Strain softening of K₀-consolidated Changi sand under plane-strain conditions

Experimental results are presented in this paper to study the strain softening behaviour of a marine dredged sand under plane-strain conditions. K₀ consolidated drained and undrained tests were conducted using a new plane-strain apparatus to characterize the strain softening behaviour of the sand under plane-strain conditions. For medium dense specimens, strain softening and shear bands were observed to occur under both drained and undrained conditions. For very loose specimens, no shear bands were observed and critical states were reached within the homogeneous deformation region in both drained and undrained tests. Strain softening was observed to occur at small strain for very loose specimens under undrained conditions. Two types of strain softening, the homogenous softening and banding softening, were identified and the conditions for strain softening were established. The results obtained from this study were compared with the studies by Han and Vardoulakis (Géotechnique 41(1):49-78, 1991), Finno et al. (J Geotech Eng ASCE 122(6):462-473, 1996, Géotechnique 47(1):149-165, 1997) and Mokni and Desrues (Mech Cohes-Frict Mat 4:419-441, 1998).