ABSTRACT
A field test was conducted by the U.S. Bureau of Mines at the Cyprus Plateau Starpoint No. 2 Mine, near Price, UT, to study the support rock interaction mechanics. Twelve instrumented, fully grouted roof bolts and eight sagmeters were installed in the roadway of a two-entry gate road to measure load changes and roof movements. Readings were taken during section development and as each longwall panel passed the test area.
Loads that resulted from development of the entries were higher than would be expected if simple suspension of the roof rock was the sole cause of loading. When the first longwall face passed the test section, massive beam behavior was exhibited over the entry and adjacent pillar. However, no significant localized bending was detected at any of the strain gauge locations. After the first panel passed the test section, all the roof bolts had at least one zone where the steel had yielded. Loading continued to increase, and when the face from the second panel was adjacent to the test section, 70 pet of the strain gauges at the 6-, 18-, and 30-in locations had passed the yield point of the steel bolt. However, even at these high load levels, the roof bolt pattern was sufficient to provide adequate reinforcement to the mine roof.
