2678 Chapter 22 



Table 22-24 — Yields of lumber and residues from 1,000 board feet Doyle log scale — 

 weighing J 4, 063 pounds — related to lumber recovery factor^ when cutting cross ties and 

 lumber from 13 -inch-diameter, 8-foot-long red oak sp. logs^ (Data from Monahan 1976) 



Lumber recovery factor (LRF) is the number of board feet of lumber recovered per cubic foot of 

 log, measured inside bark. 



^Density when green of 63 pounds per cubic foot of wood and bark. 



^Values in parentheses are percentages of lumber yield overrun (or undemin if minus) from Doyle 

 log scale. 



MINE TIMBERS 



Timbers for use in underground coal mines, primarily to support the roof in an 

 opened coal seam are traditional hardwood products cut in the Appalachian 

 bituminous coal region extending from central Alabama to northern Pennsylva- 

 nia (fig. 22-61 bottom). 



Round and split timbers are used for upright supports, while sawn timbers are 

 used primarily for horizontal supports, mainly headers and half-headers. Sawn 

 wood is also used for mine ties, floor planking, crib blocks, construction and 

 repair, and a number of minor products (fig. 22-61 top). 



Knutson (1970) found a direct relationship between the tonnage of coal mined 

 and the volume of wood used in the mines. In 1967 an average of 1 .00 board foot 

 of sawn timbers and 0.54 lineal foot of round and split timbers were used for 

 every ton of bituminous coal mined. In that year about 294 million tons of 

 bituminous coal were produced from underground mines in the Appalachian 

 region. To produce this tonnage, an estimated 295 million board feet of sawn 

 timbers and 159 million lineal feet of round and split timbers were used. In 1979, 

 bituminous coal production from the region was about 251 million tons. 



Wood usage varies with thickness of the coal seam, nature of the mine roof 

 and floor, purity of the coal, and competition from other types of roof support. 

 The type of machinery used also affects timber usage, e.g. , mines equipped with 

 coal conveyors, rather than rail cars, do not use mine ties. 



Knutson found that 1967 consumption of mine timbers in Appalachian bitu- 

 minous coal mines was divided as follows with relative price index indicated: 



