Analysis of Three-Dimensional Effects of a New Prefabricated Recyclable Retaining System

A novel, resilient, prefabricated, and recyclable retaining system is proposed for underground excavations, comprising a rigid steel frame and flexible steel panels. Laboratory model testing and finite-element simulations are conducted to evaluate the influence of three-dimensional (3D) effects on the system behavior during excavation. It is found that the length (L) and depth (He) of the excavation have a great influence on the lateral wall deflection (δh), while δh is insensitive to the variation of excavation width (B). A ground surface settlement model is proposed, consisting of a primary influence zone (0–1.5·He, and δvm at 0.15·He) and a secondary influence zone (1.5–4.0·He). The ratio of δvm/δhm varies between 0.6 and 1.2, with an average value of 0.85. Parametric analyses show that the L/B ratio can hardly affect the results of the plane strain ratio (PSR). Moreover, a modified equation for the PSR is presented to characterize the trends in the numerical results. Based on the numerical contours of failure zones, a simple theoretical model is proposed to calculate the active earth pressure (pa), which considers the impacts of wall movements and cohesion stress (c) on the mobilization of inclination angle of failure surface (θ). The derived θ-method provides better predictions on pa.