GB1589651A

GB1589651A - Dredging method and cutter head suction dredger

Info

Publication number: GB1589651A
Application number: GB76678A
Authority: GB
Original assignee: Ballast Nedam NV; Scheepswerf en Machinefabriek De Liesbosch BV; Ballast Nedam Groep NV
Current assignee: Ballast Nedam NV; Scheepswerf en Machinefabriek De Liesbosch BV
Priority date: 1977-01-31
Filing date: 1978-01-09
Publication date: 1981-05-20
Also published as: DE2801080C2; FR2378908B1; NL7700999A; AU516436B2; JPS5397239A; FR2378908A1; BE863232A; DE2801080A1; AU3244378A; NL171182B; NL171182C; JPS584134B2

Description

(54) DREDGING METHOD AND CUTTER HEAD SUCTION DREDGER (71) We, BALLAST-NEDAM GROEP N.V.

and AMSTERDAM SE BALLAST BAGGER EN GROND (Amsterdam Ballast Dredging) B.V. of No. 2, Laan van Kronenburg, Amstelveen, the Netherlands and Scheepswerf en Machinefabriek "De Liesbosch" B.V. of No. 5, De Liesbosch, Nieuwegein, the Netherlands, Body Corporates organised and existing under the Laws of the Netherlands, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of dredging with the aid of a cutter head suction dredger and to an improved cutter head suction dredger for carrying out this method.

It has already been proposed in U.S. Patent Specification No. 3, 350, 798 to provide a method of dredging with the aid of a cutter head suction dredger having a cutter head and an associated suction nozzle connected to a floating hull so that they can be raised and lowered with respect thereto, in which the hull is transversed horizontally to and fro by means of side ropes extending from winches on the hull adjacent the port and starboard sides thereof to anchorages in the ground positioned laterally outwardly of the hull to port and starboard thereof respectively, in which the hull is located in the fore and aft direction by at least one longitudinal rope extending forwardly from a winch on the hull adjacent the bow end thereof to a respective anchorage in the ground in front of the hull and at least one longitudinal rope extending aft from a winch on the hull adjacent the stern end thereof to a respective anchorage in the ground behind the hull, the longitudinal ropes being swung about their anchorages while the hull is being traversed, and in which the hull is moved forwardly or aft with respect to the ground by veering out of the longitudinal rope or ropes at one end of the hull and hauling in the longitudinal rope or ropes at the other end of the hull.

A disadvantage of this known method is that the cutter head cannot be accurately controlled due to the indeterminate sagging and extension of the longitudinal ropes. Since during the traversing movement of the hull an optimal, fixed start of the cutter head is important for an efficient dredging operation, anchoring of the cutter head suction dredger by means of ropes or cables during operation has hardly ever been carried out in practice.

Hitherto a cutter head dredger has usually been anchored by means of a spud pile because of the fixed connections between the cutter head and the fixed anchoring point of the spud pile, although in deep water dredging the construction of the spud pile has to be very heavy, dredging in a moving sea by means of spud pile anchorage requires an expensive, vertically adjustable joint between the floating body and the spud pile and the extent of the traversing movement is limited by the comparatively short radius of turn about the spud pile, so that the dredging operation frequently has to be interrupted for displacing the spud pile.

The invention has for its object to improve the control of the cutter head and to reduce the number of interruptions of the dredging process.

To this end the method according to the invention is characterized in that the tension in at least one of the longitudinal ropes is measured and at least one of the winches adjacent the bow or stern of the hull is actuated in dependence upon the measured tension.

The cutter head suction dredger according to the invention comprises a floating hull a cutter head connected with the hull so that it can be raised and lowered with respect thereto, a pump, a suction nozzle located near the cutter head and communicating through a suction pipe with the pump, winches on the hull adjacent the port and starboard sides thereof respectively, side ropes extending from these winches to respective anchoring means, at least one bow winch on the hull adjacent the bow end thereof, at least one stern winch on the hull adjacent the stern end thereof and longitudinal ropes extending between the bow and stern winches and respective anchoring means and is characterised by the provision of tension measuring means arranged to measure the tension in at least one of the longitudinal ropes and control means arranged to control at least one of the bow or stern winches in dependence upon the values of tension measured by the tension measuring means.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a plan view of a preferred embodiment of the cutter head suction dredger according to the invention, Figure 2 is a plan view of a detail II of Figure 1 on an enlarged scale, Figure 3 is a side elevation of the cutter head suction dredger of Figure 1, Figure 4 is a side elevation similar to that of Figure 3, except for the provision of an alternative anchoring arrangement in the stern region corresponding to that indicated at IV in Figure 3, Figure 5 is a diagram of a winch controlmeans of the cutter head suction dredger of Figure 1, Figure 6 is a plan view of a further embodiment of the cutter head suction dredger according to the invention, and Figure 7 is a plan view of a variant of the detail VII of Figure 5 for the cutter head suction dredger of Figure 6.

