Patent ID: 6449883
Filing Date: 2002-09-17
Classification: E02F,E21C

Abstract:
A method for dredging under water ground layers, the method comprising the steps of:providing a dredging device comprised of a mechanical dredging component having a part operative to contact the under water ground layers and exert a dredging action on the under water ground layers; and at least one water jet effective to inject water under pressure in an area where the mechanical dredging component is operative; mechanically impacting the underwater ground layers with said part of the mechanical dredging component to fracture the underwater ground layers and form fractured material; and injecting water under pressure from said at least one water jet simultaneously with the mechanical impacting to remove the fractured material so that an improved break-away pattern of material is obtained and reduced wearing of said part, wherein the at least one water jet is operated at a pressure of at least 20 bar and at least one position selected from the group consisting of (a) at a position which is the same position as that of the mechanical dredging component, (b) at a position which causes the water to flow through the mechanical dredging component, (c) at a position which is behind that of the mechanical dredging component, and (d) at a position which is in front of that of the mechanical dredging component.