Study On Side Friction Characteristics Of Super Deep Cohesive Soil Pile

After entering the 21 st century,China’s industrialization process has achieved great development,and high-rise and super high-rise buildings have been widely used in urban construction,which puts forward higher requirements for the bearing capacity and deformation performance of the foundation,Therefore,it has been widely used in urban construction projects,and has become the preferred form of all deep foundation forms.In ultra deep pile foundation engineering,cohesive soil is the most common soil layer.For a long time,the experimental analysis of pile side friction in cohesive soil is relatively scarce,and the values of pile side friction are quite different,Taking single pile and pile group in super deep cohesive soil as the research object,based on the theory of cap pile soil interaction,through the single pile static load test of Beijing Shunfeng automatic sorting center pile foundation experimental base,the single pile model and group pile model are established by FLAC3 D numerical analysis software,Numerical simulation is carried out to analyze the mechanism and variation law of pile side friction under different conditions.This paper first analyzes the previous research on pile side friction in theory,experiment and numerical simulation,discusses the functional characteristics of pile and the principle,influencing factors and calculation method of pile side friction,and carries out field experimental research on the mechanism of pile side friction in ultra deep cohesive soil According to the change curve of pile side friction,the FLAC3 D numerical analysis software is used to establish the model,and the measured value is compared with the simulated value.The results show that the side friction of the pile gradually develops from top to bottom along the pile body,and the performance in the upper part of the pile body is obviously better than that in the lower part of the pile body.The longer the length of the pile body is,the longer the time for the side friction of the pile to reach the extreme value is;With the decrease of the length diameter ratio,the time of exerting the pile side friction is more and more advanced;With the increase of the upper load,the load sharing ratio of pile side friction increases rapidly at first,and then increases slowly until it reaches the limit state.In the numerical simulation of group pile and single pile under the same load and geological conditions,it is found that the settlement of the top of single pile is much less than that of the middle pile of group pile foundation,and the settlement of the middle pile is the largest under the same pile cap,the pile side friction is the largest,and the load sharing ratio of the pile side friction is also the largest,followed by the side pile,and finally the corner pile,With the further increase of the upper load,the load sharing ratio of pile side friction is also increasing.