Numerical study of the performance of jet grout piles for braced excavations in soft clay

Jet grout piles (JGP) is a ground improvement method that is constructed beneath the final excavation level to prevent basal heave instability, control wall deflections and reduce the strut loads for braced excavations in deep deposits of soft clay. This paper presents the effects of JGP on the wall deflections and strut forces for deep excavations. Firstly, finite element analysis calibrated by an excavation case history improved by JGP is carried out, followed by parametric studies that investigate the effects of various JGP geometric and mechanical properties on the excavation performances. The numerical analyses indicate that increasing the number of piles and the areal extent of reinforcement area, as well as decreasing the pile spacing, can significantly reduce the wall deflections and strut forces for excavation in weak clay. Additionally, use of a thicker layer of jet grout slab without the jet grout pile system is also studied. The feasibility of reducing one level of struts for sake of construction time and costs while adjusting the jet grout piles' layout to maintain the stability is also discussed.