NL2010542C2

NL2010542C2 - Transplantation of a benthic soil layer.

Info

Publication number: NL2010542C2
Application number: NL2010542A
Authority: NL
Inventors: Johannes Hubertus Aloijsius Maria Jansen; Vincent Christoffel Gool
Original assignee: Bos & Kalis Baggermaatsch
Priority date: 2013-03-28
Filing date: 2013-03-28
Publication date: 2014-09-30
Also published as: WO2014158021A1

Abstract

The invention relates to a dredger with a benthic soil grab (20), wherein the benthic soil grab comprises a straight front plate (25), two straight side plates (26) and a straight back plate (27) that together form a rectangular pickup chamber (28), wherein at the bottom the front plate comprises a first cutting edge, the side plates each comprise a second cutting edge and the back plate comprises a third cutting edge, wherein the cutting edges (29, 30, 31) bound an access opening to the pickup chamber, and wherein the benthic soil grab comprises a visor cutter (40) comprising a closing plate (42) with a fourth cutting edge that is connected with the back plate by means of a hinge to open and close the access opening, wherein the benthic soil grab is lowered into the benthic soil with the front plate, the side plate and the back plate oriented vertically.

Description

Transplantation of a benthic soil layer

BACKGROUND

The invention relates to a method and device for transplantation of a benthic soil layer of an under water soil. The benthic soil layer of an under water soil comprises living organisms, both flora and fauna. An example thereof is soil rooted under water vegetation, such as sea grass .

Under water vegetation forms the basis of an aquatic ecosystem, where fish and other aquatic life reproduces. In nowadays dredging projects the conservation of the aquatic ecosystem during and after the dredging operations forms an important aspect. Up until now the under water vegetation is preserved on an ad hoc basis, wherein scuba divers harvest a portion of the under water vegetation only before the actual dredging operations start, where after the under water vegetation is implanted again when the dredging operations are finished. There is a growing need to transplant the under water vegetation on a large scale in an orderly manner.

SUMMARY OF THE INVENTION

According to a first aspect, the invention provides a method for transplantation of a benthic soil layer of an under water soil by means of a dredger with a benthic soil grab, wherein the benthic soil grab comprises a straight front plate, two straight side plates and a straight back plate that together form a rectangular pickup chamber, wherein at the bottom side front plate comprises a first cutting edge, the side plates each comprise second cutting edge and the back plate comprises a third cutting edge, wherein the cutting edges bound an access opening to the pickup chamber, and wherein the benthic soil grab comprises a visor cutter comprising a closing plate with a fourth cutting edge that is connected with the back plate by means of a hinge to open and close the access opening, wherein in the closed position of the visor cutter the fourth cutting edge extends along the first cutting edge and the closing plate closes off the access opening, and wherein in the open position the fourth cutting edge extends along third cutting edge and the closing plate extends at the opposite outer side of the back plate, wherein the method comprises at a harvesting area lowering the benthic soil grab under water to the benthic soil layer, lowering the vegetation grab with the visor cutter in its open position and with its front plate, the side plates and the back plate oriented vertically into the benthic soil layer whereby a portion of the benthic soil layer is inserted into the pickup chamber, and bringing the visor cutter to its closed position whereby the portion of the inserted benthic soil layer is separated from the soil.

In the method according to the invention a rectangular portion of the upper benthic soil layer is separated from the soil, wherein for example entangled roots of the vegetation inside separated portion remain undisturbed. The rectangular portion forms a practical block that can be shipped to an implant area or temporary storage area. In this manner the entire benthic soil layer can be transplanted on a large scale.

In an embodiment the portions of the benthic soil layer are picked up from the soil in parallel rows, wherein the benthic soil grab leaves the soil behind at a lower level than the adjacent row to be picked up, wherein the benthic soil grab is lowered into the benthic soil layer with the closing plate of the visor cutter above the soil with the lower level. The position of the closing plate ensures that the first and second cutting edges can be lowered deep enough to harvest the entire benthic soil layer.

In an embodiment the portions of the benthic soil layer are picked up from the soil in parallel rows, wherein the front plate of the vegetation grab leaves the soil behind with a vertical cutting face on the adjacent row to be picked up, wherein the benthic soil grab is lowered into the ground with the back plate aligned with the vertical cutting face. Due to the alignment the parallel rows are harvested in an efficient manner.

