Experimental Parametric Study of Suffusion and Backward Erosion

TLDR

Internal seepage in hydraulic earth structures entrains soil grains, altering particle size distributions, porosity, and mechanical and hydraulic properties, and has led to failures that underscore the need to better understand erosion processes. The study develops a novel experimental device that applies hydraulic stresses to crack‑free, reconstituted cohesive soils to characterize erosion evolution. A parametric experiment varied three key parameters to assess their effects on clay and sand erosion mechanisms using the new device. Results show that low hydraulic gradients cause clay suffusion, higher gradients trigger sand backward erosion, erosion extent depends on clay content, and confinement stresses complicate both phenomena.

Abstract

Within hydraulic earth structures (dikes, levees, or dams), internal seepage flows can generate the entrainment of the soil grains. Grain transportation affects both particle size distributions and porosity, and changes the mechanical and hydraulic characteristics of the earth’s structure. The occurrence of failures in new earth structures due to internal erosion demonstrates the urgency of improving our knowledge of these phenomena of erosion. With this intention, a new experimental device has been developed that can apply hydraulic stresses to reconstituted consolidated cohesive soils without cracks in order to characterize the erosion evolution processes that might be present. A parametric study was conducted to examine the influence of three critical parameters on clay and sand erosion mechanisms. When the hydraulic gradient was low, it was concluded that the erosion of the structure’s clay fraction was due to suffusion. When the hydraulic gradient increased, it was concluded that the sand fraction erosion initiation was due to backward erosion. The extent of the erosion was dependent on the clay content. The study underlines the complexity of confinement stress effects on both erosion phenomena.