A particulate perspective on soil internal erosion in embankment dams

Dr. Tom Shire

Embankment dams and levees constructed from soil are critical public infrastructure for flood prevention, water storage and hydroelectric power generation. Internal erosion, also known as piping, is one of the main causes of dam and levee embankment breach during floods. It occurs when soil particles are washed out of an embankment by water seepage, eroding material from within until the embankment collapses.

This presentation will consider recent work to improve our understanding of suffusion, one of the major forms of internal erosion. Suffusion involves the preferential erosion of finer grains in gap–graded or broadly-graded soils. Two conditions for suffusion are that (i) fine particles must be under low stress so that they can be easily eroded by seepage (ii) the fines must be small enough to pass through the pore throats between larger particles.

Schematic diagram of prerequisites of suffusion Image of virtual soil sample used in DEM simulations

The presentation will explore each of these conditions from a grain-scale perspective. Firstly, links between empirically-based rules used to assess suffusion and the nature of stress transmission between particles in a gap-graded soil are investigated using discrete element modelling (DEM), a grain scale technique used to study the fundamental mechanisms of suffusion.

Secondly, approaches used to measure pore throats in filters and the link between the filter particle size distribution and the throat diameters are considered. Insights from these measurements will be compared to filter rules used in practice, from Terzaghi’s original filter rule to semi-empirical approaches developed in recent years.

About the speaker

Dr. Tom Shire School of Engineering, University of Glasgow

Tom Shire is a Lecturer in Geotechnical Engineering at the University of Glasgow and a UK Chartered Civil Engineer. He has been a Research Associate in the Geotechnics section at Imperial College London for around 2 years and a Phd Graduate of Imperial College focusing on discrete element modelling (DEM) of granular filters for embankment dams and other geotechnical structures. He has been awarded the Unwin Prize for the best PhD in the Department of Civil and Environmental Engineering at Imperial. Thomas’s research interests are in geotechnical engineering including embankment dams and unsaturated soils, and granular materials in general. Thomas has experience using discrete element modelling (DEM) with high performance computing (HPC) and coupled DEM-computational fluid dynamics (DEM-CFD). He has applied these tools to topics including the internal erosion of dams and levees and other areas dealing with erosion including sand-washing in hydrocarbon recovery. He is a member of the Glasgow Computational Engineering Centre and the recipient of The Melbourne University 2019 International Visiting Fellowship award.

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