The present invention relates to an arrangement for positioning one or more objects under the water level on a sea, lake or river bottom, and to a method for such positioning.

DE 10 2021 128 776 Al discloses a depth vibrator assembly that includes several top fed depth vibrators and that is suspended by a crane via a spreader bar on land-based applications.

However, for many construction projects it would be desirable to use deep vibrators also under water in the soil covered by the water to produce stone columns or the like in the soil. This, however, is challenging at least for the following reasons:

1) A desired starting point, at which a depth vibrator is desired to enter the soil (i.e. a starting point on the sea, lake or river bottom covered by the water) is difficult to approach if the depth vibrator is fully submersed in the water since there is no visual method of finding such starting points like this is possible on land.

2) Approaching a desired starting point is also difficult because of swell and water current.

3) If the depth vibrator assembly includes several depth vibrators, a water current may act onto the assembly so that it is twisted around the vertical axis.

4) Feeding the depth vibrator assembly in an efficient and fast way with gravel or other material to allow for fast installation of material columns is difficult since the depth vibrator work is carried out under water.

One aspect relates to a positioning arrangement for positioning an object under water on a water bottom. The positioning arrangement includes a barge configured to float on the water; a carrier rig positioned on the barge; a rope arrangement by means of which the object is suspended from a mast of the carrier rig; and a positioning aid. The positioning aid includes at least one of: (a) a constraining arrangement arranged between the mast and the object and configured to restrict a lateral movement of the rope arrangement: and (b) a turntable arrangement configured to adjust a rotational position of the object about a vertical swiveling axis (a).

A further aspect relates to a method for positioning an object under water on a water bottom. The method includes: providing a positioning arrangement according to the first aspect; determining an actual position of the barge; determining an actual position of the object; controlling at least one of the constraining arrangement and the turntable arrangement to approach the object to a desired position above the water bottom based on at least one of the determined actual position of the barge and the determined actual position of the object.

Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

The examples described below can be better understood with reference to the following drawings and descriptions. The components in the figures are not necessarily to scale; instead, emphasis is placed upon illustrating the principles of the invention. Moreover, in the drawings, like reference numerals designate corresponding parts. The features of the various illustrated embodiments can be combined unless they exclude each other. Embodiments are depicted in the drawings and are detailed in the description which follows. In the drawings:

FIG. 1 A schematically illustrates a positioning arrangement that includes a carrier rig positioned on a barge with an object suspended from a mast of the carrier rig.

FIG. IB schematically illustrates the positioning arrangement of FIG. 1 A with the barge tilted by wave action.

FIG. 2A schematically illustrates a top view of an embodiment of a positioning arrangement; FIG. 2B is a cross-sectional side view of the embodiment of FIG. 2A in a cross-sectional plane A-A.

FIG. 3 A schematically illustrates a top view of a further embodiment of a positioning arrangement.

FIG. 3B is a cross-sectional side view of the embodiment of FIG. 3 A in a cross-sectional plane A-A.

FIG. 4A is a top view schematically illustrating a positioning arrangement during vibratory operation of the depth vibrator.

FIG. 4B is a top view schematically illustrating the positioning arrangement of FIG. 4A during filling of the multiple depth vibrator assemblies via hoppers with a filling material.

FIG. 4C is a cross-sectional side view of the positioning arrangement of FIG. 4B in a cross- sectional plane B-B.

FIG. 5A illustrates a conventional positioning arrangement operating at calm water.

FIG. 5B illustrates the conventional positioning arrangement of FIG. 5 A operating in swell conditions.

FIG. 5C illustrates a positioning arrangement according to one embodiment of the present invention.

FIG. 6A illustrates a positioning arrangement according to one embodiment of the present invention which includes a turntable arrangement.

FIG. 6B is an enlarged view of the turntable arrangement of FIG. 6A and an object attached to the turntable arrangement.

FIG. 7A is a top view of a swivel segment attached to the mast of a carrier rig. FIG. 7B shows the swivel segment of FIG. 7 A swiveled to the left.

FIG. 7C is a side view of the swivel segment attached to the mast of FIGS. 7B and 7C.

