Impacts of Drying-Wetting and Loading-Unloading Cycles on Small Strain Shear Modulus of Unsaturated Soils

Abstract

The small strain shear modulus (G max) is an important parameter in geodynamic problems. In order to predict G max of unsaturated soils which are normally subjected to complex drying, wetting processes, effect of hydraulic hysteresis needs to be evaluated. Although several equations have been proposed in recent years, limitations still exist, requiring more research studies in this field. In this study, G max was investigated in a multi-stage test during several drying-wetting cycles and a loading-unloading cycle of net stress. The results revealed four key factors that directly influence the magnitude of G max : the void ratio, the net stress, matric suction and degree of saturation. While variations of the void ratio, net stress, and matric suction cause persistent responses of G max (i.e. if all other factors remain unchanged, G max would then be reversely proportional to the void ratio and directly proportional to the net stress and matric suction) , variations in the degree of saturation result in different responses. A decrease in the degree of saturation may induce a reduction or growth of G max since on the one hand it reduces the effect of matric suction, while on the other hand it increases the total effect of van der Waals attractions and electric double layer repulsions. At the same stress state, a reverse trend, induced by an increase in the degree of saturation, will occur with a growth in the effect of matric suction Void ratio Void ratio function Maximum small strain shear modulus k Material constant Propagation distance

Changes of small strain shear modulus and microstructure for a lime-treated silt subjected to wetting-drying cycles

“…Nevertheless, Anggraini et al (2016) indicated that wetting-drying cycles could make the curing time longer, and therefore the durability of stabilized soils was enhanced. Similar strengthening behaviour was observed on untreated soil -Gmax increased with increasing wetting-drying cycles due to the effect of suction history-related decrease of saturation degree and void ratio (Heitor et al, 2015;Ngoc et al, 2019;Khosravi et al, 2020). Estabragh et al (2013) investigated the wetting fluid (distilled water, saline water and acidic water) effect on the volume change of swelling soil during wetting-drying cycles.…”

Very-small to large strain dynamic behaviour of unsaturated sand in a wide range of suction

“…In the literature, similar observation was reported. The observed increase in G max may be attributed to the plastic hardening as soil dries and develops suction [1,16]. Fig.…”

“…Shear moduli at very small strain (G max ) and large strains (G), are crucial parameters for predicting soil movements and response of soil-structure system when subjected to dynamic loading and when investigating the quality of earthworks via a spectral analysis of surface waves [1]. The constraint modulus (M), on the other hand, was another important soil parameter when designing buried pipe lines and pavements [2,3].…”

The Influence of Temperature and Water Content on the Behavior of Soils

“…During the drying process, the water content decreases and the air content increases, resulting in an increase in the van der Waals attraction and reduction of the electrical double repulsion. This results in the aggregation of clay particles [35]. On the contrary, during the wetting process, soil suction and van der Waals attraction between soil particles will decrease, and the electrical double layer repulsion will increase.…”