Study On Differential Settlement Control Mechanism Of Pile Groups Considering Progressive Deformation Of Pile-soil System

In the traditional design method of equivalent stiffness pile group foundation,bowl-shaped differential settlement may exist.Large differential settlement of pile group foundation will decrease use-safety requirements of building,even cause whole-building tilt and collapse.How to consider progressive failure of pile-soil system,fully develop bearing capacity of each individual pile in groups and reduce differential settlement of pile group foundation is the key problem need to be solved at present.To adress this problem,model test,numerical simulation and theoretical analysis are used in the present study to analyze the mechanism of differential settlement control of pile group foundation considering progressive failure of pile-soil system.This study presents a control method for differential settlement of group pile foundation considering progressive deformation of pile-soil system.The simplified non-linear approaches for response of pile group and the load transfer model under different working conditions are successfully applied to the analysis software,showing the practicability of the proposed theoretical system.The main work and innovative achievements can be concluded as follows:(1)According to the field measured data,the hyperbolic model is used to simulate the relationship between pile shaft resistance and corresponding relative displacement.Based on the load-transfer method,hyperbolic models of an individual pile in pile groups are proposed to consider the interactive effect among piles.Then,an iterative algorithm for response of a single pile and pile groups considering progressive deformation of pile-soil system is established.Relying on the interaction between individual piles in pile group and taking the stiffness of different pile as a means,calculation method of differential settlement control for pile group foundation considering progressive deformation of pile-soil system is established.(2)Relying on the proposed load transfer model,Visual Fortran and Fric subroutine,secondary exploration and case verification of ABAQUAS software are carried out.Subsequently,numerical simulation study of bearing behavior on single pile,two-pile,and group piles with different arrangement pattern is conducted and the"sheltering-reinforcing" effect of group piles is revealed.According to the numerical simulation results,the optimal space-length ratio and space-diameter of group pile foundation for differential settlement control is summarized and the existing theoretical formulas about interaction factors have been modified.(3)To verify the effect of variable stiffness leveling,a multi function pile foundation model test platform and corresponding data collection and analysis system are developed.A model test study on bearing characteristics of single pile and two-piles is carried out.Settlement behavior of surrounding soil adjacent to the non-loaded piles and loaded piles is investigated and the existence of'sheltering-reinforcing' effect is validated.Based on the optimal space-length ratio and space-diameter of group pile revealed by numerical simulation,model test investigations into group pile of both constant and variable stiffness are performed.The effect of variable stiffness pile arrangement on differential settlement of pile group is verified,and the design idea of variable stiffness pile arrangement is proposed,(4)Relying on the proposed approach for response analysis of group pile and load transfer model under different conditions,adopting Visual Studio development platform,a software system for calculating the differential settlement of pile groups considering progressive deformation of pile-soil system is developed.It solves the theoretical difficult problem that the bearing characteristic of pile foundation is difficult to be easily and quickly estimated,and realizes the accurate calculation and effective prediction of the bearing characteristics of the pile foundation,which can be used conveniently by the engineers.