A Numerical Simulation of the Subsidence Reduction Effect of Different Grouting Schemes in Multi-Coal Seam Goafs

Abstract

Grouting is the most widely used technology for treating coal goafs. In this study, a numerical simulation method was used to establish a model of multi-seam goafs with different spacing conditions to investigate the subsidence reduction effects of various grouting schemes on multi-coal seam goafs. By varying the range and opportunity of grouting treatments, the effects of coal seam spacing, grouting treatment range, and grouting opportunity on subsidence reduction were analyzed. The results showed that: (1) With constant overburden (OB), the subsidence reduction ratio of the subgrade center increases linearly as the interburden (IB) decreases (1 ≤ OB/IB ≤ 2), then increases exponentially (2 < OB/IB), and eventually becomes stable. (2) When treatment is conducted based on the half-width of the subgrade, the width of the subgrade, and the range of the trapezoid, residual surface subsidence tends to adopt an inclined ‘W’-shape in open cutting. The surface residual subsidence exhibits a symmetrical ‘W’-shape when full-range grouting is adopted. (3) For a multi-coal seam goaf with longer mining stoppage time, the subsidence reduction ratio of the subgrade center is lower, and it is exponentially related to the grouting opportunity. As the grouting opportunity is extended and OB/IB decreases, the subsidence reduction ratio of the subgrade center declines exponentially.