Bed failure induced by internal solitary waves
2017
Rivera‐Rosario, Gustavo A. | Diamessis, Peter J. | Jenkins, James T.
The pressure field inside a porous bed induced by the passage of an Internal Solitary Wave (ISW) of depression is examined using high‐accuracy numerical simulations. The velocity and density fields are obtained by solving the Dubreil‐Jacotin‐Long Equation, for a two‐layer, continuously stratified water column. The total wave‐induced pressure across the surface of the bed is computed by vertically integrating for the hydrostatic and nonhydrostatic contributions. The bed is assumed to be a continuum composed of either sand or silt, with a small amount of trapped gas. Results show variations in pore‐water pressure penetrating deeper into more conductive materials and remaining for a prolonged period after the wave has passed. In order to quantify the potential for failure, the vertical pressure gradient is compared against the buoyant weight of the bed. The pressure gradient exceeds this weight for weakly conductive materials. Failure is further enhanced by a decrease in bed saturation, consistent with studies in surface‐wave induced failure. In deeper water, the ISW‐induced pressure is stronger, causing failure only for weakly conductive materials. The pressure associated with the free‐surface displacement that accompanies ISWs is significant, when the water depth is less than 100 m, but has little influence when it is greater than 100 m, where the hydrostatic pressure due to the pycnocline displacement is much larger. Since the pore‐pressure gradient reduces the specific weight of the bed, results show that particles are easier for the flow to suspend, suggesting that pressure contributes to the powerful resuspension events observed in the field.
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