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Work Mechanisms of Pile Foundation in the Karst Region

The stability and deformation characteristics of the pile foundation in the Karst region of the super big railway bridge Chaogou under different loading levels are analyzed using the FDM-software, FLAC3D. In the analyses the socketed depth of piles, the properties of soil and rock mass, the scale, space position and filling situation of the Karst caves and the features of the contact interfaces between piles and soil and rock mass were taken into account. The research results show that the original design of the pile foundation is safe and the safety coefficient is greater than 2. The bond strength of the contact surface between pile and soil and rock is a controlling factor for the stability of pile foundation. Therefore, injection after construction is suggested to be used when needed, in order to increase the bond strength of the contact surface. The research leads to a conclusion that the mechanisms and the characteristics of the rock socketed piles can be more clearly interpreted in numerical analyses by referring the principle of the interaction between piles and rock, pile foundation and Karst, resistance of both pile ends and sides.