STRESS DEPENDENCY OF SHEAR WAVE VELOCITIES IN DILUVIAL GRAVEL SAMPLES DURING TRIAXIAL COMPRESSION TESTS

Abstract

Changes in shear wave velocities, V_S, which occurred during triaxial compression tests were measured on undisturbed samples obtained from a diluvial gravel deposit by an in-situ freezing method. Measurements on the reconstituted gravel samples were also conducted to compare the characteristics of shear wave velocity. The results of these measurements indicated that V_S increases at the initial stage of the triaxial compression tests, and decreases gradually until the failure of specimen and that the reduction in V_S was more noticeable for the undisturbed samples than for the reconstituted samples. The difference in the V_S reduction behaviour for the undisturbed samples and the reconstituted samples became remarkable after the expansive volumetric change occurred during triaxial compression tests. The results also revealed a unique relationship between V_S when evaluating the effect of stress ratio and confining pressure for both undisturbed and reconstituted samples at failure. Index of shear wave velocity is introduced to express uniquely the change of V_S in both undisturbed samples and reconstituted samples during triaxial compression tests.