coal Company at Coal City. Two circular shafts were sunk, one of which, the air shaft, LO feci in diameter, was finished in May, 1903. The hoisting shaft, 13 feet in diameter as 36 COAL MIXING INVESTIGATIONS shown in fig. 19, was completed in June, 1903. Both of these shafts were lined with concrete 14 inches thick from rock 40 feet deep to a point 8 feet above the surface level, making a total of 48 linear feet of concrete lining. HAULAGE The older mines in the district were opened when mechanical haul- age was not in general use. Mules are still used for moving the coal from the face to the bottom in many of these mines, although the face may be over a mile from the hoisting shaft. A tendency to supersede mules by mechanical haulage is apparent in this district. Several mines are arranging for the installation of electric locomotives. At present locomotives are found in only 3 of the 36 mines in this district; rope haulage in 3 mines. Mules are used both for main and Fig. 21. Typical shaft bottom secondary haulage in 29 mines and in one pit cars are pushed to the bot- tom by men. The costs of haulage and maintenance of haulage ways are high per ton of coal because from y± to V3 of the entire tonnage hauled to the bottom is waste. Furthermore, the continuous settling of the roof, and in many mines, the heaving of the floor, add an expense for brushing roof and floor which is not an item in room-and-pillar mines. The roadways are usually maintained 4 feet high and 7 to 9 feet wide. The miners brush the roof at the face, but the settling as the face advances necessitates a further brushing which is done in the LaSalle field by the company. Fig. 20 shows the amount of "company brushing" necessary at one mine after subsidence. This brushing of roof and floor costs the operators in the LaSalle field approximately 15 cents per ton of run-of-mine coal. Labor for haulage costs approximately 12^2 cents. Maintenance of mules and car repairing costs 5 1 /? cents. The total MINING PRACTICE 37 cost items chargeable to haulage and maintenance of haulage roadways amount to about 33 cents in a typical mine with mule haulage on both main and cross entries. The thin bed and narrow entries limit the height of cars and the capacity of the pit car generally used in the district is small. The average weight of pit cars used in the 11 mines was 900 pounds The light weight of pit cars and the slow speed Fig. 22. Receiving hopper at shaft bottom attained by the trips allow a comparatively Light rail; a 1 (3-pound rail is in some mines used in the entries and a 12-pound rail in rooms. Table 13 gives haulage statistics for the 11 mines examined. Pit cars are not generally kept in good repair but in many mines are leaky. Fig. 21 shows a shaft bottom in the vicinity of Coal City. Table 13. — Underground haulage No. mine Kind of haulage through main entries Track gage Rail weight Main Second- ary Pit cars Weight empty Capacity Ratio of load to weight of empty car Percent- age of empty car weight in total weight of car and load j Mule Third rail electric locomo- tive Mule Main and tail rope Mule Main and tail rope Main and tail rope Electric locomotive Mulei Mule Electric locomotive 33 lti hi 1,800 2,600 1.44 37 lti 12 840 2,200 2.62 42 lti lti 900 2, .-.00 2.77 26£ It) lti 900 1.700 1.88 36 hi lti 125 1,000 2. 3.'. 24 20 12 825 2, 000 2. 43 32 lti hi 500 1,000 2.00 36 30 lti 1,100 2, 700 2. 45 37 24 12 850 1,000 1.17 42 lti 12 1.200 2,650 2.21 36 3.-> 16 1, 100 2,600 2. 36 40.9 27.6 26. 5 34. 6 2*.). S 29. 2 33. 3 28.9 45.9 31.2 29.7 Cable on slope. 38 COAL MINING INVESTIGATIONS HOISTING The daily production of mines in the district is comparatively small; the average daily tonnage of the 11 mines examined varies from 200 to 1,450. Hoisting speed is lower than in some districts because the amount of coal daily raised to the surface does not necessitate high speed. A greater number of hoists is made daily than the figures for coal production disclose because about one-third as much rock as coal is taken to the surface. In one mine having a coal production of 1,450 tons a day 1,400 hoists a day are made. The shaft is 413 feet deep. Eaising waste rock to the surface requires 350 of these hoists. None of the mines examined had automatic caging at the bottom, and the self-dumping cage was found at only one mine in the district. Here an adaptation of ore skip is used. Pit cars from the face on i PL \ v 1 «fl til 1 1 jit r • J ;/i |1 ,,; ""■• : '-y-. : WHE» ** : - Fig. 23. Skip adjusted to hoist men reaching the shaft bottom have their contents dumped as shown in fig. 22 into a two-compartment hopper 9 feet deep lying below the floor. Each compartment of the hopper has a capacity of two pit cars, and automatically discharges its