采用修正塑性功硬化参数的双屈服面模型及应用

 首先对国内外双屈服面模型的发展进行回顾，指出土体模型中双屈服面概念的必要性和合理性。其次以平面应变试验结果为基础，直接推导出双屈服面模型各部分关系式，其中体积屈服面以塑性功为硬化参数，硬化函数与试验结果吻合程度较好，剪切屈服面以修正塑性功为硬化参数，满足了其与硬化面关系唯一性的要求，并可反映硬化–软化全过程。为使其能较方便地应用于数值计算方法，推导适用于双屈服面模型的弹塑性刚度矩阵。最后应用该模型对一高填土工程的变形进行计算，比较显示其与实测结果较为吻合。

A DOUBLE-YIELD SURFACE MODEL WITH REVISED PLASTIC WORK AS HARDENING PARAMETER AND ITS APPLICATION

Double-yield surface models for soils are firstly reviewed；and the necessity and reasonability of the concept of double-yield surface are confirmed. Based on a series of tests carried out by an improved plane strain test apparatus on Toyoura and Seto sands，a new double-yield surface model is proposed. The functions for elastic property，plastic volumetric property and plastic shear property in this model are derived directly from the test results with less hypothesis. Young¢s modulus and Poission¢s ratio are derived separately as functions of mean principal stress sm. The spherical surface is adopted as volumetric yield loci and the plastic work is used as hardening parameter. For shear yield loci，a function of principal stresses is adopted，which is derived from the test results and similar to that of Matsuoka model，but the hardening parameter is revised to couple with the unique relationship between hardening surface and the parameter. To simulate the hardening-softening process of the yield loci，the hardening function is built by combining a hyperbolic function and an exponential function. Nonassociated flow rule is adopted for plastic shear property based on test results. To make it convenient to be applied to numerical analysis，the elastoplastic rigid matrix of the model is derived. Finally，by using the parameters derived from the test results，verification of the model is carried out by both interpreting laboratory test results and applying it to calculation of the deformation of a high soil-fill project，Both cases agree well with each other，indicating a potential application of this model.