The invention generally relates to improving the underwater positioning of single or multiple objects (e.g. one or more depth vibrators) at a desired position (e.g. a starting point for the vibratory operation of one or more depth vibrators) on a sea, lake or river bottom under water. In the present disclosure, the term “water bottom” is intended to include a sea, lake or river bottom, or a bottom of any other water or liquid reservoir.

One aspect of the present invention is the use of a positioning aid that improves the positioning accuracy of an object immediately above a desired position on a water bottom. The positioning aid may include at least one of a constraining arrangement and a turntable arrangement, i. e. a constraining arrangement and/or a turntable arrangement.

The constraining arrangement constrains a lateral movement of a rope arrangement, e.g. one or more ropes, used to suspend an object from a mast of a carrier rig. This will be explained in more detail with reference to FIGS. 1 A and IB. FIG. 1 A schematically illustrates a positioning arrangement 100 that includes a carrier rig 1 positioned on a barge 8. In the drawings of the present disclosure, the carrier rig 1 is illustrated as crawler crane. Instead of a carrier rig 1 that can drive on the barge 8 , however, any other suitable carrier rig/suspension, such as for example a rigid tower mast (which is, for example, fixed to the barge 8, without an undercarriage with which the carrier rig 1 can drive on the barge 8), could be used as well. The barge 8 is floating on water 14 of the sea, a lake or a river. The bottom 15 of the sea, lake or river (in the following also referred to as “water bottom”) is formed by the top side of soil 16 and covered by the water 14. By means of a rope arrangement 7, an object 50, e.g. a single depth vibrator assembly 48 or a group of depth vibrator assemblies, is suspended from a mast 28 of the carrier rig 1. As illustrated, the object 50 may be fully immersed in the water 14. The rope arrangement 7 includes at least one rope 71, e.g. one, two or more than two wire ropes 71. Starting from a winch 27, from which each rope 71 is unwound and/or onto which it is wound, the rope 71 is guided over a sheave 25 which is mounted to the mast 28. Hanging on the rope(s) 71 (e. g. at end(s) 711 of the rope(s) 71), the object 50 is positioned immediately above a desired position P on the water bottom 15.

The positioning aid 60 is arranged between the sheave 25 and the object 50 and includes a constraining arrangement 4 which constrains a lateral movement of the rope arrangement 7 which in the present example is a single rope 71. In the sense of the present disclosure, “lateral” refers to a direction perpendicular to the vertical direction, wherein the vertical direction is the direction of gravity. The constraining arrangement 4 may constrain the lateral movement of the rope arrangement 7 in one, more than one or each lateral direction. According to one example, the lateral movement of a rope 71 of the rope arrangement 7 may be constrained by an open or closed ring which is part of the constriction arrangement 4 and through which the rope 71 is guided. As illustrated in FIG. 1 A, the constriction arrangement 4 may be directly or indirectly mounted to the barge 8.

When the water is calm (i.e. no waves, no water current), the object 50 is at a lateral distance dO from a reference axis r about which the barge 8 rolls.

In contrast, FIG. IB illustrates the positioning arrangement 100 of FIG. 1 A with the barge 8 tilted by wave action. For the sake of clarity, however, the surface 14t of the water 14 is illustrated by a straight line, i.e. the waves on the surface 14t of the water 14 are omitted. Compared to the situation with calm water 14, the lateral distance between the reference axis r of the barge 8 and the object 50 changes due to the tilting of the barge 8 by dl.

FIG. IB also shows by means of dashed lines that the lateral distance between the reference axis r and the object 50 would change by d2 if the rope 71 were not restricted by the constriction arrangement 4. As can be seen, dl is smaller than d2, i.e. the constriction arrangement 4 increases the positioning accuracy of the object 50. The reason, why dl is smaller than d2, is that the constriction arrangement 4 is arranged closer to the object 50 than the sheave 25. In order to enhance this effect, the constriction arrangement 4 could alternatively also be arranged adjacent to a side wall of the barge 8 in a lateral direction as exemplarily illustrated by dotted lines in FIG. 1 A. The closer the constriction arrangement 4 is positioned to the axis r of barge rotation, the smaller the deviation dl becomes. The principle described above with reference to FIGS. 1 A and IB is also used in the following examples. FIG. 2A is a top view of a positioning arrangement 100 that includes a carrier rig 1 arranged on a barge 8, and FIG. 2B is a cross-sectional view of the positioning arrangement 100 in a cross-sectional plane A-A. A rope arrangement 7 that is operated from two synchronized winches 27 mounted on the carrier rig 1 carries an object 50 which in the present example are several bottom fed depth vibrators assemblies 48. Each of the bottom fed depth vibrators assemblies 48 includes a hopper 6, a gravel tank 10, a silo tube 11 and a depth vibrator 12. The depth vibrator assemblies 48 are each connected, here via ropes 19, but possibly also fixed or with a flexible joint connection, to a same spreader bar 5 that itself is carried by two ropes 71 of the rope arrangement 7. The spreader bar 5 and the ropes 19 are parts of the object 50.

