Experimental Research On Large-scale Pile Group Foundations Of Lizigou Large-span Bridge

On the basis of the project-experimental research on large-scale pile group foundation of Lizigou large-span bridge, this paper is finished. The in-situ geological property is complicated and the bearing capacity of soil and rock is lower. The number of individual piles of the pile group foundation is from 16 to 50, and their diameter is 1.5m and the size of cap is 18.1mX 37.6mX 5m. So it is very seldom in design and construction of pile group foundation in domestic and abroad.In the paper, the calculation theories and study methods of pile group foundation are reviewed, and the in-situ data of individual piles are analyzed, the transmission characteristic of load, the bearing behavior and the influencing factor of individual piles are discussed. The model test of pile group foundation is made, and the bearing behavior, the pile-soil interaction, the effect coefficient of vertical bearing capacity of pile group and so on are analyzed too, the comparison between model testing result and existing achievements in research are made. The properties of pile group under vertical load are analyzed by the three-dimensional finite element method.On the condition of this geological property, some main conclusions are obtained. They are:l. the load distributed by central piles under vertical load are higher than by others of the pile group;2.under higher vertical load, the foundation soil shows an obvious characteristic of plastic strengthening; 3.the bearing capacity of pile group under vertical load is larger than the whole sum of bearing capacity of single piles in pile group;4.the position of the maximum or zero value of bending moment inpiles, the line shape of bending moment diagram and the value of bending moment of the same cross section of a pile under same load is different according to the lateral loading and the longitudinal loading;5. the results of theoretical calculation show that they are closed with the results of model test and are reliable, the calculation model and parameter are reasonable.