WO2002018716A1

WO2002018716A1 - Device for making a trench in the bottom of a water area, provided with linked spray arms

Info

Publication number: WO2002018716A1
Application number: PCT/NL2001/000632
Authority: WO
Inventors: Nico Van Ginkel; Anna Baukje De Jong; Cees Van Rhee
Original assignee: Hollandsche Beton Groep NV
Current assignee: Hollandsche Beton Groep NV
Priority date: 2000-08-28
Filing date: 2001-08-28
Publication date: 2002-03-07
Anticipated expiration: 2003-02-28
Also published as: AU2001294371A1

Abstract

A device (1) for making a trench (4) in the bed of an area of water, in particular for laying a pipeline or cable (5) in the bed, comprising a vehicle (1) 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 (7, 8, 17-26) which, in use, extend substantially vertically downwards next to the pipeline or cable and are provided with spray nozzles (12) for high-pressure water jets, in which device the spray arm comprises first spray nozzles and second spray nozzles which are located at a distance therefrom in the direction of forwards movement of the vehicle.

Description

DEVICE FOR MAKING A TRENCH IN THE BOTTOM OF A WATER AREA, PROVIDED WITH LINKED SPRAY ARMS

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 if 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 this device, the possible embodiments of the trench which is to be made in the ground are limited. The water jets which emerge from the spray mouthpieces have a defined range, depending on the possible pressure and soil properties. Another limiting factor is the shape of the spray arms. The straight, vertical design and limited range of the water jets means that it is impossible to remove sufficient earth from below a pipeline or cable which is to be buried. For example, if a pipeline of relatively large diameter is to be laid in the earth, this may lead to problems. Also, variations in trench depth can only be achieved in a laborious way, and such variations may be important for uniform introduction of the cable or pipeline into the bed, or to prevent unsupported parts in the case of an uneven bed.

It is an object of the invention to avoid these drawbacks 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 a plurality of spray arms are arranged on the vehicle, the spray nozzles of each successive spray arm, as seen in the direction of forwards movement of the vehicle, having a specific additional function to the spray nozzles of each spray arm in front.

According to the invention, it is advantageous that the spray arm is followed, in the direction of forwards movement of the vehicle, by a further spray arm which comprises two or more part-arms which extend at an angle to or a distance from one another. Furthermore, it is possible for the spray arm to comprise a cylinder which is provided with spray nozzles over its circumference.

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.

Before or during operation, a spray arm of this type can be moved into the operating position in the bed by means of a substantially vertical movement out of a position above the bed, or by a rotary movement out of a substantially horizontal position above the bed to a position in which it is at an angle to the horizontal plane.

To be able in particular to break up and remove the earth below a pipeline or cable which is to be laid effectively, according to the invention 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 designs, each of the short spray arms may moreover be rotated out of an inactive position, in which it lies outside the pipeline or cable, into an active position beneath the body of the pipeline or cable which is to be buried.

In one embodiment, one or more L-shaped and h-shaped spray arms are preceded, as seen in the direction of forwards movement of the vehicle, by a single vertical spray arm which clears the way for the L-shaped or h-shaped spray arms. In this case, the L-shaped or h-shaped spray arms, in their inactive position, are situated with their entire L-shape or h-shape in the shadow of or behind the said single vertical arm. In a variant, these L-shaped or h-shaped spray arms have a long arm, which can rotate about its longitudinal axis, and a short arm which is connected to the long arm in such a manner that it rotates therewith.

In another variant, the L-shaped and/or h-shaped spray arms have a non-rotatable, long arm and a rotatable, short arm which is connected to the long arm and can be rotated separately between an inactive position and an active position.

In all thes^'e embodiments, the spray nozzles are arranged on the long and/or short arms in such a manner that, in the said active position, they are directed substantially in the forwards direction. For these embodiments, it is possible that, in the case of an h-shaped arm, the long, vertical spray arm extends no further than to the horizontal connecting spray arm to which is attached the short arm which extends at a distance from the long arm.

Furthermore, according to the invention it is possible for a number of L-shaped spray arms to be arranged at a distance from one another in the direction of forwards movement of the vehicle, the vertical, long spray arms increasing in length from the front side of the vehicle towards the rear side of the vehicle. Consequently, the shorter arms of the successive L-shaped spray arms can in each case blaze away earth at different levels.

The distance between the L-arms can be varied, and the L-arms may also be rotated away into an inactive position one by one. This makes it easier to produce transitions. The transitions are required in order for a pipeline to be fed gradually to the desired depth of embedding. The spray arms are rotated during this process. On account of the difference in height between the various horizontal spray arms and the ability of the arms to rotate, the depth which can be achieved for the ditch which is made for the purpose of laying the cable or pipeline can increase or decrease very gradually. In this way it is possible, in particular for pipelines, to prevent the formation of a free span. A free span of this nature means a section of the pipeline which is not supported by or in the earth because of the unevenness in the earth being so great that it cannot be accurately followed by the vehicle. The presence of the spray arms of differing height allows disadvantageous free spans of this type to be avoided or limited.

