DK178703B1

DK178703B1 - A method for burying conduit means and a conduit burial arrangement

Info

Publication number: DK178703B1
Application number: DKPA201570076A
Authority: DK
Inventors: Farzin Hafezparast; Francesca Patrizia Del Din
Original assignee: Rambøll Danmark As
Priority date: 2015-02-09
Filing date: 2015-02-09
Publication date: 2016-11-21
Also published as: DK201570076A1

Abstract

Disclosed is a method for burying conduit means (1) in a seabed (2). The method comprises the steps of: arranging wire means (3) at the seabed (2), placing an anchoring arrangement (4) on the wire means (3), forcing the wire means (3) down into the seabed (2) by forcing the anchoring arrangement (4) into the seabed (2), connecting the conduit means (1) to a first end (5) of the wire means (3), and pulling the conduit means (1) into the seabed (2) by pulling a second end (6) of the wire means (3). A conduit burial arrangement (15) and use of a method for burying conduit means (1) in a seabed (2) by means of a conduit burial arrangement (15) is also disclosed.

Description

A METHOD FOR BURYING CONDUIT MEANS AND A CONDUIT BURIAL ARRANGEMENT Field of the invention

The invention relates to a method for burying conduit means in a seabed. The invention also relates to a conduit burial arrangement for burying conduit means in a seabed.

Background of the invention

It is well known in the art to bury conduits - such as cables, pipelines and other - in the seabed e.g. to protect the conduits from being damaged by ships, fishing equipment, icebergs dragging across the seabed, the hostile seawater environment or other.

From WO 2012/008833 it is known to first drill a passage through the seabed in a first direction and then pull a cable back through this passage in the opposite direction. But particularly the drilling equipment used in this method is complex and expensive.

An object of the invention is therefore to provide for an advantageous technique for burying conduits in a seabed.

The invention

The invention provides for a method for burying conduit means in a seabed. The method comprises the steps of: • arranging wire means at the seabed, • placing an anchoring arrangement on the wire means, • forcing the wire means down into the seabed by forcing the anchoring arrangement into the seabed, • connecting the conduit means to a first end of the wire means, and • pulling the conduit means into the seabed by pulling a second end of the wire means.

Forcing wire means down into the seabed and then subsequently using the wire means to pull the conduit means into the seabed is advantageous it provides a simple and quick method for embedding conduit means in a seabed. E.g. compared to traditional trenching or drilling methods, this method enables that conduit means may quickly and easily be installed over large distances - at least at larger burial depths such as more than 2-3 meters.

Furthermore, forcing the wire means down into the seabed by placing anchoring arrangement on top of the wire means and then forcing the anchoring arrangement into the seabed is a simple and quick way of burying the wire means in the seabed and the anchoring arrangement enables that the wire means and subsequently the conduit means may be guided into and out of the seabed in a controlled fashion.

In this context the term “conduit means” should be understood as any kind of conduit suitable for conducting electrical current, light, liquids or other. I.e. the conduit means could be any kind of pipeline, optical fibre cable, power cable or other or any combination thereof.

It should also be noted that in this context the term “wire means” should be understood as any kind of cable suitable for pulling conduit means through a seabed - i.e. any kind of steel cable, composite cable, rope, cord, line, chain or other or any combination thereof.

In an aspect of the invention, the anchoring arrangement comprises a first anchoring device and a second anchoring device and wherein the first anchoring device and the second anchoring device are spaced apart by a mutual distance.

Spacing the first anchoring device and the second anchoring device far apart by a mutual distance is advantageous in that it hereby is possible to bury the conduit means in the seabed over this mutual distance in a single operation.

In an aspect of the invention, the mutual distance is between 1 and 10,000 meters, preferably between 5 and 5,000 meters and most preferred between 20 and 1,000 meters.

If the mutual distance is too little it will take too many operations to bury the conduit means over a large distance but if the mutual distance is too big it will take too much force to pull the wire means and the conduit means through the seabed. The present distance ranges therefore presents an advantageous relationship between efficiency and realisability of the method.

In an aspect of the invention, one or more additional anchoring devices are arranged between the first anchoring device and the second anchoring device.

