Initial observations on the direct simple shear loading response of sand-silt mixtures with layers

Laboratory experimentation has contributed significantly to the current understanding of the mechanical response of coarse-grained and fine-grained soils, particularly in characterizing such materials with respect to general shear loading. In spite of this, the current understanding on the shear loading response of interbedded sand-silt layers is very limited. In most of the past studies, the experimental studies have been focused on testing uniform sand-silt specimens with homogeneous mixtures, although natural sand and silt deposits exist predominantly in the form of interbedded layers as opposed to homogeneous mixtures. This is largely due to the gravity depositional processes that occur in deltaic and marine settings. The focus of the study presented herein is to compare the monotonic and cyclic shear loading response of interbedded sand-silt specimens with that corresponding to homogeneous sand-silt mixture specimens. A limited number of undrained monotonic and cyclic direct simple shear tests were conducted on normally consolidated, reconstituted specimens of Fraser River sand and silt with pre-selected sand-silt composition, with some specimens simulating silt/sand layering, and the initial observations from this work is presented herein.