Search Results (3)

The failure of an embankment causes loss of lives, massive damage to infrastructure and the interruption of basic facilities; it has thus drawn increasing attention from researchers. When compared to other types of embankment disasters, overtopping-related embankment breaches are much more frequent. The study of the breach mechanism of embankments due to overtopping is becoming more and more essential for developing evacuation plans, early warning systems and damage assessment. To recognize the breach activities of embankments, it is necessary to find out discrete breach considerations like breach depth, breach initiation, breach width, etc. In the present study, a total of six tests were performed in a narrow flume using an embankment model. By conducting different experiments, it was observed that embankment breaching may be described in three stages, i.e., initial erosion, headcut erosion and lateral erosion. Furthermore, erosion is a three-dimensional process that occurs during embankment breaching, with the majority of erosion movement being associated with lateral broadening. The rate of headcut migration also has an impact on the widening rate. Furthermore, it depends upon the type of fill material and dam geometry. Also, the observed effect of moisture content on breach widening proved that the rate of widening was strongly influenced by water content. A drop of about 50% in moisture content causes approximately a 20% decrease in time to failure. In the present study, it is observed that breach shape could not be assumed to be regular shape like rectangle or trapezoid, as described in the literature. The trials were carried out in a narrow flume under constant hydraulic conditions, which are two of the study’s limitations. Full article

Previous studies have proved that root distribution along gully headwalls greatly alters soil properties and further affects the soil erodibility of gully heads. However, it is not clear whether the gully headcut migration is affected by root distribution and soil properties. Five representative gullies developed in different land uses were selected to clarify the variations of root distribution and soil properties and their effects on headcut migration in the rainy season (May to October 2021) in the Mollisols region of northeast China. Results showed that the 68.4%–93.3% of root mass density and 65.6–88.5% of root length density were concentrated in 0–30 cm soil layer of gully heads, and the roots of <2.0 mm accounted for >85%. The gullies developed in farmlands had relatively higher soil compactness, shear strength and aggregate stability, but lower organic matter (OMC), disintegration capacity and soil permeability than those developed in woodlands, unpaved roads in farmland and stable gully-beds. Changes in soil properties of gully heads were closely related to root density. The linear, areal, and volumetric migration rate of gully heads varied greatly and were 1.07–35.11 m yr⁻¹, 28.95–562.46 m² yr⁻¹ and 56.82–6626.37 m³ yr⁻¹, respectively, with the average of 9.07 m yr⁻¹, 156.92 m² yr⁻¹ and 1503.02 m³ yr⁻¹, respectively. The change in headcut migration rate was significantly affected by root density, soil properties and drainage area, of which soil texture, OMC, soil aggregate structure, and the drainage area were the critical factors influencing headcut migration in the Mollisols region of northeast China. Full article

The headcut migration describes the physical process of breach side slope retreat that governs the widening of the breach. Modeling the growth of a breach due to embankment failure is the first step in mapping the resulting inundation in a floodplain. As removal of soil from the toe of the headcut effectively removes physical support for the upper part, the headcut fails on the plane normal to the direction of tensile stress. This process is a typical mode of tensile failure. A numerical model of the headcut migration was established by integrating the effects of the soil tensile strength, soil permeability and embankment geotechnical characteristics. Thus, a simple analytical equation was finally obtained to predict the critical length of the headcut. Furthermore, the presented model was verified by using the limit equilibrium method (LEM) for three typical embankment scales (2, 4 and 6 m high). The comparisons between the present model and the LEM show good agreements. The present model could provide a simple method to predict the critical length of the headcut migration and easily be adopted to breach widening models. Full article