Effect of clay fraction and water content on rheological properties of sand–clay mixtures

Debris flow mobility can be expressed through rheological properties including yield stress and viscosity. These rheological properties are major parameters to describe and predict behaviors of debris flow. In the present study, the effect of clay fraction and water content on the rheological properties of sand–clay mixtures with coarse grain particles was investigated using a large vane rheometer. All soil mixtures showed non-Newtonian fluid behavior. When clay content was in the range of 5–30%, yield stress increased with an increase of clay fraction. Yield stress and plastic viscosity exponentially decreased with an increase in water content. Plastic viscosity became more sensitive to the change in clay fraction when water content increased. Empirical equations were proposed to estimate rheological properties of soil. The results indicated that yield stress and plastic viscosity are more sensitive to changes in water content than changes in clay fraction.