WO2002018715A1

WO2002018715A1 - Device for making a trench in the bottom of water area

Info

Publication number: WO2002018715A1
Application number: PCT/NL2001/000631
Authority: WO
Inventors: Anna Baukje De Jong
Original assignee: Hollandsche Beton Groep N.V.; Van Ginkel, Nico
Priority date: 2000-08-28
Filing date: 2001-08-28
Publication date: 2002-03-07
Also published as: NL1016035C2; AU2001294370A1

Abstract

A device for making a trench in the bed of an area of water, in particular for laying a pipeline or cable in the bed, comprising a vehicle or the like which can be displaced underwater with respect to the said bed and on which there are at least one or more spray arms, which extend downwards next to the pipeline or cable and are provided with spray nozzles for high-pressure water jets, means being provided for moving the spray arms in a reciprocating manner in the longitudinal direction of the spray arms during operation.

Description

DEVICE FOR MAKING A TRENCH IN THE BOTTOM OF WATER AREA

The invention relates to a device for making a trench in the bed of an area of water, in particular for laying a pipeline or cable in the bed, comprising a vehicle or the like which can be displaced underwater with respect to the said bed and on which there are at least one or more spray arms, which extend downwards next to the pipeline or cable and are provided with spray nozzles for high-pressure water jets.

A device of this type is known from US-A-4, 112, 695. In this device, there are two vertically adjustable spray arms, on which rows of spray nozzles are provided.

When using this device, the earth in the bed is fluidized by water jets which emerge from the spray nozzles. The spray nozzles are inclined in such a manner that the water jets are directed both forwards and inwards in the downwards direction. With a design of spray arms and spray nozzles of this type, problems may arise when breaking up earth with a certain cohesion, such as clay. This means that the ground is not cut into to a sufficient extent and it is impossible to remove sufficient earth.

It is an object of the invention to avoid this drawback and to provide a device which allows a trench to be made in types of earth with different degrees of cohesion, such as clay, sand and the like. To this end, the device is characterized in that means are provided for moving the spray arms in a reciprocating manner in a plane which is parallel to the longitudinal direction of the spray arms during operation. In this case, it is possible to provide means for moving the spray arms in a reciprocating manner in the longitudinal direction of the spray arms during operation.

As a result of the reciprocating movement which the emerging jets of water exert on the surrounding earth, this earth is efficiently cut into and broken up even if it is highly cohesive. In this case, the spray arms may execute a reciprocating movement in the longitudinal direction or a reciprocating rotational movement in the circumferential direction under the influence of the movement means. In addition, it is possible for the spray arms to be made to execute a lateral reciprocating movement or a lateral reciprocating rotational movement in the vertical plane, i.e. at right angles to the direction of forwards movement.

In an advantageous embodiment, at least one pair of spray arms of this type are provided next to one another, in order to act on both sides of the pipeline or cable. In a further embodiment, the spray nozzles on a spray arm are distributed in identical groups in the longitudinal direction and the circumferential direction in such a manner that the water jets emerge from a group of this type in different directions. The earth in the immediate vicinity is therefore simultaneously exposed to and broken up by these water jets from different directions. By making the distance of the reciprocating movement in the longitudinal direction preferably substantially equal to the distance between in each case two groups, it is possible to ensure that the earth is cut into efficiently. In this embodiment with uniform dimensions, fewer water jets and therefore fewer spray nozzles are required.

In this case, each group comprises at least one spray nozzle for spraying a water jet substantially forwards in the direction of forwards movement of the vehicle, and/or each group may comprise two spray nozzles for spraying two water jets obliquely inwards and obliquely outwards, respectively, at an angle of, for example, 30° with respect to one another, substantially in the direction of forwards movement of the vehicle.

Furthermore, each group may comprise two spray nozzles for spraying two water jets obliquely downwards, respectively obliquely inwards and obliquely outwards, substantially in the direction of forwards movement of the vehicle.

