TOMOGRAPHIC IMAGING OF COAL PILLAR CONDITIONS - OBSERVATIONS AND IMPLICATIONS

The U.S. Bureau of Mines (USBM) investigated the use of seismic refrac tion tomography (SRT) for identifying changes in pillar loading at the Foidel Creek coal mine near Steamboat Springs, Cole, The inherent thr ee-dimensional problem of directly imaging coal pillar conditions is r educed to a single plane by considering only the load transmitted from the pillar to the adjacent floor rock. Floor strata velocity tomogram s (at two pillar locations) illustrate that loading conditions are non uniform and nonunique, Also, time sequence monitoring, as the longwall face advanced demonstrated that SRT can be used to image spatial chan ges in loading conditions. SRT offers the mining engineer a simple and flexible technique for evaluating pillar conditions and thus, both pr esent and alternative mine designs.