Study On Pile-Soil Stress Ratio Of CFG Pile-Raft Composite Foundation In High-Speed Railway

CFG pile-raft composite foundation is a new method that is applied in reinforcing the soft soil foundation in the late 1980s in China. Due to its economic efficiency and good feasibility, it has been widely applied in civil engineering. It has been used in railway recently, but its academic research trails the project practice. Its bearing capacity and settlement calculation is imperfect, especially the pile-soil stress ratio research is at the start stage, and other pile-soil stress ratio method is used. According to above problem, this paper study and analyze the pile-soil stress ratio of CFG pile-raft composite foundation by spot experiment, FEM analysis and theory analysis. Main contents are as follows.1. Introduced the background of the article and innovation included in the thesis; and focuses on CFG pile-raft composite ground theoretical basis, as well as the research of pile-soil stress ratio nowadays at home.2. A field test is conducted for soft soil CFG pile-raft composite foundation. With this test, this paper analyzes the changing of the pile-soil stress ratio when the thickness of cushion, the length of the pile, the distance of the pile, the diameter of the pile and the degree of the load change.3. Finite element procedure Plaxis is used to analyze the pile-soil stress ratio of CFG pile-raft composite foundation. Using Plaxis 2D to simulate CFG pile raft structure simplified. A coMParison is made between the results of embankment overloading for 180 days by FEM and measured results, and analyzed the changing of the pile-soil stress ratio when compression modulus of soil between piles, compression modulus of cushion, compression modulus of sub-layer, modulus of pile, the length of the pile and the distance of the pile change.4. The deformation performance of CFG pile composite foundation under loading was discussed, and the relationship between the pile lateral friction and the piles-soil relative deformation was studied. By adopting the concept of the equal settlement section, the piles and the surrounding soil were assumed to be linear elastic masses, and the distributions of pile lateral frictions were assumed to be linear. On the basis of the deformation coordination condition of pile-soil-cushion and the load transfer method, a calculation formula of the pile-soil stress ratio of CFG pile-raft composite foundation was proposed. And the equations are used to analyze the practical project; the result calculated by the proposed formula is close to the result of test and the result of FEM.