Scour caused by stationary circular developing water jets in cohesive soils

Cohesive soil scour occurs in numerous hydraulic and geotechnical applications, yet it has received markedly less attention than scour in non-cohesive sediments. This study advances the understanding of scour processes induced by a vertical, stationary, circular, developing, low-pressure water jet impinging on cohesive soils. A series of small-scale laboratory experiments was conducted using jet pressures ranging from 4.3 to 10 kPa, with two tests extended until equilibrium scour depths were reached. The cohesive soil tested had an undrained shear strength between 4.5 and 5.9 kPa. The influence of key jet parameters, including nozzle diameter and stand-off distance, on soil erosion was investigated through measurements of erosion depth, erosion width, and erosion volume. The repeatability of cavities formed by stationary circular jets in cohesive soils was also examined. Additionally, a semi-theoretical formulation is proposed to predict the equilibrium scour depth. Unlike existing predictive models, the proposed formulation does not require soil-specific calibration parameters. The model was validated using data from the present experiments as well as independent datasets, demonstrating its robustness across different test conditions.