Use of basic soil test data in internal erosion risk assessments

Abstract

Publication of the Environment Agency (EA) Guide to Risk Assessment for Reservoir Safety Management ( Bowles et al., 2013 ) has increased the interest and awareness in undertaking risk assessments on dams in the UK. The guide introduces a three-tier approach to risk assessments. Tier 1 is qualitative and tier 2 introduces some basic quantitative tools. Tier 3 introduces more detailed quantitative methods and methods of dealing with uncertainty. A key part of undertaking successful tier 3 internal erosion risk assessments is gathering and interpreting the correct geotechnical information. The International Committee on Large Dams bulletin ( Bridle, 2013 ) contains invaluable information taken from research around the world, which adds to our knowledge of the internal erosion processes via specialist test procedures and methods. On existing dams much of the information available is from historical site investigations using conventional investigation techniques and soil and rock testing. Many of the specialist tests used to evaluate the susceptibility of materials to internal erosion are not generally available in the UK and can be prohibitively expensive. This paper aims to make the most of commonly available standard classification test data to provide a means of obtaining information on the susceptibility of embankment materials to internal erosion. In many cases this may be sufficient to provide enough information for a reasonable tier 3 assessment to be made or identify areas where further information would be beneficial depending on the risk posed and potential consequences of dam failure.