Research On Pile-soil Interaction Effect In Soft Soil Foundation

Pile group foundation is widely used in bridge structure,especially in soft soil area.Its higher bearing capacity and smaller deformation capacity can adapt to the environment well.The research on the response of pile foundation under vertical load has been relatively mature.However,the laws reflected by bridge pile foundation,especially pile group foundation under lateral load are not completely clear at home and abroad,and the calculation method of its lateral bearing capacity is not accurate enough,so it is very important to study the pile group-soil interaction under lateral load such as earthquake and wave.In this paper,the large-scale finite element software ABAQUS is used to calculate and analyze the pile group foundation under lateral static load and dynamic load.The main contents are as follows:(1)Looking up the relevant literature,we can understand the theory and law of pile-soil interaction under lateral load and the research status at home and abroad.In this paper,the classic Gibson foundation in soil mechanics is used to simulate the change of soil elastic modulus along the depth.(2)Based on the three-dimensional solid model established in ABAQUS,the response of different pile groups under lateral load,such as the number of piles,the spacing of piles and the arrangement of piles,is analyzed by using the Mohr-Coulomb model in soil mechanics.(3)The law of internal force and deformation of pile group when it reaches yield and failure under static load is studied.The distribution of internal force is angle pile > side pile > middle pile and front pile > back pile > middle pile.The above rules are not always satisfied under dynamic load,and the load distributed by middle pile is sometimes larger than that of angle pile.(4)The influence of pile number and pile spacing on pile group effect is studied.With the increase of the number of piles,the effect of pile group is enhanced;with the increase of pile spacing,the effect of pile group is weakened.The pile group under dynamic load is more sensitive to the change of pile spacing.In this paper,the critical pile spacing under static load is 6D.(5)The influence of friction coefficient and arrangement of pile-soil on the internal force of pile group is studied.Under the action of static load,the increase of tangential friction coefficient of pile-soil makes the overall rigidity of pile group increase,and the lateral bearing capacity is improved to a certain extent;the stiffness of the axial connection of single row of piles is larger than that perpendicular to the connection direction,and the lateral bearing capacity of the row of piles is larger than that of the plum pile row.(6)The cyclic load makes the soil around the pile accumulate plastic damage,and the lateral bearing capacity under the same load amplitude is much lower than that under the static load;the more the number of piles,the stronger the energy consumption of the pile group,the greater the attenuation of secant stiffness caused by the cyclic load,the more far-reaching the impact on the soil around the pile compared with the static load,and the extreme value of the positive load is greater than the reverse load.(7)The influence of the number of cycles on the lateral bearing capacity of pile groups is studied.With the increase of the number of cycles,the stress level of the soil around the pile is increasing and the bearing capacity is decreasing,which shows that the loading history has a great influence on the bearing capacity of the pile body.(8)The influence of dynamic load on dynamic stress of soil around pile is studied.It is a top-down process to improve the stress level of the soil on the pile side.When the lateral earth pressure caused by the self weight of the soil is the dominant factor,the fluctuation of the stress tends to be stable.