While the barge 8 is in approximate alignment with future stone column 13 locations on the water bottom 15, such alignment can never be precise enough to fully rely on it for navigating the depth vibrator assemblies with sufficient accuracy and precision to such point locations. In FIGS. 2A and 2B the positioning of the depth vibrator assemblies 48 is assisted by a positioning aid 60 that includes a localizer platform 2 and a movable constraining arrangement 4 mounted to the localizer platform 2.

The localizer platform 2 may move along the edge of the barge 8, i.e. substantially in a lateral direction. As schematically illustrated In FIG. 2B, the localizer platform 2 may be rolling on wheels 9. Instead of or in addition to wheels 9, any other means for moving the localizer platform 2 relative to the barge 8 may also be used.

The movable constraining arrangement 4 can connect to the rope arrangement 7, i.e. to the ropes 71, in a way that the ropes 71 are not hindered in their vertical movement but constrained by the constraining arrangement 4 in all lateral directions. As illustrated in FIG. 2A, the constraining arrangement 4 may include two constraining elements 41 each constraining a movement of one of the ropes 71 in all lateral directions. Each of the constraining element 41 is mounted to a hydraulic cylinder 3 and can be moved in a lateral direction relative to the localizer platform 2 using the respective hydraulic cylinder 3. The hydraulic cylinders 3 are in turn mounted on the localizer platform 2. According to the embodiment of FIGS. 2A and 2B, each constraining element 41 may be formed as a clamp that can open and close around one of the ropes 71. With the crane mast 28 high up above such constraining elements 41, the constraining elements 41 can be moved relative to the barge 8 by moving the localizer platform 2 relative to the barge 8 (e.g. along a sidewall of the barge 8) and by moving the constraining elements 41 relative to the localizer platform 2 (e.g. by expanding and/or contracting the hydraulic cylinders 3). Instead of or in addition the hydraulic cylinders 3, any other suitable actuator (e.g. pneumatic, electric or electromagnetic) may be used as well.

To bring the object 50 to a desired position P (see FIGS. 1A and IB) immediately above the water bottom 15, the barge 8 is positioned roughly above the desired position P. Then, a fine adjustment is made by means of which the relative position of the constraining arrangement 4 relative to the barge 8 is adjusted by suitably adjusting the relative position between the localizer arrangement 2 and the barge 8, and by suitably adjusting the stroke of the hydraulic cylinder 3 relative to the localizer arrangement 2 in such a way that the submerged object 50 is located sufficiently precisely above the desired position P.

The above-described positioning of the object 50 to the desired position P immediately above the water bottom 15 may use underwater surveying of the object 50 in order to obtain the actual (lateral) position of object 50.

When the actual lateral position of the object 50 is known, the desired lateral position P of the object 50 can be approached by means of a control electronics 90 which receives the information on the actual (lateral) position and/or the rotational position of the object 50 and which suitably adjusts the relative (e.g. lateral) position between the localizer platform 2 and the barge 8 as well as the relative (e.g. lateral) position between the constraining arrangement 4 (i.e. the constraining elements 41) and the localizer platform 2 so that the position of the constraining elements 41 affects the positions of the ropes 71 and thus also the position of the object 50. Optionally, the control electronics 90 may adjust a rotational or pivotal position of the object 50 by appropriately controlling a turntable arrangement 60 (cf. FIGS. 6 A and 6B and the related description) and/or by appropriately controlling a rotatable crane mast head 25, 30, 32, 33 (cf. FIGS. 7A, 7B and 7C and the related description) in order to approach the desired lateral position P of the object 50. Optionally, a GPS position (lateral position and/or rotational position) of the barge 8 (e.g. with the aid of differential GPS) and an inclination of the barge 8 (e.g. provided by inclination sensors) can also be taken into account in this control. The control electronics 90, e.g. a control computer, may be mounted at any suitable location, for example on the carrier rig 1 or the barge 8.

