Study on roadway deformation and control method under large mining height conditions

Focusing on the S1212 working face in Ningtiaota coal mine, this study investigates a soft mold filling wall as a primary support strategy for gob-side entry retention. The research aims to overcome the challenges of poor rock stability and complex support requirements under hard roof and large mining height conditions. A structural mechanical model of the surrounding rock was developed, from which a quantitative relationship between the support resistance of the soft mold filling wall and mining height was analytically derived. Numerical simulations were conducted to systematically investigate the effects of varying mining heights and wall widths on wall vertical stress, solid coal rib stress, and roadway deformation, thereby elucidating the load-bearing behavior of the wall and identifying optimal wall widths for different mining heights. The results demonstrate that: (1) At a constant mining height, vertical stress within the wall decreases progressively with increasing wall width, whereas at a constant wall width, increasing the mining height markedly amplifies vertical stress. (2) With increasing wall width, the solid coal rib peak stress decreases and its maximum shifts deeper into the rock mass, in contrast, under larger mining heights, the peak stress intensifies and migrates toward shallower zones. (3) Across varying mining heights, roadway floor heave exhibits an overall reduction with increasing wall width, however, the mitigation effect plateaus once the wall width surpasses a critical threshold. Integrating theoretical derivation with numerical analysis, the optimal wall width for the S1212 working face was determined as 1.4 m. Field validation further demonstrated that when the working face advanced 80 m, deformation of the surrounding rock stabilized, with a convergence deformation of 48.8 mm, thereby ensuring effective roadway stability control.