Erosion Thresholds and Rates for Sand Mud Mixtures
Engineer Research and Development Center (U.S.) Vicksburg United States
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Differences in erosion behavior of non-cohesive and cohesive sediments are widely recognized. In many natural environments, sand and mud are not completely separated and occur as mixtures. Significantly less research has been conducted on the erosion behavior of sand-mud mixtures compared to the separate treatment of sand and mud erosion. Sedflume erosion experiments were conducted on sand-mud mixtures with varying mud content to define the relationships between mud content, critical stress for erosion c, and erosion rate. Sand-mud mixtures were prepared with three mud sources 1 non-swelling clay kaolinite, 2 swelling clay kaolinitebentonite, and 3 a swelling, natural mud from the Mississippi River.Test results showed that critical shear stresses of the mixed sediments departed from that of pure sand with mud fractions on the order of 2 to 10 . Peak c was observed between 30 to 40 mud content, with swelling muds achieving a ten-fold increase in c while a five-fold increase in c was measured for kaolinite. Additionally, this study demonstrated that the introduction of small amounts 5 of mud to sand reduced erosion rates by a factor of 10 to 100. This observed abatement of erosion rate has implications for the use of dredged materials in civil and environmental engineering projects.
- Civil Engineering
- Soil Mechanics