Impact of Mud Aggregate Processes in Sediment Transport Studies
Abstract
The goal of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to communicate the effect of aggregated fine sediment on U.S. Army Corps of Engineers (USACE) mission areas, highlight research underway to quantify aggregate transport processes, and communicate the relevance and importance of these processes to project engineers within the USACE and other agencies. INTRODUCTION: The majority of sediments located within the waterways managed by the USACE are a mixture of sand, silt, and clay. Processes involved in the erosion and transport of heterogeneous sediments have been shown to be more complex than that of pure sand (Mehta et al. 1989; Mitchner and Torfs 1996). With the addition of fine material (<63 microns [m]), the sediment matrix can become more cohesive (Mitchner and Torfs 1996; Van Ledden et al. 2004; Barry et al. 2006; Jacobs et al. 2011) and result in aggregated particles upon erosion (Jepsen et al. 2010; Schieber et al. 2010). Sediment aggregates are composed of bound particles of smaller size. Typical sediment aggregates are bound by cohesive forces of clay or organic content. They are formed by varying processes, resulting in different characteristics. Flocs, a type of low-density aggregate, are formed by colliding cohesive particles in the water column. Upon deposition and burial, the loose, open structure of flocs is destroyed and compressed into the sediment bed. Another form of aggregate is that which results directly from erosion. Through erosion processes, the consolidated bed may become exposed. When consolidated cohesive beds erode, the erosion often occurs as chunks, or bed aggregates, which have a particle density equal to the bulk density of the bed. The main concern of this report is to investigate how the size, density, and durability of these bed aggregates can significantly impact the transport characteristics of sediments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 29, 2019
- Accession Number
- AD1067500
Entities
People
- David Perkey
- S. J. Smith
Organizations
- Engineer Research and Development Center