Development and Trials of a Commercially Practical Roof Fall Warning System.
Aplin JE; Fish D; Mangolds A
NTIS: PB/84-182807 Available for Reference At Bureau of Mines Libraries :157 pages
Previous studies have shown that fracturing of roof strata precedes ultimate failure, and that the fracture development causes an accompanying increase in apparent resistivity of the strata. Using this principle, a microprocessor-controlled resistivity roof fall warning system (rrfws) was developed that automatically sequences through and records up to 32 electrodes that may serve as either voltage or current electrodes. This capability permits increased coverage with a minimal number of required electrodes. The data are stored in a nonvolatile memory and on an optional printout, making the system nonsusceptible to loss of mine power. At a preprogrammed interval, the rrfws reactivates and repeats the sequence. If the absolute change or the rate of change of resistivity exceeds a predetermined limit, the system is capable of sounding an alarm. In addition to the monitor, a stainless steel modified split-set electrode was also developed that permits long-term, corrosion-free contact.
CP; Final Contract Report;
NTIS Accession No.
NTIS: PB/84-182807. Available for Reference At Bureau of Mines Libraries.