GB2280411A - Embedded anchors - Google Patents

Abstract

A sinker for use in mooring a structure on or in water is embedded up to at least one third of its volume into the soil at the bottom of the water by its self-weight and, possibly, the weight of a additional loads which are subsequently removed. The sinker has one or more vertical plates (2) extending downwards and designed to generate a horizontal holding force. The sinker can be further provided at its upper side part with a temporary fitting means for the additional loads. A vibrator may be used to facilitate embedding of the sinker. <IMAGE>

Description

DESCRIPTION A SINKER AND A METHOD OF EMBEDDING A SINKER This invention relates to a method of embedding a sinker for use in mooring a structure laid on the water such as a mooring buoy for mooring a ship (e.g. a crude oil tanker), a floating type lighthouse, or a radio communication tower, and a structure laid in the water such as an oil pipeline and a cable; and further to a sinker for use in mooring such a structure laid on or in the water.

Figure 9 of the accompanying drawings is a schematic explanatory view of a mooring facility for a crude oil tanker which is used to feed the crude oil from the tanker to storage facilities onshore.

In this figure, the crude oil tanker 01 is moored to a mooring buoy 02 at a point (usually, a head of the tanker 01 is connected via a tanker mooring cable S to the mooring buoy 02, as shown in the figure) and a floating hose FH is pulled out from the mooring buoy 02 to the sea surface.

Further, provided at the lower part of the mooring buoy 02 are underbuoy hoses UH (two hoses are shown here) designed to communicate with said floating hose FH, which are connected via a plem PLM to a marine pipeline MH.

Although, in Figure 9, two underbuoy hoses are used, there may be one hose. It is also known that an underwater float moored to a sinker is laid along the path of the underbuoy hoses UH, and the hoses UH are firmly secured to the underwater float.

In a petrochemical complex or the like, when crude oil is fed from the crude oil tanker to the storage facilities onshore, one end of the floating hose FH shown in Figure 9 is connected to a feeding outlet (not shown in the figure) of the tanker 01 so that the crude oil or the like can be fed through the floating hose FH, the mooring buoy 02, the underbuoy hose UH, the plem PLM, and the marine pipeline MH to the storage facilities.

While such oil feeding is being carried out, the crude oil tanker 01 usually sways about the mooring buoy 02 with its head directed toward the buoy 02. To follow this swaying movement, the floating hose FH is connected to a joint on a turntable which can rotate horizontally around the center of the mooring buoy 02.

In addition, there are provided around the mooring buoy 02 buoy mooring cables (hereinafter referred to as "mooring chain cables") C consisting of a plural number of chains. The lower ends of these mooring chain cables C are secured to sinkers 07 which are embedded in the bottom of the sea in positions extending radially from the center of the mooring buoy 02. In this arrangement, it is not unusual for the length of the mooring chain cables C to be hundreds of meters depending on the scale of the mooring facilities.

Piles hammered into the sea bottom or steel anchors are sometimes used in place of the sinkers 07. The sinkers 07 described above, however, are rather wellaccepted because hammering work must be carried out on a large scale for driving the piles. In the case of steel anchors, the holding power changes to a great extent due to the soil condition etc. so that they are poor in reliability.

A plural number of sinkers can be secured to the lower ends of the mooring chain cables C, but as shown in figure 9, only one sinker may be secured thereto.

Various design conditions such as the number of the mooring chain cables C provided on the mooring buoy 02 and the number of sinkers 07 to be secured at the lower ends of said mooring chain cables C can be suitably determined taking the scale of the tanker to be moored, the nature of soil E on the sea bottom, and the like into consideration.

In the case that the tanker 01 moored via the mooring cable S to the mooring buoy 02 drifts apart from the mooring buoy 02 due to the current and wind, the mooring cable S is given a tractive force which is then transmitted to the sinkers 07 via the mooring buoy 02 and the mooring chain cables C. Since the mooring chain cables C draw a catenary curve by their self-weight in the sea, this tractive force is applied almost horizontally to the sinkers 07.

