![]() ![]() However, the controlling factor in dredging the hind dune areas is the level of the water table and suction dredges may be designed to mine to depths of 120 ft, or even more, if necessary.In previous applications of suction dredges in the industry attention was directed primarily towards production and there was only limited research on fundamental techniques. In working frontal dunes, dredging depths are usually shallow since values do not persist for more than a few feet below sea level. Measurement and control of flow is important.INTRODUCTIONEconomic deposits of heavy minerals along the east coast of Australia occur in frontal dunes, which are normally unconsolidated and granular, or in hind dune areas which may contain indurated seams interspersed with loose material. Design of pipe lines depends on the transportation characteristics of the pulp, skin friction, swirl, and the avoidance of cavitation. Flow into suction nozzles depends on whether hydraulic jets or mechanical cutters are used, and on nozzle shape. Total head for the dredge pump is calculated from velocity, static, and friction heads. Important factors in dredge design are the estimation of total head, and the determination of flow in and around suction nozzles and in pipe lines.
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