The cutter head suction dredger 60 shown in Figures 1 to 3 comprises a floating hull 1, a cutter head 3 mounted in one end of a ladder 2 the other end of which is connected to the hull 1 so as to be pivotable with respect thereto about a horizontal axis 61, a pump 62, a suction nozzle 64 communicating through a suction tube 63 with the pump 62 and arranged near the cutter head 3 and a floating delivery pipe 70 communicating with the outlet of the pump 62. Side ropes 10, 12, 11 and 13 emanating from winches 30, 29 and 25, 19 respectively on port and starboard sides 65 and 66 respectively of the cutter head suction dredger 60 are anchored to the ground 67 by means of anchors 14.A bow rope 6 extending forwardly from a bow winch 16 at the bow 68 of the hull 1 is anchored to the ground 67 by means of an anchor 7 and a stern rope 8 extending rearwardly from a winch 69 at the stern 44 of the hull 1 is anchored to the ground 67 by means of an anchor 9. A tension meter 18 (Figure 5) is arranged to measure the tension in the stern rope 6 and is operatively connected to a control means 17 (Figure 2) of the bow winch 16 so that the hauling in and veering out of the bow rope 6 by the bow winch 16 are controlled in dependence upon the tension of the stern rope 6 as measured by the tension meter 18, When in use the cutter head dredger 60 is caused to oscillate over an arcuate path b by veering out and hauling in the side ropes 10, 11, 12 and 13.The hull 1 then swings around the anchor 9 of the stern rope 8, e.g. from the position indicated in solid lines in Figure 1 to the position shown in broken lines therein.

Figure 2 shows in greater detail the control means for the winches 16, 69, 30, 29, 25 and 19.

In carrying out the method according to the invention the bow rope 6 is veered out or hauled in in dependence upon the tension measured by the tension meter 18 in order to ensure that the cutter head dredger 60 oscillates over the arcuate path b, the centre of which is formed by the anchor 9 and the radius R of which is constant, with respect to the stern rope 8 which is held at the same or substantially the same length. When the radius R of the oscillating movement is increased by an amount a, the resulting cutting depth achieved by the cutting head will be substantially equal to the said amount a, which is of great importance for the optimum operation of the cutter head dredger 60.

From a control panel 43 actuating signals are applied through a control device 31 to control members 27 and 28 of the foremost side-rope winches 29 and 30, causing these winches to haul in and veer out the side ropes 12, 10 respectively so that the cutter head 3 is constrained to move along the arcuate path b. Through a computing device 22 the control device 31 applies signals to the control members 23, 20 of the hindmost side-rope winches 25 and 19 for hauling in and veering out the side ropes 11 and 13.In accordance with the positions of the ropes 10, 11,12 and 13 a lower control voltage is applied to the control members 20 and 23 than to the control members 27 and 28 so that the winches 25 and 19 haul in and veer out respectively a proportionally smaller length of rope than the winches 29 and 30 as a result of the difference in distances of the side ropes 10,12 and of the side ropes 11,13 from the anchor 9.

An angle meter 21 measures the angled between a plane 72 of the floating body I and the stern rope 8 and the measured value of this angle is applied to the computing device 22. Since the stern rope 8 has to be held closely to the plane 72, the signal of the measured angle d is combined in the computing device 22 with the signal from the control device 31 in order to govern the control members 23 and 20 of the winches 25 and 19 associated with the hindmost side ropes 11 and 13 so that the stern rope 8 is invariably held in or substantially in the adjusted plane 72.

