Laboratory Investigation of the Influence of Sediment Compaction on Wave-Induced Pore Pressure Gradient and Sediment Concentration for a Sandbar

Abstract

 In this study, a barred beach profile was constructed and installed in a small-scale laboratory wave flume. The beach profile was composed of a fixed profile containing a sandpit in the middle part of the flume. Different wave conditions were provided to evaluate the effect of sediment compaction on the vertical pore water pressure and sediment suspension. The pressure gradients were achieved by finite difference of measurements from an array of transducers. The magnitude of pore water pressure, pressure gradient, and sediment concentration with low and high sediment compaction were compared. In general, the magnitude of pressure gradients within the sediment layers with high compaction were larger compared to the low compaction conditions. Similarly, the recorded pore water pressure and sediment concentration were examined, and different behaviors such as the differences in the magnitude of the pore water pressure and pressure gradients due to different sediment compaction levels under almost the same hydrodynamic conditions were observed. The average of peak pressure gradients within the sediment layers under high compaction conditions was 1.4 times larger than the low compaction conditions. These results indicate the necessity of a detailed investigation of sediment’s influence on pore water pressure gradient and sediment concentration.