Abstract
<title>Abstract</title> <p>In-situ stress is the fundamental force driving the deformation and failure of surrounding rock masses. To elucidate its effect on roadway instability, this study introduces an enhanced numerical approach. The tangential contact force was determined by incorporating the slip change rate and maximum static friction, while an elastic-plastic failure criterion was adopted to model the yield behavior of rock deformation. Based on these improvements, an optimized Y-Mat program was developed to simulate the mechanical responses of surrounding rock after roadway excavation under both uniform stress and gradient differential stress conditions. The main conclusions are as follows: (1) In homogeneous surrounding rock, the primary deformation modes are roof subsidence and floor heave, predominantly governed by plastic flow. While high in-situ stress does not alter these deformation modes, it significantly exacerbates the degree of damage. (2) Stress with a gradient difference closely replicates actual stratigraphic stress states. Under such conditions, shear cracks frequently develop near the roadway, with the failure zone exhibiting a trapezoidal shape. The concentrated crack propagation is mainly oriented in the vertical direction, opposite to the direction of major deformation. (3) The evolution of the stress field is intrinsically linked to changes in the strain energy density field. When the strain energy density of the rock mass reaches a critical threshold under a new stress state, the rock yields or fails, releasing strain energy. The combined influence of the surrounding rock stress field and the strain energy density field dictates that roadway deformation and failure follow distinct patterns at different stages and locations. These findings provide a scientific basis for improving support design and enhancing the safety and sustainability of deep underground engineering.</p>