Geoacoustic methods in port areas: a multifrequency approach
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Data
2019-03-25
Autores
Soares, Alvaro Eduardo Silva
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Universidade Federal do Espírito Santo
Resumo
Geophysical methods are a set of indirect methods of investigation that have great relevance in the study of submerged areas and stand out from conventional methods. These methods allow easy access to the areas of research and continuous observation of the surface and subsurface along a profile. Geoacoustic investigation utilizes the physical principle of elastic wave propagation to investigate the seafloor morphology and subsurface layer thicknesses. In port regions, acoustic methods are widely applied for the determination of risks to marine navigation and dredging. Dredging projects are extremely costly and are potentially environmentally hazardous due to resuspension of contaminated materials and disruption of seabed conditions. Thus, single and multibeam bathymetry, seismic, sonographic and densitometric surveys are common activities for solving these and other issues. The acoustic signal backscatter pattern, obtained from these methods can be organized into groups and used for seabed mapping and sedimentological classification. The state of Espírito Santo has national prominence in logistics with its ports, notably the Vale's Port of Tubarão. The maintenance of the navigation channels has always been a concern for the company, for the Brazilian navy, local authorities as well as the local communities. Maritime ports generate a huge demand for resources, in addition to a series of environmental and social matters. Therefore it is of great importance to produce studies and techniques to map and identify the bottom and sub-bottom with both resolution and accuracy. The following questions are: what is the behavior of the different frequencies used on the most appropriate acoustic methods to map the sediment thickness in a navigation channel and what are the risks to navigation and dredging presented by defining such characteristics from these methods. These questions are answered through the study of the acoustic methods with a multifrequency approach to map the bottom and sub-bottom of the port areas, and the analysis of the signal response produced by these methods. In this project, acoustic techniques were used aiming at defining the best strategy and acoustic frequencies to be applied in maritime port terminals to solve questions concerning: nautical depth analysis, navigation risk assessment and the definition of the factual depth required for maintenance dredging. Acoustic multi frequency data and bottom unconsolidated density values were collected in order to respond to the abovementioned scientific questions
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Geoacoustics , Multifrequency approach , Seismic , Sonography , Densitometry , Ports , Dredging , Nautical depth , Geoacústica , Abordagem multifrequencial , Sísmica , Sonografia , Densimetria , Portos , Dragagem , Profundidade náutica