Forcing the wire means into the seabed in more points between the first anchoring device and the second anchoring device by placing additional anchoring devices between the first and the second anchoring devices is advantageous in that it will reduce the required tensioning of the wire means and it will reduce the bending angles of the conduit means during the burying process.

In an aspect of the invention, the method comprises the step of tensioning the wire means before the conduit means is pulled into the seabed.

Tensioning the wire means before the conduit means is pulled into the seabed is advantageous in that this will entail that the conduit means can be buried even deeper without having to force the anchoring arrangements deeper into the seabed.

Furthermore, a pre-tensioning of the wire means will reduce the bending angles of the conduit means during the burying process.

In an aspect of the invention, the wire means are tensioned by between 0.1 and 25.000 kN, preferably between 1 and 10.000 kN and most preferred between 2 and 5.000 kN the before the conduit means is pulled into the seabed.

If the wire means are tensioned too little the conduit means will not be buried at sufficient depth and the risk of damaging the conduit means during the burying process - due to too sharp bends - is increased. However, if the wire means are tensioned too much the risk of damaging or even breaking the wire means is increased - and the equipment for generating such large tensions will become relatively expensive. The present force ranges therefore presents an advantageous relationship between efficiency and cost.

In an aspect of the invention, the method comprises the step of displacing the anchoring arrangement a certain distance upwards before tensioning the wire means again.

No matter how hard the wire means are tensioned they will typically not run in a straight line in the seabed due to seabed resistance, obstacles, friction or other and this problem is particularly pronounced when the wire means is forced into the seabed by means of two anchoring devices spaced far apart by a mutual distance. Therefore by raising the anchoring arrangement a certain distance upwards after the wire means have been tensioned a first time the angle of the wire means will be less sharp around the penetrating end of the anchoring arrangement when the wire means is tensioned a second time. This more obtuse angle around the anchoring arrangements is advantageous in that it reduces the risk of damaging the conduit means when these are pulled past the anchoring arrangements.

In an aspect of the invention, the anchoring arrangement is forced into the seabed by rotating helical screw means of the anchoring arrangements.

Providing the anchoring arrangements with helical screw means is advantageous in that the anchoring arrangements hereby can be forced into the seabed by means of a simple rotating motion. Furthermore, when the conduit means is pulled past the penetrating end of the anchoring arrangements and/or when the wire means are tensioned, the anchoring arrangements will have to withstand a large vertical force component trying to force the anchoring arrangements upwards and out of the seabed. Screwing the anchoring arrangement into the seabed also enables it to better withstand this upward force.

In an aspect of the invention, the angle between the wire means and the surface of the sea is between 1° and 85°, preferably between 2° and 15° and most preferred between 5° and 65° during at least a part of the time when the conduit means is pulled into the seabed by pulling the second end of the wire means.

If the angle between the wire means and the surface of the sea is too little, the pulling means used for generating the desired tension of the wire means will have to be located very far from the anchoring arrangement during the tensioning process. However, if the angle is too big the vertical force component on the anchoring arrangement will be so big that the risk of pulling the anchoring arrangement out of the seabed is increased - and the angle across the penetrating end of the anchoring arrangements will be so sharp that the risk of damaging the conduit means is increased. The present angle ranges therefore present an advantageous relationship between efficiency and safety.

In an aspect, the second end of the wire means is pulled by means of at least one vessel arranged on the surface of the sea above the seabed.

Pulling the wire means by means of a seagoing vessel is advantageous in that it hereby is possible to generate the pull from the sea surface e.g. by means of tugboats or similar suited for generating a large pulling force.

In an aspect, the anchoring arrangement is forced into the seabed by means of an anchoring arrangement displacing device arranged at the seabed.

Forcing the anchoring arrangement into the seabed by means of an anchoring arrangement displacing device arranged at the seabed is advantageous in that it enables that the anchoring arrangement can be into the seabed in a more efficient and controlled manner.

In an aspect, a liquid will be released at a front end of the conduit means at least during some of the duration of the front ends travel through the seabed.