The sinkers 07 t-.hen generate the holding power corresponding to said tractive force to prevent the tanker 01 from drifting further via the mooring chain cable C, the mooring buoy 02, and the mooring cable S.

Thus, even if the tanker 01 is caused to drift by the current, wind, or the like while moored, it is still moored to the mooring buoy 02 so that oil feeding operation can be carried out without hindrance.

Figures 10(A), 10(B), and 11 are explanatory views showing a conventional method of embedding the sinker 07 into the soil E at the bottom of the sea.

In this method, as shown in Figure 10(A), a dredge boat 03 dredges first the soil under the sea. Dredging can be carried out without any prior operations if, for example, the soil E in the sea bed is sandy, but if the soil E is rocky, the dredging is done after the rock bed is crushed down.

Next, as shown in Figure 10(B), the sinker 07 is laid in the dredged recess G by a floating crane 04.

After this, as shown in Figure 11, the dredged recess G in which the sinker 07 is laid is filled in with gravel and sand through a tremie tube 09 of a tremie boat 05, by a gutter boat 06, or the like.

However, according to the conventional sinker embedding method described above, it is essential to carry out such dredging and filling-in operations. There is left the possibility of saluting the sea area, although such pollution may be limited to a local area.

Further, in the case where the soil on the sea bottom dug out by the dredging operations is not reused for filling in the dredged recess G, it is necessary for such sea bottom soil to be carried away for disposal at a remote reclamation site or elsewhere. In this case, there is still left the problem of securing the location for throwing away the sea bottom soil.

Still further, in the case that the soil dug out by the dredging operations is reused for filling in the dredged recess G, a site is necessary for such dug out soil to be kept temporarily. In the actual filling-in operations, there is also a possibility of making the sea area even dirtier.

In addition, such a conventional method including the dredging operations as described above, has a disadvantage in that a large amount of expense is be required firstly for the dredging operations, secondly for purchasing the gravel necessary for use in filling in the recess, and thirdly for throwing away the dug out soil at the reclamation site.

Moreover, the sinker embedding method according to Figures 10(A), 10(B), and 11 normally requires a working period extending several tens of days. Depending on the location of the sinker 07, this working period is subject to severe restrictions by reason of securing the safety of marine traffic.

Therefore, it is to be noted that a series of works from the dredging operations to the completion of the sinker embedding can not always be performed as scheduled within said working period because of the weather conditions or the like and thus, there has been a problem that people are forced to perform difficult operations under severe weather conditions.

It is therefore an object of the present invention to provide an improved method of embedding a sinker, employed to moor a structure on or in the water, into the soil of the sea bottom quickly and without dredging operations, and further to provide a sinker which has a strong holding power.

To accomplish the above objects, a comprehensive study has been energetically applied to the conventional sinker embedding method and as a result, the present inventors have found an improved method of embedding the sinker in a simple manner.

According to a first aspect of the present invention, there is provided a method of embedding a sinker employed to moor a structure on or in water which is characterised in that at least one third of the volume of the sinker is arranged to be embedding into the material of the water bottom by its self-weight.

Alternatively, the sinker is firstly embedded into the material of the water bottom by its self-weight and the weight of additional loads mounted on the sinker and, secondly, the additional loads are removed therefrom.

Further, in the method of embedding the sinker employed to moor the tanker mooring buoy, a sinker may firstly be laid at the water bottom and, secondly, at least one additional load can be mounted on the sinker to embed it in the material of the water bottom and, thirdly, this additional load is removed therefrom.

A sinker according to the present invention is characterized in that it is provided with at least one vertical plate adapted to generate a horizontal holding power and is disposed so as to extend downwards. It may also be provided at its upper or side part with a means to which additional loads can be provisionally secured.

