Suffusion tests on cohesionless granular matter

ABSTRACT Under internal flow, hydraulic earth structures (dikes, levees, or dams) can incur a migration of particles possibly inducing a modification of hydraulic and mechanic characteristics. With the objective to characterize this phenomenon named internal erosion and its consequences on mechanical behaviour of granular materials, a large oedo-permeameter device has been developed. An axial load is applied on specimen together with a downward flow with a constant hydraulic gradient. During the testing time, the bench can measure the spatial change of density and interstitial pressure along the specimen. Axial deformation, injected flow and extracted mass are also measured during the testing time. Erosion of fine particles is characterised by an extraction (out of specimen) of these particles on downstream specimen part and also by a fine particles migration in the whole specimen. This suffusion induces a settlement and a localized increase of interstitial pressure. Afterwards a localized blowout appears and triggers large specimen deformations.