Study On The Deformation And Destruction Characteristics Of Piled Raft Foundation In The Combination Area With Digging And Filling Loess Of High-fill Region

The uneven settlement of ground is an important reason for the deformation and failure of foundation.It is easily occurs in special rock and soil ground such as high filling ground.Piled raft foundation,as a common foundation type for high building and soft soil ground,has a good performance in improving ground bearing capacity and reducing uneven settlement of ground.There have been lots of researches on piled raft foundation at home and abroad,but few about loess high filling ground.Therefore,the study of piled raft foundation in high filling ground is very necessary.This article relies on the Shaanxi science and Technology Coordinating innovation project and the Shaanxi natural science basic research project,based on the Kang Jia Gou high filling project,use the physical model test and ABAQUS numerical simulation to study the stress law,the deformation characteristics,the uneven settlement and the layout of the piled raft foundation in high filling ground.(1)In order to get basic strain,earth pressure and settlement data,a physical model test with similarity ratio of 1:5 was carried out.The test results show that:(1)There is a tension trend on the lower side of the raft,and the strain at the middle of the long side is the largest,and the strain value in the filling area is larger than that in the digging area.(2)The settlement of the filling area is larger than that of the digging area,and the piled raft foundation tends to tilt and deflect towards the filling area.(3)If the thickness of raft is thin,the reaction force of pile top has obvious negative bending effect on raft.(2)Based on the actual engineering and physical model test parameters,the 1:1 piled raft foundation model established by ABAQUS is taken as the background of the Kang Jia Gou loess high filling project in Yanan.Monitoring and analyzing the data of stress,displacement and bending moment of the model.The results of the study show that:(1)The settlement laws of piled raft foundation and ground soil all show a "dish shape" which is inclined to the combination area of digging and filling."Saddle shape" distribution of pile top counterforce.(2)The bottom plate of the raft is tensioned and the positive bending moment is the largest,and the reaction force at the top of the side pile causes negative moment at both ends of the raft.(3)The maximum span of the raft into the combination area is 23.5% long side of the raft,and the pile foundation accounts for 25% of the total.(3)Based on the results of physical model test and numerical simulation,the deformation control method of piled raft foundation in loess high filling field is analyzed and studied.At the same time,adjust the rigidity of ground and foundation to meet the requirement of code.