Waterline Oscillation and Riprap Movement

Abstract

Eight test runs using a 1:3 glued gravel slope with an impermeable base were conducted in a wave tank to evaluate and calibrate the numerical model developed previously. For each run with the specified incident wave train generated in a burst, measurements were made of the free surface oscillation at the toe of the slope, the waterline oscillation on the slope, the temporal variation of dynamic pressure on the base of the slope, and the displacements of loose gravel units placed on the glued gravel slope. First, the friction factor associated with the rough slope is calibrated within a relatively narrow range using the measured waterline oscillation. The calibrated numerical model is shown to predict the measured hydrodynamic quantities fairly well. Second, the coefficient for the lift force acting on a sliding gravel unit is calibrated in the range 0.18‐0.4 by comparing the measured and predicted displacements of loose gravel units on the 1:3 glued gravel slope. The computed results based on the calibration of the lift coefficient alone are shown to be in reasonable agreement with the measured gravel displacements. However, these comparisons also indicate the limitations of the calibrated numerical model.