考虑土结构性影响的改进EVP压缩模型

针对原有弹粘塑性(EVP)压缩模型的局限性,建立了一种考虑土结构性影响的改进EVP压缩模型,且在建模时考虑了天然沉积结构性土半对数压缩曲线的非线性特征以及蠕变随应力水平和时间的变化性状.引用了Ariake黏土在轴向应变为常速率以及不同阶段改变速率时的一维压缩试验结果,将其与改进EVP模型的计算结果进行对比分析.结果表明,该模型能够较好地描述天然沉积土的应力-应变关系对速率的依赖性,且计算结果与试验结果基本吻合.与原有的EVP模型相比,改进的EVP压缩模型采用了双对数坐标,能够反映天然沉积结构性土半对数压缩曲线典型的倒S特征.模型中引入了与应力水平和时间相关的蠕变参数,反映出天然沉积结构性土的蠕变速率随应力水平和时间的发展呈非线性递减的蠕变变形规律.

Modified EVP model considering effect of soil structure

A modified elastic visco-plastic(EVP) model is proposed for overcoming the shortcomings of the current EVP constitutive model.The modified EVP mode takes into account the non-linear feature of semi-logarithmic compression curves for natural clays as well as the variation behavior of creep rate related to the stress level and consolidation duration time.The available one-dimensional consolidation test data of Ariake clay obtained by the constant rate of strain(CRS) and step-wise rates are adopted to compare with the calculated results based on the modified EVP model.The results show that the modified EVP model can well reflect the dependence of the stress-strain relationship on the strain rate,and the calculated results based on the modified EVP model agree well with the tested results.Compared with the original EVP model,the modified EVP model can reflect the inverse S shape of the semi-logarithmic compression curves by introducing the bi-logarithmic compression relationship.Besides, introducing the creep parameters related to the stress level and time for natural clays to the modified EVP model can reflect the non-linear decreasing change law in the creep rate related to the stress level and time.