Development of an active layer seafloor sampler as an add-on unit for portable free-fall penetrometers

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Subaqueous sediment dynamics impact on a large number of issues in the coastal zone and the marine environment, such as coastal erosion and evolution, marine slope stability, navigable water depth, stability of offshore structures, as well as the seafloor as a habitat. One of the unsolved questions with regard to subaqueous sediment dynamics is the thickness, density and particle distribution within the mobile seafloor surface layer. The project aims to develop a mobile seafloor sediment sampler as an add-on unit for portable free-fall penetrometers. The capability of sampling the density, thickness and sedimentological composition of the mobile seabed sediments would pave the way for new studies and insights in the field of subaqueous geomorphology and morphodynamics, sediment dynamics, marine geology, as well as coastal and offshore engineering and seafloor geotechnical engineering. It would contribute directly to the site-specific and systematic understanding of subaqueous sediment transport and scour, and would fill gaps in current knowledge regarding bedload transport. Thus, the resulting instrument will potentially initiate new interdisciplinary collaborations, and address a variety of modern environmental and societal issues. The development will also impact significantly on the career and following research path of the principal investigator whose work is aiming to bridge the gap between subaqueous sediment dynamics and geotechnical engineering. A graduate research assistant working on the development will be educated and trained in detail in sediment transport theories and practice, in-situ marine geotechnics, and coastal and offshore surveying. The fact that a major part of the testing will be conducted on Virginia Tech's campus will allow insight to other students, possibly full classes, and an easy transfer of the gained knowledge and procedures into the class room. Particularly, female students will benefit from the principal investigator as a role model for female researchers in the still male-dominated field of ocean technology and offshore surveying.The mobile seafloor surface layer sampler will be developed as an add-on unit for portable free-fall penetrometers which have been applied for the investigation of sediment mobilization processes for several years. A sampling tube with sealing mechanism will be integrated in the steel tip of the free-fall penetrometer, building a sampling unit that will allow collection of small sediment samples while geotechnical profiling. The project will include the development, manufacture and detailed testing of the add-on unit. Test procedures will feature controlled laboratory tests in a soil test chamber, tests of the effects of impact velocity, and proof-of-concept in the field.