Influence of seam spacing and lateral pressure on deviatoric loading of the withdrawal roadway surrounding rock under the goaf.

Abstract

Addressing asymmetric deformation, failure in the withdrawal roadway, and support crushing caused by overburden structure at final mining under the goaf. The stress evolution pattern of the surrounding rock in the withdrawal roadway and the dynamic characteristics of the maximum deviatoric stress zones (MDSZ) during this period were analyzed. The effect mechanism of the lateral pressure coefficient (LPC) and the coal seam spacing (CSS) on the stress distribution of the surrounding rock was explained.The LPC and CSS have a nonlinear effect on the rock stress redistribution of the withdrawal roadway. As the LPC increases, the peak abutment pressure on the non-mining side initially rises then stabilizes. The change in principal stress ahead of the advance working face (AWF) shows an "N"-shaped trend, and the maximum deviatoric stress (MDS) on the non-mining side first decreases and then increases. As the CSS increases, the peak abutment pressure and deviatoric stress on the non-mining side initially decrease and then increase. When the CSS is 75 m is comparable to that in the absence of an overlying goaf. The evolution model of the MDSZ in the retreat channel surrounding rock comprises four stages: low values at both sidewalls → value growth at both sidewalls → maximum value and zone at the goaf-side rib (G-SR)→ maximum value and zone at the solid-side rib (S-SR). A collaborative control scheme of "anchor cable reinforcement support on the S-SR" and "pre-splitting roof cutting on the G-SR" was proposed. Field application shows the sidewall displacement is about 150 mm, and the roof displacement is about 200 mm, which ensures the safe withdrawal of equipment. The research results serve as a valuable reference for similar engineering practices.