Study on the Evolution Mechanism of the Butterfly-Shaped Plastic Zone in Surrounding Rocks of an Underlying Roadway

The mining of the working face has a pronounced influence on the floor roadway, resulting in the intensification of deformation of the surrounding rock of the roadway and posing a threat to production safety. To clarify the failure mechanism of the surrounding rock of the dynamic pressure roadway and to understand the development pattern of the plastic zone shape, in this paper, by integrating the stress distribution law of the floor during the mining process of the working face, a mechanical model of the surrounding rock of the floor dynamic pressure roadway is established. An analytical solution for the plastic zone shape of the surrounding rock of the dynamic pressure roadway is proposed and verified through a comparison between analytical calculations and numerical simulation (using FLAC3D 7.0 software). The results indicate the following: (1) when the horizontal distance between the working face and the roadway exceeds 35 m, no obvious changes are observed in the development pattern of the plastic zone of the surrounding rock of the roadway; (2) when the horizontal distance is less than 35 m, the rate of change in the maximum value of f increases from 0.02 MPa/m to 0.205 MPa/m as the vertical distance decreases, and the β value increases from 0.09°/m to 0.79°/m. The maximum development depth increases, the butterfly leaf of the plastic zone deflects towards the working face direction, and the shape gradually transforms from a “circular” shape to a “butterfly” shape. (3) The morphological characteristics of the plastic zone obtained by the analytical algorithm are highly consistent with those obtained by the numerical simulation method, suggesting that the analytical algorithm possesses certain validity. (4) There exist certain errors between the analytical method and the numerical simulation results, and they increase with the increase in the vertical distance (the error range is 19.4%~54.9%), but they can be disregarded within the requirements of engineering accuracy.