结构性软土非线弹性模型中泊松比的取值

Poisson ratio of natural structured clays in non-linear elastic model

本文从天然土体结构性的形成机理着手,建议采用正常固结土、力学意义超固结土以及具有后沉积结构的结构性土这种分类方法探讨原位土体的性状,分析认为,软土沉积后结构性的形成抑制了次固结的发展,土的侧压力系数可近似地采用KONC。在室内试验的基础上根据切线泊松比与切线侧压力系数之间的关系研究了切线泊松比的变化规律,构建了具有后沉积结构的天然黏土以结构屈服应力和转折应力为界的泊松比三阶段模式。根据软土结构性框架,将上述思路推广到三轴加载情况,得到结构性软土切线泊松比的计算式,从而初步解决在应用非线性弹性模型时的泊松比取值问题。该公式便于计算,且能更好地反映结构性土体的应力应变关系。

According to the formation mechanism of structure the natural clays are classified into three classes： normally consolidated clay, simply over-consolidated clay and structured clay with postsedimentation structure. Based on the fact that in the process of structural deformation the faster deformation of a certain amount of bonding inhibits the development of secondary compression, so that, the lateral pressure coefficient of the clay can be assumed as the coefficient of normal consolidated soil. Based on the relationship between the tangent Poisson ratio and tangential lateral pressure coefficient and according to the test data of natural clay, it is proposed that the behavior of tangent Poisson ratio is in a pattern with three phases with turning points of gross yield stress and transition stress. The formula for calculating the tangent Poisson ratio of structured soft soil is deduced by generalizing this concept to the condition of triaxial loading. By this method the problem of determining the Poisson ratio of nonlinear elastic model can be solved.