Constant-volume cyclic bi-axial tests on assembly of metal rods with/without pre-shear histories

Abstract

Focusing on the effects of pre-shear histories on liquefaction behavior of granular media in this study, a series of cyclic bi-axial tests were conducted on assembly of metal rods, while maintaining a constant-volume condition that is equivalent to an undrained loading condition on saturated specimens. In the test cases with pre-shear histories, the cyclic loading was terminated when the double amplitude vertical strain reached a target value that was set in a range of 0.2 to 2.0%, and the specimen was re-consolidated isotropically, followed by the second cyclic bi-axial loading with the same amplitude of the cyclic deviator stress as in the first loading stage. During the tests, two digital cameras were used to record the side views of the specimen, and possible changes in the local void conditions were analyzed by conducting image analyses of the specimen photos. As a result, with the increase in the double amplitude of the vertical strain during the pre-shearing stage, densification of locally loose zones during pre-shearing became more significant, which may have induced the observed increase in the liquefaction resistance with the degrees of the pre-shearing.