Dredging Research Program. Laboratory Testing of Methods to Increase Hopper Dredge Payloads: Model Hopper Bin Facility and Centrifugal Solids Concentrator

Abstract : It is common practice to fill beyond overflow on dredge hoppers and scows to achieve load gains. However, some of the US Army Corps of Engineers Districts do not permit overflow due to actual or perceived environmental or economic reasons. It is generally not known whether overflowing is beneficial in increasing the hopper payload in fine-grained sediments (silt and clay size), although some studies have indicated a minimal increase in hopper loads when filled to overflowing. Under the Dredging Research Program (DRP) Work Unit, Technology for Monitoring and Increasing Dredge Payload for Fine-Grained Sediments, several experimental methods were investigated to determine their effect on increasing the payload of fine-grained dredged material. Several devices were tested in a scale model hopper constructed at the US Army Engineer Waterways Experiment Station Hydraulics Laboratory. These devices included three types of hydrocyclones (centrifugal separators), various diffuser designs, and different arrays of internally mounted inclined plates. A solids concentrator device was also evaluated for increasing the load of fine sediments in the model hopper. This report presents the description and method of the testing programs and the study findings. The inclined plate and solids concentrator devices demonstrated some level of success when tested with silt-sized materials (particle size 10 to 63 microns)., The inclined plate method was the most successful for increasing payload in the model hopper; however, prototype use of this technique could substantially increase the weight of a hopper dredge unless a lightweight version is developed. Diffusers, Hydrocyclones, Overflow, Fine- grained sediment, Inclined plates, Plates, Hopper dredges, Load gain.