Typically the conduit means will be significantly thicker than the wire means -particularly since the wire means according to the present invention has to cut into the seabed - and it is therefore advantageous to release a liquid at the front end of the conduit means while it is being pulled through the seabed to increase the passage formed by the wire means and to act as a lubricant reducing friction and thereby reduce the force needed to pull the conduit means through the seabed.

The invention also provides for a conduit burial arrangement for burying conduit means in a seabed. The conduit burial arrangement comprises wire means arranged to be connected to the conduit means to pull the conduit means down into the seabed and pulling means arranged to pull the wire means. The conduit burial arrangement also comprises at least one anchoring device comprising a penetrating end arranged to penetrate the seabed, wherein the anchoring device comprises wire guide means arranged to guide at least parts of the wire means and at least parts of the conduit means past the penetrating end of the anchoring device.

It is advantageous to provide the anchoring device with wire guide means arranged so that the wire means and the conduit means may be guided past the penetrating end of the anchoring device more simply and controlled - thus, enabling fast and safe installation of the conduit means in the seabed.

In an aspect, the pulling means comprises at least one propelled vessel including means for moving around on the surface of the sea above the seabed.

Propelled vessels such as tugboats and the like are capable of generating the needed force for cutting the wire means into the seabed and for pulling the conduit means through the seabed in a relatively simple and inexpensive manner.

Figures

The invention will be described in the following with reference to the figures in which fig. 1 illustrates two anchoring devices forcing wire means into the seabed, as seen from the side, fig. 2 illustrates two vessels tensioning the wire means, as seen from the side, fig. 3 illustrates that the anchoring devices are being displaced vertically, as seen from the side, fig. 4 illustrates the wire means being re-tensioned, as seen from the side, fig. 5 illustrates conduit means being prepared to be pulled through the seabed, as seen from the side, fig. 6 illustrates conduit means being pulled through the seabed, as seen from the side, fig. 7 illustrates that an anchoring device is removed while conduit means is being pulled through the seabed, as seen from the side, fig. 8 illustrates the use of more than two anchoring devices, as seen from the side, and fig. 9 illustrates an embodiment of an anchoring arrangement and an anchoring arrangement displacing device, as seen from the front.

Detailed description

Fig. 1 illustrates a conduit burial arrangement 15 which in this embodiment comprises two anchoring devices 7, 8 forcing wire means 3 into the seabed 2, as seen from the side.

In this embodiment wire means 3 is first at least partly placed on the seabed 2 by means of the vessels 12 on the sea surface 11. Once the wire means 3 is in position an anchoring arrangement 4 is placed on top of the wire means 3 where after the anchoring arrangement 4 is forced down into the seabed 2 so that at least parts of the wire means 3 is also forced into the seabed 2.

In this embodiment the conduit means 1 is also initially placed on the seabed 2 by means of the vessels 12 but in another embodiment the conduit means 1 could be fed directly from a vessel 12, from another location or it could be introduced at the seabed 2 at another time of the process e.g. just before it is pulled into the seabed 2.

In this embodiment the anchoring arrangement 4 comprises two individual anchoring devices 7, 8 spaced apart by a mutual distance MD of 500 meters. However in another embodiment the anchoring arrangement 4 could comprise only a single anchoring device 7, 8 or the two anchoring devices 7, 8 could be spaced apart by a different mutual distance MD e.g. depending on the available pulling force, the design of the anchoring devices 7, 8, the design of the wire means 3, characteristics of the seabed 2 or other.

In this embodiment the anchoring devices 7, 8 comprise a pile including some sort of releasable barb arrangement (not shown) making it relatively easy to insert the anchoring devices 7, 8 downwards in the seabed 2 whereas the barb arrangement makes it difficult to displace the anchoring devices 7, 8 vertically upwards if the barb arrangement is not released. However, in another embodiment the anchoring devices 7, 8 could be formed differently e.g. as discussed in relation with figure 9.

In this embodiment the conduit means 1, the wire means 2 and the anchoring arrangement 4 are all supplied from the vessels 12 on the sea surface 11 but in another embodiment one or more of these could be supplied and/or handled from the shore, by means submarine, by means of divers, by means of a vehicle/robot traveling on the seabed 2 or other or any combination thereof.

