Abstract: 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.

Key words: cross-anisotropy, stress distribution, strength distribution, deposit direction, damage mechanism