Study on the deformation failure mechanism and coupling support technology of soft rock roadways in strong wind oxidation zones

Due to the influence of sedimentary environment, the coal seams and overlying rocks in the wind oxidation zone exhibit developed fractures, high rock porosity, strength attenuation, and poor self-stability. It leads to the large deformation of the surrounding rock and managing the roof of roadways difficultly. This made the roadway excavation extremely difficult. And the rendering conventional "bolt-cable-mesh (belt)-shotcrete" combined support system was not applicable. In this paper, the No. 49,104 air return roadway in the strong wind oxidation zone of the Shuiquan Coal Mine was selected as the engineering background. The change trends of the coal and rock in the strong wind oxidation zone physical and mechanical properties were revealed, and the deformation and failure mechanism was analyzed. According to the deformation and failure characteristics of the roadway in the wind oxidation surrounding rock with engineering practice, a coupling support scheme "pregrouting + anchor net and sprayed concrete + inverted arch structure + U-shaped steel + high and low-pressure, deep and shallow-hole reinforcement grouting" was proposed. A roadway grouting reinforcement diffusion range model was established in COMSOL Multiphysics, and the grouting diffusion range was then imported into FLAC3D to compare and analyze the coupling support scheme reinforcement effect of roadway in the strong wind oxidation zone. And the coupling support scheme was used to reinforce the No. 49,104 air return roadway, and the reinforcement effect was monitored in situ. Results showed that the proposed coupling support and reinforcement scheme can be employed to effectively control the deformation of the surrounding rock and the expansion of plastic zone damage. And the stability and safety of the roadway were significantly improved. This coupling support scheme was reasonably designed, and it could provide an engineering reference for the support and reinforcement of roadways in weak and crushed surrounding rocks under similar geological conditions.