Failure mechanism analysis of ultra-large-section soft-rock roadway in kilometer deep coal mine and its collaborative control of "grouting-anchoring-pouring"

Deep high-stress, intense mining, and large deformation are key factors that contribute to the instability, failure, and difficulty in controlling the surrounding rock of roadways. Taking a ultra- large-section soft-rock roadway in typical kilometer deep coal mine as engineering, the failure mechanism of the roadway is analyzed using on-site test, theoretical calculation, numerical simulation, and engineering application. Firstly, the key mechanisms that induce roadway failure are systematically elucidated from the distribution of crustal stress, rock strength, and fractures development. Secondly, the expression for the limit equilibrium zone of roadway surrounding rock is derived through theoretical derivation, and the failure range at different positions is obtained through numerical simulation using deviatoric stress, plastic zone, and displacement as indicators. The key control zones are determined to be the roof and shoulder socket positions. Then, a control strategy is proposed for the anchor cable to pass through the peak stress line, and it is indicated that the minimum lengths of roadway roof, left rib, and left rib anchor cable support are 7.31 m, 7.285 m, and 7.235 m, respectively. Finally, a collaborative control of "grouting-anchoring-pouring" for ultra-large-section soft-rock roadway is proposed, and excellent control effects are achieved through engineering application, verifying the rationality of the research results.