Development of a Passive Mine Roof Fall Warning Device.
For Reference Only At Bureau Libraries :116 pages
This report describes the design and the laboratory and field testing of a passive, mechanical mine roof fall warning device. The device relies on the assumption that roof sag velocity (the velocity between the roof surface and some presumed stable horizon some distance into the roof strata) is an indicator of relative roof stability. A sag velocity above some locally determined threshold level suggests impending roof failure. This assumption has previously been empirically proven for several mining situations that are referred to in this work. Several concepts for the warning device are presented. The preferred (and most extensively field tested) solution employs a highly viscous dashpot that transduces the sag velocity into a force and is used to activate a spring preloaded latch indicator assembly. Latch preload is set equal to the force generated by the dashpot at the predetermined critical sag velocity. When this critical sag velocity is exceeded, the latch begins to open. If the sag velocity remains above the critical level for a sufficient length of time (determined by the latch stroke), the latch is tripped, and a visual warning is activated.
CP; Final Contract Report;
For Reference Only At Bureau Libraries
Ma Instit. of Technology