The underground LPG storage plant is one of the new style energy storage facilities, which have large rock caverns with high internal gas pressure. The gas storage design basically relies on the water pressure in the surrounding rock being more than the ‘escape’ pressure of the stored gas. Therefore, it is important to prevent gas leakage through the conductive fracture networks formed by fracture initiation, propagation and coalescing phenomenon due to the fluid pressure. Distinct Element Method (DEM) using Bonded Particle Model (BPM) is convenient to simulate such process of fracturing as the progressive breaking of discrete bonds. Potyondy & Cundall (1999) suggested the hydro-mechanical coupled formulation that utilizes DEM and channel and domain network concept. However, this formulation has never been extended to the threedimensional rock deformation and fracturing issue caused by the interaction of gas and liquid. Thus, in this study, the authors develop the three-dimensional hydro-mechanical coupled analysis that can express rock deformation and fracturing coupled with fluid flow of gas and liquid. The applicability of this method is examined through the case study of the actual air cushion surge chamber (ACSC), which has experienced not only the leakage of high pressured air from the rock cavern but also the air leakage-control with water curtain. The proposed method shows high performance to evaluate the air leakage and air tightness.
The underground LPG storage plant and CAES (Compressed Air Energy Storage) plant are new style energy storage facilities, which have large rock caverns with high internal gas pressure. The gas storage design basically relies on the principle ofwater pres-sure in surrounding rock being more than the ‘escape’ pressure of the stored gas. However, the surrounding fracture network effects air tightness performance of storage cavern, the leakage mechanism is governed by fracture initiation, propagation and coalescing phenomenon resulted from the variation of fluid pressure. Therefore, for the planning and designing of gas storage caverns with high internal pressure, it is required to predict the generation of fracture network due to internal gas pressure and evaluate the amount of gas leakage through the fracture network with taking the effect of groundwater flow that governs the gas penetration to rock mass into account. Particle flow code (PFC) described by Cundall & Strack (1979) is convenient to treat such process of fracturing as the progressive breaking of discrete bonds. Potyondy & Cundall (1999) suggested the hydro-mechanical coupled formulation that utilizesDEMand channel-domain network concept.
The concept of the hydro-mechanical coupled model formulated by Potyondy & Cundall (1999) is shown as in Figure 1. Rock mass is represented by the bonded particle assemble. A closed loop surrounded by the bonded particles, is called a ‘domain’ that acts as a notational void in rock mass. A segment that links two neighboring domains is called a ‘channel’that acts as a notational crack with a specific aperture.