University of Twente Student Theses


Uncertainty approach to the infill of navigation channels and trenches

Wertwijn, Cynthia (2013) Uncertainty approach to the infill of navigation channels and trenches.

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Abstract:Trenches and navigation channels are designed according to precise research in each area where they are placed. In this research the quantification of the uncertainties in the infill of these channels and trenches is studied. For studying this area the following goal is set: Quantifying the uncertainties of a deterministic morphodynamic model for sandy beds by a sensitivity and probabilistic analysis with taken into account the input parameters and their underlying relationships. The infill used to find the uncertainties needed to accomplish the goal is the amount of sediment that is placed in the trench after a time period. This infill is found by using the program SISYPHE and the by HR Wallingford recommended formulae for a flume. This goal can be split into 3 analyses, the sensitivity analysis, research of underlying relationships and probabilistic analysis. The sensitivity analysis will investigate the effect of each input parameter on the infill prediction. The settling velocity has the most influence on the infill prediction and the number of sediment classes does not have any influence on the infill prediction on its own. The research of underlying relationships between the input parameters resulted in simplified formulations. To create the simplified formulae a range is found by conducting a range for each found formula en combining these ranges to make the range that fits all the ranges for each formula. With these relations and the sensitivity analysis the probabilistic analysis is done. In this research, the Monte Carlo method is used. In the Monte Carlo approach, a model prediction will be computed multiple times, each time with different values for the input parameters. For every run, the Monte Carlo analysis chooses a value randomly for each input parameter within their ranges and uses these values to predict the sand bed infill. The different results together give a normal distribution for the sediment infill. With this normal distribution the average infill value and the uncertainty of the infill can be found. The average channel and trench infill is 0.1 m. Approximately 98% of the channels and trenches with sandy beds will have a sand infill lower than 0.35m. This infill can be taken into account with designing a channel to keep the trench depth below a needed depth, which can save time and effort in researching the sediment characteristics of the site. For the trench and channel width on trench depth 0.75m the average narrowing of the width for sandy beds is 11 m. 98% of the trenches and channel will lie between 14 and 34m. This result can also be taken into account with designing a channel to keep the trench width above a certain wide.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:38 earth sciences
Programme:Civil Engineering BSc (56952)
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