Experimental Study On The Joint Bearing Characteristics Of Piled Raft Foundation And Superstructure Of Soft Soil Foundation

Piled raft foundation is widely used in soft soil foundation engineering due to its good integrity and high rigidity.However,the traditional method separates the piled raft foundation and the superstructure to design independently,ignoring the interaction between the two after the force is deformed,and as the height of the superstructure increases,the error between this type of design method and the actual situation becomes larger and larger,resulting in Excessive cost will also have a certain impact on the stability of the building.Therefore,carrying out the experimental research on the bearing characteristics of the piled raft foundation and the superstructure,taking into account the safety and economy of the design,has certain guiding significance for the actual project.At present,scholars at home and abroad have done a lot of research on the joint effect of piled raft foundation and superstructure,but most scholars use finite element simulation method to analyze,and the research results of model test are still lacking,and they are aimed at similar models of soft soil foundations.Whether the conclusions drawn in the experiment are in line with the actual situation also needs to be further explored.On the basis of combining previous research results,this paper uses a combination of geometric similarity ratio 1:10 model test and ABAQUS finite element software numerical simulation method to study the piled raft foundation and superstructure in soft soil under different working conditions.The joint bearing deformation characteristics lead to the following main conclusions:(1)Under the combined action of the piled raft foundation and the superstructure,the soil settlement is more evenly distributed in the early stage.As the load increases,the vertical displacement of the soil between the piles is more obvious,and the settlement in the middle of the soil under the foundation is greater.The rigidity of the superstructure restricts the deformation of the foundation and improves the bearing capacity of the foundation soil.The settlement of the piled raft foundation changes linearly with the load.The settlement of the piled raft foundation increases with the increase of the height of the superstructure.Due to the influence of factors such as pile group effect,the piled raft foundation shows a basin settlement phenomenon.Improving the rigidity of the superstructure helps to increase the utilization rate of the pile and soil,thereby reducing the overall settlement,and it also has a significant control effect on differential settlement.(2)After considering the interaction of the piled raft foundation and the superstructure,the fitting curve of the bottom column and the superstructure changes linearly.Because the rigidity of the superstructure restricts the deformation of the piled raft foundation after being stressed,the differential settlement is reduced,so that the stress distribution of the piled raft foundation raft is more uniform,and the stress mutations are mainly concentrated around the piles and columns.With the increase of the load,the axial force of the corner column and the side column increased the fastest,and the center column appeared unloading.(3)When considering the interaction of the piled raft foundation and the superstructure,as the number of floors increases,the increment of the pile top reaction force gradually decreases,and the pile top reaction force changes in a logarithmic relationship with the number of floors.The bearing performance of the pile under the raft is not played at the same time.In the process of bearing the load,the internal force at the top of the pile is repeatedly self-coordinating,forming a cycle of middle pile and corner pile-side pile.In this process,the pile body and the superstructure All columns will produce a non-negligible bending moment.When designing the structure,attention should be paid to the restraint effect of the upper structure on the foundation deformation to improve the utilization efficiency of the soil and piles,and attention should be paid to strengthening the bending performance of the inner side of the pile top and the bottom column to make the building More secure and economical.