Semester of Graduation
Spring 2024
Degree
Master of Civil Engineering (MCE)
Department
Civil and Environmental Engineering
Document Type
Thesis
Abstract
Wetlands serve as essential natural barriers, protecting against the increasing threats from hurricane-induced storm surge, rising sea levels, and changing weather patterns, highlighting the need to comprehend their structural resilience. Central to this resilience is the shear strength of the wetland soil-root matrix, which is difficult to evaluate due to the complex nature of root systems and varying amounts of live biomass and necromass at different soil depths. This study utilized a Large-scale Direct Shear Apparatus (LDSA) to address a notable gap in research: the assessment of root biomass shear strength in a horizontal mode of shear for key plant species in U.S. coastal wetlands. The Atchafalaya and Terrebonne Basins in Louisiana were chosen as the focal areas for this research. Within each basin, three distinct sites spanning a salinity gradient from fresh to saline marsh environments were selected. This approach was intended to investigate how salinity variations influence the structural resilience of wetlands, providing analysis of shear strength across different ecological settings. The findings revealed a marked upward curvature in the stress-displacement response, indicative of strain hardening within the soil-root matrix. This behavior is mainly attributed to the intersecting longitudinal and diagonal roots within the shear plane, significantly enhancing the soil's ability to resist shear stress. Such insights into the biomechanical properties of wetland soils emphasize the crucial role of vegetative roots in bolstering the ecosystems' stability under the duress of extreme weather events. This investigation into the horizontal shear strength of wetland soils contributes important insights into the geotechnical aspects of wetland resilience. The outcomes of this study are poised to guide future endeavors in coastal engineering and environmental management, advocating for holistic strategies that incorporate both the biological and geotechnical elements of wetland ecosystems.
Date
3-27-2024
Recommended Citation
Hassan, Mohamed, "Large-scale Laboratory Direct Shear Testing for Wetland Root Strength" (2024). LSU Master's Theses. 5907.
https://repository.lsu.edu/gradschool_theses/5907
Committee Chair
Jafari, Navid