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Influence des interactions mécaniques eau-sol sur l'érosion interne

Abstract : Internal erosion is one of the main causes of instabilities within hydraulic earth structures (dike, levee, dam,...). The occurrence of breach in new structures underlines the urgency to quantify phenomena induced by internal erosion. Entrainment and migration of some particles under flow affect the porosity and grain size distribution, which change the hydraulic and mechanical characteristics. These phenomena in sand-clay soils are not sufficiently understood. Therefore, we focus this study on this type of soils that are frequently present in earth structures.
Preliminary tests are performed to show and to quantify the influence of four parameters (volumic weight, kaolinite percentage, hydraulic gradient and filter pore opening size). These tests permit to validate the choice of these parameters, and to define a device and an experimental procedure. The realized experimental device consists of three modified triaxial cells that allow to control the confining pressure, to prevent any parasitic flow and to follow great deformations of samples.
Downward flow under constant hydraulic gradient is applied to the samples. A computer performs automatically: flow, confining pressure, eroded mass, volume variation of samples and effluent concentration. A confrontation between a study present in bibliography and performed tests permits to validate the experimental procedure. Thanks to a parametric study, we identify a minimal value of hydraulic gradient to initiate the suffusion of clay. This critical value increases with the percentage of kaolinite and the confining pressure. When the hydraulic gradient reaches a second critical value, the backward erosion of sand accompanies the migration of clay. This erosion induces a piping and finally the samples collapse. The increasing of kaolinite percentage and the decreasing of confining pressure induce an increasing of this critical hydraulic gradient. The influence of sand characteristics on piping has been also shown up.
We propose a first 1D numerical modelling of suffusion; this model allows to represent the evolution of effluent concentration and eroded mass.
This work permits to define interesting perspectives of theoretical or experimental research.
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https://tel.archives-ouvertes.fr/tel-00355072
Contributor : Fateh Bendahmane <>
Submitted on : Monday, February 2, 2009 - 10:35:21 PM
Last modification on : Monday, March 25, 2019 - 4:24:08 PM
Long-term archiving on: : Wednesday, September 22, 2010 - 11:16:17 AM

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  • HAL Id : tel-00355072, version 2

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Fateh Bendahmane. Influence des interactions mécaniques eau-sol sur l'érosion interne. Sciences de l'ingénieur [physics]. Université de Nantes, 2005. Français. ⟨tel-00355072v2⟩

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