Stress Distribution During Extraction of Pillars in a Thick Coal Seam

Summary

This paper presents field observations on distribution of vertical stress during an experimental trial of extraction of pillars in four panels in 6.0–8.0 m thick coal seam, as a part of a Science and Technology project funded by the Ministry of Coal, Govt of India. Variation of induced stress based on continuous monitoring data for the first time in Indian coal mining scenario showed distinct anomalies and potential for better understanding of strata mechanics and warning of major roof falls during pillar extraction. Numerical model studies based on finite difference code – FLAC were also conducted for stress analysis in idealized pillar mining sequence so that the influence of each stage of extraction could be identified. The numerical model results on stress concentration over the pillars, stooks and ribs showed variation of 3.6%, 8.3% and 6.1%, respectively as compared to the field observations for 7 m thick coal seam at a depth cover of 60 m from the surface. This indicates validity of the numerical models for stress analysis in the simulated conditions of the present field experiments.