Response of dual-row retaining pile walls under surcharge load

Abstract

Deep foundation pits are usually located in densely built-up areas, and its stability is affected by adjacent structures. A few studies have considered the effect of surcharge load on the stability of foundation pits; such effect may lead to excessive deformation or even collapse. To determine the mechanical response of dual-row pile walls (DRPWs) in foundation pits under the action of surcharge loading, a physical scaling model test and numerical simulation were conducted, and a method to determine the influence of overloading was provided. Five physical scaling model test schemes were proposed; electronic displacement gauges, strain gauges, and pressure sensors were installed to test the static response of a DRPW under excavation and surcharge load. The effects of loading distance and load magnitude on the bending moment, pile head displacement, and pile shaft deformation of DRPWs were also investigated. The relationship between overload and the mechanical response of DRPWs was quantified, and the results of physical model tests were verified by numerical simulation. Results showed that surcharge loading has a negative effect on the stability of DRPWs in foundation pits, and the deformation of DRPWs is negatively correlated with the loading distance of surcharge load. The critical value of the loading distance of surcharge load is 0.5 times the excavation depth. When the loading distance is less than the critical value, the overload causes remarkable displacement and inner force of the DRPW. Moreover, the deformation of the DRPW is positively correlated with the surcharge loading magnitude. With the increase in vertical loading, the displacement of soil increases nonlinearly, and the circular sliding surface through the excavation bottom is finally formed. The results of this study provide some references for the design and construction of DRPWs.