Thermal-hydro-mechanical Model For Saturated Freezing Soil-pile Interaction

The frost heaving and thawing settlement of soil in seasonal frozen soil area is the main cause of freezing damage of structures,which can cause harm to the stability and serviceability of existing structures.Under the coupling effect of temperature field,water field and stress-strain field,the mechanism of frost heaving and pile-soil interaction is not clear,which limits the implementation of remediation measures for pile foundation frost-drawing diseases in practical engineering.In order to study the mechanical behavior of structures in cold regions during freezing and thawing of soil,the calculation theory of mechanical behavior of saturated frozen soil and pile under the coupling action of temperature field,water field and stress-strain field is summarized in this study.It is applied to the hydro thermal coupling model of saturated frozen soil pile under freezing and thawing.And the mechanical behavior characteristics of saturated frozen soil pile and the mechanism of pile freezing and pulling are obtained.The main research contents and results are as follows:(1)Based on the frost heaving theory of frozen soil and the water-heat-force coupling theory,the water-thermal-mechanical coupling theoretical model of saturated frozen soil and its control equation are summarized and deduced.According to the needs of finite element analysis,the control equation is optimized by using the introduced void ice ratio,unfrozen water content curve and porosity function.(2)Based on the derived water-thermal-mechanical coupling theoretical model of saturated frozen soil,the elastic constitutive model and coupling control equation of frozen soil are analyzed by finite element method and their rationality is verified.(3)The ABAQUS finite element analysis software and the secondary development of user subroutine are used to numerically simulate the pile force under the waterthermal-mechanical coupling effect,and the variation laws of temperature,displacement and water migration with time are obtained.(4)By changing the pile shape,the variation law of stress state of different pile types in saturated frozen soil is analyzed,and the mechanism of pile foundation freezing and pulling in frozen soil area is explained.