Numerical Simulation of the Backfilling Process of a Trench Using a Trailing Suction Hopper Dredge

Deposition of sediment by means of discharging via the bottom doors of a Trailing Suction Hopper Dredge is a method often used. This method can be deployed for land reclamation and backfilling of trenches for pipelines or outfalls. The sediment will leave the hopper as a mixture of sand and water. Sand will settle from this mixture. The shape of the under water body is governed by the dynamic settling process from a (sometimes highly concentrated) density current. Slopes angles and density of the sand body and possible segregation is depending on the discharge production, sediment characteristics, water depth and ambient current. In the paper the discharge process is simulated using a 2 dimensional numerical model based on the Reynolds Averaged Navier-Stokes equations. In this model the momentum and sediment transport equations are solved. The model includes a morphological module therefore slopes angles can be predicted. The computational results are validated using laboratory tests. The efficiency of the backfilling process, expressed as the ratio between the volumes of settled sediment in the trench and the discharged sediment, is determined as a function of the domination process parameters.