Settlement Analysis of a Large Pile Group Supporting an LNG Storage Tank

Liquefied natural gas (LNG) storage tanks are often supported by large pile groups (>100 piles). The design of such foundations is generally governed by settlement rather than bearing capacity. However, minimal information is available regarding the settlement performance of the LNG tank foundations. This article first presents a comprehensive program of the settlement analysis for an LNG tank foundation comprising 1600 driven concrete piles. The field test program, including site characterization, pile load tests, and hydrotest, was performed. The test data were used to calibrate and assess four different methods for group settlement calculation, including the equivalent raft method, equivalent pier and equivalent raft method, nonlinear interaction factor method, and 3D continuum finite element method. The parametric analyses were further conducted using these methods to evaluate the effects of different factors on the group settlement. This study highlights (1) the importance of considering the deep soil condition (below pile toe to a depth of 1.5 times group diameter), which contributes to 78%–89% of the total settlement, (2) the drastic difference in load transfer mechanisms between central piles and perimeter piles, and (3) the need for considering the self-weight of tanks in the settlement analysis.