To break up the earth which is to be removed in the transverse direction even more successfully, it is advantageous for the groups to be provided with further spray nozzles for spraying water in a direction which is substantially transverse with respect to the direction of forwards movement of the vehicle, such as in the direction of an adjacent spray arm, in order, for example, to break up and destroy a residual ridge of earth beneath the pipeline or cable.

The aim of the above embodiments is, starting from the action of the reciprocating movement of the spray arms with a grouped configuration of spray nozzles, which may vary from a simple form to more complex forms, to achieve sufficient coverage and to blast out the earth in the vicinity of the spray arm.

In this context, the term spray nozzle is to be understood as meaning a water outlet opening, of which, if necessary, two or more with the same or different exit directions may be incorporated in one combined spray nozzle.

In order, in particular, to be able to effectively break up and remove the earth beneath a pipeline or cable which is to be laid, it is possible for one or more of the spray arms to be L-shaped and to be formed by a substantially vertical long spray arm, which is provided at its end with a substantially horizontal short spray arm, provided with spray nozzles. It is also possible for one or more of the spray arms to be h-shaped and to be formed by a substantially vertical long arm and a shorter arm which is connected thereto by means of a connecting spray arm. In these embodiments, each of the short spray arms may moreover be rotated from an inactive position, which lies outside the pipeline or cable, into an active position beneath the body of the pipeline or cable which is to be buried.

The vehicle may comprise a carriage which is guided by a ship, a caterpillar vehicle or a self-propelled vehicle, and may be displaceable both above and along the bed or along the pipeline itself.

If the vehicle is able to float, so that the friction can be reduced, it is possible to reduce the pulling force required. Obviously, the device may advantageously also be used to remove sand and similar material.

The invention will now be explained in more detail with reference to the figures.

Figure 1 shows a view of a device according to the invention, which is guided over the seabed by a ship, while it is laying a pipeline or cable in the bed.

Figure 2 shows a diagrammatic drawing of the device in side view.

Figure 3 shows a diagrammatic depiction of the device in front view.

Figure 4 shows a diagrammatic depiction of the device in plan view.

Figure 5 shows a cross section on line V-V in Figure 4.

Figure 6 shows a cross section on line NI-NI in Figure 4.

Figures 7a and 7b respectively show a plan view and a side view of a spray arm with possible spraying directions.

Figure 8 shows a view of two spray arms which are provided with ftrther spray nozzles for spraying water substantially in the horizontal direction.

Figures 9a, 9b and 9c show various forms of compensation for reactive forces. Figure 10a shows the front view of an embodiment of L-shaped spray arms in the active position, with a lateral reciprocating movement indicated.

Figure 10b shows the front view of an embodiment of L-shaped spray arms in the active position, with lateral reciprocating rotational movement indicated.

Figure 11 shows the front view of an embodiment of h-shaped spray arms in the active position, with reciprocating movement in the longitudinal direction of the spray arm indicated.

The diagrammatic drawing in Figure 1 shows a carriage which is pulled or guided over the seabed by a ship 2 using a cable 3, a trench 4 being made in the seabed, which consists, for example, of clay, and a pipeline or cable 5 being buried in the trench.

The carriage 1 bears a frame 6. As seen in the normal direction of forwards movement of the carriage, the frame bears two spray arms 1, 8, and two suction arms 9, 10 which are arranged behind the spray arms and are known per se. There are means which are not shown (for example, hydraulic cylinders) for moving both the spray arms and the suction arms out of the position illustrated by solid lines in Figures 2 and 3, in which the bottom end of the arms is situated on or just above the sea bed, into an operating position, which is indicated by dashed lines in Figures 2 and 3, and back. Moreover, there are means 11 for causing the spray arms 7 and 8 to execute a reciprocating movement in an operating position. This reciprocating movement of the spray arm may be a movement in the longitudinal direction, i.e. along the longitudinal axis, or a rotational movement in the circumferential direction, i.e. about the longitudinal axis. In addition, the reciprocating movement may be a lateral horizontal movement or a rotational movement in the vertical plane out of a point or rotation point at the means 11. Combinations of reciprocating movements, such as a reciprocating movement in the longitudinal direction with a rotational movement in the circumferential direction, are also possible.