In an embodiment the inserted portion of the benthic soil layer is lifted by the benthic soil grab and placed on a floating barge above the water line.

In an alternative embodiment the inserted portion of the benthic soil layer is lifted by the benthic soil grab and placed on a submerged barge below the water line. By bringing the barge to the harvesting place, the displacements of the portions of the benthic soil layer between picking up and placing back again can be minimized.

In an embodiment the inserted portion of the benthic soil layer is lifted by the benthic soil grab and placed on a carrier, wherein at an implant area the carrier with multiple portions of the benthic soil layer is lowered onto the soil and left behind. The portions of the benthic soil are then placed on the soil at the implant area in large groups.

In a practical embodiment the carrier is placed on a floating barge, which can be shipped over large distances in the case that the implant area is far remote from the harvesting area.

In an embodiment the carrier is slid from the barge via a slide that extends between the barge and the soil.

In an embodiment the carrier is made of biodegradable material, which gradually dissolves whereby the roots can set into the soil below.

In an embodiment thereof the carrier comprises a willow mat.

In an alternative embodiment the carrier comprises a geo textile, which can give long term stability, for example at the base of a dyke.

In an embodiment the carrier is provided with buoyancy bodies that can be filled with water or air, wherein at the harvesting area the carrier is submerged to the soil. In this manner the same carrier can be used to receive the portions of the benthic soil layer at the harvesting area and to ship them to the implant area.

In an embodiment the carrier is provided with buoyancy bodies that can be filled with water or air, wherein at the implant area the carrier is submerged to the soil. In this manner the same carrier can be used to ship the portions of the benthic soil layer to the implant area and to implant them there.

In an embodiment the portion of the benthic soil layer forms a cohesive portion, which can be handled easily.

In particular, the benthic soil layer comprises soil rooted under water vegetation, wherein the portion of the benthic soil layer forms a clod. The clod forms a cohesive unit due to the entangled roots of the under water vegetation.

According to a second aspect, the invention provides a with a benthic soil grab, wherein the vegetation grab comprises a straight front plate, two straight side plates and a straight back plate that together form a rectangular pickup chamber, wherein at the bottom side the front plate comprises a first cutting edge, the side plates each comprise a second cutting edge and the back plate comprises a third cutting edge, wherein the cutting edges bound an access opening to the pickup chamber, and wherein the benthic soil grab comprises a visor cutter comprising a closing plate with a fourth cutting edge that is connected with the back plate by means of a hinge to open and close the access opening, wherein in the closed position of the visor cutter the fourth cutting edge extends along the first cutting edge and the closing plate closes off the access opening, and wherein in the open position the fourth cutting edge extends along the third cutting edge and the closing plate extends at the opposite outer side of the back plate.

In an embodiment the closing plate is curved with a constant radius with respect to the hinge, wherein in the closed position the second cutting edges extend along the closing plate. This ensures that the portion of the benthic soil is cut all around from the surrounding soil.

In an embodiment dredger is a backhoe dredger comprising a body and a backhoe arm that is pivotally connected with the body, wherein the benthic soil grab is connected to the end of the backhoe arm with the front plate facing the body.

The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications .

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which:

Figure 1A-1E subsequent steps of taking out and shipping from an underwater soil separate sea grass clods comprising the fertile soil fraction surrounding the roots of the sea grass by means of a benthic soil grab according to the invention;

Figures 2A and 2B a side view and an isometric view of the benthic soil grab according to figures 1A-1E;

Figures 3A and 3B an alternative method for taking out a sea grass clod with the fertile soil fraction with the benthic soil grab according to the invention;

Figures 4A-4C illustrate an alternative method of implanting earlier taken sea grass clods on an underwater soil, and details of a willow mat used therein according to the invention;

Figures 5A and 5B illustrate an alternative method of shipping and implanting of sea grass clods according to the invention; and

Figures 6A and 6B illustrate an alternative method of taking out and shipping sea grass clods according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure LA-IE show subsequent steps of taking out sea grass clods 3 from a harvesting area with a benthic soil grab 20 according to the invention. The benthic soil grab 20 is connected to the end of a backhoe arm 21 of a not shown floating backhoe dredger.

