Abstract: Large diameter piles have the advantages of high axial capacity and small settlement and are increasingly used in large bridge projects across the river and sea. The coral reef limestone formed by bio-deposition has weak cementation and high porosity characteristics, when the pile foundation of the bridge rock-socketed in this stratum, the side friction has its own characteristics and the traditional method of estimating the pile side friction resistance and axial capacity is not applicable. Combined with a bridge project in Maldives, the characteristics of the side friction resistance and axial capacity of the large diameter bridge pile foundation in the coral reef strata are studied by means of laboratory model test and field self-balancing load test. The test results are compared with the code suggested values. The results show that the coral reef stratum has large side friction resistance and axial capacity, and the large diameter pile foundation can be used as a common foundation form. The side friction of the reef limestone piles has experienced four stages: contact compaction, elastic shear, shear failure and friction shear. The strength of the reef limestone has a large structure, and the drilling process has a great disturbance to the reef limestone stratum, which makes the mechanical properties of the reef limestone significantly reduced.

Key words: Coral Reef Limestone, Large Diameter Piles, Side Friction, Axial Capacity Characteristic