Study on Reasonable Chain Pillar Size in a Thick Coal Seam

Abstract

In order to solve the problem of low coal recovery rate caused by leaving large coal pillars in deep mines, the study determined the reasonable width of the section pillar, which based on the theory of coal pillar stress distribution, taking the 4102 headgate of Wenjiapo coal mine as the engineering background. Field monitoring and numerical simulation results show that the influence range of the lateral abutment pressure in the goaf is 50~56 m, and the abutment stress distribution in the coal pillar resembles a hump with two peaks of 38.9 MPa and 33.6 MPa, respectively. The positions of the double peaks are located at 12 m and 36 m in the coal pillar, respectively. In the range of “hump,” the section pillar vertical stress is in the original rock stress and is relatively stable. It can be regarded as an elastic zone in the coal pillar with strong bearing capacity, the coal in other areas have already undergone plastic yielding, and the bearing capacity has been reduced; the width of coal pillars in the determined section has been reduced from 46 m to 33 m, which is a reduction of 13 m. The research results have been applied in the 4106 headgate in the same mining area, and good test results have been obtained. The maximum subsidence of the roof-to-floor and rib-to-rib convergence is 286 mm and 150 mm, this indicates that its deformation was within the allowable limits, and the cross-section area was sufficient to satisfy the requirements.