As schematically shown in figure 1A, the clods 3 originate from an underwater soil 1. The water 8 can be salt water or fresh water. The underwater soil 1 comprises on top a benthic soil layer, in this embodiment a fertile top layer 2 with sea grass 10 or any other useful soil rooted under water vegetation. The sea grass 10 comprises roots 11 that are firmly anchored and entangled in the fertile top layer 2. In order to let the sea grass 10 survive transplantation, it is essential that the roots 11 and the fertile soil fraction surrounding the entangled roots 11 are taken out unperturbed.

As shown in figures 2A and 2B the steel benthic soil grab 20 comprises a straight, rectangular top plate 24, and a straight, rectangular front plate 25, two straight side plates 26 and a straight, rectangular back plate 27 that are connected to each other by welding to define a hollow, rectangular pick up chamber 28 with an open lower side. The lower edges of the front plate 25, the side plates 2 6 and the back plate 27 are bevelled to form downwardly directed cutting edges 29, 30, 31 along the opening of the pick up chamber 28.

The benthic soil grab 20 comprises multiple supports 35 for two hinges 3 6 that extend above the top plate 24. A visor cutter 40 is connected to the hinges 36 to be opened and closed in direction A. The visor cutter 40 comprises two straight side plates 41 and a curved bottom plate 42. The bottom plate 42 is its free side bevelled to form a cutting edge 43. The curvature of the bottom plate 42 is cylindrical whereby the distance between the bottom plate 42 and the cutting edge 31 of the back plate 27 remains constant and small when the visor cutter 40 is opened and closed. The lower side of the two side plates 27 follows at its cutting edges 30 the curvature of the bottom plate 42 to keep the distance between its cutting edges 29 and the bottom plate 42 constant.

The visor cutter 40 is provided with a back beam 44 and multiple supports 45 on the back beam 44 that are hingeably connected with hydraulic cylinders 47. At the opposite side the hydraulic cylinders 47 are hingeably connected with supports 46 on the top plate 24 and the back plate 27. By activation of the hydraulic cylinders 47 the visor cutter 40 can be moved in direction A from an open position as shown in figure 2A and 2B, wherein the cutting edge 43 of the visor cutter 40 extends along the cutting edge 31 of the back plate 27, and a closed position wherein the cutting edge 43 of the visor cutter 40 meets the cutting edge 29 of the front plate 25.

Figures 1A-IE show subsequent steps of taking out sea grass clods 3 from the underwater soil 1. The sea grass clods 3 are subsequently taken out from parallel rows 60-63 of the soil 1. In figure 1A is shown that a first row 60 and a second row 61 have already been harvested and that the third row 62 is to be harvested next.

The benthic soil grab 20 is thereto positioned straight above the first clod 2 of the third row 62 with the visor cutter 40 fully opened in direction A. The visor cutter 40 is located above the space that is left behind by harvesting the second row 61, wherein the back plate 27 is aligned with the vertical cutting face 5 that was left there. Subsequently, the benthic soil grab 20 penetrates the soil 1 in vertical direction B, wherein the cutting edges 29, 30 of the front plate 25 and the side plates 26 cut into the fertile top layer 2. The vertical orientation of the front plate 25, the side plates 26 and the back plate 27 is set and maintained by means of an inclinometer on the sea grass grab 20 that gives feed back to the operator of the backhoe dredger. In this manner the entangles roots 11 are cut only at the circumference of the clod 2 and the sea grass clod 2 enters the pick up chamber 28. At the level of the entangled roots the clod 2 behaves as a peaty soil 11.

The benthic soil grab 20 is pushed downwards in vertical direction B until the vertical cutting face 5 is located fully inside the pick up chamber 28, which is shown in figure IB. The penetration depth into the soil 1 is about 1 meter. As the visor cutter 40 is positioned above the space that is left behind by harvesting the second row 61, the benthic soil grab 20 is freely moved downwards despite the projecting position of the visor cutter 40. The operator of the backhoe dredger will notify that the benthic soil grab 20 has reached sufficient penetration depth when the opened visor cutter 40 hits the transition from the vertical cutting face 5 and the curved cutting face 4 of the previous row 61.

Subsequently the visor cutter 40 is fully closed in direction B as shown in figure 1C, wherein the fertile top layer 2 is cut below the roots 11 of the sea grass 10 by the cutting edge 43. The sea grass clod 2 is then fully separated from the soil 1 without disturbing the entangled roots 11 inside the sea grass clod 2. Finally the benthic soil grab 20 lifts the sea grass clod 3 as shown in figure ID, where after the sea grass clod 3 is put on a floating barge 50. The cutting and raising of subsequent sea grass clods 3 is repeated until the barge 50 is fully loaded.

