Verification of a Predictive Formula for Critical Shear Stress with Large Scale Levee Erosion Experiment

Abstract

Apart from the soil erodibility parameter, the critical shear stress is the most important parameter in predicting erosion rates. On the basis of experiments several empirical formulas have already been de-veloped which relate the critical shear stress to soil properties. Based on these findings and supported by new large scale experiments, a new predictive relation between the critical shear stress and soil properties is proposed here. In support of this study, Delft University of Technology collaborated with Saitama University in the preparation and execution of a large scale levee erosion experiment in Janu-ary 2019. The erosion experiments were performed in the on a 1.8m high levee with a sand core and respectively clay and loam cover types. The cover types were subjected to a constant overflow dis-charge of approximately 70 l/m/s. The test levee was constructed in the Flood Proof Holland test pol-der in Delft, The Netherlands. During the experiment, time lapse measurements of the erosion depth were obtained at 15 locations along the landside slope. Before and after overflow tests were performed on each cover type, soil samples were collected along the landside slope at 8 locations. This paper out-lines how these large experiments were used to evaluate the effectiveness and application limit of the new predictive equation for the critical shear stress. A comparison between the predicted and meas-ured erosion rates shows that by applying the new empirical relation for the critical shear stress, meas-ured erosion rates could be predicted around ±30 % errors.