Scour of a cohesive soil by submerged plane turbulent wall jets

This paper presents the results of a laboratory study undertaken to examine the effect of hydraulic variables on the scour of a cohesive soil produced by submerged plane turbulent wall jets. The velocity and thickness of the jet were varied in tests with one cohesive soil in part to determine if repeatable scour experiments by these jets could be performed in cohesive material. Measurements were taken of the scour hole profiles at the asymptotic or equilibrium state of scour, including the maximum depth of scour, the location of the maximum scour depth, and the length of the scour hole. Dimensional analysis is used to show that the scour hole dimensions at asymptotic state can be expressed as a function of the velocity at the nozzle, the density of the eroding fluid, the nozzle thickness, and the critical shear stress of the soil. The scour hole profiles are shown to scale with the maximum depth of scour and the distance from the nozzle where the scour is half the maximum scour depth. Observations of the growth of the scour holes are also presented.