Further, the sinker can be characterized in that it is provided with a vertical plate adapted to generate a holding force and is disposed so as to extend downwards and it is further provided on its upper or side part with a means to which additional loads can be provisionally secured, and is still further provided with a vertical surface adapted to generate said holding force and at its lower part with a protrusion to be embedded.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1(A) is an explanatory view showing a first embodiment of a sinker according to the present invention and Figure 1(B) is an explanatory view showing an example of an additional load to be mounted on said sinker; Figure 2(A) is an explanatory view showing a second embodiment of a sinker according to the present invention and Figure 2(B) is an explanatory view showing an example of the additional load to be mounted on said sinker; Figure 3(A) is an explanatory view showing a third embodiment of a sinker according to the present invention and Figure 3(B) is an explanatory view showing an example of the additional load to be mounted on said sinker;; Figure 4(A) is an explanatory view showing a fourth embodiment of a sinker according to the present invention and Figure 4(B) is an explanatory view showing an example of the additional load to be mounted on said sinker; Figure 5 is a view illustrating the sinkerembedding process using a sinker as shown in Figure 1(A); Figure 6 is an enlarged view in the vicinity of the sinker when the sinker is applied to a one point mooring buoy as shown in Figure 1(A); Figure 7 is a schematic explanatory view when the sinker shown in Figure 3(A) is applied to a floating type radio communication tower; Figure 8 is a view showing another embodiment in which the sinker is provided with a vibrator; Figure 9 is an explanatory view showing the outline of a mooring facility where a tanker is moored at one point thereof;; Figure 10 is an explanatory view showing, in conjunction with Figure 11, a conventional method of embedding a sinker in the soil of the sea bed; and Figure 11 is an explanatory view showing, in conjunction with Figure 10, the conventional method of embedding the sinker in the soil of sea bed.

Embodirtnts of the present invention will now be described below in detail. A sinker embedding method according to the present invention is applied firstly when a mooring buoy is installed for a tanker mooring; secondly when various kinds of structure disposed on or in the water (e.g. in the sea, river, lakes, or marshes), such as a floating type lighthouse, a radio communication tower, or an advertising tower, are laid on the water; and thirdly when an oil pipeline, a cable, or the like is laid in the water.

Further, a sinker according to the present invention is suitably applied in the execution of said embedding method. The sinker is usually made of a reinforced concrete for production and economic reasons, but it may be made of a metal such as steel or of a combined material such as the concrete-made sinker surrounded by metal plates (especially, on the surfaces forming the vertical portions of the sinkers).

In the case where additional loads are mounted on the sinker, said sinker is required to have enough strength against the external force acting perpendicularly downward from said additional loads.

said strength can be increased considerably if the sinker is made of metal or a concrete piece surrounded by metal plates.

Using the present invention, there are two sinker embedding methods; one is the method of embedding the sinker by its self-weight, and the other is the method of embedding the sinker by its self-weight and the weight of additional loads mounted on the sinker.

In the former method a sinker which has a shape for easy embedding in the soil beneath the water, for example, a sinker of which the whole or part is composed of a vertical plate and has a relatively heavy selfweight is preferably used. Further, a protrusion for assisting embedding a sinker in the soil is formed, for example, in the shape of a wedge. Still further, the sinker can also be embedded by dividing it into two or more components, for example, into upper and lower components.

Since such a sinker is designed to have a small bottom area so as to provide a high embedding pressure (weight per unit bottom area), or is provided with a sharp-pointed end, it is easily embedded into the soil at the bottom of the water by simply placing it on the soil - unless the nature of the soil is hard like a rock bed.

Needless to say, in the latter method, a sinker of the above shape can also be used. However, any shape of sinker, including a shape which is not easily embedded by its self-weight in the soil at the water bottom, is applicable in this method, so long as it can be embedded by adding the weight of the additional loads.

