Development of Design Criteria for Cut Slopes in Loess: Fid-Bau Portal

Development of Design Criteria for Cut Slopes in Loess

Highway cut slopes in loess were studied throughout Missouri to evaluate the relationship of performance to slope angle, orientation, stratigraphy and various physical properties. Deep cuts for which preconstruction data was available were studied in detail. Samples were obtained by various techniques to determine effects on density and moisture content. It was concluded that stratigraphic identification, while useful, was less valuable than determination of physical properties for prediction of slope behavior. Moisture content and grain size distribution were found to correlate well to observed performance and types of failure. Freeze damage, of a form analogous to subgrade frost heave, was found to be a significant source of degradation of vertical slopes. It was concluded that severe limitations should be placed on use of vertical slopes in loess. Procedures and criteria are proposed for slope selection, methods of stability analysis and types of sampling and testing to be performed during the soil survey. Particular emphasis is given to moisture and clay content, slope orientation, accurate logging of water tables and zones of saturation and to sampling from dry (augered) holes.