Soil Strength Improvement Ability of <em>Spartina alterniflora</em>, Smooth Cord Grass, Established on Dredged Soils in Louisiana Coastal Area

This research focused on studying the soil improvement ability provided by the roots of smooth cordgrass, Spartina alterniflora, flourishing in the dredged soil of the Sabine Refuge Marsh Creation Project in the coastal area of Louisiana, USA. Field vane shear tests were conducted to obtain the in-situ undrained shear strength of the soil vegetated with Spartina alterniflora. Direct shear tests were performed on undisturbed rooted soil samples to investigate the overall effect of roots on soil shear strength. Laboratory tensile tests were conducted on the roots of Spartina alterniflora to estimate their tensile strength. In this research, the W&amp;W model and the fiber bundle model (FBM), were adopted and the modified ones were proposed to study the correlation between root-induced cohesion and nominal root tensile strength. The model outcomes were compared with field and laboratory measurements. The research results showed that the roots of Spartina alterniflora significantly increased soil shear strength, with an increase in cohesion of up to 130% at one location. The increases varied at different locations depending on the root area ratio (RAR), soil sample depth, and root tensile strength.