Mechanical response of diaphragm wall supporting deep launch shaft induced by braced excavation and pipe jacking operation

Abstract

The stability of braced structures for the launch pit in pipe jacking plays a vital role in structural safety during excavation and jacking drive. Through a deep launch pit in Foshan, the real-time deformation and mechanical response of the diaphragm walls, internal struts, and the soil behind the wall induced by braced excavation and pipe jacking operation are obtained from in-situ monitoring and three-dimensional finite element model. The internal struts restrict the further wall deflection and earth pressure in the braced excavation, displaying the apparent time–space effect or corner effect of the limited-scale & deep launch pit. Moreover, pipe jacking operation influences the reaction wall within a certain zone, contributing to the apparent spatial effect. The outward deformation and the increase in the soil pressure occurred in the disturbed zone. Although part of the mucky soil reaches the ultimate equilibrium during the deep excavation and jacking drive, the diaphragm walls still indicate superior strength and stiffness.