Effects of initial suction and degree of saturation on dynamic properties of sand at large strain

Soil deposits may experience different hydraulic states in terms of suction ( ) and saturation degree (Sr) while being subjected to large strain caused by dynamic loading during earthquakes. This phenomenon was investigated by considering the effects of initial , initial (Sr, sample preparation method, drainage condition, and cycle number (N) on dynamic properties. Shear modulus (G) and damping ratio (D) were specifically studied for unsaturated sand using a modified cyclic simple shear device for all zones of Soil Water Retention Curve (SWRC). Results revealed the relative significance of both and Sr in relation to SWRC on observed trends in G and D. Based on the analysis of some results in the literature, it was shown that most of the data followed a sigmoid function on the plane of normalized stiffness (G/Gsat) versus the suction normalized to the air entry value. It was also revealed that minimum damping was not in conjunction with maximum stiffness due to the contribution of other mechanisms in damping like inter-particle water lubrication. The comparison between results of two testing methods indicated the notable in fluence of initial fabric on G. Furthermore, the overall trends in G and D against N were marginally in fluenced by initial and Sr.