Buckling Failure Mechanism of a Rock Plate Under Multi-directional Constraints

Buckling failure is one of the common failure modes in the process of deep tunnel excavation, which poses severe challenges to the safe construction of tunnels. To investigate the failure mechanism of surrounding rock buckling of rock plates in a deep tunnel, multi-directional constrained buckling experiments under different lateral stresses were conducted on red sandstone plates using a true-triaxial testing system. The buckling failure experiments were undertaken to investigate the mechanical properties, buckling failure process, failure mode, and buckling failure mechanism of rock plates. The results show that when the lateral pressure is the same (σ x = σ y ) and the lateral pressure is small (σ x = 0–6 MPa), an X-shaped failure occurs, and there is a plastic deformation stage seen before reaching the peak of the load–deflection ( F − ω ) curve; with the increase of lateral pressure (σ x = 15–42 MPa), the failure mode of the rock plate gradually changes to spalling failure. The X-shaped crack shape and spalling shape of rock plate are controlled by the ratio of lateral stresses. According to the numerical simulation, when the X-shaped failure occurs in rock plate, the crack starts from the bottom center and then propagates to the edge under the maximum tensile stress; when spalling failure occurs, the maximum tensile stress on the bottom surface forms an elliptical area, and the cracks initiate and expand under the action of the maximum tensile stress, and finally coalesce to form a macroscopic fracture surface.