Title

Slip 'N Slide: Quantifying the effect of pore fluid on landslide travel distance

Abstract

If you had a Slip 'N Slide toy as a child, it would likely come as no great revelation to you that the presence of water on a slip plane reduces the available frictional resistance and increases landslide travel distance. But how can we quantify how pore pressure affects travel distance? Can it be explained just using effective stress, or is it more complicated? Does that answer depend on whether the debris can generate and maintain excess pore water pressures? In this presentation, we use large-scale flume tests to explore the mechanisms through which pore pressure affects landslide travel distance. Starting with the case of "no pore pressure", we release progressively larger volumes of dry material from 0.2 m3 to 1 m3 to explore the relationship between landslide volume and runout using high-speed imaging and LIDAR scans of the deposit. This base case is the easiest case to model [monodisperse (single sized) dry granular flows with a large particle size of 3 mm] and defines our friction coefficient. We then increase the degree of difficulty by adding water as a pore fluid into the pore spaces of this same material. How does this relationship change? We then increase the degree of difficulty yet again by switching to a material that has a sufficient particle size distribution to permit the generation of excess pore water pressures on release. At rest, our new widely-graded debris flow material has a coefficient of consolidation that results in excess pore water pressure dissipation in 0.7 seconds. What would happen if the travel time of this material took 7 seconds? Would the pore pressures dissipate during travel? How can we tell? How do we measure pore pressures at the base of a landslide? Join us as we use physical modelling to explore the answers to these questions, which are vitally important to be able to assess whether increased extreme precipitation events associated with climate change may not only make landslides more frequent, but also exhibit heightened mobility and consequences.

Bio

Dr Andy Take is Professor and Canada Research Chair in Geotechnical Engineering at Queen's University, Canada. Andy's team uses physical modelling and new monitoring techniques to explore topics of infrastructure climate change resilience, failure mechanisms of landslides and tailings dams, and to advance infrastructure field monitoring techniques. The work of Andy and his team of graduate students have been recognized with major international awards including the RM Quigley Award and Fredlund Award of the Canadian Geotechnical Journal, the Casimir Gzowski Medal of the Canadian Society for Civil Engineering, the Tso Kung Hsieh Award of the UK's Institution of Civil Engineers, and the International Geosynthetics Society Award of the International Geosynthetics Society.