Analysis of spatiotemporal evolution characteristics of floor rock mass and roadway failure under mining influence

Clarifying the distribution law of mining induced stress in the working face floor, achieving precise grasp of the degree of damage to the floor rock mass and roadway under the influence of mining, can effectively prevent deformation and instability of the floor roadway. To this end, according to the limit equilibrium theory, the mechanical model of advanced mining stress of coal and rock mass is constructed, and the mechanical distribution law of floor rock mass in the supporting pressure disturbance stage and the goaf unloading stage is obtained. Based on the compression shear failure criterion and rock unloading damage mechanism, the spatiotemporal evolution characteristics of floor rock and tunnel surrounding rock failure were obtained, and further reliability verification was conducted using numerical simulation. The results show that as the mining height increases, the range of plastic zone in front of the working face increases, the concentration coefficient of advanced support pressure decreases; The larger the supporting pressure of the advanced mining, the smaller the principal stress difference in the bottom slate rock body, and the smaller the Mohr stress circle radius, and the strength of the impact on the bottom plate weakens, specifically manifested as a decrease in the depth of rock compression shear failure in the bottom plate; After unloading, the stress state of the bottom rock mass is the same. With the increase of the unloading starting point of the rock mass, the unloading amount increases, and the unloading tension failure intensifies. The plastic zone of the bottom rock mass presents a “saddle shaped” shape; During the advancement process, the plastic zone of the surrounding rock of the tunnel undergoes a spatiotemporal evolution from “elliptical” to “butterfly” to “vertical elliptical”. The greater the mining support stress, the more severe the tunnel damage, and the damage is mainly concentrated in the roof and shoulder corners. The initial mining height is designed to be 3.5 m. Through the deployment of an optical fiber testing system, the spatiotemporal evolution of deformation and failure of the floor rock mass and roadway during the mining process as the working face advances was obtained. The maximum depth of damage to the floor rock mass was measured to be 16.7 m, and the maximum depth of damage to the roadway rock mass was 5.2 m. The surrounding rock mass of the tunnel remains stable throughout the entire monitoring period, without any destructive effects, meeting production safety requirements. © 2024 China Coal Society. All rights reserved.