Groynes were constructed west of the Volta river mouth sand spit in Ghana to mitigate the local average beach retreat of 6 m/year. Even though severe swell events occurred during the construction of the first couple of groynes, the sand spit retreat of about 150 m over less than 1 year was surprising. An in-depth analysis was done by performing a hindcast over that year with the 2DH morphological model XBeach. It qualitatively reproduced the sand spit evolution as measured in situ. The governing processes of the severe erosion of the sand spit, in addition to the effect of the groynes, were identified to be a longshore sediment transport gradient and differences in overwash occurrence. A second hindcast, without groynes, has shown that the groynes were not the main cause. It also demonstrated that the beach, which was to be protected, has clearly benefitted from the construction of the groynes.
As part of a new harbor development, a new offshore breakwater will be constructed, for which the use of coastal protection plain precast concrete elements (AccropodesTM II) is required. The applicable exposure class is S1 (ACI 318). Over 4'000 elements have been produced. The owner required guarantees on the sulfate resistance of the elements before accepting them for usage in the project. For this, a revision of the documentation available was conducted, complemented by a thorough field investigation, measuring the coefficient of air-permeability kT (Swiss Standard SIA 262/1) of preselected elements (damaged during transportation) and elements representing the 28 weeks of production. The site NDTs confirmed a high quality of the majority of elements that were judged fit for the purpose. However, the NDTs confirmed the questionable quality of those cast during the initial period, requiring further evaluation before acceptance.The paper presents the results of: water aggressiveness, cement chemistry, strength quality control and air-permeability kT, and the criterion used to assess sulfate resistance of the elements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.