The invention also encompasses the possibility of a plurality of h-shaped spray arms being arranged at a distance from one another in the direction of forwards movement, it being possible for the distance between the vertical, long arm and the associated shorter arm extending parallel thereto to increase gradually from the front side. Consequently, the shorter arms of the successive h-shaped. spray arms can in each case extend .further below the pipeline, it being possible for each h- shaped spray arm to be rotated into the active position or to be held in the inactive position.

The possibility of varying the number of short spray arms which can be rotated beneath the pipeline, as well as the adjustable distances in the direction of forwards movement and in the transverse direction, in this way allows relatively wide trenches to be produced, even in cohesive types of earth. According to the invention, it is possible for various combinations of L-shaped and h-shaped spray arms as described above to be arranged next to one another in the direction of forwards movement of the vehicle, at a distance from one another, and/or transversely with respect to the direction of forwards movement of the vehicle. Consequently, it is possible, if necessary, for example in the case of varying soil conditions, to flexibly adapt the spraying capacity of the device, so that the earth can continue to be broken up and removed effectively.

To break up earth, spray arms are provided with spray nozzles or groups of spray nozzles. The distribution of the spray nozzles or groups of spray nozzles, as well as the direction of the water jets which emerge from the spray nozzles, determine the extent to which the earth is effectively broken up.

In one 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.

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 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.

It is possible to make the spray arms execute a reciprocating movement. This improves the range and therefore the effectiveness of the spray nozzles. 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 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. The possibilities also include a combination of the said reciprocating movements.

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.

According to the invention, it is possible for the spray arm to comprise a cylinder which is provided, over its circumference, with spray nozzles. It is possible to provide means for rotating the cylinder about its longitudinal axis.

The present invention uses the term "cylinder". The word cylinder is not intended to indicate a precise mathematical shape of body, but rather refers to a substantially cylindrical tube or pipe. It will be clear that a slightly oval-shaped tube or pipe which is not completely round could also be used within the scope of the present invention. Furthermore, it is possible for the tube to be provided with a polygonal periphery, such as a hexagonal periphery.

On account of the rotational movement of the spray arm, the water jets which emerge from the spray arm will efficiently cut into and break up the earth in which a trench is to be made. As a result, the earth, even when it is highly cohesive, is removed efficiently in order to form a trench in the ground. According to the invention, it is possible for the spray nozzles to be designed as bores or openings in the wall of the cylinder. As an alternative, it is possible for the spray nozzles to be designed as attachments which are fixed on or in the outer wall of the cylinder.

In use, the vehicle which ca move underwater will move in the direction in which it is desired to make a trench in the bed. Only the water jets on that side of the cylinder which is directed in the direction of forwards movement of the vehicle, i.e. on the front side, can contribute to the effective removal of earth in order to form the desired trench in the bed. After all, the earth on that side of the cylinder which is directed away from the direction of forwards movement, i.e. on the rear side, has already been removed.

Furthermore, it is possible for a spray arm to comprise a plurality of cylinders. In this case, it is possible for various designs of cylinders to be arranged exchangeably and replaceably on one spray arm.

To improve the efficiency of the device according to the invention further, it is advantageous for there to be means for, in use, covering the spray nozzles on that side of the cylinder which is directed away from the direction of forwards movement of the vehicle which can move underwater. As a result, the entire capacity of the device is used to remove the earth.

A spray arm may be provided with one or more cylinders. For example, a spray arm may be provided with two identical or different cylinders one above the other. The cylinder casings may differ from one another with regard to, inter alia, the diameter, length or number of spray nozzles.

The various cylinder designs may be exchangeable. This allows different configurations to be arranged on a spray arm, so that it is possible to take advantage of changing ground conditions. In this case, the cylinder casings are also easy to replace.

According to one embodiment, it is possible for at least two cylindrical spray arms of this type to be provided next to one another, acting on both sides of the pipeline or cable. According to the invention, it is possible for the exit direction of the spray nozzles to be directed substantially perpendicular to the axis of rotation of the cylinder. These measures ensure that a relatively wide trench is dug in the earth. The width of this trench will correspond to the diameter of the spray arm plus twice the penetration depth of the high-pressure water j ets .

Alternatively, it is possible for the spray arm or each spray arm to comprise one or more spray mouthpieces which are arranged directed substantially downwards at an angle of between 0° and approximately 90° with respect to the longitudinal axis of the spray arm. This results in a relatively narrow trench being made in the ground, the width of which trench will correspond more to the diameter of the spray arm.

According to the invention, it is possible for the spray mouthpieces to be distributed uniformly over the circumference of the cylinder. In this case, it is possible for the spray nozzles on the spray arm or the spray arms to be arranged in identical groups over the circumference of the cylinder. Furthermore, it is possible for the spray nozzles to be arranged in at least one helical row over the circumference.

