Abstract
Internal erosion is a complex phenomenon which represents one of the main sources of risk to the safety of earth hydraulic structures such as embankment dams, dikes and levees. Its occurrence may cause instability and failure of these structures with consequences that can be dramatic. Erosion by suffusion corresponds to the process of detachment and transport, under the action of hydraulic flow, of the finest soil particles within the porous media formed mainly of large grains. Its occurrence usually causes change of the initial microstructure and hence a change in the physical, hydraulic and mechanical characteristics of the soil. In this study, we present first an experimental characterization of the erosion mechanism during its occurrence within a granular soil. Particular emphasis was put on the role of hydraulic conditions in triggering of fines migration. Thereafter, we present a preliminary microstructural characterization of the erosion process through direct visualization by optical techniques of particles migration using crushed glass samples as model materials.
Highlights
The suffusion phenomenon corresponds to the process of detachment and transport under the action of hydraulic flow of the finest soil particles within the porous media formed mainly of large grains
The hydraulic gradient governing the onset of internal erosion is named "critical hydraulic gradient", and has been widely studied to better understand the hydraulic conditions leading to the initiation of internal erosion
This work was tackled by suffusion tests on real soil samples which showed that the erosion phenomenon could occur before reaching the hydraulic gradient corresponding to the observed wash-out of fine particles
Summary
The suffusion phenomenon corresponds to the process of detachment and transport under the action of hydraulic flow of the finest soil particles within the porous media formed mainly of large grains This phenomenon, often termed as internal instability, was first observed in studies related to base soil-filter compatibility against seepage flow. Skempton and Brogan [5] argued that the “segregation piping” occurs at the hydraulic gradient one third to one fifth of the Terzaghi’s critical gradient for a homogeneous granular material of the same porosity These critical hydraulic gradients are measured just before the onset of erosion for which the hydraulic forces generated by seepage flow are large enough for detached particles to pass through. The real hydraulic gradient causing the initiation of erosion (first movement of particles) could be underestimated
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