Effect of Inherent Anisotropy on the Behavior of Fine-Grained Cohesive Soils

摘要

Study on shear strength and compressibility characteristics of soils considering anisotropy phenomenon is essential to the accurate design of structure foundations and stability analysis of earth structures. In this research, a series of triaxial and oedometer tests were used to study the mechanical behavior of a fine-grained cohesive soil considering the effect of inherent anisotropy on the behavior. For this purpose, a special soil sampler was made and different directions were selected to collect the samples from the site. All triaxial samples were isotropically consolidated under the effective stresses of 200, 300 and 500kPa, and loaded at the rate of 0.05mm/min. The results showed that the shear strength and compressibility of the soil intensively depend on the sampling direction. With an increase in the anisotropic angle, the shear strength values decreased and the settlement values increased. However, at the anisotropic angle of 72 degrees, the shear strength and settlement have minimum and maximum values, respectively. In addition, a review of failure surface illustrates that as the angle between the failure surface and the bedding direction decreases, the failure surface tends to be closer to soil stratification and it causes an increment in pore water pressure and reduction in shear strength. In general, samples cored perpendicular to the bedding direction showed dilative behavior, whereas the other ones exhibited contractive behavior.