GB2242698A

GB2242698A - Dredging method

Info

Publication number: GB2242698A
Application number: GB9107050A
Authority: GB
Inventors: Anthony John Slater
Original assignee: Translift Freight Ltd
Current assignee: Translift Freight Ltd
Priority date: 1990-04-04
Filing date: 1991-04-04
Publication date: 1991-10-09
Anticipated expiration: 2011-04-04
Also published as: GB9107050D0; GB2242698B; GB9007609D0

Abstract

A method for the dredging of the beds of areas of water is provided wherein there is a vessel (10) on the surface of the water and connected thereto a working head (18). The working head (18) is dragged along the surface of the bed wherein there is caused the removal of material from the bed and into the working head by means of a high pressure water jet being directed into a venturi (26). The said material is then passed through a pipe means (16) to the vessel (10) wherein the material can be sorted and filtered and the value of such material analysed. <IMAGE>

Description

Improvements relating to Dredging Methods This invention relates to dredging methods, and in particular concerns a method for dredging relatively deep water beds for the purposes amongst other things, of searching for and recovering gravel materials from the beds of bodies of water.

Traditional dredging methods for searching for and recovering gravel materials from the beds of rivers, lakes and the sea typically comprise the utilisation of a large diameter and relatively rigid suction pipe which is suspended from a dredging vessel so that a lower end of a pipe is located in the vicinity of the bed of the body of water. The upper end is connected to a powerful suction pump on the vessel, and the material on the bed is simply drawn up with water from the body of water and examined and retained if of good aggregate material. Alternatively, the material can be screened, unwanted material being returned to the sea bed.

Because of the rigid nature of the suction tube, these methods are applicable generally speaking to the dredging in bodies of water of the order of maximally 30 metres deep.

For greater depths, the suction pump is fitted some distance down the dredge pipe.

The instant invention lends itself to the dredging of the beds of bodies of water which are much deeper, for example in the order of 40 m - 60 m or more.

In accordance with the present invention a dredging method comprises the utilisation of flexible piping connecting a working head for location on the bed of a body of water and a dredging vessel at the surface of the body of water, said working head comprising a coupling to a high pressure supply pipe through which water at high pressure is supplied to the working head, and a coupling to a return pipe through which material of the sea bed is returned to the dredging vessel, said working head including a nozzle from which the high pressure water issues directly into the return pipe for the inducement of material from the bed of the body of water into the return pipe and delivery to the dredger vessel for sampling or retention.

The working head may be of any appropriate construction, and may typically be of a form conventionally used for removing sand from wells and pits and the like. The working head may include the elements of a special purpose syphon known as an eductor which are used where there is an accumulation of sand, mud or other material not easily handled by suction.

Cutting nozzles may be fitted to the working head where hard or compacted materials are involved.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing wherein: Fig. 1. is a view illustrating a dredging operation involving the dredging of a bed of a body of water; Fig. 2. is a diagrammatic sectional elevation of the working head.

Referring to the drawings, in Fig. 1. a dredger 10 is at the surface of a body of water 12 which has a depth H, which may be in the order of 40 - 60 metres or more. The dredger has the pump unit 14 which is adapted to pump water at high pressure through a flexible pipe line assembly 16 leading to a working head 18 which rests on the bed 20 of the body of water.

As best seen in Fig. 2, the pipe assembly 16 which is flexible includes a high pressure delivery pipe 16a and a return pipe 16b. High pressure water from the pump unit 14 is forced through pipe 16a to an outlet nozzle 22 so that the water issues in the form of a high speed jet into a venturi end 24 of the pipe 16b. This action causes the water and the aggregate surrounding the venturi end 24 to be induced into that end as indicted by arrows 26, and in fact the water and gravel or other material of the bed 20 are forced into and up the pipe 16b and are collected at the dredging vehicle 10.

The material delivered can be analysed and returned to the sea bed if the equipment is being used for prospecting or alternatively if the equipment is being used for full scale dredging operations, the material can be retained or screened as required.

The pipe assembly 16 is of suitable flexibility to enable the working head 18 to be dragged along the bed of the body of water and the movement of the working head 18 can be controlled by cables or other means (not shown).

The vessel 10 can be equipped with an automatic tensioning device to compensate for swell in the body of water, and also the contours of the bed 20.

The tensioning device may consist of a powered drum 29 having rotation pipe connections which also serve as bearings. The tensioning device will roll up the pipes and cables lifting the working head clear of the water when the equipment is not in use.

The apparatus and method can be used for sampling the material of the bed 20, or, scaled up if necessary, to provide for dredging operations to remove aggregate from the sea bed to provide a material suitable for example for use in building and other construction work.

Claims

1. A dredging method comprising a utilisation of flexible piping connecting a working head from the base of the bed of a body of water and a dredging vessel at the surface of the said body of water, the said working head comprising a coupling to a high pressure supply pipe, a coupling to a return pipe and a nozzle from which high pressure water issues directly into the said return pipe for the inducement of material from the bed of the body of water into the return pipe and delivery to the dredging vessel.

2. A dredging method as described in Claim 1 wherein the said high pressure supply pipe so mentioned allows water at high pressure to pass therethrough and is supplied to the working head.

3. A dredging method as described in Claim 1 wherein the material from the bed of the body of water is directed through a return pipe to delivery on the dredging vessel for sampling or retention of said material.

4. A working head for use in the dredging method so described in Claim 1 wherein the said head may be of any appropriate construction, and typically of a form conventionally used for removing sand from wells and pits and the like.

5. A working head for use in a dredging method so described in Claim 1 wherein the said head includes an element of a special purpose syphon known as an eductor which is used where there is an accumulation of sand, mud or other material.

6. A working head for use in the dredging method so described in Claim 1 wherein there is fitted thereto cutting nozzles for use in conjunction with the working head.

7. A method substantially as hereindescribed with reference to the accompanying drawings.

8. An apparatus substantially as hereindescribed with reference to the accompanying drawings.