Study on deformation and failure characteristics and support optimization of surrounding rock in strong water-drenching soft rock roadway

Under the dual effects of mining influence and water erosion in soft rock roadway, the deformation and failure of surrounding rock of roadway are serious, and the water spray makes the anchoring agent fail, resulting in the attenuation of anchoring force of bolt and anchor cable and the decrease of bearing capacity, which seriously affects the safety production of working face. Taking a coal mine as the engineering background, the research methods of physical similarity simulation, numerical simulation and field measurement are used to analyze the failure range and fracture development of water-drenched soft rock roadway under the influence of mining and different support parameters. The deformation and failure characteristics of surrounding rock of water-drenched soft rock roadway under mining are revealed and reasonable support parameters are given. The results show that the deformation and failure modes of surrounding rock in soft rock roadway affected by mining are asymmetric, and the failure range of surrounding rock in roadway increases further under the condition of water spraying. As the length of the anchor cable increases from 9m to 10m, the damage range of the surrounding rock of the roadway decreases by 4.3 %. The failure range of the roof and two sides of the 12.2m long anchor cable is larger than that of the 9m anchor cable and the 10m anchor cable. The main reason is that the 12.2m anchor cable penetrates into the roof aquifer, which leads to the aggravation of water seepage and the further softening of the surrounding rock of the roadway. When the combined support of ' 9.2m long anchor cable + 4.2m short anchor cable ' is used, the surrounding rock damage and water seepage of the roadway are significantly reduced compared with the previous support parameters. Compared with the 10 m anchor cable with the smallest damage range in the first three support schemes, it is reduced by 37.5 %. According to the results of physical similarity simulation and numerical simulation experiment, the combined support method of ' 9.2 m long anchor cable + 4.2 m short anchor cable ' is proposed. The field application shows that the subsidence of roadway roof is obviously reduced, and the deformation and failure of roadway surrounding rock are effectively controlled.