Behavior of a Colluvial Slope

Methods of supporting the toe of a potentially unstable colluvial slope are discussed with reference to a site in the panhandle of West Virginia. The geology of the site is described, relating to the use of the applicable effective stress strength parameters—the residual, peak, or in-between. Field and laboratory evidence is presented to advance the hypothesis that healing of the slickensides has occurred, although the mechanism is not Known. The stress path technique is used to describe the most economical means of toe support, which is a drainage System for long-term stability, and a sheet pile wall anchored with tensioned earth ties that precompressed the toe of the slope for short-term stability. Construction control, by means of a compressive instrumentation system, is described. Field observations of pore pressures, subsurface movements, and anchor tie loads are presented to support the concepts.