Interpreting undrained instability of mixed soils by equivalent intergranular state parameter

The instability behaviour of loose saturated granular soils has been investigated extensively in recent decades. Most of these studies were conducted on clean sands (Castro, 1969; Sladen et al., 1985; Alarcon-Guzman et al., 1988; Lade, 1992). These studies have shown that very loose saturated sand can exhibit flow failure during undrained shear. As most granular soils contain a certain amount of fines (< 75 μm) in nature, the focus has shifted recently to the mixed soils (Pitman et al., 1994; Lade & Yamamuro, 1997; Zlatovic & Ishihara, 1997;...