Effects of sand and water contents on the small-strain shear modulus of loess

Characterizing soil properties at small-strains (<10(-5)) is a subject of long-standing interest for geotechnical engineers at both academic and practical levels. Compared to conventional soil types, such as sand or clay, the small-strain properties of loess are less extensively studied and remain poorly understood. This paper presented an experimental study to investigate the influence of sand and water content on the small-strain shear modulus (G(0)) of Yan'an loess. A specifically designed experimental program was conducted for a sequence of sand-loess mixtures under unsaturated conditions using the resonant column technique. It was found that, in general, the G(0) of loess decreases with the water content. By using the water content as a state variable, its dependence on G(0) was established. The study also showed that under otherwise similar conditions, the G(0) of the sand-loess mixture is lower than that of loess without sand. However, a further increase of sand content beyond a threshold value (15%) induces no remarkable difference in terms of G(0). These findings suggested that the presence of sand plays an important role in the small-strain behaviours of loess. The underlying reasons behind these observations were provided, along with a detailed interpretation at the micro-scale level. To enhance the practicability, an empirical model was also proposed for sandy loess, and it could provide reasonable estimates of G(0) for both loess samples in the current study and loess data in the literature.