According to the invention, it is furthermore possible for there to be provided, on the at least one spray arm, first spray nozzles and second spray nozzles, the exit directions of which are opposite to one another, in order to internally compensate for reactive forces in the spray arm.

Mounting the spray mouthpieces in such a manner that the exit openings of the groups of spray mouthpieces are opposite to one another leads to internal compensation for reactive forces in the spray arm itself. This means that the spray arm itself will not apply any further reactive forces to the vehicle. Consequently, the vehicle will not be "pushed out of the ground" while making the trench.

In the device according to the invention, it is possible for the spray arms to be arranged in a vertically fixed position on the vehicle. It is also possible for the spray arms to be moved vertically downwards, so that the spray arms can project at the bottom of the vehicle. For different types of earth, it is advantageous to provide means for rotating the at least one spray arm out of a rotation point thereof through an angle in the vertical longitudinal plane, between an inactive position, in which the spray arm is directed substantially towards the rear, and an active or operating position, in which the spray arm is directed substantially downwards. In operation, making of the trench is commenced by gradually tilting or rotating the at least one spray arm out of the said inactive position, in which the spray arm is directed towards the rear in line with the longitudinal direction of the vehicle, into the active, downwardly directed operating position. This rotation of the spray arm through an angle of up to substantially 90° with respect to the horizontal is carried out while the vehicle is moving forwards. As the spray arm rotates into position, the pump capacity of the jets is gradually increased. It has been found that this device according to the invention produces an advantageous and flexible way of cutting into and breaking up the earth in types of earth with little or no cohesion, such as sand, but also in types of earth with more cohesion, such as clay.

According to the invention, it is furthermore possible for at least one spray arm to comprise two or more part-arms which extend at an angle to or at a distance from one another.

In this case, it is possible for at least one spray arm to be substantially h-shaped, with a long arm and a short arm running parallel thereto, it being possible to rotate the short arm out of an inactive position, in which it lies outside the pipeline or cable, into an active operating position beneath the pipeline or cable. Furthermore, it is possible for at least one spray arm to be substantially L-shaped, with a long arm and a short arm which is positioned transversely with respect to the long arm, it being possible to rotate the short arm out of an inactive position, in which it lies outside the pipeline or cable, into the active position beneath the pipeline or cable.

Both in the case of the h-shaped spray arms and in the case of the L-shaped spray arms, it is possible for one or more part-arms to be provided with at least one cylindrical body, in accordance with the invention.

In addition to the device described above, the present invention also relates to a method for making a trench in the bed of an area of water, in particular for laying a pipeline or cable in the bed, the trench being made in the bed by locally blasting away the bed with the aid of high-pressure water, jets, which high-pressure water jets are emitted from spray nozzles which are arranged in at least one spray arm of a vehicle which can move underwater.

According to the present invention, the method is characterized in that while the trench is being made in the bed, the cylinder or the spray arm is rotated, in order for the high-pressure water jets to execute a cutting movement through the bed. According to the invention, it is possible to determine the penetration or erosion depth of the high-pressure water jets in the direction of forwards movement and to adapt the rotational speed of the spray arm and the forwards movement of the vehicle which can move underwater in such a manner that the vehicle moves substantially over a distance which is equal to the penetration or erosion depth of the water jets, during one complete revolution of the spray arm.

If the vehicle is being pulled over the bed, the high-pressure water jets will blast earth out of the bed in order to form a trench in the bed. Therefore, it is possible to determine the penetration depth of the high-pressure water jets in the direction of forwards movement of the vehicle and then to adapt the rotational speed of the cylinder on the spray arm and the forwards movement of the vehicle which can move underwater in such a manner that the vehicle moves substantially over a distance which is equal to the penetration depth of the water jets during one complete revolution of the spray arm.

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, with the spray arms having been moved vertically into the earth.

Figure 3 shows a diagrammatic depiction of the device in side view, with the spray arms having been moved into the earth by a rotational movement.

Figure 4a shows the front view of a design of L-shaped spray arms in the active position, with the lateral reciprocating movement indicated.

Figures 4b and 4c respectively show a plan view and a front view of a design of an L-shaped spray arm, it being possible for the horizontal spray arm to rotate separately into the active position.

Figures 4d and 4e respectively show a plan view and a front view of a design in which an L-shaped spray arm which can be rotated into the active position is preceded by a single spray arm. Figures 5a, 5b and 5c respectively show a plan view, a side view and a front view of a configuration of spray arms as shown in Figure 4, with the length of the vertical part of the spray arm increasing continuously.

Figure 6a shows the front view of an embodiment of h-shaped spray arms in the active position, with the reciprocating movement in the longitudinal direction of the spray arm indicated.

