Spatial and temporal progression of internal erosion in cohesionless soil

TLDR

The study used permeameter tests on four widely graded cohesionless soils to assess their susceptibility to internal erosion. Specimens were reconstituted as saturated slurries, consolidated, and subjected to multi‑stage seepage flow with increasing hydraulic gradient while monitoring internal instability qualitatively via visual observations and quantitatively through changes in gradient and axial displacement. The tests revealed how seepage‑induced internal instability progresses spatially and temporally, showing that suffusion and suffosion are governed by a critical combination of hydraulic gradient and effective stress.

Abstract

Permeameter tests were performed on four widely graded cohesionless soils, to study their susceptibility to internal erosion. Test specimens were reconstituted as a saturated slurry, consolidated, and then subjected to multi-stage seepage flow under increasing hydraulic gradient. The occurrence of internal instability is described qualitatively, from visual observations through the wall of the permeameter during a test and from post-test observations; it is also described quantitatively, from change of hydraulic gradient within the specimen and from axial displacement during a test. The results provide a novel insight into the spatial and temporal progression of seepage-induced internal instability. This insight yields an improved characterization of suffusion and suffosion in cohesionless soils, the progression of which appears governed by a critical combination of hydraulic gradient and effective stress.