| Coal mine bumps have presented serious mining problems in the United States throughout the 20th century. Persistent bump problems not only threaten the safety of miners, but also have caused the abandonment of large coal reserves and have led to premature mine closures. Current application of yield pillars shows that it can prevent coal bumps in some Longwall mines. In this dissertation, the need for a new method to design yield pillars in bump prone conditions is established. In order to fulfill this need, a PC-design program based on finite element modeling was developed. This program can design stable yield pillar systems for most of bump prone conditions. The preliminary applications of this program illustrated its ability to evaluate the stability of yield pillars with respect to coal bumps.; To achieve a realistic Longwall panel simulation, coal and gob property models were developed. In this study, a yield pillar was divided into three zones; namely core, transition and rib zones. An appropriate stability criterion was assigned for each zone. A number of stability measures were introduced to evaluate the yield pillar stability, namely; yield pillar ratio (YPR), rib zone ratio (RZR), pillar bump index (PBI) and roof-to-floor convergence (C). An interpolation model correlating the pillar stability measures and the geological and geometrical factors was developed. In this study, a yield pillar was designed to yield with acceptable levels of bump index (PBI) and roof-to-floor convergence (C).; Finally, a PC program to evaluate the Longwall yield pillar stability (ELYPS-model), was developed based on the developed interpolation model. The ELYPS-model can be used to design and to evaluate 2-entry yield pillar systems for wide ranges of geological and geometrical factors. |
