Surrounding rock stability and engineering practice of the 52607 working face approaching a fault-protected coal pillar

To clarify the instability behavior of surrounding rock and its control effect when a heading face approaches a fault-protected coal pillar, a combined approach involving in-situ stress measurement, theoretical analysis, three-dimensional numerical simulation, and field monitoring was adopted to investigate the displacement response, plastic-zone evolution, and applicability of the existing support system under different protective coal pillar widths. The results show that the in-situ stress field in the study area is a type-II stress field dominated by horizontal tectonic stress. The coupled effect of fault-induced structural weakening and stress concentration in the protective coal pillar significantly aggravates the deformation and plastic failure of the surrounding rock, and the surrounding rock stability is highly sensitive to the protective coal pillar width. Under fault dip angles ranging from 54° to 70°, representative protective coal pillar widths of 10, 20, 30, and 40 m were selected for theoretical analysis and numerical simulation. The results show that the displacement response and plastic-zone development of the surrounding rock exhibit obvious zonal characteristics with decreasing protective coal pillar width. In particular, when the protective coal pillar width decreases to 10–20 m, the fault-induced disturbance has a more significant influence on roof deformation, rib convergence, and plastic-zone expansion; when the protective coal pillar width increases to 30–40 m, the fault disturbance effect weakens markedly. Numerical simulation results further indicate that when the width of the protective coal pillar is less than 20 m, the plastic zone of the coal pillar expands significantly and its stability decreases markedly. Field monitoring results are generally consistent with the numerical simulation results, indicating that the existing bolt-cable support system can effectively control the deformation of surrounding rock in near-fault roadways. The results can provide a basis for stability analysis and support design of roadways in fault-protected coal pillar zones.