The spray arms 7 and 8 are connected to a high-pressure water pump (not shown) for producing water at a pressure of, for example, 10 to 100 bar. The spray nozzles 12 have a diameter of, for example, 1 to 15 mm. The Z-shaped suction arms 9, 10 can be rotated through an angle of approximately 45° (cf. Figure 4) about the centre axis of the vertical body. There are means (not shown) for bringing about this rotation. These suction arms are substantially used when burying pipelines in sand.

The suction arms 9, 10 are connected to a centrifugal pump, a Venturi pump or an airlift pump. If appropriate, the Venturi pump may be driven by means of the high- pressure water which is generated by the high-pressure pump. The outlet mouthpiece of the suction arms (cf. Figure 5) is situated, for example, approximately 3 metres above the sea bed. It is also possible for the outlet point to be moved further away by lengthening the outlet tube upwards or sideways. When starting up (cf. Figures 3 and 4), the suction arms 9 and 10 are situated in a position which is indicated by dot-dashed lines in Figure 4 and in which the inlet piece and the outlet piece extend parallel to the direction of forwards movement of the carriage 1 which is indicated by the arrows.

When high-pressure water emerges through the spray nozzles 12 of the spray arms 7, 8 and the spray arms are subjected to a downward load, for example by hydraulic means, the spray arms will be lowered into the earth and will form a hole. The suction arms 9, 10 are likewise moved downwards and are rotated into the position shown by the continuous lines in Figures 4 and 5. When the carriage 1 moves forward and the spray arms are moved in a reciprocating manner by means 11, the clay soil will be cut into and broken up and can easily be sucked up by the suction arms. As indicated by a small arrow in Figures 4 and 5, the earth is deposited on the sea bed to the sides of the carriage.

Each of the spray arms 7 and 8 is provided with groups of spray nozzles 12. In each group there is at least one spray nozzle with an exit direction pointing directly ahead, and/or two spray nozzles with exit directions ahead and sideways. Furthermore, there may be two spray nozzles, with exit directions which are inclined downwards towards the front and towards the side, provided for each group. The pattern of high-pressure water jets can be seen from Figures 7a and 7b, which respectively show a plan view and a side view of a spray arm.

One spray nozzle is shown for each position in the figures. It will be clear that this should be understood as meaning the above-described spray nozzles which are either integrated in a spray nozzle which has been screwed into the spray arm or are screwed separately into the spray arm immediately adjacent to and/or above one another. Figure 8 shows two spray arms 7, 8 which are positioned next to one another and are provided with spray nozzles 12. The spray arms also comprise further spray nozzles 13 for spraying water substantially in the lateral direction. The spray nozzles 13 are arranged in such a manner that the water is directed at an adjacent spray arm and preferably in an offset manner from the water jets which are directed towards one another. This means that two spray arms which are directed next to one another together can effectively break up the earth between the spray arms.

On account of the water jets released by the spray nozzles having different exit directions, both horizontally and at angles thereto, reactive forces will be exerted on the vehicle in directions which are opposite to the said exit directions. To prevent the vehicle, in operation, from moving sideways or upwards, in the prior art thrusters are generally fitted to the top and/or the sides of the vehicle, in order to substantially compensate for these reactive forces. To enable this use of the thrusters to be avoided, in the present embodiments further spray nozzles are provided in the spray arms, the exit directions of which further spray nozzles are substantially opposite to those of the abovementioned spray nozzles.