In one embodiment of the method, the barge 50 is subsequently shipped to the remote implant area. At the implant area the individual sea grass clods 3 can be picked up again with the benthic soil grab 20 and implanted on the under water soil 1. Alternatively, the sea grass clods 3 are lifted individually or in groups with a deck crane of a working vessel and implanted on the under water soil 1.

Figures 3A and 3B show an alternative method for taking out a sea grass clods 3 with the benthic soil grab 20 according to the invention. In this method, the barge 50 is submergible. The barge 50 is submerged to rests on the soil 1 where the first row 60 and second row 61 of the soil 1 have already been harvested, close to the third row 62 to be harvested. In this manner the benthic soil grab 20 can efficiently release the grass clods 3 close to the location where they have been taken out. After loading the barge 50 with the sea clods 30, it is raised again and shipped to the remote implant area. At the implant area, the grass clods 3 can be picked up as described here before, or the barge 50 is submerged again to reduce the distance between the stock of grass clods 3 and the position where they are implanted.

A further method of harvesting and implanting sea grass clods 3 according to the invention is illustrated in figures 4A-4C. Figure 4A show the floating barge 50 as described here before. The sea grass clods 3 are placed in groups on a willow mat 7 0 which is shown in figures 4B and 4C.

The willow mat 70 comprises multiple parallel and spaced apart first elongated bundles 71 of willow branches and perpendicularly thereon multiple parallel and spaced apart second elongated bundles 72 of willow branches. Above the second bundles 72 extend multiple dense layers 73 of willow branches which extend perpendicular to each other to form a stable supporting layer 76. Above the supporting layer 76 the willow mat 70 comprises multiple parallel and spaced apart third elongated bundles 74 of willow branches and perpendicularly thereon multiple parallel and spaced apart fourth elongated bundles 75 of willow branches. The first bundles 71 and the second bundles 72, and the third bundles 74 and fourth bundles 65 are interconnected to each other with biodegradable ropes, and the supporting layer 76 is sandwiched there between by biodegradable ropes stitched through the supporting layer 76.

The willow mat 70 or multiple willow mats 70 are placed on the barge 50 and the sea grass clods 3 are placed by the sea grass grab 2 0 on the supporting layer 7 6 in the matrix of the third bundles 74 and fourth bundles 75. Subsequently the barge 50 is shipped to the implant area as shown in figure 4A. At the implant area a slide to the soil 1 is formed by means of parallel pipes 51. The willow mats 60 are subsequently slid downwards in direction C from the barge 50 under the weight of the sea grass clods 3, wherein the willow mats 70 are installed against each other onto the soil 1.

Figures 5A and 5B illustrate an alternative method of taking out, shipping and implanting of sea grass clods 3 with the sea grass grab 20 according to the invention. In this method, the willow mat 70 is provided with additional floating bodies 77 that enable the willow mat 60 to temporally float on the water while carrying the weight of the sea grass clods 3. As shown in figure 5A, sea grass clods 3 are placed on the floating willow mat 70 at the harvesting area to be shipped to the implant area. Alternatively, earlier picked up sea grass clods 3 are placed on the floating willow mat 7 0 at the implant area.

Subsequently the floating bodies 77 are filled with water to allow the willow mat 70 with the sea grass clods 3 to sink in downward direction D to the soil 1 as shown in figure 5B.

Figures 6A and 6B show an alternative method of taking out and shipping sea grass clods 3 with the sea grass grab 20 according to the invention. In this method the willow mat 70 with the additional floating bodies 67 is firstly sunk to the soil 1, where after the sea grass clods 3 are picked up and installed as a group on the willow mat 70 under water. Subsequently the floating bodies 77 are filled with air whereby the willow mat raises to the water surface. The floating willow mat 70 can be shipped to the implant area to be sunk as described before.

In above embodiments a willow mat 70 is used to carry the sea grass clods 3. Alternatively, a biodegradable geo textile is used, or a bundled combination of geo textile and branches is used.

It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the spirit and scope of the present invention.

