Analysis on the Effect of Excavation by Sections for Large Foundation Pit Without Horizontal Struts

Abstract

Excavation by sections is usually used in large foundation pits without horizontal struts. The pile inclination monitoring of the excavation of Bailonggang underground wastewater treatment plant shows that the adjacent soil can provide significant restraining effects for the piles of 1^st excavation section, and the excavation of the 2^nd excavation section has great impacts on the piles in the 1^st excavation section. Based on the monitoring result, a numerical calculation model by the finite difference method is built to study the effects of construction sequences and section width. The parametric study showed that the deformation of the excavation can be effectively controlled with the construction of the cushion and raft. The restraining effect to the piles from the cushion is just a little lower than the raft, while the deformation of the pit could be quite large before the cushion is constructed. The deformation of the retaining structure is reduced when the excavation section width is smaller. The analysis in this paper reveals that there is an optimal excavation section width, and the deformation of retaining structure cannot be additionally reduced if the excavation section width is smaller than the optimal width.