For example, additional spray nozzles 14 may be arranged on a spray arm with exit directions which, with respect to the horizontal plane, form a mirror image of those of the spray nozzles which are directed obliquely towards the front, sideways and/or downwards, as indicated in Figure 9a. For example, to compensate for the forwardly directed spray nozzles, it is possible to provide one or more spray nozzles 15 which are directed towards the rear, as illustrated in Figure 9b. Not only does this compensation reduce or eliminate the forces required for the thrusters, but also the forces and powers with which the spray arms are rotated and are moved onwards are reduced considerably or even to zero. Figure 9c shows the spray nozzles 13, as described in Figure 8, it being possible for these spray nozzles to be attached to the spray arms 7, 8 rotated towards the rear, so that a reactive component is produced in the direction of forwards movement.

The spray arms 7 and 8 may be designed as an L-shaped body, as shown in Figure 10. An L-shaped spray arm of this type is composed of a substantially vertical, long spray section and a substantially horizontal spray section which can rotate between an inactive position and an active position. The vertical, long spray arm 16 is connected to the horizontal spray arm 18, and the vertical, long spray arm 17 is connected to the spray arm 19. Each of the horizontal and, where necessary, vertical arms is provided with spray nozzles 12 and possibly also spray mouthpieces 13.

In a variant, the vertical, long spray arms 16, 17 are positioned so that they can rotate through an angle of at most 90° about their longitudinal axis into the active position, as shown in front view in Figure 10.

The reciprocating movement at the L-shaped spray arms may be a lateral, horizontal movement in a vertical plane from a point at the means 11, in such a manner that the horizontal arm executes a short horizontal movement along its longitudinal axis. This is shown in Figure 10a. In addition, the reciprocating movement may be a lateral rotational movement, in a vertical plane which comprises the L-shape, out of a rotation point at the means 11, in such a manner that the horizontal arm executes a short movement in the lateral direction. This reciprocating movement is indicated in Figure 10b.

It is also possible for the spray arms to be designed as an h-shaped body which is illustrated in Figure 11. An h-shaped spray arm of this type comprises a vertical, long arm and a shorter vertical arm which extends at a distance therefrom and can be rotated between an inactive position and an active position. The vertical, long spray arm 20 is connected to the shorter vertical spray arm 22 extending at a distance therefrom by means of the substantially horizontal connecting spray arm 24. In this way, the vertical, long arm 21 is also connected to the shorter, vertical spray arm 23, by means of connecting spray arm 25. Each of the shorter spray arms, connecting spray arms and, where necessary, long vertical arms, is provided with spray nozzles 12 and possibly also spray mouthpieces 13.

In a variant, the vertical, long spray arms 20, 21 are arranged so that they can rotate through an angle of at most 90° about their centre axis into the active position, as shown in front view in Figure 11.

As shown in Figure 11, the reciprocating movement for the h-shaped spray arms may be the vertical movement in the longitudinal direction of the spray arms.

In the possible L-shaped and h-shaped embodiments, the spray nozzles are arranged on the spray arms in such a manner that they are directed substantially towards the front in the said active position. In the case of the L-shaped or h-shaped spray arm as shown in Figure 10 or 11, the short arm is rigidly attached to a long arm which can rotate about its longitudinal axis, or the short arm is attached to a non-rotatable long arm and can be rotated separately. In both variants, the short arm can then be rotated out of an inactive position outside the pipeline or cable into an active operating position beneath the pipeline or cable. In the embodiments with these L-shaped or h-shaped spray arms, in the forward direction they are often preceded by a single, vertical spray arm which clears the way.

The device according to the invention is intended in particular for types of soil which are cohesive, such as clay, but can also be used in less cohesive earth, for example sand, silt and the like.

It will be clear that further variants are possible within the scope of the invention. For example, numerous arrangements of h-shaped and/or L-shaped spray arms are possible, and the h-shaped arms may additionally be provided with at least one further, shorter, vertical spray arm. It is also possible for the L-shaped spray arms to be additionally provided with at least one extra horizontal spray arm.

