横观各向同性土的简明破坏机制解释

由于沉积等作用使得天然土材料内部颗粒排列表现为各向异性。土材料的各向异性使得材料内各平面滑动的内摩擦角不同。因此，在分析各向异性土的破坏问题中，除了考虑来自外部的应力分布以外，还需考虑土材料内部的强度分布。以横观各向同性土为例，阐述了同时考虑材料外部应力分布与材料内部强度分布下各向异性土的破坏机制。为说明，文中假定横观各向同性土内部各平面的内摩擦角正切值随空间方向而线性分布。外部加载进行时，横观各向同性土材料内部各处的应力不断变化，当其内部某处首次出现的应力达到该处的强度时，土材料发生破坏。进一步通过类比得出：区别于金属，各向同性土不是在最大剪应力面而是在最大剪压比面发生破坏；区别于各向同性土，各向异性土不是在最大剪压比面而是在最大剪压强比面发生破坏。

Concise interpretation of damage mechanism for cross-anisotropic soil

Due to sedimentation, particles in natural soil arrange anisotropically. Anisotropy diversifies the internal friction angles between relative sliding planes at different directions in soil material. Thus in failure analysis of anisotropic soil, except for conventional stress distribution coming from outside of material, strength distribution inside the material should also be taken into account in addition. Taking cross-anisotropic soil for example, failure mechanism considering both stress distribution and strength distribution is demonstrated. In the discussion, for simplicity, a linear relationship between the tangent value of the internal frictional angle of some planes in the cross-anisotropic soil and the spatial direction of the plane is presumed. For a cross-anisotropic soil sample in loading, when the condition that the stress state in somewhere of the sample achieves the strength where occurs at the first time, the cross-anisotropic soil sample is announced to be failed. Furthermore, more interesting results can also be obtained by analogy among the failure condition of three different typical materials which are metals, isotropic soils and cross-anisotropic soils. Failure occurs at the maximum shear stress plane for the metals, while for isotropic soils, the failure occurs at the maximum shear-compression ratio plane. Moreover, for cross-anisotropic soils, the failure occurs at the maximum shear-compression-strength ratio plan.