Referring to the side elevation of Figure 3, the anchor 9 is arranged at a comparatively large distance from the floating body 1. The stern rope 8 is thus subjected to such a high tension that the chain line between the floating body 1 and the anchor 9 guarantees such sagging of the rope that the tope does not or will hardly touch the ground. The same measures are applies to the other ropes 6, 10, 11, 12 and 13, so that also their extension is limited and accurate positioning is possible.

The detail of Figure 4 illustrates anchoring means 38 comprising a pontoon 39 connected to the ground 67 by means of anchoring ropes 40 and holding a fall pole 36 the lower end of which engages in the ground 67. A fastening ring 37 for the stern rope 8 is provided at a low level on the fall pole 36. The fall pole 36 can be elevated by means of a lifting device 73 whilst being guided vertically in a guide tube 74. The delivery pipe 70 preferably extends via the pontoon 39 to its intended place of action (not shown) and the pipe portion 76 between the cutter head suction dredger 60 and the pontoon 39 is very flexible, whereas the portion 77 located rearwardly of the pontoon 39 may be substantially rigid.

If the cutter head suction dredger is to be employed for dredging a channel 81 having a width t (Figure 11), the anchors 14, 7 and 9 are put in place, the anchors 7 and 9 being arranged substantially in the longitudinal central plane 80 of the channel 81 and the anchors 14 on the two opposite sides of the cutter head dredger 60. The cutter head dredger 60 is first located in a starting position in the longitudinal central plane 80, after which the ropes 6, 8, 10, 11, 12 and 13 are stretched to their predetermined tensions by means of the winches 19, 25, 29 and 30 and the stern rope 8 by means of the winch 16 of the bow rope 6. The cutter head dredger 60 is then moved into its working position shown in solid lines in Figure 1 and, after lowering the ladder 2 with the cutter head 3 to the predetermined depth, it is ready to make a first cut.The ropes 10 and 11 are then slowly veered out, whereas the ropes 12 and 13 are hauled in at a rate determined by the nature of the soil 67 to be loosened by the cutter head dredger 60. During each complete swing of the cutter head section dredger 60 across the channel 81, the tension of the stern rope 8 is maintained at a substantially constant value by being measured by the tension meter 18. The measured value amplified in an amplifier 52 (Figure 5) is shown by an indicator 51 on the control panel 43 and the amplified measured value is applied through a lead 35 to the control member 17, which delivers a control signal to the bow winch 16 after comparison with a tension of the stern rope 8 adjusted by setting means 48.The signal delivered by a control member 58 to the control device 31 of the foremost side rope winches 29 and 30 produces a signal at the control member 28 of the foremost side winch 29 to haul in the rope 12 and at the control member 27 of the foremost side winch 30 to veer out the rope 10 from the winch 30, whilst a residual tension is maintained. The singal of the control member 58 on the panel 43 is furthermore applied to the adapter 49 of the hauling rate of the hindmost side rope winches 25 and 19, said signal being applied to the computing device 22 of the hindmost side rope winches 25 and 19, to which computing device 22 is furthermore applied the signal of the angle meter 21 amplified by an amplifier 55.In dependence upon the position of an angle-indicating pointer 56 of the angle meter 21, the signals emanating from the computer 22 are applied to the control member 20 of the winch 19 for hauling in, so that the stern 44 of the cutter head dredger 60 shifts to the right at the correct rate and to the control member 23 of the hindmost side rope winch 25, so that the latter veers out the rope 1 1 with the predetermined residual tension. After a cut has been completely dredged away, the cutter head dredger 60 has to be advanced by a distance corresponding to that shown at a in Figure 1, which is performed by adjusting a setting member 59 on the control panel 43 to a value corresponding to this distance.The signal of the setting member 59 is applied to the control member 57 of the stern winch 69, which is energized with the aid of a switching knob 50 to veer out a length of the rope 8 equal to the distance a, Owing to the disappearance of the tension of the stern rope 8, which is measured by the tension meter 18, the result being passed through the amplifier 52 to the control member 17 of the bow winch 16, the latter is immediately actual ed so that the adjusted tension of the stern rope 8 is restored. The control member 17 can respond so rapidly that, upon veering out the stern rope 8, the bow rope 6 is immediately hauled in so as to maintain a constant tension in the stern rope 8.The winch 69 delivers, in addition, a signal corresponding to the length of the stern rope 8 through an amplifier 54 to an indicator 53 and to the adapter 49 of the hauling rate of the hindmost side winches 25 and 19. As soon as the stern rope 8 has reached such a length that swinging about the anchor 9 is no longer possible without the rope dragging along the ground 67 over a considerable length, the cutter head dredger 60 has to be anchored by means of the anchors 14, 7 and 9 being arranged at new places.

