Roof stability analyses of deeply-buried cavities based on nonlinear Baker criterion

Dynamic roof stability analyses of deeply-buried cavities were investigated in this study by an upper bound limit analysis, adopting a more general nonlinear Baker criterion, in contrast to Hoek-Brown and Mohr-Coulomb criterion which are mainly applicable to rock and soil medium, respectively. A curved failure mechanism for roof collapse was proposed in the realm of Baker criterion. Vertical seismic loading was considered herein. Work rate balance equation was then established after having computed external and internal rates of work. Based on the variational principle, the upper-bound formulation of roof collapse mechanism was derived with/without considerations of vertical earthquake effects. Accordingly, closed-form solutions of the failure surface, collapse height and width are explicitly obtained. At the same time, ABAQUS modelling was applied to verify the robustness and validity of closed-form solutions. Parametric studies were carried out to investigate the change law of the roof collapse mechanism under different parameters. The results indicate that apart from rock/soil properties, the upward seismic force has a significant effect on the failure region above cavity roof.