Summarized, the control electronics 90 may permanently regulate the relative position between the barge 8 and the constraining arrangement 4 and/or the rotational position of the object 50 in order to approach the desired position P of the object 50 on the water bottom 15. Such control electronics 90 may control the position of the constraining arrangement 4 (if provided), the position(s) of the end(s) 711 of the one, two or more than two ropes 71 (i. e. the ends 711 hanging down from the mast 2) via the rotational position(s) of the winch(es) 27 and the rotational position of the turntable arrangement 45 (if provided) via the turntable drive 22 and alternatively also control an angle cp of the hinge 31 (cf. FIGS. 7A-7C and the related description).

There are various ways to achieve underwater surveying of the object 50 (e.g. multiple depth vibrator assemblies). One way is schematically illustrated in FIG. 2B, where an echo sounding device 37 is attached to an extension rod 36 that is itself connected to the barge 8. By the echo sounding signal 38 from the echo sounding device 37 the distance between the barge 8 and the object 50 can be determined. The barge 8 itself may be permanently surveyed by differential GPS. Optionally, inclination sensors may acquire the inclination of the barge 8 in two lateral (e.g. perpendicular) directions which leads to an at any time known position of the echo sounding device 37. Several such echo sounding devices 37 (e.g. an array) may be used to properly triangulate the position and optionally also the orientation of the object 50 under water. For the sake of clearness, these additional echo sounding devices are omitted in FIG. 2B.

FIGS. 3A and 3B schematically illustrate an example of positioning arrangement 100 that employs an alternative embodiment of the constraining arrangement 4. FIG. 3 A is a top view and FIG. 3B is a cross-sectional side view in a cross-sectional plane A-A. The construction and operation principle of the localizer platform 2 may be the same as described with reference to FIGS. 2 A and 2B. As also described with reference to FIGS. 2A and 2B, a movable constraining arrangement 4 is mounted to the localizer platform 2, and the movable constraining arrangement 4 can also connect to the rope arrangement 7, i.e. to the ropes 71, in a way that the ropes 71 are not hindered in their vertical movement but constrained by the constraining arrangement 4 in all lateral directions. In the embodiment of FIGS. 3A and 3B, the constraining arrangement 4 includes pairs of bifurcated (e.g. v-shaped) constraining elements 42.

Each of the bifurcated constraining elements 42 is operated by a respective hydraulic cylinder 3 to which the respective constraining element 42 is mounted. Thereby, the two free ends of the bifurcated constraining element 42 point away from the hydraulic cylinder 3. Arranging the two bifurcated constraining elements 42 of a pair and the respective hydraulic cylinders 3 such that each of the constraining elements 42 can be moved towards and/or away from the other one of the constraining elements 42 allows the pair of constraining elements 42 to assume an unconstrained configuration and a constrained configuration.

In the constrained configuration, the constraining elements 42 of the pair can embrace one of the ropes 71 such that the pair constrains the lateral movement of the rope 71 in each lateral direction. For example, the respective rope 71 may be fully surrounded by the bifurcated constraining elements 42. In FIG. 3 A, the left two constraining elements 42 form a pair that is in the constrained configuration.

In the unconstrained configuration, the constraining elements 42 of the pair are spaced far enough apart that they do not constrain the lateral movement of a rope 71. In FIG. 3 A, the right two constraining elements 42 form a pair that is in the unconstrained configuration.

