|M.Sc Student||Nawatha Hana|
|Subject||A Study of the Behavior and Strength of Undisturbed Sand|
Samples in Drained Triaxial Tests
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Mark Lloyd Talesnick|
|Professor Emeritus Sam Frydman|
The objective of this thesis is to investigate mechanical anisotropy of undisturbed sand specimens and the influence of fabric on their behaviour in drained triaxial tests. Testing was performed on both undisturbed and reconstituted samples for two kinds of sands. The tests on the undisturbed specimens were conducted in orientations parallel and perpendicular to the direction of sedimentation.
According to the results of the tests, the undisturbed samples for the two kinds of sand showed higher strength and higher stiffness than those of the reconstituted samples. This difference in behaviour indicates the influence of the original fabric on the response of the sand.
Comparison of the tests results for specimens tested parallel and perpendicular to the direction of sedimentation lead to the conclusion that one of the sands exhibited isotropic behaviour, while the second exhibited anisotropic response. In that which displayed anisotropic response it was found that the material stiffness in directions coincident with the direction of sedimentation was greater than its perpendicular counterpart. This difference in stiffness between the parallel and the perpendicular directions decreased as strain increased, so that at the end of the test specimens from the two directions displayed the same strength parameters.
In addition to these conclusions, two stress-dilatency theories (Rowe (1962) and Frydman (1972)) were examined and found to be valid from unset of shear through to failure, for both reconstituted materials and undisturbed specimens. The constants which were obtained according to the theories were different than the expected.