Water Hummer Technology for Soil Destruction on Dredgers

Abstract

The present investigation aims to propose a solution of the problem which is connected with slurry processing during the dredger’s operation under difficult conditions. On dredgers, depending on the degree of air dryness or low ambient temperatures very often arises technical problem that creates difficulties for the crew. It is connected with the fact that soil surface layer is very dense. It is very difficult to dredge the soil during extraction under water surface or unloading from the hold of a vessel at low ambient temperatures. The top layer of the very soil is characterized by a high degree of compaction and can be destroyed in two ways only. The first way is to use very powerful mechanical equipment (percussion mechanisms, vibration equipment, etc.). This method is associated with high energy spending and its use on a vessel is technically difficult. The second way is to use the soil cutting process with the use of mechanical cutters. Dredger’s operation with the use of milling equipment is always characterized by the fact that during soil mechanical treatment there is always occurs breakage of the cutter teeth or rapid wear of the cutting surfaces. A similar problem occurs when sandy or clay soil is extracted under water, which is compacted by its properties. In investigation a non-trivial solution was used to solve the problem of destruction of the compacted soil layer during the operation of the dredger. It was proposed to use the hydrodynamic method based on water hammer as the main mechanism for the destruction of compacted soil. As a result of the interaction of the compacted soil layer and high pressurized directed water jets, good performance of the dredger can be achieved. The two-dimensional mechanism of destruction of the compacted soil layer can be described by the condition of dynamic equilibrium of the three main flows - the jet, which flows from the conical nozzle and two flows along the soil surface. For these streams, a reactive force evaluation has been performed. Destructive jets can be generated by standard marine pumps in combination with the use of water hammer. Based on the results of the experiments, it was found that the qualitative destruction of the surface layer of compacted soil occurs using two or three phases of hydraulic water hummer.