Laboratory modeling of hydraulic dredges and design of dredge carriage for laboratory facility

Abstract

The deepening and maintenance of the world's ports and navigable waterways has been an integral part of the world economy for centuries. In recent years, cutterhead and draghead hydraulic suction dredges have performed a majority of the dredging work. The ongoing design and testing of hydraulic dredges is important for maintaining efficient dredging operations within the limits set by increasing environmental regulations. The high cost of building and operating a hydraulic dredge makes field testing of full-scale prototypes very expensive and time consuming. Moreover, the testing conditions are generally difficult to control, and the natural unpredictability of the sea can render experimental results inconclusive. These factors substantiate the need for laboratory model testing of hydraulic dredging operations. The usefulness of any hydraulic model depends on the degree of geometric, kinematic, and dynamic similarity between the model and its prototype. The primary challenge in establishing useful similitude criteria for model dredge studies is proper kinematic scaling of the suction inlet velocity, average particle settling velocity, dredge swing velocity, and cutter rotational speed. Despite the inherent challenges, model studies of hydraulic dredge equipment have proven useful for obtaining qualitative results. The new Coastal Engineering Laboratory at Texas A&M University is equipped with model dredge testing facilities ideal for performing such experiments. The tow/dredge carriage has a fully adjustable dredge ladder, a 14.9 kW (20 hp) cutter drive, and a 2.54 cm (3 in) dredge pump. A Programmable Logic Controller (PLC) provides computer numerical control and real-time data collection and analysis during model dredging operations. The purpose of this thesis is to investigate scaling relationships for hydraulic dredge model studies and to design a model dredge carriage for the new laboratory facilities recently constructed at the Texas A&M University College Station campus. Pursuant to the design of the new dredge modeling facilities, a rationale for scaling the model dredge operating parameters based on previous model studies is put forward. Examples of model studies that could be performed with the proposed facilities are discussed as well as how the scaling methodology is applied to each experiment to allow the quantitative interpretation of experimental data.