Effects of Large Number of Cyclic Loading on Deformation Characteristics of Dense Granular Materials

Abstract

This paper describes the results from a series of large-scale triaxial tests on dense sand and gravel to investigate the effect of large number of cyclic loading on their deformation. Specimens were prismatic with dimensions of 50 cm in height and 23 cm times 23 cm in cross-section. Deformation was measured locally to avoid the effects of membrane penetration at the side surface of the specimen and of bedding error at the top and bottom ends of the specimen on the measured strains. It is observed that by applying ten thousand cycles of vertical loading at a certain amplitude, the overall stress-strain relationship at a larger stress amplitude changed largely; for example, its shape changed from concave to convex. In addition, after enough pre-straining by cyclic loading, dense granular materials showed almost non-linear elastic behaviour. The test results also suggest the existence of threshold of stress amplitude so that if a large number of cyclic loading with this amplitude is applied, dense granular materials would become stable. This amplitude would be linked with the other factors, such as the density of the specimen, the state of neutral stress and the number of cycles. On the other hand, small strain Young's moduli are affected only to a limited extent by a large number of cyclic loading.