Abstract
Abstract Constructed slopes are traditionally given a planar form. However, natural slopes are more likely to be concave in cross section. In addition, laboratory and computational studies have demonstrated that concave slopes yield less sediment than planar slopes. With current autoguided construction equipment, it is now possible to construct slopes with concave profiles and a more natural appearance, yet a simple method to describe such concave slopes for a given level of mechanical stability does not exist. This article begins with an examination of concave shapes satisfying a desired degree of stability and compares results with those from the FEM and limit-equilibrium method of analysis. An erosion model is used to demonstrate that the concave slopes proposed here yield 15–40% less sediment than planar slopes with the same factor of safety. Finally, a sensitivity analysis suggests that reasonable construction deviations do not compromise the stability of typical concave slopes.
Highlights
Slopes traditionally designed to be planar in cross section...Land-forming Geomorphic Reclamation approachesCan include the construction of concave shapes in the transversal and longitudinal directionsMore natural features with improved stability and erosion resistanceAnaheim Hills (Schor and Gray 2007)Transversely Longitudinally concave concaveGravitational stresses in slopes increase with depthTo maintain a uniform Factor of Safety (FS) the inclination must decrease downslopeErosional stresses on the surface of the slope increases with inclination and distanceIf the slope inclination decreases as we move downslope, the erosional stresses are more uniform and lowerFor these reasons, slopes observed in nature are usually not planar (Adapted from Schor and Gray 2007)
High K factors occurred during rill development, followed my slope erosional stabilty
SEDCAD model was sensitive to selection of Curve Number (CN), for example a 40 % deviation in selection would approximately double sediment yields from the model
Summary
Methods exist to estimate: 1) mechanical slope stability, and 2) hillslope sediment delivery. Methods have been developed for planar slopes, and existing studies would suggest concave slopes may improve stability coupled with reductions in surface erosion. In this presentation we: Summarize field experiments quantifying the Revised Universal Soil Loss Equation (RUSLE) erodibility (K) factor for Appalachian surface coal mining reclamation sites. Demonstrate that concave slopes may provide improved performance than planar slopes in terms of both mechanical and erosional resistances. Demonstrate that RUSLE2 model is suitable for estimating sediment yields from reclaimed soil materials and slopes with concave geometries
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