Stability Analysis of Bleeder Entries in Underground Coal Mines Using the Displacement-Discontinuity and Finite-Difference Programs.

摘要

The stability of bleeder entries is essential for both mine ventilation and personnel travelling through the entries. Therefore, it is imperative that bleeder pillars remain stable and bleeder entries safe during their service life. Surprisingly, there are few published investigations on ground control issues in the bleeder entries. This thesis is an attempt to analyze the ground control problems in bleeder entries especially, the structural integrity of the bleeder entry. Two numerical programs (a) displacement discontinuity program-LaModel and (b) the finite difference program-FLAC were used to investigate these problems. Modeling results from the LaModel program indicated that the vertical stresses in bleeder pillars would first increase and then remain unchanged during retreat mining. The active longwall did not influence the stress concentrations and safety factors in the bleeder pillars of the adjacent mined-out panel in multiple longwall panels. The vertical stress concentration on bleeder pillars increased with depth. For detailed analysis of roof, pillar and floor of the mine entry simulation was performed in the finite difference program-FLAC. For realistic analysis, coal was assigned as strain-softening material and the gob was simulated with double yielding material. Results showed that the roof displacement in bleeder entries increased during second mining. The stability of the bleeder entry was affected by the behavior of the gob and active mining zone.