In this embodiment the wire means 3 is formed as a straight steel cable but in another embodiment the wire means 3 could comprise irregularities in the form of radially extending pins, rods or other, balls, plates or other or any combination thereof e.g. to increase the size of the path cut by the wire means 3, to loosen the ground surrounding the wire means 3, to enable a sawing-effect (e.g. by moving the wire means 3 back and forth during tensioning) or other.

Fig. 2 illustrates two vessels 12 tensioning the wire means 3, as seen from the side.

In this embodiment the wire means 3 are tensioned by two vessels 12 in the form of high-power tugboats traveling in opposite directions while being connected to opposite ends 5, 6 of the wire means 3 to force the wire means 3 between the first anchoring device 7 and the second anchoring device 8 into the seabed 2. However, in another embodiment one end 5, 6 of the wire means 3 could be fixed - e.g. by connecting it to a fixed point on shore, on the seabed 2 or other - while the other end 5, 6 of the wire means 3 is being pulled by one, two or more vessels 12.

In this embodiment conduit means 1 is an oil pipeline arranged to transport oil from an offshore arctic drilling site to an onshore oil refinery. In arctic areas there is a considerable risk that icebergs will drag across the seabed 2 and since the average weight of an iceberg is 100,000-200,000 tons it is essential that the pipeline is embedded in the seabed 2 at sufficient depth to protect it from being damaged by an iceberg collision or deformation of the surrounding ground. Thus, in this embodiment the penetrating end 17 of the anchoring devices 7, 8 is arranged approximately 40 meters into the seabed 2 and the wire means 3 is pulled at either ends 5, 6 by a force of approximately 10,000 kN which entails that the middle of the wire means 3 between the first anchoring device 7 and the second anchoring device 8 will cut approximately 10 meters into the seabed 2. However, it is obvious to the skilled person that these parameters can be varied infinitely e.g. depending on the diameter of the wire means 3 - which in this case is 0,2 meters -, the condition of the seabed 2, the available pulling force, the design of the anchoring devices 7, 8 and other.

In another embodiment of the invention the wire means 3 would not be tensioned before the wire means 3 is used for pulling the conduit means 1 into/through the seabed 2 - e.g. if only a single anchoring device 7 was used for guiding the conduit means 1 under a relatively narrow obstacle such as other transversal conduits, a seabed channel or other or if the wire means 3 would be sufficiently tensioned by pulling the conduit means 1 or other.

In this embodiment the angle A - in the direction of the anchoring means 7, 8 -between the wire means 3 and the surface 11 of the sea is around 10° to ensure a smooth bend on the conduit means 1 during entrance into the seabed 2 and when passing the anchoring devices 7, 8. However, at larger water depths the angle A might be bigger to avoid that installation could only be made with very long wire means 3. Or at more shallow water or if the pulling means 16 was arranged at the seabed 2 - instead of on the sea surface 11 - the angle A could be smaller.

Fig. 3 illustrates that the anchoring devices 7, 8 are being displaced vertically, as seen from the side and fig. 4 illustrates the wire means 3 being re-tensioned, as seen from the side.

In an embodiment of the invention the first end 5 of the wire means 3 would now be connected to the conduit means 1 so that the conduit means 1 could be pulled through the seabed 2 as explained in relation to figures 5-7. However, in this embodiment the anchoring devices 7, 8 are now displaced vertically upwards e.g. so that the penetrating ends 17 of the anchoring devices 7, 8 are only approximately 10 meters into the seabed 2. Here after the wire means 3 are re-tensioned by again pulling either ends 5, 6 of the wire means 3, whereby the wire means will substantially form a straight line between the penetrating ends 17 of the anchoring devices 7, 8 or whereby the curvature of the wire means 3 - and subsequently the conduit means 1 - between the anchoring devices 7, 8 will at least be reduced so that the bending angle 1 of the wire means 3 and the conduit means 1 around the anchoring devices 7, 8 will be reduced.

Fig. 5 illustrates conduit means 1 being prepared to be pulled through the seabed 2, as seen from the side, fig. 6 illustrates conduit means 1 being pulled through the seabed 2, as seen from the side and fig. 7 illustrates that an anchoring device 7 is removed while conduit means 1 is being pulled through the seabed 2, as seen from the side.