With the aid of the device according to the invention it is possible, for example, to bury from 500 to 2000 metres of pipeline with a diameter of approximately 1 metre in clay earth with a cohesion of from 100 to 20 kN/m² every day. The device can be used at water depths of between 5 and 3000 metres and for a pipe diameter of from 200-1300 mm. Similar or higher speeds can be reached in sandy ground. Similar speeds can also be achieved when laying cables, the diameter of which is generally smaller.

Claims

1. Device for making a trench in the bed of an area of water, in particular for laying a pipeline or cable in the bed, comprising a vehicle or the like which can be displaced underwater with respect to the said bed and on which there are at least one or more spray arms, which extend downwards next to the pipeline or cable and are provided with spray nozzles for high-pressure water jets, characterized in that means are provided for moving the spray arms in a reciprocating manner in a plane which is parallel to the longitudinal direction of the spray arms during operation.

2. Device according to Claim 1, characterized in that the said means are designed to move the spray arms in a reciprocating manner in the longitudinal direction of the spray arms during operation.

3. Device according to Claim 1 or 2, characterized in that the said movement means cause the spray arms to execute a lateral reciprocating movement in a vertical plane.

4. Device according to Claim 1, 2 or 3, characterized in that the said movement means cause the spray arms to execute a lateral reciprocating rotational movement in a vertical plane.

5. Device according to one of the preceding claims, characterized in that the said movement means cause the spray arms also to execute a reciprocating rotational movement in the circumferential direction.

6. Device according to one of the preceding claims, characterized in that the said movement means cause the spray arms to execute a combination of reciprocating movements.

7. Device according to one of Claims 1 to 6, characterized in that the spray nozzles on a spray arm are distributed in the longitudinal direction and/or the circumferential direction in such a manner that the high-pressure jets emerge in different directions.

8. Device according to Claim 7, characterized in that the spray nozzles on a spray arm are distributed in identical groups in the longitudinal direction.

9. Device according to Claim 8, characterized in that the reciprocating movement of the said movement means of the spray arms is substantially equal to the distance in each case between the groups of spray nozzles.

10. Device according to Claim 8 or 9, characterized in that each group of spray nozzles comprises at least one spray nozzle for spraying a water jet substantially forwards in the direction of forwards movement of the vehicle.

11. Device according to Claim 8 or 9, characterized in that each group of spray nozzles comprises two spray nozzles for spraying two water jets obliquely inwards and obliquely outwards, respectively, substantially in the direction of forwards movement of the vehicle.

12. Device according to Claim 8 or 9, characterized in that each group of spray nozzles comprises two spray nozzles for spraying two water jets obliquely downwards, respectively obliquely inwards and obliquely outwards, substantially in the direction of forwards movement of the vehicle.

13. Device according to Claim 10, 11 or 12, characterized in that each group of spray nozzles also comprises a spray nozzle for spraying a water jet substantially transversely with respect to the direction of forwards movement of the vehicle.

14. Device according to one of the preceding claims, provided with the said spray nozzles on the spray arm(s) characterized in that further spray nozzles are provided on the spray arms, the exit directions of which further spray nozzles - in order to compensate for reactive forces - are substantially opposite to those of the abovementioned spray nozzles.

15. Device according to one of the preceding claims, characterized in that at least one spray arm comprises two or more part-arms which extend at an angle to or at a distance from one another.

16. Device according to Claim 15, characterized in that the at least one spray arm is substantially L-shaped, with a vertical, long arm and a horizontal, short arm.

17. Device according to Claim 15, characterized in that the at least one spray arm is substantially h-shaped, with a vertical, long arm and a shorter arm which extends at a distance therefrom.

18. Device according to one of Claims 15, 16 and 17, characterized in that the short arm can be rotated out of an inactive position, which lies outside the pipeline or cable, into an active operating position beneath the pipeline or cable.