Group efficiency and load transfer mechanisms of semi-rigid soil–cement piles: integrated experimental, 3D numerical, and analytical evaluation

Understanding the group behavior of semi-rigid soil–cement piles remains a major challenge in deep-mixed foundation engineering. Unlike conventional displacement piles, soil–cement columns exhibit transitional stiffness and composite interaction with the surrounding ground, leading to settlement-dependent mechanisms that are not captured by existing group-efficiency approaches. This study integrates rare full-scale load tests, carefully calibrated three-dimensional finite-element analysis (3D FEA), and systematic analytical benchmarking to establish a mechanistic basis for evaluating group efficiency in soil–cement pile groups. Instrumented field tests on single, three-pile, and five-pile groups (S/D = 2)…