Dredging and scouring

Abstract

The present invention relates to dredging and scouring. In particular, we will describe dredging and scouring apparatus for removing sand, silt, clay and like materials from sea or river beds. There is described an apparatus comprising a body having a bottom face and comprising an outlet flow path in which is mounted thrust means to direct, in use, a wash of water downwards towards an area of sea or river bed or the like, orientation means to connect said apparatus, in use, to a support means to orientate said apparatus with respect to the sea or river bed, and at least one inlet flow path through which water is supplied, in use, to the thrust means; characterised in that the inlet and outlet flow paths are provided with respective openings in the bottom face of the body. In the preferred embodiments, the inlet and outlet flow paths are parallel, but of opposite directions,

Description

BACKGROUND TO THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to dredging and scouring. In particular, we will describe dredging and scouring apparatus for removing sand, silt, clay and like materials from sea or river beds.

[0003] A suction dredger is the most widely used apparatus for removing such material, suction being created by a motor and pump unit, somewhat like a vacuum cleaner. A modified form of the suction method, which is used in tidal waters, is to provide a vertical length of pipe above the area to be cleared near the lower end of which air is fed under pressure to pass upwardly through said pipe. This creates buoyancy within the water column, which will act to lift the sand, silt and like material and set it in suspension with the water, whereafter it may be carried up a pipe into a hopper. This method is reliable in reducing the possibility of small/lightweight articles being lost, but is time consuming due to the relatively small diameter of the pipe, normally around 0.5 metres, and hence restricted area covered.

[0004] 2. Description of the Related Art

[0005] WO89/07691 discloses a method of and apparatus for dredging in flowing water comprising lowering a casing of a wing shape downwardly towards the area to be cleared, the casing carrying thrust means arranged so that the thrust means is directed downwardly, the orientation of the wing casing being adjusted in the water so that it presents a surface relative to the flow which causes a resultant downward vertical component of force to counteract the upward force provided by the thrust means, the thrust means directing a wash of water towards the areas to be cleared so that the turbulence created clears the sand, silt or like material covering the area. Such apparatus is commonly referred to as a ‘wing dredger.’

[0006] WO97/32091 describes a modification of this arrangement in which additional apparatus is provided to enable full adjustment of the wing dredger in a side to side manner.

[0007] Another method, which can be used in relatively shallow tidal waters, e.g. up to about 10 metres in depth, comprises mooring a tug, ship or other vessel in a fixed position above the area to be cleared and deflecting the propeller wash downwardly using a suitable guide plate. The wash disturbs the material around the wreck, which material is thereby lifted, set in suspension and carried away from the area by the tide. A significant restriction of this method lies in the minimum depth to which the vessel may operate.

[0008] Accordingly, the present invention seeks to provide an apparatus suitable for dredging or scouring sea or river beds in shallow waters.

BRIEF SUMMARY OF THE INVENTION

[0009] In its broadest sense, the present invention provides an apparatus comprising a body having a bottom face and comprising an outlet flow path in which is mounted thrust means to direct, in use, a wash of water downwards towards an area of sea or river bed or the like, orientation means to connect said apparatus, in use, to a support means to orientate said apparatus with respect to the sea or river bed, and at least one inlet flow path through which water is supplied, in use, to the thrust means; characterised in that the inlet and outlet flow paths are provided with respective openings in the bottom face of the body.

[0010] Preferably, the inlet and outlet flow paths are parallel, but of opposite directions.

[0011] Preferably, the outlet flow path comprises a duct formed with an outlet in the undersurface of a central section of the body.

[0012] Preferably, the thrust means comprises at least one impeller assembly comprising an impeller mounted within the duct or within a housing in fluid communication with the duct.

[0013] Suitably, an adjustable flow director is provided adjacent the outlet of the outlet flow path, the director being adapted to adjust the direction of flow of the water wash from the outlet. Typically, the flow director comprises a louvre assembly. Typically, but not essentially, the director is mounted internally of the outlet from the undersurface of the body.

