On the distinct phenomena of suffusion and suffosion

Abstract

Seepage-induced internal instability is a phenomenon whereby fine particles are transported from a non-plastic soil. A distinction can readily be made between a washed-out soil structure that remains intact and one in which some form of destruction or collapse of the structure accompanies the migration of fine particles. The three variables of a measured value of mass loss, a measured value of volume change and a value of change in hydraulic conductivity, deduced from measurements of hydraulic gradient and flow rate, are sufficient to quantify, and hence distinguish between, seepageinduced internal instability phenomena. The term 'suffusion' is advocated to describe the nondestructive response, which may be quantified by a mass loss, no change in volume and an increase in hydraulic conductivity. The term 'suffosion' is recommended to describe the instability phenomenon whereby the transport of fine particles by seepage flow is accompanied by a collapse of the soil structure. Accordingly, this distinct internal instability phenomenon may be quantified by a mass loss, a volumetric contraction and a change in hydraulic conductivity.

Experimental Investigation of Suffusion in Dam Core Soils of Glacial Till

“…By definition, suffused soils should not exhibit change in bulk volume (Fannin and Slangen 2014). This agrees with the unstable specimens in this study, thus indicating suffusion as the likely cause for the erosion.…”

“…It is a timedependent process triggered by a hydraulic gradient increase (Garner and Fannin 2010) that results in mass loss and changes in hydraulic conductivity but unchanged volume (Fannin and Slangen 2014), which may evolve over the timespan of months to years (Fell et al 2003). Typically, suffusion leads to seepage increase (ICOLD 2013); however, reported secondary effects are the formation of zones with low permeability and high gradients (Garner and Sobkowicz 2002).…”

Review of Application and Innovation of Geotextiles in Geotechnical Engineering

“…In an internally unstable soil, seepage may cause the phenomenon of suffusion; the transport of fine particles by seepage flow is accompanied by a collapse of the soil structure [28][29][30]. Because geotextiles have positive permeability and air permeability, they can be placed in the soil structure to allow the liquid in the soil to pass through and discharged, and play a role of soil conservation, which can effectively prevent the loss of soil particles, fine sand, and small stones in the upstream, prevent soil damage, and effectively avoid the phenomenon of suffusion [31][32][33].…”

Flume-scale experiments on suffusion at bottom of cutoff wall in sandy gravel alluvium

“…Suffusion, a type of subsurface or internal erosion, refers to the migration of fine particles in a coarser soil matrix; it can occur in the presence of widely graded or gap graded soils. With the loss of fine particles, local cavities and deformation (Fannin and Slangen 2014) can occur.…”

“…Suffusion-induced deformation, which is termed as "suffosion" by Fannin and Slangen (2014), and sinkholes in an embankment are specific concerns of dam safety. Understanding the mechanism of suffusion in deep sandy gravel alluvium, especially around cutoff walls, is of great importance for dam safety and is the subject of this study.…”