In order to characterize the hydraulic behaviors in the vicinity of underground LPG storage cavern, the authors conducted the in-situ air-tightness experiment in an unlined cavern and the numerical assessment to evaluate the air-tightness of experiment cavern during pressurization in advance. For the numerical air-tightness assessment, firstly, various hydraulic conductivity data and monitored hydraulic behaviors are applied in a new 3-dimensional hydro-geological modeling method to characterize the hydraulic behaviors in fractured rock mass with high accuracy. Secondly, based on the constructed hydro-geological model, the authors simulated the in-situ air-tightness experiment by the new self-developed hydro-mechanical coupling analysis method based on discrete element method (DEM).With detail hydraulic behaviors characterization at the vicinity of unlined cavern, the assessment achieved to predict the leakage occurrence accurately.


In Japan, the constructions of the world largest underground LPG storage facilities are proceeding at two sites, in Namikata and Kurashiki. The hydraulic containment system is adopted to prevent leakage of the reserved LPG by hydraulic flowdirection to the cavern at the two sites. Consequently, the hydraulic behaviors in the vicinity are essential to ensure the air-tightness of the unlined LPG storage cavern. In order to characterize the hydraulic behaviors in the fractured rock, the authors conducted an in-situ air-tightness experiment at an unlined cavern in Namikata, Japan. Additionally, the author also conducted a numerical air-tightness assessment of the experiment cavern based on the self-developed hydro-geological modeling method and hydro-mechanical coupling analysis method. The assessment results were compared with the in-situ experiment results to verify the applicability.

2.1 Location and layout

The in-situ air-tightness experiment site was located at Namikata underground LPG storage base. The elevation of experiment site (EL −125 m) is above the storage tanks (EL −150 m).

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