循环荷载作用下饱和软土的各向异性边界面模型

Anisotropic bounding surface model for saturated soft clay under cyclic loading

在临界状态弹塑性力学的框架内,建立了可以考虑循环荷载作用下各向异性对饱和软土力学特性影响的边界面塑性模型。该模型采用非关联的流动法则,引入了反映土体各向异性的内变量,利用该内变量的初始值描述初始各向异性,采用一种理论更为严谨、模型参数确定更为恰当的旋转硬化法则描述循环加载过程中各向异性的演化,利用更新映射中心的径向映射法则和与塑性偏应变路径长度有关的塑性模量插值规律,保证模型能够模拟循环加载时应力-应变响应的非线性、滞回性、应变累积性等基本特性,解释了模型参数的物理意义和确定方法,特别是给出了一种合理确定描述土体初始各向异性状态变量方法。通过文献中等压固结和偏压固结饱和黏土的循环三轴试验结果与模型预测结果的对比验证了模型的合理性。

A new bounding surface plasticity model considering the effect of anisotropy on the behavior of saturated soft clay under cyclic loading is proposed within the framework of critical state elastoplasticity. A non-associative flow rule and an internal variable reflecting the anisotropy of soil are introduced in the model. The initial anisotropy is depicted by the initial value of the internal variable and the evolution of anisotropy produced by cyclic loading is described by a rotational hardening rule with robust rationale and availability of model parameters. A radial mapping rule with the updated projection center and an interpolation function of plastic modulus associated with the length of the deviatoric plastic shear strain trajectory are adopted in the model to describe the fundamental behaviors including nonlinearity, hysteresis and strain accumulation of stress-strain responses of soft clays subjected to cyclic loads. The roles played by model parameters and their determinations are also explained. In particular, a rational method to calibrate the initial internal variable for describing anisotropy of specimens is developed. The validity of the new model is verified by comparing the predicted results with the cyclic triaxial test results under isotropically consolidated and anisotropically consolidated conditions for saturated soft clay.