Claims

A method for transplanting a benthic bottom layer from an underwater bottom layer by means of a dredging device with a bethic bottom grab, the benthic bottom grab comprising a straight front plate, two straight side plates and a straight back plate which together form a rectangular pick-up chamber, the bottom side the front plate comprises a first cutting edge, the side plates each comprise a second cutting edge and the back plate comprises a third cutting edge, wherein the cutting edges define an access opening to the pick-up chamber, and wherein the benthic bottom gripper comprises a visor cutter, including a closing latch with a fourth cutting edge coupled to the back plate by means of a hinge to open and close the access opening, wherein in the closed position of the visor cutter the fourth cutting edge extends along the first cutting edge and the closing plate closes the access opening, and wherein in the open position the fourth cutting edge is along the the third cutting edge extends and the closing plate extends on the opposite outside of the back plate, the method comprising lowering the benthic bottom grab to the benthic bottom layer in a wing area, lowering the benthic bottom grab with the visor cutter in its open lower the position and with its front plate, the side plates and the back plate vertically directed into the bethic bottom layer thereby bringing a portion of the benthic bottom layer into the pick-up chamber, and bringing the visor cutter to its closed position whereby the portion of the inserted benthic bottom layer is separated from the bottom.

Method according to claim 1, wherein the portions of the benthic bottom layer are picked up in parallel rows of the bottom, the benthic bottom grab leaving the bottom at a lower level than the adjacent row that still needs to be picked up, the benthic bottom grab being lowered placed in the benthic bottom layer with the face plate of the visor cutter above the bottom with the lower level.

A method according to claim 1 or 2, wherein the portions of the benthic bottom layer are picked up in parallel rows of the bottom, the face plate of the benthic bottom gripper leaving the bottom with a vertical cutting surface on the adjacent row to be picked up, the benthic bottom layer bottom gripper is lowered into the benthic bottom layer with the back plate aligned with the vertical cutting surface.

A method according to any one of the preceding claims, wherein the introduced portion of the benthic bottom layer is raised by the benthic bottom grab and placed on a floating container above the waterline.

A method according to any one of the preceding claims, wherein the introduced portion of the benthic bottom layer is raised by the benthic bottom grab and placed on a sunken tank below the waterline.

A method according to any one of the preceding claims, wherein the introduced portion of the benthic bottom layer is raised by the benthic bottom grab and placed on a support, wherein in an implantation area the support with several portions is lowered from the benthic bottom layer to the bottom and is left behind.

The method of claim 6, wherein the carrier is placed on a floating container.

A method according to claim 7, wherein the carrier is slid off the tray via a slide that extends between the tray and the bottom.

The method of any one of claims 6 to 8, wherein the carrier is made of a biodegradable material.

The method of any one of claims 6-9, wherein the carrier comprises a mat of willow toes.

The method of any one of claims 6-10, wherein the carrier comprises a geotextile.

12. Method as claimed in any of the claims 6-11, wherein the carrier is provided with floating bodies which can be filled with water or air, wherein the carrier is sunk to the bottom in the wing area.

A method according to any one of claims 6-11, wherein the carrier is provided with floating bodies that can be filled with water or air, wherein the carrier is sunk to the bottom in the implantation area.

A method according to any one of the preceding claims, wherein the portion of the benthic bottom layer forms a coherent portion.

A method according to any one of the preceding claims, wherein the benthic soil layer comprises rooted under water vegetation, wherein the portion of the benthic soil layer forms a root ball.

16. Dredging device with a benthic bottom gripper, wherein the benthic bottom gripper comprises a straight front plate, two straight side plates and a straight rear plate which together form a rectangular pick-up chamber, wherein on the bottom side the front plate comprises a first cutting edge, the side plates each having a second cutting edge and the back plate comprises a third cutting edge, the cutting edges delimiting an access opening to the pick-up chamber, and wherein the benthic bottom gripper comprises a visor cutter, comprising a closing plate with a fourth cutting edge which is hinged to the back plate to open and close the access opening, wherein in the closed position of the visor cutter the fourth cutting edge extends along the first cutting edge and the closing plate closes the access opening, and wherein in the open position the fourth cutting edge extends along the third cutting edge and the closing plate extends on the opposite outside of the back plate.

A dredging device according to claim 16, wherein the closing plate is curved with a constant radius relative to the hinge, the second cutting edges extending along the closing plate in the closed position.

A dredging device according to claim 16 or 17, wherein the dredging device is a backhoe with a body and a backhoe arm that is hingedly coupled to the body, the benthic bottom grabber being coupled to the end of the backhoe arm with the face plate facing the body .