Evaluation of Super Large Diameter Pile Group Foundation under Multi-Directional Loads

Haixin Bridge is an important link connecting the north and south axis of Guangzhou, has a complicated heterotypic structure system, which causes the lower pile foundation to bear multi-directional loads. The three-dimensional fine numerical analysis model for the super large diameter group pile foundation of Haixin bridge was established considering soil-structure interaction. The mechanical response of the foundation and the soil around piles were analyzed and the safety margin of structural bearing capacity as well as the soil stability coefficient were quantified. The reliability of pile group foundation under multi-directional loads were evaluated comprehensively. The results show that the maximum displacement of the foundation is less than 10% of the limit and the minimum bearing capacity safety factor is 2.56. The maximum stress is significantly less than the strength design value, while no cracks and strength failure appears in the structure. The soil around the foundation pile subjects to extrusion and shear, and the minimum stability factor of soil is 2.58, so no plastic failure occurs in the pile surrounding soil. Based on the analysis of soil and structural mechanical properties, the pile group foundation of an example meets the reliability requirements. When subjected to multidirectional loads, the force and deformation consistency of the foundation manifesting under unidirectional load no longer exists. The influence of cap-soil interaction characteristics on internal force of the pile foundation is significent, so it should be fully considered for calculation. After the implementation of the project, some numerical calculation results were compared with the actual measurements, and the effectiveness of the model was verified. The results of numerical calculation compared with that calculated by m-method, while some suggestions for amendments to the limitations of the m-method were given, which can provide references for similar projects.