Figures 6b and 6c respectively show a plan view and a front view of a design in which the shorter spray arm together with the connecting spray arm can be rotated separately into the active position.

Figures 6d and 6e respectively show a plan view and a front view of a design in which an h-shaped spray arm which can be rotated into the active position is preceded by a single spray arm.

Figures 7a, 7b and 7c respectively show a plan view, a side view and a front view of a configuration of spray arms as shown in Figure 6, with the distance between the short part and the long part of the spray arm progressively increasing.

Figures 8a and 8b respectively show a plan view and a side view of a spray arm with possible spraying directions.

Figure 9 shows a front view of two h-shaped spray arms which are provided with further spray nozzles for spraying water substantially in the horizontal direction.

Figures 10a, 10b and 10c show various forms of compensation for reactive forces.

Figure 1 lb shows a side view in accordance with Figure 2a, with the spray arm in an active position.

Figure 12 shows a view of a spray arm according to the invention which is designed with a cylinder.

Figure 13 shows a side view of the spray arm according to the invention with a central element around which a cylinder rotates.

Figure 14 diagrammatically depicts the position of a helically arranged row of spray nozzles. Figure 15 shows the blank for a cylindrical spray arm on which, for internal compensation, an even number of rows of spray nozzles are arranged.

Figure 16 shows a spray arm in which there is a cover for closing off the spray mouthpieces which are not facing in the direction of forwards movement of the spray arm.

Figures 17, 18, 19 and 20 show possible configurations of different cylinders.

The diagrammatic drawing in Figure 1 shows a carriage 1 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 a spray arm 7, 8, which in this case is h-shaped. There are means 11 for moving the spray arms out of the position which is indicated by solid lines in Figures 2 and 3, into an operating position, which is indicated by dot-dashed lines in Figures 2 and 3, and back.

The spray arms 7, 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.

When high-pressure water emerges through the spray nozzles 12 of the spray arms 7, 8 and the spray arms are moved downwards, the spray arms will sink into the ground and form a hole. As the carriage 1 is moved forwards, the clay soil will be cut into and broken up.

According to the invention, the spray arms may be designed as a L-shaped body, as shown in Figure 4. 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 13 is connected to the horizontal spray arm 15, and the vertical, long spray arm 14 is connected to the spray arm 16. Each of the horizontal and, if necessary, of the vertical arms is provided with spray nozzles 12. According to the invention, the vertical, long arms 13, 14 are preceded by single spray arms 17 and 18. The horizontal spray arms 15, 16 are then connected to the vertical arms 13, 14, which can rotate about their centre axis through an angle of at most 90° and are arranged behind and therefore in the shadow of the single spray arms 17 and 18. This variant is represented by Figures 4d and 4e, which respectively show a plan view and a front view.

In a variant, the vertical, long spray arms 13, 14 are arranged so that they can rotate about their centre axis, through an angle of at most 90°, into the active position, as shown in the front view illustrated in Figure 4a. Another possible design is for the vertical, long spray arms 13, 14 to be provided at a defined height with means for rotating the horizontal spray arms 15, 16 separately through an angle of at most 90° about the centre axis of the vertical, long spray arms into the active position, as shown in Figures 4b and 4c, which respectively show a plan view and a front view. In all these designs, the spray nozzles are arranged in such a manner on the spray arms that they are directed substantially forwards in the said active position.

When the device is starting up, the horizontal spray arms 15 and 16 are situated, as seen in the direction of forwards movement of the carriage, directly behind the vertical long arms 13 and 14, respectively.

When high-pressure water passes through the spray nozzles of the spray arms and the spray arms are moved downwards, the spray arms will be lowered into the ground and form a hole. When the desired depth is reached, in one variant the rotatable horizontal spray arms 15, 16 are separately rotated about the axis of the vertical spray arms 13, 14, respectively, and in the other variant the rotatable arms 13 and 14 arranged behind the fixed arms 17 and 18 are rotated about their centre axis, until the spray arms 15 and 16 have reached the operating position, i.e. are situated beneath the pipeline 5 which is to be laid in the ground.

The spray arms shown in Figure 4 may be designed in such a way that the respective vertical spray sections vary in length. Figure 5a shows a plan view of the situation in which four L-shaped spray arms are arranged in succession, preceded on each operating side by a single vertical arm 17 and 18. Figures 5b and 5c respectively show a side view and a front view. In this case, the vertical sections 19, 20, 21, 22 decrease in length, as seen in the direction of forwards movement of the vehicle. Moreover, each of the horizontal spray arms 23, 24, 25, 26 can rotate about the centre axis of each of the vertical arms 19, 20, 21, 22. This means that the respective horizontal spray sections 23, 24, 25, 26 can rotate out of an inactive position (in the direction of forwards movement of the vehicle) into an active or operating position (at right angles to the direction of forwards movement of the vehicle). The difference in height of each of the horizontal spray sections 23, 24, 25, 26 makes it possible to ensure that, depending on whether the respective spray sections are rotated in or out, the spraying action can change gradually as a function of depth. This means that the depth of the ditch which is made for the purpose of laying a pipeline or cable can increase or decrease gradually.

