Akimasa IHARA
Anisotropy of undrained strength on anisotropically consolidated cohesive soils
Hirofumi TOYOTA
When structures and embankments are constructed on the ground, stresses in the ground are acting from the various directions, which varies in each point of the ground. Because the stresses of ground are different in each point, the shear strength considering the stress state of real ground should be used in the stability analysis on the ground. Then, Bjerrum etc. proposed the experimental method to estimate real ground strength. However, it is impossible to decide ground strength using only one experimental test. Therefore, the evaluation method, which can estimate the strength anisotropy using only one experimental test, were tried to established. Anisotropic consolidations were carried out from various directions using a torsional shear apparatus, and then undrained shear strengths of the consolidated specimens were measured. Using the experimental result, rational evaluation method was proposed for estimation of anisotropy of undraind strength.
The main results are summarized as follows:
1. When the difference in direction between consolidation and shearing was larger, larger excess pore water pressure and smaller undrained strength generated during shearing. Similar tendency was also confirmed in the plane strain conditions.
2. When the difference in intermediate principal stress between consolidation and shearing was larger, larger excess pore water pressure and smaller undrained strength generated during shearing.
3. The effects of the direction and intermediate principal stress on undrained strength show the same tendency between Yoneyama silt and Kaolin clay.
4. Concerning about over consolidated specimens, the similar trend was appeared in the anisotropy of undrained strength.
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