Evaluation and Remediation of a Small Landslide in Colluvium

A landslide in colluvium near Grafton, West Virginia was evaluated for cause and remediation. Monitoring was conducted for 15 months to observe further movements prior to remediation. The observed failure surface, slide geometry and groundwater conditions were used to back-solution for an effective residual friction angle ( φr’) . The φr’ was found to agree well with index property correlations cited in the literature. Slope failure resulted from excessive pore water pressures due to seasonably high groundwater levels. Stability analyses using the back-solutioned φr’ were performed to design and position seepage cutoff drains for slope remediation. As of this writing, September 1992, the drains have performed well and the slope has remained stable for three (3) years