Collaborative Research: Geotechnical Investigation of Bivalve-Sediment Interaction with regard to Bivalve Farms as a Self-sustained Scour Mitigation Method

North Carolina State University, Raleigh NC

Investigators

Abstract

Scour is a serious problem throughout the world where structural foundations are in or adjacent to running water. For example, the most common cause for bridge failures in the U.S. is scour around bridge piers. Previous studies have suggested that bivalve colonies reduce local erosion through different processes, and that bivalves feature a high resistivity to strong flow. However, there exists a current gap in knowledge regarding the impact of bivalve colonies on geotechnical seabed parameters. This hampers the assessment and development of bivalve farms as a potentially self-sustained scour mitigation method. This fundamental study will address this gap in knowledge by use of field and laboratory testing. In this way, the study will represent a crucial step towards the use of bivalve farms as a scour mitigation strategy, as well as advance the field of bio-geo-engineering in coastal environments. In the framework of this project, new interdisciplinary, domestic and international collaborations will be initiated, and multiple graduate and undergraduate students will benefit from participation in this creative, interdisciplinary and international project. The project will also seek to increase diversity in the field of geotechnical engineering by emphasizing the recruitment of female students and students from diverse socioeconomic backgrounds. The project will test the following working hypotheses: H1) The presence of bivalve colonies reduces local scour and erosion. H2) Bivalve colonies form morphologies applicable to scour protection design. H3) Bivalve adhesive protein increases sediment strength and decreases erodibility. H4) Bivalve dislodgement from soil surfaces occurs as ?block failure? for single bivalves, but becomes irrelevant for erosion issues in the case of bivalve groups. These hypotheses will be tested through an interdisciplinary and multi-method approach featuring: (i) field investigations at two bivalve colony locations in Virginia and North Carolina, (ii) an analytic comparison of bivalve colony morphology and flow resistivity to modern scour protection designs, and laboratory tests investigating (iii) the change of sediment strength and erodibility resulting from mixing bivalve adhesive protein with sediment and (iv) soil failure behavior during bivalve dislodgement. The study may pave the way for a new direction in bio-inspired geotechnical engineering in submerged environments, and scour protection. In a narrower focus, the project will deliver information, and address knowledge gaps relevant for multiple disciplines and research communities (geotechnical engineering, biology, ecology, environmental engineering, aquaculture developers). It will complement existing efforts of characterizing bivalve habitats and their role in coastal protection during storm events by providing a novel geotechnical perspective. It will also enable new insights into the process of bivalve dislodgement. To the best knowledge of the PIs, mussel adhesive proteins will be tested for the first time to evaluate their impact on soil mechanical properties. The results may offer a new direction in temporary soil improvement in a sustainable manner. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.