[0014] In one particular embodiment, the body is in the form of a wing having an angled face at at least one of leading and trailing edges thereof. Such face or faces may be provided by means of an additional wing profile attachment to the body.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0015] The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which:

[0016] FIG. 1 is a perspective view of an embodiment of an apparatus in accordance with the present invention;

[0017] FIG. 2 is a front view of the embodiment of FIG. 1;

[0018] FIG. 3 is a side view of the embodiment of FIG. 1;

[0019] FIG. 4 is a plan view of the embodiment of FIG. 1;

[0020] FIG. 5 is a cross-section along line V-V in FIG. 3;

[0021] FIG. 6 is a cross-section along line VI-VI in FIG. 5;

[0022] FIG. 7 is an underneath view of the embodiment of FIG. 1;

[0023] FIG. 8 is a part detailed view of FIG. 5 illustrating in greater detail the principle features of the thruster assembly of the apparatus of FIGS. 1 to 7;

[0024] FIGS. 9 and 10 are perspective views illustrating combinations of a plurality of the embodiment of FIG. 1 into multiple linear apparatus;

[0025] FIG. 11 is a perspective view illustrating a modification of the embodiment of FIG. 1 including additional wing extension elements;

[0026] FIG. 12 is a perspective view illustrating a combination of two embodiments of

[0027] FIG. 1 into a bi-directional apparatus; and

[0028] FIG. 13 is a perspective view from underneath illustrating the use of an additional manual scraper on an apparatus in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] Referring initially to FIGS. 1 to 7, an embodiment of the apparatus of the present invention is illustrated comprising a body or tank 10 of generally lightweight construction, steel being a suitable construction material. Tank 10 has side walls 11, front and rear walls 12, top face 13 and bottom face 14 together defining a cavity 15. Sealable inspection or access covers 16 are provided on the top face 13. A duct 20 is formed extending upwardly from an opening or outlet 21 formed substantially centrally in the bottom face 14 of the tank 10. Duct 20 terminates at its upper end within the cavity 15 with a bell-mouth opening 22. A bell-mouth shape is preferably for reasons of fluid flow, but not essential.

[0030] Two apertures 23 are formed in the bottom face 14 of the tank 10 defining inlets to the tank. Adjacent the inlets 23 are provided inclined fillets 25. These act to prevent build up of material taken into the tank, the inclined surfaces acting to direct material falling thereupon towards the inlet. Typically, the fillets 25 are formed from concrete to provide additional ballasting. In the arrangement illustrated in FIGS. 5 and 6, fillets 25 form a complete ring around each inlet. In the modification illustrated in FIG. 7, fillets 25 are provided along only the leading and trailing edges of the apparatus, that is to say, along the junctions of the bottom 14 of the tank with the front and rear walls 12.

[0031] Mounted within the duct 20 adjacent outlet 21 is an impeller 30 driven by means of sheathed shaft 31 coupled through a flexible coupling 32 to a prime mover device 33 such as an electric, hydraulic or pneumatic motor. A Denison M30 hydraulic motor has been found to be particularly useful, but many alternatives are available and will be apparent to the skilled person. Advantageously, -the flexible coupling 32 is adapted to shear above a predetermined level of applied torque to avoid damage should the shaft 31 become seized, for example by ingress of foreign objects. Typically, the motor is mounted on the upper surface of the tank 10 rather than inside the tank. As the apparatus will be working in shallow depths of water, it is important that the motor will be capable of operating both in air and underwater. Sheathed shaft 31 is retained centrally within the duct 20 by means of supporting fins or vanes 34. As shown, typically two sets of fins are used, an upper set 34a and a lower set 34b.

[0032] An internal grille 24 is provided over each inlet 23 to prevent ingress of large particulate material. Typically, the grille is formed from a plurality of plates aligned with the long axis of the tank and inclined at around 45°. The plates may be in the form of adjustable louvres such that their angle may be varied so as to adjust the degree of reactive force and the rate of water entry into the tank. Preferably the inclination of the plates on the two inlets shown in the described embodiment are opposite. The slope on the plates acts to deflect the inflowing water and provide a reactive force to counter the turning moment created by the impeller 30. As this reactive force varies with the velocity of flow through the inlets, which in turn is dependent upon the flow through the duct 20 and the rotational speed of the impeller, the system remains rotationally balanced regardless of the speed of the impeller. Non-rotation of the tank 10 is particularly important when a single module is being operated in deeper water from a single support wire. Accordingly, it will be appreciated that provided an even number of inlets 23 is the most suitable arrangement, typically two inlets disposed either side of the outlet duct 20. To avoid destruction of the balancing water flows, the tank may be divided into two separate compartments by means of a central bulkhead wall 27 (FIG. 6) which extends upwardly to substantially the same height as the bell-mouth opening 22 of the duct 20. The compartments remain in fluid communication above the bellmouth opening. Alternatively, the bulkhead wall 27 may extend to the top face 13 of the tank, in which case one or more openings are provided in the bulkhead wall 27 above the bell-mouth duct opening to provide the necessary fluid communication. Further alternative inlet arrangements will, however, be apparent to those skilled in the art. In particular, of course, the grille 24 could be externally mounted.