The setting member 75 then actuates the winch 69 of the stern rope 8, so that the cutter head dredger 60 is moved to a new starting position.

With the aid of the cutter head dredger 60 the ground 67 can, so to say, be peeled off in horizontal layers 84 (Figure 3), the cutter head 3 being constantly held at the same level in a given layer. In this way dredging can be carried out with high efficiency.

In order to avoid overload of the bow rope 6 during the swinging movement of the cutter head dredger, a preferred embodiment of the cutter head dredger 60 as shown in Figure 6 is provided with two bow ropes 45 instead of only one bow rope 6. These two bow ropes 45 extend at an acute angle to each other and have associated winches 46 and 47 and associated, relatively spaced anchors 78 and 79.

If two bow ropes 45 (Figure 6) are provided, the detail VII of Figure 5 has the structure shown in Figure 7. The control member 17 of Figure 7 is, in addition, influenced by a deflect ion-signal generator 42 of a compass 86, the control member 17 governing the winches 46 and 47.

The tension meter 18 comprises, for example two guide rollers 82 in a frame 83 and an auxiliary frame 85 adapted to pivot with respect to the frame 83 and holding a guide roller 41. The auxiliary frame 85 is linked to the frame 83 through a rod 33 provided with tension-measuring members 32, for example strain guages.

WHAT WE CLAIM IS: 1. A method of dredging with the aid of a cutter head suction dredger having a cutter head and an associated suction nozzle connected to a floating hull so that they can be raised and lowered with respect thereto, in which the hull is traversed horizontally to and fro by means of side ropes extending from winches on the hull adjacent the port and starboard sides thereof to anchorages in the ground positioned laterally outwardly of the hull to port and starboard thereof respectively, in which the hull is located in the fore and aft direction by at least one longitudinal rope extending forwardly from a winch on the hull adjacent the bow end thereof to a respective anchorage in the ground in front of the hull and at least one longitudinal rope extending aft from a winch on the hull adjacent the stern end thereof to a respective anchorage in the ground behind the hull, the longitudinal ropes being swung about their anchorages while the hull is being traversed, and in which the hull is moved forwardly or aft with respect to the ground by veering out the longitudinal rope or ropes at one end of the hull and hauling in the longitudinal ropes or ropes at the other end of the hull, characterised in that the tension in at least one of the longitudinal ropes is measured and at least one of the winches adjacent the bow or stern of the hull is actuated in dependence upon the measured tension.

2. A method as claimed in Claim 1, characterised in that the or each longitudinal rope of which the tension is measured extends from a winch adjacent one end of the hull and the or each winch that is actuated in dependence upon the measured tension is located adjacent the other end of the hull.

3. A method as claimed in Claim 1 or 2, characterised in that the or each longitudinal rope of which the tension is measured is a longitudinal rope extending from a winch adjacent the stern end of the hull.

4. A method as claimed in any of Claims 1 to 3, characterised in that the hull is traversed to and fro over an arc, the centre of which is at the anchorage of the or one of the longitudinal ropes extending aft from a winch on the hull adjacent the stern end thereof and that, during the traversing of the hull, the length of this longitudinal rope is maintained constant.

5. A method as claimed in any of the preceding claims, characterised in that the hull is prevented from moving astern by at least two bow ropes extending forward from respective winches on the hull adjacent the bow end thereof to respective anchorages in the ground in front of the hull.

6. A method as claimed in any of the preceding claims, characterised in that the angle between the longitudinal centre-line of the hull and one of the longitudinal ropes is measured and at least one of the winches from which side ropes extend is actuated in dependence upon the angle measured.

7. A method as claimed in Claim 6, characterised in that the winch or winches actuated in dependence upon the angle measured are actuated in such a manner as to counteract changes in said angle.

