Initial Observations on Laboratory Shear Loading Response of Sand-Silt Mixtures

An experimental research program has been undertaken to investigate the monotonic shear loading response of sand-silt mixtures covering the complete range of sand-silt compositions in the mixtures. Initial observations and findings from the undrained monotonic triaxial compression and extension testing, as well as from drained triaxial compression tests, performed on non-plastic Fraser River silt, Fraser River sand, and 50%-50% mixture of the same two materials, are presented. The specimens of Fraser River sand were prepared using water-pluviation, and specimens of silt and sand-silt mixtures were prepared via slurry deposition. The results presented provide an initial insight to the complex behavioral patterns emerging from drained, undrained, compression, and extension loading responses, under some select sand and silt compositions. The findings illustrate the variation of the key soil parameters such as stiffness, shear strength/friction angle as the soil transitions from a coarse-grained to fine-grained matrix.