The use of computational models for assessing trench infill
Type:
Presented during:
CEDA Dredging Days 1999 - Dredging Challenged (tunnels and hydrodynamic dredging), Amsterdam
Authors:
M P Dearnaley, W Roberts and T N Burt
Abstract: Trenches are dredged for a variety of purposes. They may be constructed perpendicular to the shoreline or they may cross an estuary or river. The cross section may be small, as befits a pipeline or outfall, or larger, as required for an immersed tube tunnel. The length may vary from a few tens of metres to several kilometres. One of the key aspects of the design process is assessing the potential for sedimentation in the trench during the course of it being constructed, prior to placement of the pipeline, cable or tunnel, during placement and prior to backfilling.
Computational modelling techniques are available to establish the flow and wave patterns over the trench and a variety of methods are available for predicting rates and patterns of sedimentation. The paper reviews the methods available and refers to appropriate case studies in which the authors have been involved.
The successful application of hydraulic models relies on the correct calibration and subsequent validation of the model. In order to calibrate the model and check the validity of the simulations, good data on the environmental conditions and sediment regime in the vicinity of the trench must be available.
The paper discusses the requirements for such data and identifies where often assumptions have to be made in the absence of long term, seasonal information on factors such as freshwater discharge, suspended sediment concentrations and the potential for bedload transport during storm and flood events.
Keywords: Trench, infill, siltation, model, prediction