Numerical simulation on overburden stability during successive mining of large mining height working faces

To address the stability issues of surrounding rock during successive mining in large-height mining faces, this study establishes a numerical model using Phase 2D finite element software to systematically investigate the evolution characteristics of plastic zones in overburden strata, surface subsidence, roof convergence, and stress distribution in protective coal pillars under different mining heights. The results demonstrate, With the increase of mining disturbance, the scope of overburden failure and the degree of deformation gradually increase. When the mining height is 5 m, the number of failure units in the overburden plastic zone is 547 after the first mining face is mined, and surges to 3984 after the second mining face is mined. The plastic zone exhibits an arched feature of "wide upper part and narrow lower part" and expands toward the roof. The maximum surface subsidence increases from 0.14 m to 0.52 m; the roof subsidence increases from 0.30 m to 0.65 m; and the peak abutment pressure of the protective coal pillar increases from 58.36 MPa to 130.16 MPa. Enhanced mining heights significantly reduce overburden stability during successive mining operations. When mining height increases from 3 m to 5 m, the plastic failure units increase by 107%, surface subsidence escalates by 271%, roof convergence amplifies 282%, and the abutment pressure coefficient in coal pillars rises from 3.68 to 8.38. This research reveals the substantial impacts of mining height and face succession on overburden stability.