Effectiveness of Jet-Grouted Slab on Excavation: A Case Study

Abstract

Jet-grouted slab is a possible solution to reduce the wall deformation induced by the excavation, especially for cases in soft clay. By replacing a layer of a certain thickness of the soft clay inside the excavation fully by chemical or cement grout, it could limit the lateral displacement of the wall to remain the serviceability of the excavation. In this paper, a 16.7 m deep excavation using semi top-down construction method in Taipei was selected to examine the behaviour of the excavation. The jet-grouted slab was adopted in the excavation and then the effectiveness of jet-grouted slab was evaluated. Except the grouted slab, the pit was retained by a 1.2 m thick, 38 m deep reinforcement concrete diaphragm wall with 3-level of steel struts and slabs. A series of finite element analysis was conducted using soft-soil creep and hardening soil with small strain models to carry out after-event predictions and the results were verified by field observation data. It was found that this method could effectively reduce wall deformation up to 33%. Moreover, the enhancement of young’s modulus of the jet-grouted slab does not affect the wall deflection significantly. The jet-grouted slab also was simulated by adopting two different constitutive models namely linear elastic and Mohr-Coulomb (MC) to have a better understanding of the performances by the use of jet-grouted slab. It shows that both constitutive models give similar results.