Asymmetric failure behavior of surrounding rock in the deep roadway: A semi-analytical solution

With increasing buried depth, the true three-dimensional asymmetric stress environment of deep strata changes the failure mode of roadways. Therefore, a mechanical model under the superposition of the geostress field and the mining stress field is established to highlight the failure characteristics of the surrounding rock. Based on four different strength criteria, the semianalytical solution of the plastic zone (PZ) boundary under asymmetric stress is derived. The influence of the roadway buried depth, geostress deflection angle, lateral pressure coefficient, and mining stress concentration coefficient on the polymorphic evolution of the PZ are analyzed. The results show that the asymmetric concentration of stress, especially shear stress, is the internal cause of asymmetric failure behavior in roadways. The rock's nonlinear mechanical behavior and intermediate principal stress significantly affect the shape and size of the PZ. The PZ presents three different shapes: circular, oval, and petal-shaped, and the shape is closely related to the newly introduced equivalent lateral pressure coefficient. Furthermore, the proposed solution is used to analyze a field case, and the calculation results align well with the measured data. This paper contributes valuable insights into the PZ in deep surrounding rock and guides the design and construction of deep roadways.