This embodiment of the constraining arrangement 4 has the advantage that no clamping mechanism is as for the clamping elements 41 described with reference to FIGS. 2A and 2B is required. The use of two independent but in synchronized winches 27 (cf. FIGS. 2B and 3B) allows for an adjustment of the spreader bar 5 to not have any deviation from the horizontal. This is important when a group 50 with multiple depth vibrator assemblies 48 is subjected to water currents and also in connection with the use of the above-described localizer platform 2. Having the spreader bar 5 horizontal helps in achieving a more vertical penetration of the group of multiple depth vibrator assemblies 48 into the soil 16. FIG. 4A shows the group of multiple depth vibrator assemblies 48 during vibratory action in which the soil 16 (cf. FIGS. 1 A, IB, 2A, 2B, 3A, 3B) is compacted by the depth vibrators 12 of the multiple depth vibrator assemblies 48. FIGS. 4B and 4C show the multiple depth vibrator assemblies 48 while being filled via the hoppers 6 with a filling material like stones, gravel, sand, bentonite, cement, concrete, etc. from a supply silo 18 that is arranged on the bark 8. FIG. 4C is a cross-sectional side view in a cross-sectional plane B-B in FIG. 4B. During such filling, the whole localizer platform 2 can slide out of the way of the spreader bar 5 and the multiple depth vibrator assemblies 48 suspended below it (e.g. to the very right side of the barge 8 as illustrated in FIG. 4B).

In the filling position, the arrangement of the spreader bar 5 is no longer perpendicular to the crane mast 28. This can be achieved with one of the following three ways:

1) By sliding the group with the multiple depth vibrator assemblies 48 along the side wall 81 of the barge 8, allowing for the wire ropes 71 to twist over the distance from the spreader bar 5 to the sheave 25.

2) By a turntable 21 that can be rotated by a motor drive 22 as described below with reference to FIGS. 6 A and 6B.

3) By a mast head that has a top that can be rotated by some control mechanism as described below with reference to FIGS. 7A-7C.

Instead of filling the hoppers 6 of the depth vibrator assemblies 48 individually from the material silo 18, the filling material can also be transported with air or water as transport media through hoses to each such hopper 6 individually. In this case, the process of filling may also take place with the depth vibrator assemblies 48 completely immersed in the water 14.

In yet another variant, the multiple hoppers 6 can be filled from an additional so-called distribution tank, which is located between the spreader beam 5 and the group of depth vibrator assemblies 48. Such distribution tank can be filled either from the material silo 18 or via hoses. These alternatives are not shown in the drawings. As is clear from the description of FIGS. 1 A and IB, the lateral movement of the multiple depth vibrator assemblies 48 relative to their desired positions P on the water bottom 15 is minimum, if the movement of the ropes 71 in all lateral directions is restricted at a level that is very close to the center of rotation of the barge 8, even if the rolling motion of the barge 8 is very large. Therefore, such a low position of the constraining arrangement 4 (e.g. the constraining elements 41 described with reference to FIGS. 2 A and 2B or the constraining elements 41 described with reference to FIGS. 3A and 3B) and also of the localizer platform 2 is advantageous. For instance, the constraining arrangement 4 and the optional localizer platform 2 (if provided) may be arranged adjacent to a side wall 81 of the barge 8 in a lateral direction. This is schematically illustrated in FIG. 5C.

Compared to FIG. 5C, FIGS. 5A and 5B show a conventional positioning arrangement 99 which differs from the positioning arrangement 100 according to the invention shown in FIG. 5C in that there is no constraining arrangement 4 (and also no optional localizer platform 2). FIG. 5A shows the conventional arrangement in calm sea conditions (no waves, no water current) with the depth vibrator assemblies 48 immediately above the respective desired position P on the water bottom 15, and FIG. 5B shows the arrangement according to FIG. 5 A, but in swell conditions, whereby the barge 8 is tilted and the depth vibrator assemblies 48 are laterally displaced with respect to the respective desired position P. In comparison, the barge 8 in FIG. 5C has the same tilt as in FIG. 5B, but the lateral offset of the depth vibrator assemblies 48 from the respective desired position P is much smaller due to the constraining arrangement 4 (and the optional localizer platform 2). Furthermore, there is an added benefit that forces on the crane mast stay closer to the axis of the mast 28 in the arrangement 100 of the present invention than in the conventional arrangement 99. Thereby, the sideways forces onto the mast 28 are reduced, which in turn increases the overall stability of the crane and makes it workable over a larger range of wave heights.