Once the wire means 3 is correctly placed in the seabed 2 the first end 5 of the wire means 3 is connected to the conduit means 1 where after the second end 6 of the wire means 3 is pulled to pull the conduit means 1 down into the seabed 2 past the first anchoring device 7 and the second anchoring device 8 and then up and out of the seabed 2.

In this embodiment the first anchoring device 7 is removed when the conduit means 1 has passed the first anchoring device 7 and the second anchoring device 8 is removed when the conduit means 1 has passed the second anchoring device 8. However, in another embodiment the anchoring devices 7, 8 could be removed at another time during the installation of the wire means 3 or the conduit means 1 in the seabed 2 - e.g. when the front end 14 of the conduit means 1 has reached a desired depth - or the anchoring devices 7, 8 could be designed for one-time use and thus be left in the seabed 2.

In this embodiment the conduit means 1 is pulled out of the seabed 2 once it has passed the second anchoring device 8 and pulled so far out of the seabed 2 that it can be connected to an onshore refinery. However, in another embodiment this installation process would only be the first of two or several consecutive processes and the conduit means 1 would therefore be left in the seabed 2 so that it was ready to be pulled further forward during a subsequent installation process or so that it was ready to be connected to conduit means 1 installed in a subsequent process. Or the conduit means 1 would only be pulled slightly out of the seabed 1, so that it could be connected to another conduit means 1 before, after or during installation of this conduit means in the seabed 2 - so that the connection between the conduit means 1 would be left on the seabed 2 or so that this connection subsequently (or during the installation process) could we buried at desired depth in the seabed 2.

In this embodiment an excavation 19 is made where the conduit means 1 is supposed to enter the seabed 2 to facilitate the penetration of the conduit means 1 into the seabed 1 with a smooth angle to protect the conduit means 1 from too sharp bends. However, in another embodiment the conduit means 1 would be pulled into the seabed 2 substantially in the same angle as the wire means 3 originally was or other means could be provided to ensure a smooth transition of the conduit means 1 such as simplified anchoring means, special fittings or other.

In this embodiment the conduit means 1 is provided with means - e.g. in the form of nozzles or jets - enabling that a liquid can be released from the front end 14 of the conduit means 1 while it is being pulled through the seabed 2. This liquid would most likely be seawater but it could also be some other type of liquid suited for being sprayed out in front of the front end 14 of the conduit means 1 to aid in the installation process by acting as a lubricant and/or to increase the size of the passage formed by the wire means 3.

In another embodiment the front end 14 of the conduit means 1, the first end 5 of the wire means 3 or other could also or instead be provided with a drilling device, a deflector or another device reducing friction and/or aiding the conduit means 1 penetration though and/or into the seabed 2.

Fig. 8 illustrates a conduit burial arrangement 15 comprising more than two anchoring devices 7, 8, as seen from the side.

In this embodiment a single additional anchoring device 9 is arranged between the first anchoring device 7 and the second anchoring device 8 to reduce the curvature of the wire means 3 before and after tensioning and to reduce the required force needed to tension the wire means 1 so much that a desired depth is reached in the seabed 2.

In another embodiment further additional anchoring device 9 could be arranged between the first anchoring device 7 and the second anchoring device 8 e.g. at varying depths e.g. to pass an obstacle embedded in the seabed 2, to enable branching or other.

Fig. 9 illustrates an embodiment of an anchoring device 7, 8 and an anchoring arrangement displacing device 13, as seen from the front.

In this embodiment the anchoring device 7, 8 comprises two helical screw means 10 interconnected by transversal struts 20 rotatably connected to the helical screw means 10 so that the distance between the helical screw means 10 may be maintained constant while the two helical screw means 10 may be individually rotated.

The lower transversal strut 20 is in this embodiment formed as wire guide means 18 in that the lower transversal strut 20 is formed with a curvature so that the wire means 3 and conduit means 1 are centred substantially in the middle between the two helical screw means 10. This wire guide means 18 will then guide the wire means 3 and the conduit means 1 past the penetrating end 17 of the anchoring device 7, 8.

