Numerical investigation into ground treatment to mitigate the permanent train-induced deformation of pile-raft-soft soil system

The piled-raft foundation in soft clay ground for high-speed trains has suffered serious settlement due to cyclic train loading in recent years. It was urgent to implement countermeasures to improve the natural ground. In this research, firstly, a ground treatment technique was proposed to reduce permanent train-induced deformation. Permeation grouting was injected into the bearing strata of group piles with constant pressure. Then numerical simulations based on sophisticated constitutive model and soil-water coupled finite element-finite difference (FE)-(FD) compound arithmetic, were carried out to explore the mitigation effect of the proposed technique. The employed numerical method was validated by using the in-situ monitoring data of lateral ground displacement and surface settlement. The calculation results indicated that reinforcement in the bearing strata of group piles could efficiently increase the tip resistance of piled-raft foundation. Consequently, the surface settlement and sectional forces of group piles can be reduced to a large extent. The proposed ground treatment method was useful for reinforcing pile-raft-soft soil system and had great potential to be applied in practical situations.