Shiho HASHIMOTO
Effects of Drained Conditions on Anisotropy of Shear Strength in Saturated Cohesive Soil
Supervisor: Hirofumi TOYOTA
Simple mechanical element tests such as the unconfined compression test are usually conducted using undisturbed samples obtained from the real ground for the conventional slope stability analysis. However, precise shear strength cannot be inferred from the simple tests because the stresses in the ground have acted from the various directions after the structures were constructed on the ground. Bjerrum et al. proposed the experimental methods to estimate the real ground strength, and they observed the anisotropy of saturated undrained shear strength in the real ground by combination of simple mechanical element tests.
However, drained strength is necessary to discuss the long-term stability of the ground. Especially, the drained strength is important in the over-consolidated clay because it tends to be smaller than the undrained strength. Therefore, anisotropy of the drained shear strength was examined using saturated cohesive specimens, which are changed over-consolidation ratio, OCR, and the major principal stress direction by the hollow cylinder torsional shear apparatus.
The main results are summarized as follows:
1. There is the anisotropy of the elastic shear modulus in normally and lightly over-consolidated soils. Elastic shear modulus decreases with the increase of the difference of major principal stress direction between consolidation and shearing.
2. However, there is not the anisotropy of the elastic shear modulus in heavily over-consolidated soils.
3. There is the anisotropy of the drained shear strength in heavily over-consolidated soils. The drained shear strength decreases with the increase of the difference of major principal stress direction between consolidation and shearing.
4. However, there is not the anisotropy of the drained shear strength in normally and lightly over-consolidated soils.
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