Investigation of piled behaviour due to an adjacent excavation: 3D numerical modelling

In congested cities, excavations are unavoidably constructed adjacent to high rising building supported by piled raft foundations which reduces differential settlements in the buildings. Since the excavations inevitably induce soil movement and stress changes in the ground, it may cause differential settlements to nearby piled raft foundation. In this numerical study, a 3D coupled consolidation numerical analysis (using a hypoplastic model, which considers strain dependent and path-dependent soil stiffness) was conducted to investigate a (2×2) piled raft responses to an adjacent 25-m deep excavation in saturated clay. The computed results have revealedthat the rate of piled raft settlement increased significantly beyond excavation stage h/He=0.5. This is because of the degradation of stiffness of clay with strain due to excavation-induced stress release. Differential settlement (i.e. tilting) was induced in the piled raft due to non-uniform stress release.Owing to separation of the raft from the ground due excavation, some of the working load was transferred to the four piles. The maximum positive bending moment was 200 kNm at Z/Lp=0.67. However, no any bending moment was induced in both the piles at the toes