Numerical Analysis on the Effectiveness of the Preloading Method on Reinforcement of the Pile Foundation during Apartment Building Remodeling with Vertical Extension

Foundation reinforcement using micropiles can enhance the bearing capacity of foundations and reducing the settlement of structures in building remodeling with vertical extension. However, in the process of vertical extension following foundation reinforcement, the allowable bearing capacity of the existing piles is still likely to be exceeded due to the additional load. This study presents a preloading method used to carry a partial load from the existing piles and to mobilize skin friction along the reinforcing piles in advance to ensure that the carried load on the existing piles does not exceed the pile’s allowable bearing capacity. Two cases, foundation underpinning without preloading and with preloading, were compared using FEM analysis with PLAXIS 3D. The analysis results showed that the preloading method using jacking equipment had a significant influence on mobilizing the skin friction along the reinforcing pile and reducing the carried load on the head of the existing piles.