Residual strength characteristics of Bothkennar clay

The Paper describes a series of ring shear experiments which were performed to assist the interpretation of instrumented pile tests carried out at Bothkennar. Data are presented from soil-soil and soil-interface experiments. The interface used was a sand blasted annulus of stainless steel and tests were made at a variety of displacement rates. The large displacement shearing behaviour was found to be turbulent, despite the soil's high clay fraction and plasticity index, with slow residual ' ~ 30°. There was no sign of the large difference often seen with high' clays between soil-soil and soil-interface tests. Marked reductions in shearing resistance were found (post-peak) in high-speed tests. These were transitory and probably associated with a change in the basic mechanisms of shearing, rather than the creation of highly ordered residual soil fabric.