降雨影响下残积土中基坑围护桩变形三维数值分析

Numerical Analysis on Deformation Response of the Retaining Piles to Excavation and Rainfall in Residual Soil

依托厦门残积土层中某基坑案例,采用数值分析手段,研究了开挖与降雨作用下残积土中基坑围护桩变形特性。在有限差分软件中建立三维数值模型模拟施工过程,将考虑土体刚度随应变衰减的土体小应变刚度曲线嵌入摩尔库伦本构,通过强度参数折减方法模拟降雨引起的遇水弱化特性,结合现场实测数据,研究了开挖与降雨作用下残积土中基坑围护桩变形特性。结果表明:使用考虑土体小应变刚度特征的数值方法能够较好地模拟残积土基坑围护结构的变形特性;由降雨造成残积土结构弱化会增大1.5～2.0倍围护桩侧向变形。

In this study,a numerical method is adopted to investigate the responses of the retaining piles to unloading effect and rainfall based on a foundation pit in residual soil in Xiamen. Three-dimensional numerical model is developed in a finite difference method to simulate the construction process of the pit. The stiffness degradation is considered by embedding the small strain stiffness curve in the Mohr-Coulomb constitutive model. The water-weakening effect of the residual soil is simulated by reducing strength of the residual soil.The effect of the rainfall and the excavation on pile deformation is analyzed through a comparison between the numerical results and the field measurement. Results show that this numerical simulation scheme proposed in this study is capable to capture the deformation response of the retaining piles to excavation and rainfall in residual soil. The structure-weakening of the residual soil caused by rainfall will increase 1.5 ~ 2 times lateral deformation of the retaining piles.