Scouring by submerged steady water jet vertically impinging on a cohesive bed

摘要

In this study, an experimental apparatus was designed and set up a in laboratory to observe the vertical submerged jet scouring of cohesive beds. The critical conditions for the onset of scouring, as well as the scour hole dimensions were investigated. The test cohesive beds had different water contents and contained 12.5% clay, 73.5% silt, and 14% fine sand. Based on the experimental and dimensional analysis results, the scour hole dimensions are predicted as functions of the jet velocity, scouring duration, impingement height, jet nozzle diameter, water content, and critical shear stress of the bed sediments. In addition, a scour rate formula for the initial stage is proposed in terms of the dimensionless water content and the dimensionless excess shear stress. As these parameters are defined and already known, the developed functional relationships have immense potential and application in engineering works such as dredging or extraction of objects such as anchors from sediment bed.