Study On Model Test Of Bearing Deformation Characteristics Of Piled Raft Foundation In Deep Soft Soil

Pile raft foundation is a common foundation form in soft soil foundation,which can effectively improve the bearing capacity of the foundation and reduce the differential settlement of the foundation,and can significantly improve the shortcomings of the insufficient bearing capacity of the soft soil foundation.There have been a lot of researches on pile raft foundation at home and abroad,but the research on the bearing characteristics of pile raft foundation in the deep soft soil area in the inland needs to be improved.At the same time,the research on the working characteristics of pile raft foundation under different raft thickness and pile arrangement needs to be further studied.In this paper,based on the previous research,the bearing deformation characteristics of pile raft foundation under different working conditions are studied by combining physical model test and ABAQUS numerical simulation.Some research results with practical value are obtained,which can provide reference for practical engineering design.The main research contents and conclusions are as follows:(1)The physical model test with a geometric similarity ratio of 1:10 is carried out.The data of foundation settlement,earth pressure,raft internal force and pile axial force are collected in the test.The test results show that:(1)the settlement of pile raft foundation can be divided into three stages: linear stage,nonlinear stage and failure stage;(2)increasing the thickness of raft has a great influence on the relative rigidity of raft,when the relative rigidity of raft is in the rigid state,increasing the thickness of raft can effectively reduce the total settlement and differential settlement,and the form of internal strong and external weak pile arrangement can increase the overall settlement but reduce it For differential settlement,the external strong and internal weak pile arrangement will slightly reduce the overall settlement but increase the differential settlement;(3)after increasing the raft thickness,the raft and the soil under the slab will bear more load;(4)the foundation reaction under the slab shows a trend of large small edge on both sides.(5)Increasing the thickness of the raft will increase the overall bending moment of the raft,and the form of internal strong and external weak pile arrangement can reduce the bending moment of the raft,while the form of external strong and internal weak pile arrangement will increase the bending moment of the raft;(5)with the increase of the thickness of the raft,the maximum pile top load changes from the middle pile to the angle pile,and the form of external strong and internal weak pile arrangement can effectively reduce the difference of pile top reaction at different positions.(2)According to the physical model test conditions and the actual project,a 1:1 pile raft foundation model is established with ABAQUS.The settlement and deformation of raft,the stress and displacement of soil and the internal force and deformation of pile under different conditions are analyzed.The results show that:(1)the deformation of the raft and the soil under the raft presents a typical "bowl bottom shape",that is,the large edge in the middle is small,and the overall soil stress presents a trend of large on both sides and small in the middle;(2)the axial force of the pile increases from the bottom to the top,but the upper part of the pile bears most of the load,increasing the thickness of the raft will reduce the difference between the axial force and the balanced axial force of the pile;(3)the bending moment of the pile produces The reason lies in the differential settlement of raft,which can effectively reduce the pile moment.(3)Based on the results of physical model test and numerical simulation,this paper analyzes and summarizes the deformation control measures of pile raft foundation in the deep and soft soil area in the inland.In the design,the settlement control idea should be followed.For the foundation soil,dynamic compaction,replacement and vacuum combined with surcharge preloading can be adopted.For the pile raft foundation,the relative rigidity of raft can be adjusted as rigidity In order to achieve economic and practical results,the design idea of reducing differential settlement of foundation and using different forms of pile arrangement in different areas and sections is adopted...