Geotechnical Properties of Mud-Capped Dredge Pits: Comparison of In-Filled Sediment across the Northern Gulf of Mexico

Louisiana’s barrier islands have been experiencing high rates of land loss during the last decade. Therefore, coastal restoration efforts have increased to combat land loss. Buried paleo-river channels are suitable sand sources for restoration because of their location and complex buried network of available material. Excavated borrow pits in paleo-river channels are referred to as mud-capped dredge pits or MCDPs. However, the use of these paleo-river channels is limited by the setback distance, which is currently set to be 1,000 ft. Therefore, this study aims to investigate the geotechnical properties of the MCDPs at two locations in the northern Gulf of Mexico (Raccoon Island and Peveto Channel), where these data could be used to examine the stability of the pit-wall. Vibracores were collected inside and outside MCDPs to study their shear strength and index properties. The torsional ring shear device was used to find the peak and residual shear strength under various effective stress and displacement rates. The results showed that the sediment outside the pit has higher shear strength than inside the pit in the two MCDPs. This study will provide a better understanding of the MCDPs behavior and provide insights into minimizing setback distance, which will reduce dredging costs and allow using the sand source more effectively in the northern Gulf of Mexico.