contents into the skip. The skip is pro- vided with a vertically-sliding door which is automatically lifted in the tipple, discharging the contents of the skip on to the screens. The skip can be adjusted to hoist men as shown in fig. 23. Weighing is done at the bottom. Hand caging and hand unloading are common at the smaller mines,but the steam ram and transfer table are used in the tipple in the larger mines. This method of automatic unloading is not general in Illinois. MINING PRACTICE 39 At several mines in the district cages built to hold two pit cars tandem were used as shown in fig. 24. Fig. 24. Tandem cage At the mines examined all but one of the direct connected with cylindrical drums. Table 1-i gives hoisting data tor the 11 mines examined. Table 14. — Hoisting equipment Aver- No. age mine dailv tonnage Type of cage Hoisting shaft Depth Size in feet Kind of lining Num- ber of com- part- ments Hoisting engine Firs! or second Size motion Drum - Diam- eter in feel Length in feet 150 750 550 ion 700 200 1,000 1,200 Tandem plat- form Platform Platform Skip Platform Platform Platform Self dumping Tandem plat- form Platform 413 12 x 12 465 Six 12 398 9 xl2 546 7 xl2 135 6 Xl2 100 *13 200 7 x lti 300 7 x 16 Slope 6x8 480 12 x 16 530 9 x 12 Timber ..do ..do ..do ..do Concrete and t Lmber Timber ..do ..do ..do ..do 2 First . . . 24 x 12 8 2 ..do.... 24 x 36 li'. 2 ..do.... 20 x 32 8 2 ..do.... 13*X 42 .) 2 ..do.... 18 x 36 8 3 ..do.... 14 x 20 :'.'. 2 ..do.... lti x 30 :"> 2 ..do.... 32 x 12 s 1 Second. 14 x 20 ti 2 First . . . 24 x42 8 2 ..do.... 24 x 12 8 * Diameter; circular shaft, a Largest diameter if conical. 40 COAL MIXING INVESTIGATIONS PREPARATION OF COAL The amount of lump coal over ±14 inches made in proper longwall mining is 15 to 20 per cent higher on the average than is made in room- and-pillar mines, but when shooting is allowed in longwall work the percentage of lump coal is not so large. In this district the amount of l 1 /^ inch lump as reported by the mine operators varies from 65 to 83 per cent. In those mines where no shooting is allowed the coal breaks in large blocks. At several of the mines in the district the following sizes of coal are made at the tipple : Name Size Lump Over 6 inches Chunk Over 3£ inches, through 6 inches Egg Over 1J inches through 3J inches Screenings Through 1 J inches Four of the 11 mines examined send their screenings to washeries where a further separation is made into 3 sizes. Name Size No. 1 nut : Over 1 inch, under 1^ inches No. 2 nut Over | inch, under 1 inch Slack Under I inch Two mines shipped run-of-mine coal only Table 15. — Tipple equipment Materia] of tipple Primary sizing screen Rescreened or washed coal No. mine Type Screening surface Inclin- ation Shakes per minute Per cent of lump coal over Length in feet Width in feet l\ inches 1 2 Timber Timber Shaking ..do... 24 43 34 27 57 22 24 48 6 6 6 6 6 6 6 6 1 in 4 1 in 4 1 in 4 1 in 4 1 in 4 1 in 4 1 in 4 1 in 4 120 85 110 80 80 90 120 75 Neither ..do 80 83 3 ..do... ..do Rescreened Washed ..do ..do Neither 79 4 Timber.. . do . 65 5 ..do 70 6 8 Timber Timber and steel. Steel ..do ..do ..do 80 *73 *73 J9 Timber 10 Steel Shaking ..do 50 8 5 1 in 5 1 in 5 60 60 Both f83 11 Washed 83 * Over 1J inches. t Over | inch. X Run-of-mine. Table 15 gives data on coal preparation at each mine. The surface plants of the district are not generally so compact as the average surface plant of a room-and-pillar mine. Fig. 25 shows a representative tipple of the district. The comparatively small outputs do not require rapid continuous hoisting and consequently the power plants of the 11 mines are comparatively small. Table 16 contains data on power plant equipment at each mine visited. 41 42 COAL MINING INVESTIGATIONS Table 16. — Power plant equipment Car storage above tipple Number loading tracks Boilers Electric generators Number mine Number Total H. P. Average steam pressure K. W. Volts 1 50 25 10 15 10 50 20 25 9 80 20 4 4 2 3 3 3 3 3 1 3 3 6 6 4 2 4 2 6 3 2 6 9 900 720 600 300 300 300 200 800 200 900 90 115 90 106 85 140 75 100 90 90 112 2 3... . 125 275 4 100 250 5 6.. . 8 9 150 i2o' 250 10 250 11... PUBLICATIONS OF THE ILLINOIS COAL MINING INVESTIGATIONS Bulletin 1. Preliminary Report on Organization and Method of Investigations, 1913. Bulletin 2. Coal Mining Practice in District VIII (Danville), by S. O. Andros, 1914. Bulletin 3. A Chemical Study of Illinois Coals, by Prof 8. W. Parr, 1914 Bulletin 4. Coal Mining Practice in District VII (Mines in bed 6 in Bond, Clinton, Christian, Macoupin, Madison, Marion, Montgomery, Moultrie, Perry, Randolph, St.Clair, Sangamon r Shelby and Washington counties), by S. O. Andros, 1914. Bulletin 5. Coal Mining Practice in District I (Longwall), by S. O. Andros, 1914.