Optimization design of retaining system for deep foundation pits under complex environmental conditions

The increase of embedded depth of retaining wall, reinforcement of foundation soil and set-up of partition wall between foundation pits and buildings are widely-used techniques to protect the surrounding facilities. The problems of budget and construction period can be possibly reduced by optimization design. Currently, the optimization design of the foundation pits focuses mainly on types of retaining wall and structural members and not on the whole retaining system. Based on a deep foundation pit close to a metro station in operation and a large-diameter water pipe, a 3D finite element model is proposed. The behaviors of soils are assumed to conform to Drucker—Prager model, and three different construction sequences are simulated. Considering the distinct stress states of soils during construction, loading and unloading modulis of each soil type are adopted. The results show that the implementation of the temporary partition wall can be canceled, and the basement floor No. 1 and No. 2 can be excavated downward simultaneously. The design of retaining system is optimized, and the settlement-sensitive municipal facilities are safe.