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Construction variants for a Sandbar breakwater in a dynamic coastal area

Wilbrink, W. (2019) Construction variants for a Sandbar breakwater in a dynamic coastal area.

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Abstract:Conventional breakwaters are often built by rocks or concrete elements. Recently, CDR-International designed a new constructing philosophy for a portal breakwater. Using the concept of ‘Building with Nature' the idea is to develop a so-called ‘sand breakwater'. CDR-International has implemented this new concept of a breakwater for a port project at Lekki, Lagos State Nigeria. The construction of this Sandbar breakwater has been completed in the summer of 2018. The Sandbar breakwater is constructed in a highly morphodynamic area. Significant sediment losses during construction of the breakwater have been occurred due to wave and current impacts on the breakwater. Since this concept. For the construction of the Lekki Sandbar breakwater a certain method and sequence is devised which was on forehand seen as the most practical and financial profitable. However due to the lack of experience, an analysis of the construction process of the Lekki project regarding the occurred conditions, the executed construction method and the accompanying sediment losses would be useful. Since the Sandbar breakwater is a new concept and due to the fact that during the construction process certain moments significant nourished sand volumes was naturally moved outside the design profile, the idea arose that apart from the Lekki project construction method it would be useful to also investigate other construction methods or sequences. Based on the experiences and the large amount of data which have been collected during the Lekki project, CDR and Boskalis first want to analyse the construction process of the Lekki Sandbar breakwater project regarding the observed conditions and the occurred sand losses. Then, this Lekki project can be compared to other construction alternatives regarding not only morpho-dynamic behavior (sediment losses) but also on costs and feasibility by investigate what the best construction method is for the Sandbar breakwater concept. In order to be able to assess the morphodynamic behaviour of different construction variants for the Sandbar breakwater a morphodynamic model XBeach has been used. Before the assessment of the construction variant, first the performance of the model in the dynamical coastal system at Lekki is investigated. Then the sediment losses and the naturally accreted sediment into the design profile is quantified for all construction variants, followed by a financial cost and practicability assessment of these variants.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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