Constitutive model for soil considering induced and inherent anisotropy

土壤沉积物在自然界中具有各向异性。然而，大多数土的弹塑性本构模型都是建立在各向同性硬化理论的基础上的，没有考虑各向异性。通过对天然粘土和一维固结粘土的不排水三轴试验和直剪试验，研究了粘土的各向异性，建立了能合理考虑土的各向异性的本构模型。所观察到的各向异性行为进行了独特的分析，使用运动硬化模型的粘土，其中应力引起的各向异性考虑。另一方面，实验表明，沉积砂的各向异性不同于粘土，各向异性的主要原因是固有的各向异性。考虑组构各向异性张量的砂土弹塑性模型能较好地描述沉积砂在各向同性压缩、三轴压缩和平面应变试验中的各向异性应力-应变关系和强度。

Soil deposits have anisotropy in nature. However, most of elastoplastic constitutive models for soils do not take into anisotropy, because these are formulated on the basis of isotropic hardening theories. Investigating the anisotropic behavior of sand and clay, we formulated constitutive models for sand and clay in which soil anisotropy could be taken into account properly.Anisotropy of clay was investigated on the basis of undrained triaxial tests and direct shear tests on natural clay and one-dimensional consolidated clay. The observed anisotropic behavior was uniquely analyzed using a kinematic hardening model for clay in which stress induced anisotropy was taken into consideration. On the other hand, it was experimentally shown that anisotropy of deposited sand was different from that of clay, and the main cause of anisotropy was inherent anisotropy. An elastoplastic model for sand incorporating the fabric anisotropic tensor was able to describe well the anisotropic stress-strain relationship and strength in isotropic compression, triaxial compression and plane strain tests on deposited sand.