Experimental Study And Simulation Study On The Horizontal Force Characteristics Of Pile Raft Foundation

At present,the group pile foundation and raft foundation forms has been commonly used in high-rise buildings in China.In order to take full advantage of the controllable group pile foundation settlement and overall stability of the raft foundation,the vertical bearing capacity is greater,the combination of two forms are formed composite foundation form of piled raft This foundation form has good vertical bearing capacity,also,it has good anti-overturning ability when subjected to horizontal loads such as seismic excitations and wind loads.Additionally,this foundation form perfect more economic than those group pile foundations under the premise of satisfying the control of foundation settlement.This article was based on existing results from previous researchers about group pile foundation,raft foundation and lateral load.This paper study the mechanical properties under the horizontal load by pile-raft foundation under scale model tests in room and finite element analysis.The main research work and related results are as follows(1)Horizontal static load tests were carried out with different length-to-diameter ratios,pile types,vertical loads and pile spacing.Additionally,the horizontal displacement of the pile raft model and changes in pile internal force were monitored.The relevant results are as follows:firstly,increasing the number of piles and the length-to-diameter ratio can effectively limit the horizontal displacement of the piled raft foundation,reduce the bending moment and shear force of the pile body,and significantly improve the horizontal bearing capacity of the piled raft foundation;Secondly,increasing the pile spacing of the piled raft foundation can drive greater range of soil between piles,the internal force law of the pile body remains the same and the change value is small;thirdly,increasing the vertical load will play a compacting effect on the pile raft contact with the soil,and the friction resistance will increase at the bottom of the raft.Thus it could increase the strength of the soil.Also,effective reducing on horizontal displacement and the internal force of the pile body,and have a definite improvement effect on the bearing capacity.(2)Aiming at the horizontal static load model test condition,a finite element analysis method was built to determine a pile raft foundation model to simulate the entire process of horizontal load.While checking the accuracy of the model test,the displacement field and plasticity deformation development of the soil during horizontal load were further analyzed.The results show that the soil displacement concentrated area is located on the load side of the pile top,also,local plastic deformation of the soil occurs;the plastic deformation area of the soil diffuses deeper with the increase of horizontal load,eventually,this area penetrates and becomes the front side of the pile top,the bottom side of the pile bottom and the complete shear zone of soil between piles.