However, even though in FIG. 5C the position of the constraining arrangement 4 (and the optional localizer platform 2) laterally adjacent to a side wall 81 of the barge 8 was described as optimal, also higher positions have a large advantage compared to the conventional positioning arrangement 99 of FIGS. 5A and 5C without a constraining arrangement 4. It is expected that with a constriction arrangement 4 and - optionally - a localizer platform 2, the work offshore can be extended to higher wave heights than without such devices and that at the same wave height the accuracy and precision of locating any object 50 (a depth vibrator assembly 48 or a group of depth vibrator assemblies 48) at a desired position P on the water bottom 15 is greatly improved.

As further illustrated in FIG. 6 A, the positioning aid 60 may include a turntable arrangement 45. FIG. 6B is an enlarged view of the turntable arrangement 45 of FIG. 6A and the object 50 (in the present example a group of depth vibrator assemblies 48 commonly mounted to a spreader bar 5) attached to the turntable arrangement 45.

The turntable arrangement 45 may be provided in addition to or - as illustrated in FIG. 6A - instead of a constriction arrangement 4 as explained with reference to the above Figures. As illustrated in FIG. 6B, the turntable arrangement 45 may include a turntable 21, a motor drive 22 and a holding bar 24. The holding bar 24 is mounted to the ropes 71. The motor drive 22 is configured to rotate the turntable 21 relative to the holding bar 24 about a vertical swiveling axis a. The object 50 (here the spreader bar 5 and the group of depth vibrator assemblies 48 mounted thereto) is mounted to the turntable 21 so that a rotation of the turntable 21 caused by the motor drive 22 will also rotate the object 50 relative to the holding bar 24 so that a desired orientation (rotary position) of the object 50 can be adjusted by appropriately driving the motor drive 22.

For example, the turntable arrangement 45 may be used to rotate the spreader bar 5 so that it stays parallel to the edge of the barge 8 when the spreader bar 5 and the group of depth vibrator assemblies 48 is moved to the filling silo 18 (FIGS. 4B and 4C).

The turntable arrangement 45 could also be used together with a localizer platform 2 and a constriction arrangement 4 if the group of depth vibrator assemblies 48 must be turned left and right, e.g. by 60 degrees, to work in a triangular and not square stone column grid pattern. In this case, most of the positioning would be achieved by the turntable, and the constraining arrangement 4 mounted to the localizer platform 2 would only constrain the ropes 71 as good as possible in each lateral direction without bothering about the 60 degree rotation of the depth vibrator assemblies 48 away from that lineup, as this later part would be taken over by the turntable arrangement 45. FIGS. 7A, 7B and 7C show the top of a mast 28 that is prepared to operate two independent ropes 71 that can be synchronized during normal operation. In this sense, "synchronized" means that the two ropes 71 are wound and unwound in the same direction and at the same speed by the two winches 27 (FIGS. 2A, 2B, 3B, 4C and 6A). However, there can also adjustments be made to such synchronization to assure that a spreader bar 5 as explained with reference to the previous Figures remains horizontal.

Attached to the upper end of the mast 28 there is a swivel segment 32 that can be swiveled about a swiveling axis b using a hinge 31 that pivotably couples the swivel segment 32 to the mast 28. In FIG. 7A, the swivel segment 32 is in the center position (neutral position), while in FIG. 7B it is pivoted to the left by an angle cp relative to a longitudinal axis 128 of the mast 28. Similarly, the segment 32 can also be pivoted to the right relative to the longitudinal axis 128 of the mast 28. In the center position (neutral position; FIG. 7A), the angle cp is 0°.

The hinge 31 includes a control motor configured to adjust a desired pivotal position of the swivel segment 32 relative to the mast 28. Attached to the swivel segment 32 there is a hammerhead 33 which swivels about the hinge 31 together with the swivel segment 32. For each of the ropes 71, the hammerhead 33 contains a deflection sheave 25 which deflects the respective rope 71 coming from one of the winches 27 downwards. The deflection sheaves 25 also swivel about the hinge 31 together with the swivel segment 32 (and the hammerhead 33).

