Viscoelastic Analysis Of Settlement Of Pile Groups Based On Damage Theory

With the rapid development of high-rise buildings and high-speed railways at home and abroad,the importance of differential settlement control of foundation has become increasingly prominent.In order to ensure the safe service of these buildings and railways during the operation period,it is necessary to conduct in-depth research on the differential settlement of pile group foundations under long-term loads.This paper considers the viscoelastic characteristics and damage characteristics of soil around piles respectively by means of theoretical analysis,and proposes a more realistic calculation method for pile group foundations settlement.The main research contents are as follows:(1)Considering the viscoelastic characteristics of the soil,a three-parameter solid viscoelastic model is introduced.Based on the Mindlin stress solution considering the influence of the pile diameter,the viscoelastic solution of pile group foundation settlement in the three-dimensional layered foundation is deduced by using Laplace transform and inverse transform.The rationality of the method is verified by formula degradation and comparison of example,and the influence of pile length,pile diameter,and soil viscoelastic parameters of the pile end bearing layer on the long-term settlement of pile group foundation is analyzed.(2)Considering the weakening of the modulus of each parameter caused by the damage of the soil structure,the dual scalar damage theory is introduced to establish an isotropic soil damage model.Based on the Mindlin stress solution,the analytical solution of the pile group foundation settlement considering the soil structure damage is given,and combined with example to carry out calculation analysis.The calculation results show that the theoretical value obtained by the elastic solution of the pile group foundation is small,and the calculation result of the pile group foundation settlement considering the soil damage is more consistent with the measured value,which verifies the correctness of the calculation formula.(3)Considering the viscoelastic characteristics and damage characteristics of the soil,a three-parameter solid viscoelastic model and damage theory are introduced to establish a coupled soil creep damage model.Based on the Mindlin displacement solution considering the load sharing ratio,the analytical solution of creep settlement of pile group foundation considering soil structure damage is given by using Laplace transform and inverse transform,and the sensitivity of calculation parameters is compared and analyzed when soil structure damage is considered and soil structure damage is not considered.The calculation results show that the damage degree of the soil structure increases,the instantaneous settlement of the pile group foundation remains unchanged,and the final settlement and the time required to reach the final settlement increase accordingly.The change trend and rate of long-term settlement of pile group are the same as when the damage of soil structure is not considered.The initial shear modulus of soil has a significant impact on the instantaneous settlement and final settlement of the pile group foundation.The shear modulus mainly affects the final settlement of the pile group foundation,and the viscosity coefficient affects the time required to reach the final settlement.