Three-dimensional distinct element modelling and dynamic runout analysis of a landslide in gneissic rock, British Columbia, Canada

The McAuley Creek Landslide is a 6 million m³ gneissic rock slope failure that occurred in British Columbia (Canada) in late May–early June 2002. The geological strength index was used to characterize the quality of the overall rock mass and its reduced (damaged) quality near tectonic structures and alteration zones. Potential slope failure mechanisms were investigated using four analysis techniques including: kinematic analysis, surface wedge limit equilibrium (combination) analysis, block theory and three-dimensional distinct element models. Results from all four analyses suggested that the dominant slope failure mechanism was wedge sliding along the intersection of the gneissic foliation and a steeply dipping discontinuity set striking perpendicular to the slope. Of the 6 million m³ of material involved in the landslide, an estimated 5 million m³ was deposited immediately below the source area against the opposite valley wall, with the remaining 1 million m³ travelling an additional 1.6 km downstream. The runout behaviour was investigated using a three-dimensional dynamic analysis code.