Interpreting filtration-based suffusion criteria using micro-Computed Tomography and laboratory filter tests

Taylor, H. and O’Sullivan, C. and Sim, W. (2016) Interpreting filtration-based suffusion criteria using micro-Computed Tomography and laboratory filter tests. In: ICSE 2016 (8th International Conference on Scour and Erosion), 12-15 September 2016, Oxford, UK.

PDF PA_1_10-Taylor-H.pdf Download (1MB)

Abstract

In a cohesionless soil containing a mixture of coarse and fine particles, suffusion is the erosion of the fine particles which can be transported through the void space between the coarse particles. Two commonly used criteria for suffusion are Kézdi (1979) and Kenney & Lau (1985), both of which were determined empirically and both include a limiting factor of 4 between fine and coarse particle sizes. This factor of 4 is often interpreted based on simple filter criteria, as the ratio between the size of coarse particles and the size of constrictions in the void space, with some factor of safety. To fully understand the suffusion mechanism it is necessary to consider the size of void constrictions, but also how far fine particles can move before they are retained and the potential for the fine material to self-filter. Several researchers have used empirical and numerical results to show that the criteria are conservative, however these studies could not clearly distinguish between the issues of constriction size, particle movement and self-filtration. This paper uses micro-Computed Tomography (microCT) images to examine the underlying filter criteria, by measuring constriction sizes relative to particle sizes for three materials. Laboratory filter tests, with minimal self-filtration, are then presented to observe particle movement. The results provide a new means to interpret the physical significance of the filter criteria, on which suffusion criteria are based.

Actions (for site administrators only - login required)

View Item