第12讲part1 Camclay(Cam-clay model剑桥模型).ppt

* 北京航空航天大学 * Cam-clay model (剑桥模型) 超固结粘土、密砂 理想土 理想土与实际土 压硬性 剪胀性 摩擦性 应力历史依存性 应力路径依存性 软化特性 各向异性 结构性 蠕变特性 颗粒破碎特性 温度特性 …… 亚基本特性 基本特性 正常固结粘土，松砂 超固结粘土，密砂 压硬性 高岭土等向压缩试验结果(Roscoe et al. 1963) 压硬性的数学描述： 最简单的--饱和正常固结土(重塑粘土)的等向压缩试验： 单向或等向压缩过程中所表现出的应力应变关系 土材料的体积模量： 正常固结粘土的剪切试验 剪胀性 应力剪胀方程 * 性擦摩 Weald 粘土的三轴剪切强度结果 对正常固结土摩擦性的描述： 约束压力 剪切强度 重塑苏州软黏土的剪切特性 Introduction to Cam-clay Model (剑桥模型) Cam-clay model was developed by Roscoe et al. at Cambridge University in the 1960s Being a conceptual elastoplastic model that can represent mechanical behavior of normally consolidated clay Original (1963)(原始) Modified (1968)(修正) Theory of plasticity Plastic potential(塑性势) Yield function (屈服函数) Hardening parameter(硬化参数) Strain hardening rule (硬化法则) Key points Relation between stress ratio and strain increment ratio Determination of the volumetric strain in isotropic stress using a linear e-log p relation and its extension to general stress on the basis of Henkel’s water content contours. Original Cam-clay model(原始剑桥模型) a)??Principal direction of the plastic strain increment Assumption that principal directions of stresses and plastic strain increments are coaxial(共轴) b) Determinations of the plastic potential and yield function Plastic potential defines direction of plastic strain increment. Yield function specifies whether plastic strain increments occur when subjected to a new loading increment c)?Determinations of hardening parameter and strain hardening rule The strain hardening rule affects magnitude of plastic strain increment Principal directions of plastic strain increment and stress Stress variables(应力变量) 等效应力/应力强度 Strain increment variables(应变增量变量) 等效塑性应变 Determining plastic potential(塑性势确定) 1. Normality condition(正交法则 ) q, d ε d p p, d ε v p 0 g(p,q) ＝ 0 (d ε v p ,d ε d p ) 　 Plastic potential and strain increment vector Determining plastic potential(塑性势确定) 2 Direction of plastic strain increment vectors(塑性应变增量方向) Relation betw