According to the invention, it is also possible for the spray arms to be designed as an h-shaped body as illustrated in Figure 6. An h-shaped spray arm of this type comprises a vertical, long arm and a shorter, vertical arm which extends at a distance from the long arm and can be rotated between an inactive position and an active position.

The vertical, long spray arm 27 is connected to the shorter, vertical spray arm 29 extending at a distance therefrom by means of the substantially horizontal connecting spray arm 31. In this way, the vertical, long arm 28 is also connected to the shorter, vertical spray arm 30 by means of connecting spray arm 32. Each of the shorter spray arms, connecting spray arms and, if necessary, long vertical arms is provided with spray nozzles 12.

In a variant, the vertical, long spray arms 27, 28 are arranged so that they can rotate about their centre axis through an angle of at most 90° into the active position, as shown in a front view in Figure 6a.

Another possible design is for the vertical, long spray arms 27, 28 to be provided, at a defined height, with means for separately rotating the shorter spray arms 29, 30 and the connecting spray arms 31, 32 through an angle of at most 90° about the centre axis of the vertical, long spray arms, into the active position, as shown in Figures 6b and 6c, which respectively illustrate a plan view and a front view. In another variant, the vertical, long arms 27, 28 are preceded by the single spray arms 17, 18. The shorter spray arms 29, 30 are then attached, by means of connecting spray arms 31, 32, to the separate vertical arms 27, 28, which can rotate through an angle of at most 90° about their centre axis and are arranged behind and therefore in the shadow of the single spray arms 17, 18. In this case, it is possible for the vertical, long arms to extend no further than to the connecting spray arms with the shorter spray arms thereon. This is indicated in the figure by that part of the vertical, long arms 27, 28 which extends beyond the connecting spray arms being indicated by dashed lines. This variant is illustrated by Figures 6d and 6e, which respectively show a plan view and a front view. When the device is starting, the shorter spray arms 29, 30 and the connecting spray arms 31, 32 are situated, as seen in the direction of forwards movement of the carriage, directly behind the vertical, long arms 27 and 28, respectively. For this design too, it is the case that when the desired depth is reached, in one variant the rotatable combinations of connecting spray arms 31, 32 and short, vertical spray arms 29, 30 are rotated separately about the axis of the vertical, long spray arms 27, 28 and that in the other variant the rotatable arms 27 and 28 which are arranged behind the fixed arms 17 and 18 are rotated about their centre axis, until the combinations of connecting spray arms 31 and 32 and short, vertical spray arms 29 and 30 have reached the operating position, i.e. are situated beneath the pipeline 5 which is to be laid in the ground.

The h-shaped spray arms shown in Figure 6 can be configured in such a way that the connecting spray arms vary in length between the respective vertical, long sections and shorter, vertical spray sections. Figure 7a shows a plan view of the situation in which four spray arms are arranged in succession, preceded on each operating side by a single vertical arm 17 and 18. Figures 7b and 7c show a side view and a front view. In this case, the connecting spray arms 33, 34, 35, 36 decrease in length, as seen in the direction of forwards movement of the vehicle. Each of the shorter, vertical spray arms 37, 38, 39, 40 is, moreover, able to rotate, together with the connecting spray arms 33, 34, 35 and 36, about the centre axis of each of the vertical, long arms 41, 42, 43, 44. This means that the respective shorter spray sections 37, 38, 39, 40 can rotate from an inactive position (in the direction of forwards movement of the vehicle) into an active or operating position (at right angles to the direction of forwards movement of the vehicle).

The distances between the rotatable, vertical, long arms 41, 42, 43, 44 in the direction of forwards movement are adjustable. Therefore, it is possible for the fa- shaped arms to be positioned opposite one another on either side of the cable or pipeline which is to be buried, in such a manner that the connecting spray arms point towards one another in the active position.

The width of the trench which is to be dug can be varied in many ways on account of the difference in range beneath the pipeline which is to be buried between each combination of the connecting spray arms 33, 34, 35, 36 and shorter, vertical spray arms 37, 38, 39, 40 as well as the adjustable distances between them in the direction of forwards movement and in the transverse direction.

Each of the spray arms described above 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 8a and 8b, which respectively show a plan view and a side view of a single spray arm 17.

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 9 shows two h-shaped spray arms which are positioned next to one another and are provided with spray nozzles 12. The spray arms also comprise further spray nozzles 45 for spraying water substantially in the lateral direction. The spray nozzles 45 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.

