Numerical Analysis On Negative Friction Of Pile Groups Under Freeze-Thaw And Load Conditions

The negative friction of pile,as the name implies,is the downward skin frictional resistance to the pile caused by the settlement of pile and surrounding soil due to self-weight consolidation,collapsibility and ground load.etc.,which makes the pile stress situation complicated and changeable.Especially for the pile group,this trend seems more serious and relative research is lacking.So,a considerable amount of attention has been paid on it in home and abroad.In this paper,the finite element model of Abaqus Group Pile Foundation is established based on the previous test scheme,compared with the test results,to verify the validity of the model.Besides,the model parameters are changed to apply to several other different working conditions to guide similar engineering problems.The main contents and achievements of this paper are as follows:(1)Abaqus finite element software is utilized to pick the right pile body and soil constitutive model to establish the nonlinear contact between pile and soil.A new method of earth stress balance is adopted and the time increment and boundary condition of the flow-solid coupling analysis step are set up correctly to verify the three-dimensional model of group pile by comparing the finite element results with the experimental results.(2)The model parameters are changed on the basis of the former finite element model to discuss the variation law of the negative friction of pile group and the soil consolidation settlement by analyzing different pile quantity,pile spacing,load order,load grade,friction coefficient of pile-soil contact interface corresponding to different working conditions.(3)The variation of internal temperature field disribution with external temperature during freezing and thawing of soils is discussed.Then,the temperature field is introduced into the fluid-solid coupling model to analyze the heat-fluid-solid coupling conditions.That is the consolidation settlement and the pile side frictional resistance distribution of soil under two conditions of load and freeze-thaw.