The stress-strain graph which we got was different, it has both a strain softening and hardening region. I had gone through this procedure for sand with the condition that samples were subjected to inclined principal stress during anisotropic consolidation. I have attached a sample stress-strain graph from a published journal.
Pls explain under which conditions the tests have been performed? (in graph)
Ko consolidated sample is subjected to a stress induced anisotropy in a tri-axial cell by varying both major and minor principal stresses to a required target value .
The above attached graph was test conducted on a sand sample and subjected to major principal of some inclination .
In a triaxial test, you can either use α=0 or α=90 you cannot change α inbetween. Can you explain how you do this?
For the graph i can infer that this softening and again hardening is due to phase transformation stage (i.e. when the material changes from contractive to dilative).
Sir, we done normal conventional tri-axial test but instead of isotropic consolidation, we did anisotropic consolidation. As you said we did test α=0 , but stress strain graph we obtained is like which i attached in my post. Here i attache one more graph from ASTM journal . They did test on clay sample and stress induced anisotropic consolidation but the stress strain graph is different from what i got. I followed the same procedure.
This phase transformation will happen on clay also. I got a paper which was stated that initial water content is reason for this pase transformation. But we were following slurry consolidation technique. If you have any paper supporting this can you tell .
There is a chance. It depends on what your initial stress directions are. If you consolidate your sample under kc condition with the horizontal stress higher than the vertical one and then shear it under compression, then you have a 90' rotation of stress. The reverse can occur under extension loading mode.
See this: https://curve.carleton.ca/system/files/theses/28575.pdf
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