Frozen earth pressure on the inground LNG tank wall

LNG, when stored inground, will freeze the surrounding ground with its low temperatures (about-160° C). Therefore the surrounding ground expands due to freezing of pore water and to formation of ice lenses from water sucked from the unfrozen soil. Consequently the surrounding unfrozen ground is pressed and the tank wall sufferes frozen earth pressure as a reaction. To measure the frozen earth pressure, earth pressure cells are usually set up on the tank wall, but it is difficult for conventional cells to measure in the frozen soil because of its a low- temperature and high-stiffness. Therefore, there have been very few reports on frozen earth pressure on a practical LNG tank wall. This report describes the frozen earth pressure being measured on a inground LNG tank with a capacity of around 60,000Kl which have been operating about 5 years. The frozen earth pressure is directly measured by a specific low temperature earth pressure cell with a diameter of 60 cm pressure-sensitive part. The measured values correspond relatively well with the calculated values by axial symmetrical FEM.