Vertical Vibration Of A Pile In A Double-layered Stratum Under The Freezing And Thawing Processes Of Saturated Porous Media

At present,China is actively promoting the "Belt and Road" strategy,and with it,engineering construction in permafrost regions has gradually increased.A prominent feature of the frozen soil engineering problem is the existence of freeze-thaw phenomena,which are affected by climate and human activities.Freeze-thaw layering will occur on the surface of seasonal frozen soil or permafrost,which will affect the safety of the project.Due to the special physical properties of frozen soil and the good bearing characteristics of pile foundations,pile foundations have been widely used in buildings in frozen soil regions.Therefore,the vertical vibration characteristics of foundation piles in frozen and thawed foundations have been studied.The design and construction of pile foundations in seasonal or frozen soil areas is of great significance and engineering value.The main research contents of this dissertation:(1)Starting from the theory of single-phase elasticity,saturated dynamic consolidation theory,and frozen porous media theory,the analytical method is adopted to analyze the vertical vibration of the pile under the condition of limited soil layer under the condition of arbitrary excitation force on the pile top.This solution considers the interaction between the contact surface of the pile and the soil layer,and establishes a vertical coupling vibration model of the non-end bearing pile.Analyze the performance of three different media models under freezing conditions.(2)To study the effect of soil layer delamination caused by freezing and thawing on the vertical vibration of piles under the condition of arbitrary excitation force on the pile top,and to establish a simplified model of pile vibration in double-layer freeze-thaw foundation.In simplified model one,single-phase elastic medium is used to simulate frozen soil,saturated two-phase porous medium is used to simulate unfrozen soil or thawed soil;in simplified model two,frozen saturated three-phase porous medium is used to simulate frozen soil,and saturated dual-phase porous medium is used to simulate unfrozen soil.Or molten earth.Data analysis and discussion of the two models were performed to analyze the effects of the parameters of the frozen and thawed soil layer on the complex stiffness,vertical wave reflection curve and admittance curve of the vertical vibration of the pile.