Effect Of Strength Anisotropy Research Articles

Effect of strength anisotropy on undrained slope stability in clay

The influence of strength anisotropy on the two-dimensional undrained slope stability analysis in soft clay is evaluated herein. Because of the inherent anisotropy of clay, the mobilized undrained shear strength tends to vary as the inclination of the failure surface changes. To deal with this problem, the limit state analysis and a total stress strength criterion, which represents the anisotropic undrained shear strength along the slip surface, are used to calculate the anisotropic factor of safety against sliding (Fs,A). However, since it is too complicated in practice for engineers to directly apply the anisotropic shear strength to the slope stability analysis, a method is proposed here to calculate the anisotropic factor of safety in terms of the location of the slip surface and the soil strength anisotropy ratio (Ar = Sue/Suc) obtained from the CK0U triaxial extension and compression tests, respectively. For any given slip surface, its Fs,A can be calculated from the Fs,A/Fs,I ratio determined with the proposed method, where the isotropic factor of safety (Fs,I) can be determined from the routine isotropic slope stability analysis. However, it should be borne in mind that the slip surface with the lowest Fs,I may not necessarily be the same slip surface with the lowest Fs,A. Therefore, the methods used to determine the slip surface of the lowest Fs,I should be adopted to locate the slip surface with the lowest Fs,A. Finally, the influences of slip surface location and strength anisotropy ratio on the Fs,A are also evaluated.

Effect of Strength Anisotropy on Bearing Capacity of Shallow Footing in a Dense Sand

Stress components in an anisotropic soil is analyzed on the assumption that it behaves like an anisotropic-rigid-plastic material. Numerical solutions by the stress characteristics indicate that the bearing capacity factor Nγ by self-weight is easily over-estimated about 40%∼50% when the effect of the strength anisotropy of sandy soils is neglected. The bearing capacity tests by means of a small testing box also support the possibility of the over-estimation. The ultimate bearing capacity is maximum when a strip footing is penetrated perpendicular to the bedding plane, while when a strip footing is penetrated parallel to the bedding plane, the bearing capacity becomes minimum. The ratio of the maximum to the minimum is 1.6 for dense Toyoura sand. In spite of the remarkable effect of the strength anisotropy on the bearing capacity, the residual bearing capacity is constant without any effect of the strength anisotropy. On the basis of the qualitative accordance between the experimental results and the anisotropic-rigid-plastic solutions taking account of the effect of the mean pressure, it can be said that the so-called scale effect of Nγ is mainly caused by the decrease of mobilized angle φ with the increase of the mean pressure.