Characterizing the variation of small strain shear modulus for silt and sand during hydraulic hysteresis

¹ Assistant Professor, School of Civil Engineering, Sharif University of Technology, Tehran, Iran
² Graduate Student, School of Civil Engineering, Sharif University of Technology, Tehran, Iran
³ Professor, School of Civil Engineering, Sharif University of Technology, Tehran, Iran

^a Corresponding author: khosravi@sharif.edu

Abstract

Experimental studies have indicated that the small strain shear modulus, G_max, of unsaturated silt and clay has a greater amount during imbibition than during drainage, when presented as a function of matric suction. However, due to material properties and inter-particle forces, different behavior is expected in the case of sand. Although considerable research has been devoted in recent years to characterize the behaviour of G_max of sand during drainage, rather less attention has been paid to the effect of hydraulic hysteresis on G_max and its variations during imbibition. In the study presented herein, an effort has been made to compare the G_max behavior of specimens of silt and sand during hydraulic hysteresis. In this regard, a series of bender element tests were carried out in a modified triaxial test device with suction-saturation control to evaluate the impact of hydraulic hysteresis on G_max for specimens of silt and sand. Trends between the G_max and matric suction for unsaturated sand were found to be different from those for silty specimens. The variations in G_max showed an up and down trend in both drainage and imbibition paths for sandy specimens, where plotted as a function of matric suction. Results also indicated smaller magnitudes of G_max upon imbibition than those during drainage; a behavior which is believed to be attributed to variations in suction stress with matric suction. In silty specimens, a stiffer response was measured during imbibition which was hypothesized to be due to drainage-induced hardening experienced by the specimens that was not fully recovered during imbibition.