In this study, behaviors of rock mass and discontinuities around cavern are simulated using mechanical and thermal properties of rock at low temperature. Simulation results show that temperature difference between before and after storage. When low temperature materials are stored in cavern, the temperature gradient is steep in early stage but it becomes gradual with time. UDEC simulation for LNG cavern shows that the range of the plastic zone induced by low temperature is approximately equal to a Width of the cavern.
As the consumption of LPG, LNG and refrigerated food increase, demands of the storage caverns for these materials are increasing in Korea. It is very likely that new facilities are located in underground space, because of the lack of ground space and safety concerns. The maintained temperature of LPG is about -40 to -45K and that of LNG is about -160K. Therefore, it is necessary to understand the characteristics of rock mass and discontinuities under the low temperature. In this paper, FLAC and UDEC programs using mechanical and thermal properties of rock at low temperature are used to simulate behaviors of rock mass and discontinuities around cavern.
Generally, strengths and Young's modulus of rock increased as temperature lowered. (Inada, 1989, 1993) Rocks become stronger and stiffer as they are refrigerated. They become weaker and softer if they undergo thermal cycle.(Park at al, 1998) For thermal conductivity of rock, Kuriyagawa (1980) reported that thermal conductivity is 10 to 20% higher at -l00K than at room temperature. Sundberg (1988) reported that the thermal conductivity of granite is similar with gneiss, and that rock has the higher thermal conductivity according to amount of quartz. According to these results, authors choose the input data as table 1. For analysis, commercial programs, FLAC and UDEC were adopted with user-defined functions to consider thermal dependent characteristics for mechanical properties of rocks. The user-defined function is in consisted of formula that isin correlation between mechanical properties of rock and low temperature. As the programs have being calculated, it is started with data like table 1. However, as the calculation is progressed.