To improve the effectiveness of the spray nozzles still further, it is possible to provide means for making the spray arms execute a reciprocating movement in an operating position. This reciprocating movement of a 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 movement or a rotational movement in the vertical plane out of a point or rotation point for the said means. Combinations of reciprocating movements, such as a reciprocating movement in the longitudinal direction with a rotational movement in the circumferential direction, are also possible. For illustration purposes, Figures 4a and 6a show one possible, associated reciprocating movement for the L-shaped and the h-shaped spray arm, respectively. For clarity, the abovementioned means are denoted by number 46.

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 47 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 10a. For example, to compensate for the forwardly directed spray nozzles, it is possible to provide one or more spray nozzles 48 which are directed towards the rear, as illustrated in Figure 10b. 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 10c shows the spray nozzles 45, as described in Figure 9, it being possible for these spray nozzles to be attached to the h-shaped spray arms rotated towards the rear, so that a reactive component is produced in the direction of forwards movement.

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, 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. In addition, the different configurations of spray nozzles can be used on any design of spray arms.

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. It can be seen from Figure 11 that the device 101 comprises a carriage 106 on which there is a frame 107. At least one spray arm 108 with at least one cylinder 109 is attached to the frame 107. As shown in Figure 11, the spray arm 108 is moved vertically downwards out of an inactive position into an active position, in which it projects below the carriage 106. Therefore, there are means which are not shown, for example hydraulic cylinders, for moving the spray arm 108 out of the position illustrated in Figure 11, in which the bottom end of the spray arm 108 is situated above or just above the seabed, into an active position, the operating position illustrated in Figure 1 lb.

Moreover, the device 101 comprises means 111 for rotating the spray arm 108 about the longitudinal axis of the spray 108. It is also possible for the spray arm according to the invention to rotate as a result of the reactive forces to which the water jets are subject when they leave the cylinder.

The spray arm 108 is connected to a high-pressure water pump (not shown) in order to produce water at a pressure of, for example, 10 to 100 bar. The spray nozzles have a diameter of, for example, 1 to 15 mm, removing a section of from 10 to 15 mm.

As an alternative to the spray arm 108 being moved vertically downwards, it is also possible for the spray arm to be pivoted, via a pivot pin, out of a substantially inactive, horizontal position, into an operating position, in which the spray arm 108 extends substantially in the vertical direction.

The spray arm 108 is shown in more detail in Figure 12. Figure 12 shows a top section 110 which can be rotated with the aid of the means 111, which are diagrammatically illustrated in Figure 11. A section 112 which is designed as a cylinder is attached to the underside of the section 110. In use, the spray 108 is rotated in order to ensure that the high-pressure water jets 113 which leave the spray 114 are able to efficiently cut through the earth which is to be removed on account of the rotational movement of the arm 108.

Figure 13 shows a variant of the spray arm 108, which comprises a central element 117 which extends "substantially along the centre axis 116 of the spray arm. A sealing pfate 118 which forms the underside of the spray arm is attached to the element 117. As shown in Figure 13, the cylindrical spray arm is enclosed by the tubular section 110 and the sealing plate 118. In this design, it is possible for there to be mechanical drive means for rotating the spray arm about its centre axis. It is also possible to provide a hydraulic drive which is formed, for example, by the reactive force which the emerging water experiences. The advantage of this solution is that there is no obstacle to the flow of water leaving the spray arm and that there is no need to provide further features in the spray arm. For sufficient rotation of the spray arm, the outlet openings of the spray nozzles have to be correctly aligned.

In accordance with Figures 12 and 13, the spray nozzles 114 are all directed downwards. In an alternative embodiment, it is possible for some of the spray nozzles 11 to have an exit direction which is opposite to the exit direction shown in Figure 12. The result of this measure is that there is a certain degree of internal compensation in the spray arm 108, so that no vertically directed forces are exerted on the carriage 106, and consequently the carriage 106 does not come off the ground when the spray arm 8 begins to be used. This is explained below with reference to Figure 15.

As shown in Figures 12, 13, the spray nozzles 114 are provided by making openings in the wall 115 of the section 112. It is possible for the section 112 to be designed, for example, as a casting. It is also possible for the spray nozzles 114 to be made by drilling holes in the wall 115. Of course, it is also possible for the spray nozzles 114 to be formed by attachments fitted on or in the wall 115 of the section 112 (not shown).

h accordance with Figure 12, the high-pressure water jets 113 form an angle of between 0° and 90° with the longitudinal centre axis 116 of the spray arm 108.

As an alternative, it is possible for the high-pressure water jets 113 to emerge at an angle of substantially 90° with respect to the longitudinal centre axis 116 of the spray arm 108. In that case, the trench 104 which is made in the ground with the aid of a spray arm 108 is wider than in the situation shown in Figure 12. Tests carried out by the applicant have shown that the spray arm 108 according to the invention can be used for effective removal of earth in order to make a ditch in the ground.

