FAILURE INITIATION AND MODES OF HOEK-BROWN ROCK MASSES SURROUNDING UNDERGROUND STORAGE WITH HIGH INTERNAL PRESSURE

The critical issue for the design of highly pressurized caverns is the uplift failure. A reasonable evaluation of the failure path including the initial failure location and direction of the crack propagation is needed. A series of numerical analyses based on the finite element method was conducted in the framework of the 2D axisymmetric model by considering the variety of rock mass properties, cavern depth, and in-situ stress ratio. The wide range of the natural rock mass properties (rock strength) and initial stress conditions surrounding the cavern, which include in-situ stress ratio and depth of tunnel were considered in this investigation. To detect and distinguish the location of failure initiation and failure modes between tensile and shear failure, the tensile criterion and Hoek-Brow failure criterion are utilized, respectively. The numerical results indicated that the rock strength has a strong effect on the initial failure mode while the initial failure location strongly depends on the in-situ stress ratio and rock strength. The charts of failure mode and initial failure location were created by using the relationship between unconfined compressive strength and tensile strength of rock mass and initial stress condition, respectively.