406 



TIMBER RESOURCES FOR AMERICA'S FDTCPRE 



repair are developed. Compared to the medium 

 projection, the lower projection is about 4 percent 

 less in 1975 and about 14 percent less in 2000 — and 

 the factors of lumber-use per dollar of expenditure 

 are correspondingly reduced : 



Million 

 board- 

 feet 



Consumption in 1952 4, 500 



Projections to 1975: 



Lower 4,800 



Medium 5,000 



Projections to 2000: 



Lower 6,000 



Medium 7, 000 



Upper 7, 400 



Lumber for Construction in Mines 

 Expected To Double by 2000 



About 2 percent of the lumber consumed in the 

 United States in recent years has been used in 

 mining operations. Sawed ties are used in mine 

 railways. Sawed timbers, crossbars, capblocks, 

 and wedges (normalty in combination with round, 

 split, or hewn timbers) are used in the "timbering" 

 that supports the roof of underground mines. 

 Boards and dimension lumber are used as brattice 

 (lining material) in air passages of mine ventilat- 

 ing systems, in chutes, in bulkheads, and in vari- 

 ous other facilities — including tipples and other 

 mine structures above ground. 



Almost all the lumber consumed in mining 

 is used by underground mines. Strip, open-pit, 

 quarry, and placer operations require virtually 

 no lumber. 



The quantity of lumber consumed per toi^ of 

 product extracted from underground mines varies 

 greatly from mine to mine. In general, the mining 

 of seams lying at a tilt requires more elaborate 

 timbering than the mining of seams that are com- 

 paratively level, ^^^lere overlying strata are firm 

 and hard, the mine roof can be bolted from below 

 with expansible-nut bolts and thus held up with 

 little or no timbering, but this method of roof 

 support can be used only where the mineral seam 

 is overlaid by suitable rock structure. 



Mechanization of cutting and loading operations 

 at the underground working face requires the 

 elimination of props to the maximum extent pos- 

 sible — so that machines can be freely maneuvered 

 into working position. These mechanized opera- 

 tions also favor the use of continuous conveyor 

 systems for transportation of extracted mineral 

 to the hoisting shaft. Such equipment eliminates 

 the need for track and mine-track ties. The 

 damp conditions in most underground mines cause 

 wood to decay quite rapidly. There is some trend 

 toward the use of treated material in semiperma- 

 nent underground structures, with consequent de- 

 crease in the rate at which those facilities have to 

 be replaced. 



On the other hand, about half of all fatal mine 

 accidents are caused by roof falls ,^^^ and the worst 

 mine disasters are caused by explosions of accum- 

 ulated gases. In the interest of safety, there is 

 continuing pressure for improved systems of roof 

 support and for improved ventilating systems. 

 In man}' instances such improvements entail in- 

 creased consumption of lumber and other wood 

 products per ton of output. There is also a trend 

 toward the substitution of sawed timbers for 

 round and hewn timbers. This does not increase 

 the wood requirements per ton of output, but it 

 does increase the lumber requirements. 



Surveys to determine the quantity of timbei- 

 products consumed in mining include four that 

 were nationwide. According to these, the quan- 

 tities of timber products consumed by under- 

 ground mines were as follows: '-^ 



T , . , ,. , . . Million board-feel 



Lumber, mcludmg sawed mme ties 



and sawed timbers: '^s ms i9S5 mo 



Coalmines 242 296 347 597 



Other mines 194 211 120 239 



Total 436 507 467 836 



Round, split, and hewn mine tim- Million cubic feet 



bers : '■ 



Coalmines 135 152 102 90 



Other mines 31 22 11 18 



Total 166 174 113 108 



.\11 timber products: 



Coalmines 188 218 179 222 



Other mines 73 68 37 70 



Total 261 286 216 292 



Although tlie quantity of lumber consumed in 

 mining during 1950 appears to have been greater 

 than in previous survev years, the volume of 

 round, split, and liewn material was less. Con- 

 sumption of all timber products in 1950 was the 

 highest of all survey years. Reduced consmnp- 

 tion in 1935 was obviously due to the depression. 



Considerably more than three-fourths of all 

 timber products consumed in mining, and about 

 70 percent of the lumber, is used by imderground 

 coal mines. Coal production from underground 



■" U^. S. Department of the Interior, Bureau of Mines. 

 Questions and Ansrvers on Roof Support in Biiuniinous- 

 Coal Mines, p. 1. Washington, D. C. 1951. 



123 Kellogg, R. S. Timber Used in Mines in the United 

 States in 1905. U. S. Dept. Agr., Forest Serv. in coopera- 

 tion with the U. S. Dept. Int., Gcol. Sur. Forest Serv. 

 Cir. 49. Washington, D. C. 1906. 



U. S. Dept. Comm., Bur. Census in cooperation with 

 U. S. Dept. Agr., Forest Serv. and U. S. Dept. Int., Gaol. 

 Sur. Mine Timber Used Underground. Goverimient 

 Printing Office, Washington, D. C. ' 1925. 



Brush, W. D. Timber Requirements for Mines in the 

 United States. U. S. Dept. Agr., Forest Serv., Wash- 

 ington, D. C. 1938. 



U. S. Dept. Agr., Forest Serv. Unpublished estimates 

 for 1950 based on data collected by regional forest experi- 

 ment stations in connection with a survey of equipment, 

 supplies, and manpower used by forest products industries. 



