Theoretical And Experimental Researches Of Stress Analysis For Rock Slope Bridge Pile Foundations

With the carrying out of Chinese strategy of western development, the constructions of high-level highways often traversed in the mountainous regions. The conventional highways around the mountains cannot satisfy the communications and transportation's needs of speed, safety and facility. In order to protect the vegetations in the mountains, it is impossible to fill and excavate large earth in such areas, therefore, tunnels and viaducts are adapted, which often include the piles foundations in engineering practices. In this case, the stress of pile foundations is very complex that bearing mechanism and analysis methods are quite different from the conventional pile foundations and the conventional calculation method is not applicable to such pile foundation. By integrating with the Natural Science Foundation of China"study on the numerical simulation and design theory for rock slope bridge pile"(NO.50578060) and the Transportation Technology Projects of Hunan Province"study on the design and protect technique for slope bridge pile"(NO.200513), and based on the analytical method, numerical method, methods testing in analogous room and in field, this paper discussed the bearing mechanism and stress analysis of pile foundation of bridge in rock slope. Mainly research and investigation are done as the following:Firstly, based on comprehensive analyses of the domestic and world related references, the bearing mechanism and behaviors of pile foundation in rock slope under complex load condition are discussed and summarized. Considering complex stress condition of pile foundation and borrowing analytical thought about stress and deformation of conventional pile in the plain under clining loads, the externality loads include axial load, horizontal load, lateral distribution thrust and resistance from pile side rock. By simplifying the distribution of resistance and thrust and establishing the calculation model of bridge pile foundation in rock slope, the stress analytic solution of pile foundation is deducted through power series method. In order to fully research the characteristics of bridge pile foundation in rock slope, the irregular and diversity of thrust will be considered, and the flexibility differential equation was replaced with the finite difference model of pile shaft. The thrust of slope acted on the pile shaft with discretionary form as design load to consider the interaction of pile and slope, and the finite difference model applicable to stress and displacement calculation of bridge pile foundation in rock slope is deduct. Compiling related program and combining with the example, the influences on stress and displacement of bridge pile foundation in rock slope with different thrust distribution model, amount, position and boundary condition is fully researched. In order to fully discussing the bearing characteristics and affecting factors of pile foundation in rock slope, the international advanced nonlinear finite element analysis software Marc is adapted. Based on considering nonlinear factors including discontinuous deformation between pile and rock contact area, the three-dimensional elastoplastic model for the bridge pile foundation in rock slope is established, and the stress distribution is obtain according to different characteristic in different construction stage. The stress characteristic is achieved under different load condition through calculation. In addition, according to orthogonal experiment principle, the orthogonal finite element analysis model is constituted, and the five factors including E(elastic modulus),φ(friction angle), c(cohesion), d(pile diameter) and slope angle are analyzed.Furthermore, based on similar theory, the similarity criterion for pile foundation in rock slope is deduced through equation analytic method. The indoor model test for pile foundation in rock slope is designed and finished according to the similar criterion. Four model groups and sixteen model piles tests are carried out. The affecting factors of pile foundation are researched with different load mode, different pile shaft free length, different pile shaft fixity depth and different slope angle etc. Combined with the supported engineering and compared with the theoretical results and the measured test data from in-fields, the reliability of the presented theory method is further proved.