For the two ropes 71 to not fall off the top sheaves 25 there are guide wheels 29, 30 that guide the ropes 71 around a left or right curve as the hammerhead 33 is pivoted accordingly. The guide wheels 29 are mounted to the mast 28 and the guide wheels 30 are mounted to the swivel segment 32 and swivel together with the swivel segment 32 about the hinge 31. The assembly that includes the swivel element 32, the hammerhead 33, the deflection sheaves 25 and the guide wheels 30 can also be considered as pivotable or rotatable mast head.

Such a rotatable crane mast head 25, 30, 32, 33 may be used instead of a turntable arrangement 35 as described with reference to FIGS. 6A and 6B, or may be omitted. Alternatively, such rotatable crane masthead 25, 30, 32, 33 can complement the turntable arrangement 35 as a fallback device for orienting the depth vibrator assemblies 48 alongside the edge of the barge 8 when the depth vibrator assemblies 48 are moved into a position close to the filling silo 18. However, it is also possible to omit both the rotatable crane mast head 25, 30, 32, 33 and the turntable arrangement 35.

It is to be noted that the features described in connection with the above figures can be combined unless they are mutually exclusive.

In the following, some example embodiments of the present invention are summarized. Other embodiments can also be understood from the entirety of the specification and the claims filed herein.

Example 1. Arrangement of for example multiple depth vibrator assemblies or other needle shaped multiple probes or generally any objects that need to be located with some accuracy on the seabed while being suspended by at least one wire rope from a carrier rig standing on a floating barge, such that the wire rope is guided through some fixed point via a localizer platform (2) and constraining devices (4, 41, 42), thereby improving greatly the positional accuracy of the objects in case of rolling movement or any other movement of the barge (8).

Example 2. Arrangement according to example 1 for example multiple depth vibrator assemblies or other needle shaped multiple probes or generally any objects that need to be located with some accuracy on the seabed while being suspended by at least two independent but synchronizable wire ropes from a carrier rig standing on a floating barge, such that both wire ropes are guided through some fixed points via a localizer platform (2) and constraining devices (4, 41, 42), thereby improving greatly the positional accuracy of the objects in case of rolling movement or any other movement of the barge (8). Such positioning is improved further when the level of the constraining devices (for example 4, 41, 42) is located close to the level of rotation of the barge (8).

Example 3. Arrangement according to example 2, whereby the position accuracy of the spreader bar (5) is not only improved around the vertical (z) axis by the constraining devices (4, 41, 42) but also in its horizontal orientation by using two independently controllable winches (27) to lower one of the two ropes or raise the other, until the spreader bar (5) is horizontal. Example 4. Arrangement according to example 1 and 2 with added ability to rotate the spreader bar (5) around the z-axis (vertical direction) by means of a turntable arrangement according to Figures 6 A and 6B.

Example 5. Arrangement according to example 1, 2, and 3, whereby the turntable according to example 3 is replaced or complemented by a rotatable mast head according to Figures 7A, 7B and 7C.

Example 6. Arrangement under example 1 to 4 for which the method of constraining the x and y direction movement of the wire ropes (7) is achieved with any other constraining device, not only the two examples shown in Figures 2A, 2B, 3A and 3B. The hydraulic cylinders may be replaced by other elements that can provide controlled lateral movement of devices that constrain the movement of the wire ropes (7) in the x and y direction (lateral directions).

Example 7. Arrangements under example 1 to 5, supported by echo sounding devices mounted to the bottom of the barge to triangulate the position of the multiple depth vibrator assemblies and / or the spreader bar (5) relative to the position of the barge itself.

Example 8. Echo sounding or any other under-water distance measuring devices that measure the absolute position of the depth vibrator assemblies with the distance sounding devices are connected to defined locations on the seabed.

Example 9. Sounding devices per examples 6 and 7, sending the depth vibrator assemblies locations electronically real time to a control computer (not shown in the Figures) that permanently adjusts the x-y location (lateral position) of the constraint points for the two wire ropes (7) on the localizer platform (2).

Example 10. Control computer per example 8 that also controls the turntable according to example 3 and 4 and the rotatable mast head (see Figures 7A, 7B and 7C) with the aim to improve the overall position accuracy of the depth vibrator assemblies or any objects on the seabed (15).