Numerical Calculation Of Equivalent Modified Cam-clay Parameters For PHC Pipe Pile Composite Foundation Of An-Ci Expressway

At present,the research on PHC pipe pile composite foundation mainly focuses on single pile and group piles with less piles,which is quite different from the actual situation of more piles in expressway engineering.This paper focuses on the research of PHC pipe pile composite foundation.Through on-site dynamic monitoring,deformation characteristics of composite foundation are analyzed from macroscopic response.Based on the assumption of homogenization theory,the equivalent modified Cam-clay parameters of PHC pipe pile composite foundation are obtained by using ABAQUS finite element software.The in-situ numerical model was established and compared with the field measured values to verify the effectiveness of the numerical calculation of the equivalent modified Cam-clay parameters of PHC pipe pile composite foundation.By sensitivity analysis and orthogonal test,the regression equations between PHC pipe pile length,pile diameter,pile spacing and equivalent modified Cam-clay parameters of composite foundation were obtained.It provides data support for solving the optimal design of PHC pipe pile composite foundation transition section.The main contents and conclusions of this paper include:(1)Based on the construction dynamic monitoring of An-Ci expressway in Hunan Province,the treatment effect of treating soft soil section with PHC pipe pile was analyzed,and the deformation characteristics of PHC pipe pile composite foundation under the load of subgrade soil were obtained.(2)Based on the assumption of homogenization theory,the PHC pipe pile composite foundation is numerically simulated,and the equivalent modified Cam-clay parameters of the composite foundation and their variation rules are obtained by simulating the lateral compression test and triaxial compression test.The equivalent compression parameters and equivalent rebound parameters decrease with the increase of pile length,decrease with the increase of pile diameter,and increase with the increase of pile spacing.The equivalent critical state stress ratio increases with the increase of pile length,increases with the increase of pile diameter,and decreases with the increase of pile spacing.(3)The two-dimensional finite element model established by equivalent modified Camclay parameters is used for in-situ numerical simulation.The model calculation results are compared with the field measured values to verify the effectiveness of the numerical calculation of the equivalent modified Cam-clay parameters.Through comparative analysis,the equivalent modified Cam-clay parameters can better simulate the characteristics of foundation settlement and deformation.(4)Based on the orthogonal test,the influence level of PHC pipe pile length,pile spacing,pile diameter and other factors on the equivalent correction of Cam-clay parameters is obtained.SPSS software is used to fit the relationship expression between PHC pipe pile length,pile spacing,pile diameter and equivalent modified Cam-clay parameters,so as to provide data support for the study of PHC pipe pile treating the transition section of structures.