Fine-grained colliery discard and its susceptibility to liquefaction and flow under cyclic stress

A spectrum of fine-grained colliery discards (tailings and slurries) has been tested in a cyclic loading triaxial rig.

The granular types are shown to be the most susceptible to liquefaction, compared with the more plastic discards which exhibit a slow build-up in pore-water pressure and gradual drop in effective stress with increasing shear strain. Plasticity index is consequently advocated as a useful physical parameter in assessing the general liquefaction potential of sediments of this type.

Observations of the mobile or “flowing” discards following liquefaction suggest that effective stress is the most important determinant of apparent viscosity. The post-liquefaction behaviour is believed to be pertinent to other inertia flows observed in nature.