软土的各向异性损伤对剪切带形成的影响

Influence of Anisotropic Damage on Shear Band Formation Analysed by Elastoplastic Damage of Soft Soil Model

在软土各向异性弹塑性损伤模型的基础上,把小应变模型扩展到有限应变模型,推导出不排水平面应变条件下的剪切带形成条件,分析K_0固结状态下各向异性损伤对剪切带形成的影响。以上海软土为例,分析临界状态参数β=0.9时,损伤变量D_1,D_2的不同组合的剪切角和简单剪切模量与有效平均主应力比(g/p′)的关系曲线。计算结果表明,损伤变量越大,越接近不稳定状态,垂直方向损伤对剪切带的影响比水平方向的强烈。 特别指出:无论土为横观各向同性损伤的情况,还是各向异性损伤的情况,在本文研究的条件下,不稳定状态(g/p′为最小值)相应两个剪切角约在50°和130°,这对研究弹塑性损伤对剪切带形成与变化有指导意义。

In this paper the elastoplastic damage constitutive equations with small strain are extended to that with finite strain. The conditions for shear bands formation taking into account anisotropic damage are derived under the undrained plane strain condition. Shanghai soft soil is taken as an example in order to illustrate the influence of anisotropic damage on shear band formation. The relations between shearing angle and g/p' with damage variables D1,D2,B=0. 9(0<0<1, the critical state at B=1.0) and D3 = 0 show that the bigger damage accumulation under K0-consolidation, the easier shear bands come into being . The influence of damage variable D2 in the vertical direction on the shear band formation is more serious than that of Dj in the horizontal direction. It should be pointed out that the study on the influence of cross-anisotropic and anisotropic damage on shear band formation has obtained the interesting data, i. e. there are two angles of shear corresponding to the minimal value of g/p', which are approximately 50 and 130, respectively. Such data may be very useful for guiding the shear band test.