[0033] Grab handles 18 are provided on the forward and leading edges of the top face 13 of the tank 10. In the preferred embodiment, these are formed from hollow tubing in fluid communication with the inside of the tank 10. Non-return valves (not shown) are mounted upon the grab handles 18 towards the outer ends thereof and allow air to vent freely from the tank during initial submergence, but close when the apparatus is in operation due to the lower pressure inside the tank 10. This also allows the tank to be partially lifted out of the water during operation in very shallow waters without allowing the introduction of air into the tank 10 which would interfere with the water flows therewithin.

[0034] As is illustrated in FIGS. 9 to 12, several of the tanks described above may be coupled together to provide an enlarged scouring and dredging device. FIGS. 9 and 10 illustrate coupling two or three tanks side by side to provide a wider coverage apparatus. FIG. 11 illustrates a modification of the embodiment of FIG. 6 in which additional front and rear profiled wing extension elements 40 are added. The wing extension elements serve to provide give the apparatus a profile generally similar to the ‘wing’ arrangement illustrated in the prior art described above.

[0035] In the arrangement illustrated in FIG. 12, two devices are mounted with opposed front faces but inclined by means of a short connector element 41 coupling the devices at each end along their bottom edges and a long connector element 42 coupling the devices at their upper edges, such that the outlets 21 are both directed to impinge upon a common or focal point. The twin apparatus can then be supported, for example by means of wires 43, above an area to be scoured, such as a pipeline 44 upon a seabed. With such an arrangement, as the washes of water from both apparatus are directed to the same point, the scouring effect is enhanced.

[0036] Whilst such modular arrangements are particularly advantageous, they are not essential to the working of the present invention. It will be appreciated that where modular operation is not required, the tank 10 need not be generally hexahedral in shape, but may be of substantially any shape, such as generally circular.

[0037] Suitably, an adjustable flow director is provided adjacent the outlet, the director being adapted to adjust the direction of flow of the water wash from the outlet. Typically, the flow director comprises a louvre assembly 17 (FIG. 3) and may be mounted internally or externally of the outlet 21 from the undersurface of the body. Clearly this arrangement may be omitted where, for example, internal grille is adjustable.

[0038] FIG. 13 illustrates the addition of a mechanical scraper 50 to assist in the excavation of particularly hard soils, such as very dense and/or cemented sands and very stiff to hard clays. The scraper 50 consists of a bar or tube 51 mountable to the under surface 14 of the tank at the leading edge thereof A plurality of tines 52 are mounted upon the bar 51. The bar 51 is free to rotate upon its mounting and thus the tines 52 are free to pivot within the constraints dictated by the design of the tank 10 and its various mounting points. The weight of the tines is such that the tines 52 normally hang vertically downwards. The tines 52 have hardened steep cutting points 53 adapted for ripping and scarifying the seabed surface. By weakening and disaggregating the surface, the impeller jet is more readily able to excavate the surface material. With a scraper attachment provide on the leading edge of the apparatus only, the forward pass would be with mechanical assistance, but the return pass would include water jetting only as the tines would pivot away from engagement with the seabed. The scraper could be include a locking arrangement to prevent pivoting of the tines out of such engagement, but more preferably scraper attachments 50 are mounted upon both the leading and trailing edges of the tank 10 such that both forward and rearward passes would provide the cutting facility.

Claims

1. An apparatus comprising a body having a bottom face and comprising an outlet flow path in which is mounted thrust means to direct, in use, a wash of water downwards towards an area of sea or river bed or the like, orientation means to connect said apparatus, in use, to a support means to orientate said apparatus with respect to the sea or river bed, and at least one inlet flow path through which water is supplied, in use, to the thrust means; characterised in that the inlet flow path and outlet flow path are provided with respective openings in the bottom face of the body.

2. An apparatus as claimed in claim 1 wherein the inlet and outlet flow paths are parallel, but of opposite directions.

3. An apparatus as claimed in claim 1 wherein the outlet flow path comprises a duct formed with an outlet in the undersurface of a central section of the body.

4. An apparatus as claimed in claim 2 wherein the outlet flow path comprises a duct formed with an outlet in the undersurface of a central section of the body.

5. An apparatus as claimed in claim 1 wherein the thrust means comprises at least one impeller assembly comprising an impeller mounted within the duct or within a housing in fluid communication with the duct.

6. An apparatus as claimed in claim 1 wherein an adjustable flow director is provided adjacent the outlet of the outlet flow path, the director being adapted to adjust the direction of flow of the water wash from the outlet.

7. An apparatus as claimed in claim 6 wherein the flow director comprises a louvre assembly.

8. An apparatus as claimed in claim 6 wherein the director is mounted internally of the outlet from the undersurface of the body. 9. An apparatus as claimed in claim 1 wherein the body is in the form of a wing having an angled face at at least one of the leading and trailing edges thereof.