8. A cutter head suction dredger for carrying out the method claimed in any of the preceding claims, comprising a floating hull, a cutter head connected with the hull so that it can be raised and lowered with respect thereto, a pump, a suction nozzle located near the cutter head and communicating through a suction pipe with the pump, winches on the hull adjacent the port and starboard sides thereof respectively, side ropes extending from these winches to respective anchoring means, at least one bow winch on the hull adjacent the bow end thereof, at least one stern winch on the hull adjacent the stern end thereof and longitudinal ropes extending between the bow and stern winches and respective anchoring means, characterised by the provision of tension measuring means arranged to measure the tension in at least one of the longitudinal ropes and control means arranged to control at least one of the bow or stern winches in dependence upon the values of tension measured by the tension measuring means.

9. A cutter head suction dredger as claimed in Claim 8, characterised in that the tension measuring means is arranged to measure the tension of the longitudinal rope or one of the longitudinal ropes that extend from a winch adjacent one end of the hull and the said control means is arranged to control the longitudinal rope or one of the longitudinal ropes that extend from a winch adjacent the other end of the hull.

10. A cutter head suction dredger as claimed in Claim 8 or 9, characterised in that the tension measuring means is arranged to measure the tension of the or one of the long - itudinal ropes that extends from a winch ad jacent the stern end of the hull.

11. A cutter head suction dredger as claimed in any of Claims 8 to 10, characterised in that it is provided with at least two longitudinal ropes extending between respective bow winches and respective anchoring means.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the detail VII of Figure 5 has the structure shown in Figure 7. The control member 17 of Figure 7 is, in addition, influenced by a deflect ion-signal generator 42 of a compass 86, the control member 17 governing the winches 46 and 47. The tension meter 18 comprises, for example two guide rollers 82 in a frame 83 and an auxiliary frame 85 adapted to pivot with respect to the frame 83 and holding a guide roller 41. The auxiliary frame 85 is linked to the frame 83 through a rod 33 provided with tension-measuring members 32, for example strain guages. WHAT WE CLAIM IS:

1. A method of dredging with the aid of a cutter head suction dredger having a cutter head and an associated suction nozzle connected to a floating hull so that they can be raised and lowered with respect thereto, in which the hull is traversed horizontally to and fro by means of side ropes extending from winches on the hull adjacent the port and starboard sides thereof to anchorages in the ground positioned laterally outwardly of the hull to port and starboard thereof respectively, in which the hull is located in the fore and aft direction by at least one longitudinal rope extending forwardly from a winch on the hull adjacent the bow end thereof to a respective anchorage in the ground in front of the hull and at least one longitudinal rope extending aft from a winch on the hull adjacent the stern end thereof to a respective anchorage in the ground behind the hull, the longitudinal ropes being swung about their anchorages while the hull is being traversed, and in which the hull is moved forwardly or aft with respect to the ground by veering out the longitudinal rope or ropes at one end of the hull and hauling in the longitudinal ropes or ropes at the other end of the hull, characterised in that the tension in at least one of the longitudinal ropes is measured and at least one of the winches adjacent the bow or stern of the hull is actuated in dependence upon the measured tension.

12. A cutter head suction dredger as claimed

in any of Claims 8 to 11, characterised in that an angle meter is provided for measuring the angle between the longitudinal centre-line of the hull and one of the longitudinal ropes and at least one of the winches is controlled by control means responsive to measurements of the said angle made by the angle meter.

13. A cutter head suction dredger as claimed in any of Claims 8 to 12, characterised in that at least one of the longitudinal ropes is provided with anchoring means comprising a pontoon, a fall pole connected by lifting means with the pontoon and connecting means on the fall pole for enabling the respective longitudinal rope to be connected to the fall pole.

14. A cutter head suction dredger as claimed in Claim 13, characterised in that the or each fall pole has a lower end part for engagement in the ground and the respective connecting means is located at a level above but in close proximity to said lower end part.

15. A cutter head suction dredger as claimed in Claims 13 or 14, characterised in that a delivery pipe connected to the pump extends via the pontoon.

16. A method of dredging substantially as described with reference to and as shown in Figures 1 to 3 and 5, or Figures 1,2,4 and 5, or Figures 6 and 7 of the accompanying drawings.

17. A cutter head suction dredger substantially as described with reference to and as shown in Figures 1 to 3 and 5, or Figures 1, 2, 4 and 5, or Figures 6 and 7 of the accompanying drawings.