Design of systematic support system for development and depillaring in underground coal mines

Abstract

Bord and pillar method is the most widely practiced underground mining method in India. Nevertheless about 61% of underground coal mining accidents are due to roof and side fall of bord and pillar. Design of systematic support is essential to avoid strata control problem and to provide safe working condition. Three distinct methodologies; empirical approach, numerical modeling and field monitoring were followed and compared in the project to provide a comprehensive design of systematic support. A case study of 1AS2 panel of RK-6 Incline, SCCL is chosen for the design of systematic support. The empirical design of support is developed using RMR and Q-system and validated with numerical modeling and field monitoring. The systematic support developed by RMR with factor of safety greater than 2 for the gallery was 1.5 m spacing of 1.8 m full column grouted bolts with spacing of 1.4 m between rows. Junction support was 33% extra full column grouted bolts. Systematic support designed for slices and goaf edges with Q-System was skin to skin chocks with corner props and breaker line bolt with 1 m spacing. Maximum convergence measured with telescopic convergence rod in the field at the station 6F- 57LS was 48 mm. Maximum deformations observed by numerical modeling in the gallery was 58 mm. The numerical model was almost validated with the field monitoring data with 17% approximation, thus the numerical model can be used for prediction of strata behavior of future working.