On account of the rotational movement executed by the spray arm according to the invention, it is important that the spray nozzles be well distributed over the outer surface of the spray arm. Uniform distribution of the position of the spray nozzles makes it possible to prevent uneven loads on the device caused by the spray arm starting to oscillate. Moreover, an uneven distribution of the spray nozzles would lead to insufficient use being made of the capacity of the device, since it would be impossible for earth to be removed continuously by an identical number of spray nozzles.

Figure 14 diagrammatically depicts a row in which spray nozzles can be positioned on the outer casing of the spray arm. The spray nozzles together form a helical row. A plurality of rows positioned adjacent to one another can together fill the entire surface of the spray arm.

Since the exit directions of the spray nozzles will be at least partially directed downwards, for at least some of the spray nozzles, an upward reactive force is exerted on the device by the emerging water jets. According to the invention, it is advantageous for an identical number of first and second spray nozzles to be arranged on the outer casing of the spray arm, the exit directions of which first and second spray nozzles are opposite to one another, in such a manner that the reactive forces on the emerging water jets will compensate for one another. This positioning of the spray nozzles compensates for the reactive force internally, i.e. without the addition of further components.

Figure 15 shows a blank for a cylindrical casing of a spray arm according to the invention. As shown in Figure 15, an even number of rows 118 (numbered on the underside of the blank shown in Figure 15) are present on the outer casing of the spray arms.

Figure 16 shows a cross section through the spray arm 108 according to the invention, with a cover 120 arranged on that side of the spray arm 108 which faces away from the direction of movement of the spray arm. With the aid of the cover 120, the supply from the spray arm 108 to the spray nozzles 114 on the side from which the earth has already been removed is closed off. Only the spray nozzles 114 which lie on that side of the spray arm on which earth is to be removed are provided with a supply of water. This measure ensures that the capacity of the water supplied and the pump pressure are employed optimally for the removal of earth.

Various embodiments of the spray arm according to the invention are illustrated in Figures 17 and 18. In accordance with Figure 17, it is possible for a spray arm 108 to comprise various outer casings 112 positioned above one another. These casings may differ from one another in terms of diameter, length or the number of spray nozzles arranged on the casing. It is advantageous if the spray arm is designed in such a way that the various outer casings are exchangeable and can easily be replaced.

The situation may also arise in which a device for making a trench in the bed of an area of water comprises at least two spray arms, which act behind or next to one another, on both sides of the cable or pipeline. The spray arms of a device of this type may, according to the invention, be provided with one or more cylindrical outer casings. Figure 18 shows a possible embodiment according to the invention, in which two spray arms 108 are attached directly behind one another to a device. In the advancing direction, a front spray arm is provided with a relatively small cylindrical outer casing 112, while the rear spray arm is provided with a longer outer casing 112 which, moreover, has a greater diameter. A device with an arrangement of this type forms the trench in the ground in steps.

A further embodiment is shown in Figure 19. As shown in Figure 19, there are two h-shaped spray arms 108 on either side of a pipeline 105. The part-arms are each provided with cylindrical, rotating outer casings 112. The result is a trench 104 of considerable size.

Figure 20 shows a further embodiment, in which a device according to the invention is provided with two L-shaped arms 108, on either side of a pipeline 105. In this case, the horizontal part-arms are provided with cylindrical, rotating outer casings. The L-shaped spray arms may in this case be positioned next to one another, so that in this way a trench 104 which can be made to an increasing depth is obtained.

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, in use, extend substantially vertically downwards next to the pipeline or cable and are provided with spray nozzles for high-pressure water jets, characterized in that a plurality of spray arms are arranged on the vehicle, the spray nozzles of each successive spray arm, as seen in the direction of forwards movement of the vehicle, having a specific additional function to the spray nozzles of each spray arm in front.

2. Device according to Claim 1, characterized in that a single vertical spray arm clears the way in the direction of forwards movement of the vehicle and is followed by a further spray arm, which comprises two or more part- arms which extend at an angle to or a distance from one another.

3. Device according to Claim 1 or 2, characterized in that a spray arm comprises at least one cylinder which is provided with spray nozzles over its circumference.

4. Device according to Claims 1-3, characterized in that 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.

5. Device according to Claims 1-4, characterized in that at least one spray arm is substantially L-shaped, with a vertical, long arm and a horizontal, short arm.

Device according to Claims 1-4, characterized in that at least one spray arm is substantially h-shaped, with a vertical, long arm and a short arm which extends at a distance therefrom.

Device according to Claim 5, characterized in that a plurality of L-shaped spray arms are arranged on the vehicle, the vertical, long arms of which L- shaped spray arms increase in length from the front side of the vehicle towards the rear side of the vehicle.

8. Device according to Claim 6, characterized in that a plurality of h-shaped spray arms are arranged on the vehicle, of which h-shaped spray arms the distances between the vertical, long arms and the shorter arms extending parallel thereto increase from the front side of the vehicle towards the rear side of the vehicle.

9. Device according to Claims 7 and 8, characterized in that a combination of a plurality of L-shaped and h-shaped spray arms is arranged on the vehicle.

