A dual spring solution for lateral pile-soil interactions considering disassembly responses induced by tunnelling

When employing a two-stage analysis method to evaluate the impact of tunnel excavation on existing pile foundations, the differences in pile-soil interactions between the side distant from the tunnel (passive side) and the side adjacent to the tunnel (active side) are generally neglected. Homogeneous soil springs are commonly used, which fail to accurately capture the true stress and deformation behaviour of piles, thus limiting computational accuracy. To improve the accuracy of analytical predictions, this study proposes a dual-spring analysis method that separately accounts for pile-soil interactions on the passive and active sides. By distinguishing the soil springs on the two sides, the proposed method provides a more refined representation of the mechanical behaviour of the pile-soil system under tunnel excavation. Furthermore, methods for determining the stiffnesses of these springs are presented. The soil spring models incorporate CPT test data, enhancing their practical relevance and engineering applicability. Comparisons with a centrifuge test case and results from a conventional two-stage analysis method using a single soil spring validate the accuracy and superiority of the proposed method. This study provides a valuable reference for relevant engineering analyses.