Elastic–Brittle–Plastic Analysis of Circular Deep Underwater Cavities in a Mohr-Coulomb Rock Mass Considering Seepage Forces

Abstract

In a drained underwater cavity, seepage forces and pore-water pressure that develop around the cavity may affect the response of the rock mass. In this paper, a fully analytical solution is proposed for analysis of underwater cavities excavated in elastic–brittle–plastic and Mohr-Coulomb rock material, considering the induced seepage forces under steady-state flow. The initial stress state is assumed to be hydrostatic, and the seepage flow is assumed to be radial; thus, the problem is considered axisymmetric. In the proposed solution, in contrast to the failure processes that are represented as a function of Terzaghi’s effective stresses, the induced deformations are considered as a function of Biot’s effective stresses. The proposed solution is used to explain the behavior of cavities under different hydromechanical conditions. The results show that, in the case of drained cavities, seepage flow causes the induced radial displacements to increase and the stability of the cavity to decrease. From a practical point of view, the simplified analytical solution presented in this study can be used to approximate the design of circular cavities, such as a tunnel excavated below a water table, under seepage forces.