In this embodiment an anchoring arrangement displacing device 13 in the form of a robotic device arranged to travel across the seabed 1 is connected to both helical screw means 10 at once so that both helical screw means 10 may be rotated simultaneously by the same anchoring arrangement displacing device 13.

In this embodiment the pitch of the helical screw means 10 is arranged so that the two helical screw means 10 has to be rotated in opposite directions to be moved in the same vertical direction. This is advantageous in that the torque transferred to the two helical screw means 10 will counteract each other and thereby simplify the mounting and dismounting process.

The embodiment of an anchoring device 7, 8 and an anchoring arrangement displacing device 13 disclosed in fig. 9 is however only one of many different embodiments possible. I.e. in another embodiment the anchoring device 7, 8 could only comprise a single helical screw means 10, the anchoring device 7, 8 would not comprise any kind of barb arrangement - and would instead be held down by means of weights, tethering or other - or the anchoring device 7, 8 could be formed in another way. Likewise, the anchoring arrangement displacing device 13 could instead be some sort of pile driving device either sea surface based, seabed based or a submarine-like device.

The invention has been exemplified above with reference to specific examples of anchoring arrangements 4, conduit means 1, anchoring arrangement displacing devices 13, pulling means 16 and other. However, it should be understood that the invention is not limited to the particular examples described above but may be designed and altered in a multitude of varieties within the scope of the invention as specified in the claims.

List 1. Conduit means 2. Seabed 3. Wire means 4. Anchoring arrangement 5. First end of wire means 6. Second end of wire means 7. First anchoring device 8. Second anchoring device 9. Additional anchoring device 10. Helical screw means 11. Surface of the sea 12. Vessel 13. Anchoring arrangement displacing device 14. Front end of conduit means 15. Conduit burial arrangement 16. Pulling means 17. Penetrating end of anchoring device 18. Wire guide means 19. Excavation 20. Strut A. Angle between wire means and the surface of the sea MD. Mutual distance between first anchoring device and second anchoring device

Claims

1. Fremgangsmåde til nedgravning af kanalmiddel (1) i en havbund (2), hvilken fremgangsmåde omfatter følgende trin: • arrangering af ledningsmiddel (3) ved nævnte havbund (2), • placering af et forankringsarrangement (4) på nævnte ledningsmiddel (3), • tvingning af nævnte ledningsmiddel (3) ned i nævnte havbund (2) ved at tvinge nævnte forankringsarrangement (4) ned i nævnte havbund (2), • tilslutning af nævnte kanalmiddel (1) til en første ende (5) af nævnte ledningsmiddel (3), og • trækning af nævnte kanalmiddel (1) ned i nævnte havbund (2) ved at trække i en anden ende (6) af nævnte ledningsmiddel (3).A method of burying channel means (1) in a seabed (2), comprising the steps of: • arranging conduit (3) at said seabed (2), • placing an anchorage arrangement (4) on said conduit (3) ), • forcing said conduit (3) down into said seabed (2) by forcing said anchorage arrangement (4) into said seabed (2), • connecting said channel means (1) to a first end (5) of said conducting means (3), and pulling said channel means (1) down said seabed (2) by pulling at another end (6) of said conducting means (3).

2. Fremgangsmåde ifølge krav 1, hvor nævnte forankringsarrangement (4) omfatter en første forankringsindretning (7) og en anden forankringsindretning (8), og hvor nævnte første forankringsindretning (7) og nævnte anden forankringsindretning (8) er anbragt med en indbyrdes afstand (MD).The method of claim 1, wherein said anchorage arrangement (4) comprises a first anchorage device (7) and a second anchorage device (8), and wherein said first anchorage device (7) and said second anchorage device (8) are spaced apart ( MD).

3. Fremgangsmåde ifølge krav 2, hvor nævnte indbyrdes afstand (MD) er mellem 1 og 10.000 meter, fortrinsvis mellem 5 og 5.000 meter og især mellem 20 og 1.000 meter.The method of claim 2, wherein said spacing (MD) is between 1 and 10,000 meters, preferably between 5 and 5,000 meters and more preferably between 20 and 1,000 meters.

