Sediment fluidization system for nautical depth maintenance under monitored environmental currents

Oceanic ships are getting larger and costs of dredging are increasing, which largely justify the research on new practices for harbour entrance maintenance. In fact, the sedimentation of sands transported along coast reduces the navigable depth and requires a continuous dredging to ensure the entry of the vessels in secure conditions. As new practice for reducing the dredging operations it is proposed a sediment fluidization system, which can maintain the required water depth by pumping water under the bed of the port entrance. Conditions to cause the sediment/fluid mixture to behave as a fluid could be achieved by the introduction of pressurized sea water through the sediment deposition. This results in heavily loaded fluid that can be removed by environmental currents. In this way erosion and deposition can be driven to maintain nautical depth and on the basis of monitored environmental currents. Sand fluidization as opposite to sediment dewatering could be applied to mobilize depositions in the intertidal zones, when suitable currents take place to remove low depths barrier to navigation and harbour entrance. In the chemical industry the fluidization is usually realized within reactors, while, in the case of nautical depth maintenance, pump systems similar to dewatering system could be applied and controlled by means of Acoustic Doppler Current Profilers (ADCP) to monitor tidal and long shore currents. A first application of the fluidization system was made on the commercial harbour of Ravenna (Italy), by means of the numerical code Mik21, to study the sediment transport near the port entrance. Ravenna represents the only commercial port of the Emilia Romagna Region and, thanks to its geographical position, is a leader in Italy for trade with the East Mediterranean Sea and the Black Sea, and also plays an important role for trade with the Middle and Far East. A first analysis indicates that the fluidization system can be used instead of dredging operations for removing the clean sediments from the entrance of the harbour by means of coastal currents.