Numerical modelling of retaining structure displacements in multi-bench retained excavations

Abstract

This investigation aims to analyse the influencing factors on performance and the optimal retaining layout of multi-bench retained excavations in clay. A numerical model incorporating the hardening soil small strain model, capable of reasonably estimating the retaining structure displacement and ground settlements, is first validated with a case history in Tianjin, China. Subsequently, the geometric parameters, including the bench width (B), the second row of retaining piles length (L2), the first row of retaining piles length (L1), and the second excavation depth (H2), on the retaining structure displacement (δh1,max) are analysed. Furthermore, a sensitivity analysis is performed, and the optimal layout of a multi-bench retaining system is estimated through a multivariate adaptive regression splines procedure. The results indicate that the influencing parameters have a coupling effect on the retaining structure performance. The B value is the most sensitive factor on the δh1, max value, followed by the L1, the H2, and L2 values. A large bench width weakens the interaction effect between two rows of retaining piles, but it significantly reduces the δh1, max value and provides a cost-effective solution for engineering practice. An optimal H2 value of 0.5 He (He is the excavation depth) is found.