Abstract: Pile groups with members of different lengths can mitigate differential settlement among foundation piles, prevent basin settlement, and ensure consistent reliability indicators across individual piles. This paper presents an approach for analyzing the reliability of pile groups with dissimilar pile lengths in spatially variable expansive soils under rainfall. The variation of soil matric suction with depth under rainfall infiltration conditions was analyzed by numerical simulation software. The Karhunen-Loève (KL) expansion method is used to discretize random fields. The pile-pile and pile-soil interactions in a pile group with dissimilar pile lengths, and the influence of the reduction of matric suction on the ultimate bearing capacity of the piles are analyzed using the modified load transfer method (LTM). The first-order reliability method (FORM) is employed to solve the reliability indices of each pile in a pile group, and the sequential component method (SCM) is adopted to estimate the reliability index of the pile group. Parametric studies show that increasing rainfall intensity and duration reduce the reliability indices of both individual piles and the pile group.

Key words: spatial variability, reliability, pile, load transfer method, random field