The Field Testing of Several Mine Roof Fall Alarm Systems in an Anticipated Natural Roof Fall in the White Pine Mined-Out Windpipe Area

摘要

The Bureau of Mines has developed prototype instruments promising to improve the ability to warn of imminent roof falls. An unusually good opportunity to test these comparatively under natural caving conditions was afforded by the forecasted caving in August 1977 of a mined-out region of the White Pine mine where the rock strata closely resembles those in many coal mines. The anticipated cave was of the competent roof-weak-pillar type and occurred as and when predicted. Automated convergence and bed separation gages agreed well with the standard manual convergence gage measurements. A microseismic gage was insensitive to the fall and may require different test conditions for effectiveness. A roof resistivity unit was tested under a separate Bureau of Mines contract. An unplanned addition to the field test, the tiltmeter, showed interesting potential.