Modelling of internal erosion by suffusion in soils

Internal erosion by suffusion may develop in the bulk of a soil volume when the particle size grading and the porosity are such that the fine fraction of the soil can migrate through the skeleton formed by the coarse fraction. During this phenomenon, fine solid particles are firstly detached by the action of water seepage, secondly transported through the empty space between the coarse grains, and finally redeposited (filtered) within the interstitial space of the soil itself, possibly resulting in a clogging and the reduction of the porosity. Suffusion is generally considered as a low kinetic phenomenon but recent experimental results have shown that this last step of filtration and clogging may initiate a second erosion phase, characterised by a much higher kinetic, which was observed to be very aggressive for the soil micro-structure. Therefore this second erosion phase may be damaging for the durability of water retaining structures made of soil, and would allow very little time to take actions.

The objective of the project is to characterize the conditions under which the transition between these two phases is observed, and to improve in particular the description and the understanding of this second quick and aggressive erosion phase.

Our investigations are principally based on numerical simulations performed with the coupled DEM-PFV method (1) in order to take into account both fluid and solid behaviours. These numerical investigations will benefit from the coupling with laboratory tests performed in the GeM Institute (Civil Engineering and Mechanics) where experimental devices dedicated to the characterization of suffusion have been developed.

(1) Discrete element method and Pore Network Finite Volume, implemented in the code YADE and developed at 3SR Laboratory