On the soil-pile interaction system of piles adjacent to tunnelling: A reaction curve approach

The two-stage method has been widely used to analyse the behavior of passive piles subjected to excavations. However, this simplified method ignores the constraint effect of the pile on lateral soil movement and adopts approximately the same soil stress-strain characteristics around the pile. Moreover, it cannot capture the tunnelling process and unloading effects on the variation in nonlinear soil springs. Therefore, it is essential to transcend the two-stage analytical framework and develop a directly coupled one-step solution approach grounded in the actual response of piles adjacent to tunnelling. In this study, a reaction curve approach for a soil-pile interaction system due to tunnelling was proposed, and its performance was verified by comparison with the two-stage method. The reaction curves derived from a sufficient number of numerical operations with different parameters of piles, soil, and tunnels describe the coupled response of the soil-pile system, specifically, the relationship between the lateral pile displacement and the reaction force applied to the pile shaft owing to excavation-induced soil movements. Furthermore, cone penetration test (CPT) profiles were incorporated into the reaction curve model to enhance its practicality. The reaction curve approach demonstrates substantial advantages in predicting the lateral responses of piles adjacent to tunnelling.