Study On Horizontal Bearing Capacity Of Variable Stiffness Pile-underground Wall Foundation Under Loading

Compared with the traditional foundation,the new combined foundation of piles and underground walls provides horizontal stiffness through the upper underground wall,and the lower piles ensure the foundation is embedded,which has high horizontal bearing capacity and good economic benefits.Based on this,the new foundation is analyzed and studied by the changing the overall stiffness distribution of the foundation to reduce the differential settlement of the structure and reduce the foundation internal force and lateral displacement.Firstly,based on MATLAB finite element software,the theoretical calculation of the combined foundation of the variable stiffness pile and the underground wall under the pile is carried out,and the variable stiffness factors affecting the internal force and deformation of the combined foundation are analyzed.Then the internal force and deformation data is obtained through multiple sets of indoor model tests,and then use the PLAXIS 3D software numerical simulation to obtain the internal force deformation data of the variable stiffness pile-underground wall foundation under the pile load and compared with the data obtained from the model test.Finally,the simulation and research on the internal force and deformation regularity of the combined foundation when changing the pile length,pile diameter and pile number respectively,and summed up the optimization scheme of variable stiffness combination foundation,providing reference and help for the practical engineering application of the adjacent piled structures.The main conclusions from the above studies are:(1)Through the theoretical analysis of MATLAB,it can be known that the variable stiffness theory(such as reasonably configuration the length of the front and behind pile)can make the overall settlement of the pile-underground wall combined foundation more uniform and meet the settlement control requirements,and also meet the safety and economic design concept.Changing the pile diameter in variable stiffness has the greatest influence on the combined foundation.Therefore,the overall bearing capacity of the pile-underground wall foundation can be improved by appropriately increasing the pile diameter during construction,and the differential settlement of the foundation can be reduced.(2)The indoor model test analysis results show that the overall top of the combined foundation moves to the stack side under the load.The settlement difference of the front and back walls of the five piles under the same pile load is less than the settlement difference of the front and back walls of the six piles,it shows that the number of piles is adjusted by the variable stiffness theory can improve the uneven settlement of the combined foundation.In addition,the internal force and deformation tendency of the load-bearing surface and the back-loading surface of the pile-underground wall combined foundation is also different.Therefore,appropriately increasing the reinforcement of the front and rear walls and reducing the reinforcement of the pile body and even reducing the number of piles can save the cost of construction in actual engineering.(3)After adjusting pile length,pile diameter and pile number of the combined foundation by PLAIXS 3D numerical simulation,it is found that the most important influence on the uneven settlement of the structure is the pile diameter,followed by the pile length and the number of piles.Through the results of the optimization test scheme prove the overall stiffness distribution of the foundation can be changed by adjusting the design method of pile length,pile diameter and number of piles in the actual project,so that the differential settlement of the building can be effectively controlled,and the foundation internal force and lateral displacement can be reduced.All the piles are fully functional.