Study On Analytical Solution And Finite Element Analysis Of Settlement Calculation Of Pile-soil Composite Ground Under Flexible Foundation

Recently, with the strong support of transportation infrastructure of our country, the scale of highway construction was expanding gradually, composite foundation was widely used in construction projects, but the theory research was far behind practice, the existing research was mostly based on theory analysis and calculation of composite foundation under the rigid foundation, however, the working behavior was different between composite foundation under the flexible and the rigid foundation, if the existing research results of was applied to composite ground under flexible foundation, the bigger errors would be generated. Therefore, it was of important practical significance to study on the load transfer mechanism and settlement characteristics of pile-soil composite ground under flexible foundation.The "typical unit body" and "virtual soil and pile" calculation model was adopted in this paper, which regarded the flexible foundation-cushion-composite foundation-underlying layer soil as a whole with consider of the effect of interaction among them, according to the equilibrium analysis of micro-unit, stress equilibrium equations and deformation compatibility equation among the sections of the whole system could be obtained.and the calculation formula of indexes which could reflect the working behavior of system directly such as pile-soil stress ratio, deformation of the pile sticking into cushion and underlying layer soil, axial force of pile shaft and side friction of pile also could be deduced by solving the equations. Finally, an example indicated that the analytical method which was presented in this paper could better reflect the load transfer mechanism and settlement characteristics of pile-soil composite ground under flexible foundation.By using the presented analysis method, the influence factors on working behavior of pile-soil composite ground under flexible foundation were qualitatively studied. Those factors included height and compression modulus of fills, thickness and compression modulus of cushion, pile replacement ratio, length of pile, compression modulus of subsoil, compression modulus of pile, compression modulus of underlying layer soil.Based on the study mentioned above, through the analysis of ANSYS procedure, two-dimensional axial symmetry analysis model of the pile-soil composite ground under the flexible foundation was established, meanwhile, the frictional contact of the pile-soil interface was considered. According to the analysis, the influence laws of the height and compression modulus of fills, thickness and compression modulus of cushion, pile replacement ratio, length of pile, compression modulus of subsoil, compression modulus of pile, compression modulus of underlying layer soil on the settlements of pile and soil.