10. Device according to one of Claims 5 and 6, characterized in that, of the further spray arm, the short arm can be rotated out of an inactive position, which is located outside the pipeline or cable, into an active operating position beneath the pipeline or cable.

11. Device according to Claim 10, characterized in that the vertical, long arm can be rotated about its centre axis, and the short arm is fixedly connected to the long arm and rotates therewith.

12. Device according to Claim 10, characterized in that the long arm cannot rotate, and in that the short arm is an arm which is connected to the long arm and can rotate separately between an inactive position and an active position.

13. Device according to one of the preceding claims, 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.

14. Device according to Claim 13, characterized in that the spray nozzles on a spray arm are distributed in identical groups in the longitudinal direction.

15. Device according to Claim 13 or 14, 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.

16. Device according to Claim 13 or 14, 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.

17. Device according to Claim 13 or 14, 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.

18. Device according to Claim 13 or 14, characterized in that spray nozzles are provided for spraying a water jet substantially transversely with respect to the direction of forwards movement of the vehicle.

19. 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.

20. Device according to one of the preceding Claims 1 or 2, characterized in that means for enabling one or more spray arms to execute a reciprocating movement are provided on the vehicle.

21. Device according to Claim 3, characterized in that means for rotating the cylinder about its longitudinal axis are provided.

22. Device according to Claim 21, characterized in that the spray nozzles are designed as bores or openings in the wall of the cylinder.

23. Device according to Claim 21 or 22, characterized in that the spray nozzles are designed as attachments which are fixed on or in the outer wall of the cylinder.

24. Device according to one of Claims 21-23, characterized in that there are means for, in use, covering the spray nozzles on that side of the cylinder which is directed away from the direction of forwards movement of the vehicle which can move underwater.

25. Device according to one of Claims 21-24, characterized in that a spray arm comprises a plurality of cylinders.

26. Device according to one of Claims 21-25, characterized in that various designs of cylinders may be arranged exchangeably and replaceably on a spray arm.

27. Device according to one of Claims 21-26, characterized in that at least two cylindrical spray arms of this type are provided next to one another in order to act on both sides of the pipeline or cable.

28. Device according to one of Claims 21-27, characterized in that the exit direction is directed substantially perpendicular to the axis of rotation of the cylinder.

29. Device according to one of Claims 21-28, characterized in that the spray arm or each spray arm comprise(s) one or more spray mouthpieces which are arranged directed substantially downwards at an angle of between 0° and approximately 90° with respect to the longitudinal axis of the spray arm.

30. Device according to one of Claims 21-29, characterized in that the spray mouthpieces are distributed uniformly over the circumference of the cylinder.

31. Device according to one of Claims 21-30, characterized in that the spray nozzles on the spray arm or the spray arms are arranged in identical groups over the circumference of the cylinder.

32. Device according to one of Claims 30 or 31, characterized in that the spray nozzles are arranged in at least one helical row over the circumference.

33. Device according to one of Claims 21-32, characterized in that first spray nozzles are provided on the at least one spray arm, and second spray nozzles are provided, the exit directions of which are opposite to one another, in order to internally compensate for reactive forces in the spray arm.

34. Device according to one of Claims 21-33, 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.

35. Device according to one of Claims 21-34, characterized in that means are provided for rotating the at least one spray arm out of a rotation point thereof through an angle in the vertical longitudinal plane, between an inactive position, in which the spray arm is directed substantially towards the rear, and an active or operating position, in which the spray arm is directed substantially downwards.

36. Device according to one of Claims 21-35, characterized in that at least one spray arm is substantially h-shaped, with a long arm and a short arm running parallel thereto, it being possible to rotate the short arm out of an inactive position, in which it lies outside the pipeline or cable, into an active operating position beneath the pipeline or cable.

37. Device according to one of Claims 21-36, characterized in that at least one spray arm is substantially L-shaped, with a long arm and a short arm which is positioned transversely with respect to the long arm, it being possible to rotate the short arm out of an inactive position, in which it lies outside the pipeline or cable, into the active position beneath the pipeline or cable.

38. Method for making a trench in the bed of an area of water, in particular for laying a pipeline or cable in the bed, the trench being made in the bed by locally blasting away the bed with the aid of high-pressure water jets, which high-pressure water jets are emitted from spray nozzles which are arranged in at least one spray arm of a vehicle which can move underwater, characterized in that while the trench is being made in the bed, the spray arm is rotated, in order for the high-pressure water jets to execute a cutting movement through the bed.

39. Method according to Claim 38, characterized in that the penetration depth of the high-pressure water jets in the direction of forwards movement of the vehicle is determined, and the rotational speed of the cylinder on the spray arm and the forwards movement of the vehicle which can move underwater are then adapted in such a manner that the vehicle moves substantially over a distance which is equal to the penetration depth of the water jets during one complete revolution of the spray arm.