Remote roof stability monitoring for underground nonmetal mines.
Grau-RH III; Iannacchione-AT; Prosser-LJ
Proceedings of the 1999 Structures Congress, New Orleans, LA, April 18-21, 1999. Reston, VA: American Society of Civil Engineers, 1999 Apr; :727-730
Unrecognized roof beam failure is responsible for most of the falls of ground fatalities and injuries occurring in U.S. underground stone mines. Observational techniques to inspect roof integrity, such as sounding the rock, observing drilling performance, etc., have always been available to miners. These techniques can be enhanced by monitoring mine roof movement on a regular basis. Monitors can be divided into two basic types: 1) roof-to-floor convergence monitors, and 2) roof and rib extensometer monitors. Because most stone mine development rooms average 7.1 m (23 ft) and bench rooms average 16.4 m (54 ft) in height, roof-to-floor convergence monitors are difficult to install, maintain, and analyze. Roof and rib extensometers have enjoyed wider use than convergence monitors; however, they are difficult to read because of their location on the roof line or back. In its simplest form, roof and rib extensometer monitoring can be accomplished with a scratch tool. This device can detect separations and provide an indication of loose rock layers or roof beam deflection. Information on the location and size of the separation can be marked on the roof and used to assess potential future roof degradation. Extensometers permanently installed in drill holes have been used for many years in underground mines to detect ground fall hazards. Sonic probe extensometers have been widely used in the United States, the United Kingdom, and Australia. The probe is temporarily inserted when measurements are made. Homemade mechanical extensometers have been used for decades in metal mines in Michigan, Missouri, and Idaho. For example, in the Missouri lead belt district a deflection rate of 0.007 in/month is considered a good warning of strata failure. Extensometers have been used as real-time hazard warning devices. Parker 1973 discussed an ingenious method to alert miners of strata movement by adding a warning light to an extensometer.
Mining-industry; Underground-mining; Room-and-pillar-mining; Ground-control; Ground-stability; Statistical-analysis; Accident-prevention; Injury-prevention; Monitoring-systems; Workplace-monitoring; Workplace-studies; Injuries; Traumatic-injuries; Stone-mines; Hard-rock-mines
Proceedings of the 1999 Structures Congress, New Orleans, LA, April 18-21, 1999