A Case Study on Determining the Optimal Supporting Structure Scheme in Deep Excavation in River Channels by 3D FEM Analysis

Abstract

A deep excavation with a maximum depth of 13.6 m in one river channel before the construction of a sluice is presented in this paper. The working environment of the deep excavation is rather complex, in which the surrounding 11-story building, underground pipeline, underground water and large areas of excavation are included. To ensure the security and stability of the foundation pit and the surrounding environment, and combined with the characteristics of the foundation pit, a gridding diaphragm wall or anchored diaphragm wall is designed in both sides of the river channel in advance, which constitutes multiple schemes for the supporting structures. A better understanding of their behavior through the three-dimensional finite element method could result in more reliable predictions and efficient designs, in which various phases, such as dewatering, soil excavation and anchor installation, are simulated. The simulation results of different schemes and the technical code for monitoring building foundation pit engineering are analysed and compared with a focus on the structural performance of supporting structures, the settlement of the 11-story building and the ground surface settlement behind the diaphragm walls. Then, the optimal supporting structure scheme is obtained to guarantee the economy and safety of foundation pit engineering. Finally, the real-time monitoring data during the foundation pit excavation are analysed, which demonstrates that a reliable supporting structure scheme can be achieved through simulation methods in advance. It is expected that this paper will provide a useful basis for similar excavations in river channels.