4. Fremgangsmåde ifølge krav 3, hvor et eller flere yderligere forankringsindretninger (9) er anbragt mellem nævnte første forankringsindretning (7) og nævnte anden forankringsindretning (8).The method of claim 3, wherein one or more additional anchoring devices (9) are disposed between said first anchoring device (7) and said second anchoring device (8).

5. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor nævnte fremgangsmåde omfatter et trin til opspænding af nævnte ledningsmiddel (3), inden nævnte kanalmiddel (1) trækkes ned i nævnte havbund (2).A method according to any one of the preceding claims, wherein said method comprises a step of clamping said conductor (3) before said channel means (1) is pulled down into said seabed (2).

6. Fremgangsmåde ifølge krav 5, hvor nævnte ledningsmiddel (3) opspændes med mellem 0,1 og 25.000 kN, fortrinsvis mellem 1 og 10.000 kN og især mellem 2 og 5.000 kN, inden nævnte kanalmiddel (1) trækkes ned i nævnte havbund (2).The method of claim 5, wherein said conduit (3) is clamped between 0.1 and 25,000 kN, preferably between 1 and 10,000 kN, and more preferably between 2 and 5,000 kN, before said channel means (1) is pulled down into said seabed (2). ).

7. Fremgangsmåde ifølge krav 5 eller 6, hvor nævnte fremgangsmåde omfatter et trin til forskydning af nævnte forankringsarrangement (4) med en vis afstand opad, inden nævnte ledningsmiddel (3) opspændes igen.A method according to claim 5 or 6, wherein said method comprises a step of displacing said anchorage arrangement (4) at a certain distance upwardly before said conduit means (3) is tightened again.

8. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor nævnte forankringsarrangement (4) tvinges ned i nævnte havbund (2) ved at dreje et spiralformet skruemiddel (10) af nævnte forankringsarrangementer (4).A method according to any one of the preceding claims, wherein said anchorage arrangement (4) is forced into said seabed (2) by turning a helical screw means (10) of said anchorage arrangement (4).

9. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor vinklen (A) mellem nævnte ledningsmiddel (3) og havets overflade (11) er mellem 1° og 85°, fortrinsvis mellem 2° og 75° og især mellem 5° og 65° i løbet af i det mindste en del af den tid, hvor nævnte kanalmiddel (1) trækkes ned i nævnte havbund (2) ved at trække i nævnte anden ende (6) af nævnte ledningsmiddel (3).A method according to any one of the preceding claims, wherein the angle (A) between said conduit (3) and the surface (11) of the sea is between 1 ° and 85 °, preferably between 2 ° and 75 ° and especially between 5 ° and 65 ° during at least a portion of the time during which said channel means (1) is pulled down into said seabed (2) by pulling at said second end (6) of said conduit means (3).

10. Kanalnedgravningsarrangement (15) til nedgravning af kanalmiddel (1) i en havbund (2), hvilket kanalnedgravningsarrangement (15) omfatter ledningsmiddel (3), som er indrettet til at blive forbundet med nævnte kanalmiddel (1) for at trække nævnte kanalmiddel (1) ned i nævnte havbund (2), trækmiddel (16), som er indrettet til at trække i nævnte ledningsmiddel (3), og mindst én forankringsindretning (7, 8), som omfatter en penetrationsende (17), der er indrettet til at gennemtrænge nævnte havbund (2), hvor nævnte forankringsindretning (7, 8) omfatter ledningsstyremidler (18), som er indrettet til at styre i det mindste dele af nævnte ledningsmiddel (3) og i det mindste dele af nævnte kanalmiddel (1) forbi nævnte penetrationsende (17) af nævnte forankringsindretning (7, 8).A channel excavation arrangement (15) for burying channel means (1) in a seabed (2), which channel excavation arrangement (15) comprises conduit means (3) arranged to be connected to said channel means (1) for drawing said channel means ( 1) into said seabed (2), pulling means (16) adapted to pull in said conducting means (3), and at least one anchoring device (7, 8) comprising a penetration end (17) adapted for penetrating said seabed (2), wherein said anchoring device (7, 8) comprises conduit guide means (18) adapted to guide at least portions of said conduit means (3) and at least portions of said channel means (1) past said penetration end (17) of said anchoring device (7, 8).