Cement soil stabilization for underground liquid natural gas storage

Abstract

The underground liquid natural gas (LNG) storage system in soil at a shallow depth has benefits in terms of low LNG weathering in tanks due to radiant heat from the sun, less land occupation, and high safety. However, the soil surrounding the underground LNG storage system may experience subzero temperatures and freeze-thaw (F-T) cycles, which may cause damages to adjacent facilities due to freezing expansion and weaken the soil strength. Hence, this study proposed the use of cement stabilization to improve the surrounding soil for the underground LNG system. For this purpose, physical, mechanical, and thermal properties of cement-stabilized soils under subzero temperatures and F-T cycles were investigated. The volumetric expansion of stabilized soils (1.3–1.7%) was significantly lower than that of untreated soils (4.2–10%) at subzero temperatures, which is beneficial for mitigating the potential damages to adjacent facilities due to freezing expansion. A significant deformation was observed in untreated soils after one F-T cycle, while no visible cracks or deformations were observed in stabilized soils with slight strength reduction after 12 F-T cycles, indicating good resistance under F-T cycles. The thermal conductivity of stabilized soils was 19–36% lower than that of untreated soils at both ambient and subzero temperatures, which can decrease the heat transfer rate between the internal and external environment. Overall, cement soil stabilization is beneficial for improving the performance of underground LNG storage system.