The in-ground type of LNG storage tank is constructed below ground level, except for its roof, and has a slurry wall bearing soil and pore water pressure to store LNG in a safe condition. During the long-term operation, soil freezing occurs around the in-ground storage tank, despite the insulation provided inside the concrete tank, due to the cryogenic temperature of LNG. Experimental and numerical studies were conducted on the soil-freezing characteristics and on the temperature distribution for an LNG storage tank constructed in coarse-grained and fine-grained soil; these are presented. A major concern is the ability to predict the freezing pressure from the results of laboratory freezing tests. The freezing pressure arising within the soil samples and the temperature of the samples inside were monitored with elapsed time. The degree of saturation versus freezing pressure curve is presented for fine-grained soil samples, and the maximum pressure is closely related to this curve. A time domain reflectometry apparatus was used to measure the volumetric water content by measuring the unfrozen water contents of frozen soils. This paper presents the results of the numerical analysis for the LNG storage tank in the West Sea LNG Receiving Terminal to evaluate the temperature distribution of 4 in-ground storage tanks. The connected observation between the results of a laboratory freezing test and the numerical analysis has revealed that the temperature variation of the concrete structure and soil is predictable, and the results are applicable in designing the in-ground storage tank.
INTRODUCTION The first liquefied natural gas (LNG) storage tank in Korea was completed at the Pyeongtaek terminal in 1986. The ice-lenses were developed downward against the side wall of the storage tank, because of the shearing stress from the freezing pressure (Goto and Ryokai, 1980; Goto et al., 1985).