Roof Collapse Mechanism of Weak Surrounding Rock for Deep-Buried Tunnels under High Geostress Conditions

High geostress, a typical attribute of tunnels located at significant depths, is crucial in causing stress-induced failure and influencing the stability of the tunnel crown. This study developed an analytical method for the failure mechanism that occurs in deep-buried tunnel roofs, taking into account the influence of geostress. The limit analysis theory was utilized for deriving analytical solutions about the geometry of the collapsing surface and the limit supporting pressure. The collapsing surface obtained by the analytical solution was validated by the findings of the physical model test, which shows a high level of agreement with the actual one. An extensive investigation was done to explore the effects of the lateral pressure coefficients, the tunnel buried depth, the geological conditions of the surrounding rock, the long-short axis ratio, and the size of the tunnel profile. The findings indicate that an increase in the lateral pressure coefficient from 0.5 to 1.5 results in a reduction in the height of the collapsing zone by 2.08 m and the width of the collapsing zone by 1.15 m, while simultaneously increases the limit supporting pressure by 18.9