Analysis of sliding mechanism of soil material based on non-coaxial finite deformation theory

为了模拟土体在大变形过程中经常观察到的局部化剪切带的形成，我们首先将著名的小应变模型推广到有限应变/变形模型，然后在模型中加入了一个非同轴项。最后，将变形限制在不排水的平面应变条件下，考察了非同轴项对剪切带形成的影响。结果表明：1)非同轴项的加入对法向应力差的瞬时剪切模数没有影响，但使剪应力的瞬时剪切模数变小。2)非同轴项便于进入椭圆/双曲线边界。3)作为衡量剪切带形成可达性的新指标--简单剪切模量法的行为表明，在临界状态附近，非共轴模型是。独立…与同轴模型相比，更多的运动约束更容易由于变形局部化而失稳。此外，我们还采用非共轴凸轮-粘土模型用有限元方法研究了剪切带的形成。基于修正的拉格朗日格式，将有限应变有限元方法描述为土/水耦合形式。在一个经典的刚性冲压问题中，在没有引入任何初始缺陷的情况下，给出了剪切带形成的演示。1)基于达西定律，基于有限应变理论，给出了耦合问题的控制方程。2)基于改进的拉格朗日格式，对控制方程进行离散，得到有限元格式。这里创建的程序名为SHEBLA。3)不在材料元素中引入任何缺陷。通过有限元网格的变形和局部应变分布，论证了冲压问题在地基中剪切带的形成。4)观察剪切带的形成过程，发现剪切带首次出现在载荷板的边缘，并向对称轴方向延伸。形成剪切带的单元的应力状态达到双曲线区，最后达到抛物线区。然而，首先出现剪切带的单元不一定首先通过E/H边界。5)观察有效应力路径，发现在剪切带扩展过程中，被剪切带包围的楔形体中的单元和加载板正下方的单元都经历了一次卸载。6)最后。结果表明，在巴赫台阶上的地基应力分布与粘性土的经验结果基本一致。较少

In order to simulate the formation of localized shear bands, which is commonly observed during large deformation of soils, we first presented a systematic extension of the well known Cam-clay model developed for small strains to the model for finite strain/deformations and then incorporated a non-coaxial tern in the model. Finally, confining the deformation to undrained plane strain conditions, we examined the effects of the non-coaxial term on the shear bands formation. As a result: 1)The incorporation of the non-coaxial term has no effect on the instantaneous shear modulus for the normal stress difference and it makes the instantaneous shear modulus for the shear stress smaller. 2)The non-coaxial term makes easy of access to the elliptic/hyperbolic boundary. 3)The behavior of the simple shearing modulus, which is proposed here as a new measure to see the accessibility to shear bands formation, shows that, in the neighborhood of critical state, the non-coaxial models are. independentl … More y of the kinematic constraint, more inclined to instability by localization of deformation than the coaxial model.Furthermore we investigated the formation of the shear bands by employing the finite element method with a non-coaxial Cam-clay model. This finite element method for finite strains is formulated as a soil/water coupling form based on the updated Lagrangean scheme. A demonstration of shear bands formation is given in a classical rigid punch problem without introducing any initial imperfections into the material elements. We can offer the following remarks as conclusions: 1)Assuming Darcy's law for the notion of pore fluid, we summarized the governing equations for the coupling problem based on the finite strain theory. 2)We derived the finite element formation by discretizing the governing equations based on the updated Lagrangean scheme. The program created here is called SHEBLA. 3)Without introducing any imperfections into the material elements. we demonstrated the formation of shear bands in the ground for the punch problem as the deformation of finite element meshes and also as the localized strain distribution. 4)Observing the process for the formation of shear bands, we found that the shear bands occur for the first time just arround the edge of the loading plate and extend towards the symmetric axis. The stress state of the elements which form the shear bands reaches the hyperbolic region and then finally the parabolic region. The element in which a shear band occurs first, however, does not necessarily pass the E/H boundary first. 5)Observing the effective stress path, we discovered that both the element in the wedge surrounded by the shear bands and the element just beneath the loading plate experience unloading once during the extension of the shear bands. 6)And finally. we found that the distribution of footing stress at bach step is similar to the empirical results for cohesive soils. Less