Design optimization and observed performance of a super-large foundation pit excavation subjected to unsymmetrical loading in water-rich floodplain: A case study

Abstract

In this work, a whole-process solution was presented to reduce the risks of a super-large foundation pit excavation in water-rich floodplain and subjected to unsymmetrical loading. Firstly, numerical simulations were conducted to study the “size effect”, and the optimal control measures were proposed, i.e., 2 circles of diaphragm wall were used to divide the original super-large foundation pit into the inner and the outer pits, and the central-island style zoned excavation was adopted. Similarly, the “unsymmetrical loading effect” was studied, and the optimal control measure was proposed, i.e., an additional level of horizontal struts was added at the side with unsymmetrical loading. Then, considering the above suggestions, the design optimizations of supporting system, water proof system, and construction sequence were conducted. Next, a numerical model considering the adopted design optimizations was established to predict the excavation-induced retaining wall deflection, ground settlement, etc. Finally, an automatic and manual monitoring combined system was established, and the deformation and force behaviors of the foundation pit excavation were captured to verify the rationality of the adopted design optimizations. According to the observed performance, the risk assessment, warning, and disposal were conducted. The research can provide useful experience for similar projects.