Investigation of Rate of Erosion of Soils in Embankment Dams

TLDR

Slot and hole erosion tests were developed to characterize soil erosion in embankment dam cracks, using the erosion rate index and critical shear stress as key metrics. The study aims to use these erosion characteristics to evaluate the risk of dam failure from piping erosion. Erosion rate indices ranged from 0 to 6, indicating up to a million‑fold difference in erosion rates, with higher rates linked to soil fines, clay content, plasticity, dispersivity, compaction water, density, saturation, clay mineralogy, and cementing materials, and coarse‑grained noncohesive soils eroding faster and having lower critical shear stresses than fine‑grained soils.

Abstract

The slot erosion test and the hole erosion test have been developed to study the erosion characteristics of soil in cracks in embankment dams. The erosion characteristics are described by the erosion rate index, which measures the rate of erosion, and the critical shear stress, which represents the minimum shear stress when erosion starts. Values of the erosion rate index span from 0 to 6, indicating that soils can differ in their rates of erosion by up to 106 times. The rate of erosion is shown to be dependent on the soil fines and clay sized content, plasticity, and dispersivity; compaction water content, density and degree of saturation; and clay mineralogy, and possibly the presence of cementing materials such as iron oxides. Coarse-grained, noncohesive soils, in general, erode more rapidly and have lower critical shear stresses than fine-grained soils. Knowledge of the erosion characteristics of the soil in the core of an embankment dam aids in the assessment of the likelihood of dam failure due to piping erosion.