Whether the sinker sinks or not depends on the bearing power of the ground immediately under the sinker. That is to say, if a sinker, whose weight is above the permissible bearing capacity of the ground, is put on the soil at the water bottom, the sinker begins to sink. Naturally, the permissible bearing capacity of the ground is a numerical value related not only to the nature of the soil, but also to the depth of the embedded sinker and the shape of the sinker employed.

When sinkers of the same weight are used, the extent to which they are embedded varies depending on their shapes. The embedding stops and the sinkers reach a stationary state when the bearing capacity of the ground is balanced by the pressure of the surface immediately under the sinker.

According to some versions of the present method, the sinker can be embedded into the soil at the bottom of the water by mounting a plurality of additional loads on the sinker and, after this, the whole or part of the additional load is removed.

In the case where the whole of the additional loads mounted on the sinker are required to remain as they are without being removed, they may be originally designed to constitute an integral part of the sinker. Both the additional loads and the sinker thus constitute one sinker consisting of two or more components described above.

According to the present invention, although the sinker can be embedded in the soil of the sea bottom without requiring dredging operations it is needless to mention that dredging operations can also be additionally used if desired. In such a case, as compared with the case where the sinker is embedded in the soil of the sea bed only by dredging operations, it is only necessary to do the dredging operations in quite a small scale and, as a result, the possibility of pollution of the surrounding sea area can be reduced substantially.

If the nature of the soil of the sea bottom is relatively hard like a rock bed, it is also possible to crush the rock bed down in advance by a stone crusher boat or the like. Furthermore, embedding the sinker into the soil at the bottom of the water by its selfweight and the weight of the additional loads mounted thereon can be accelerated by the application of an external force, such as an impact driver or using vibration from above.

With this construction, the embedding of the sinker according to the present invention can be done regardless of the soil conditions at the bottom of the water.

In the embedding method of the sinker employed to moor a mooring buoy which is moored to one point of the tanker, the pipeline facilities (e.g. the mooring buoy, the floating hose, etc.), the mooring chain cables, and the like which are used in the conventional mooring facilities can also be used in the method of the present invention.

The present invention is applied not only to the case where a mooring buoy is newly provided or a new sinker is additionally connected to the existing mooring buoy, but also to the case where new sinkers are embedded in place of a part or the whole of the existing sinkers.

A sinker according to the present invention can be provided with a vertical plate which is adapted to generate horizontal holding power and be disposed downwardly, wherein said vertical plate may be a single piece or a plural number. The vertical plate may be, for example of a flat shape or be curved.

For example, the sinker may be formed by combining a plurality of plates so as to have a horizontal section of H, T, +,t, or &num; shape. These sinkers are usually produced by placing concrete in an H-shaped or T-shaped box which is reinforced by steel rods. Alternatively, each plate can be separately made and finally connected to each other as a unit, if the sinker is relatively light in weight.

In the case where sinker is used which is provided at its top or side with a provisional fitting means for the additional loads, there is usually provided a means for securing said provisional fitting.

For example, the upper part of the sinker is provided with a recessed portion or a protruded portion, while the lower part of the additional load is provided with a protruded portion or a recessed portion detachably engaged with said recessed or protruded portion of the sinker to achieve said provisional fitting. In another example, the sinker is provided at one or more of its portions (usually, at a plurality of portions) with a wire fitting ring, and the additional load is provided with communicating holes for passing guide wires therethrough, respectively, so that the additional load can be provisionally mounted on the sinker by pulling said guide wires upward.

Furthermore, a sinker may be embedded into the soil by using an additional load which has the same structure as the sinker. In this case, the additional load used here can be reused next time as a sinker when a sinker is to be newly embedded. This method ensures an improvement in the work efficiency; for example, a sinker which has been used as the additional load can be effectively moved to another sinker embedding point.

In addition, the sinker can be provided with a vibrator which can help the sinker to embed reliably into the soil at the bottom of the water. A waterproof and electric-powered type vibrator is commonly used as the vibrator and it is retrieved after embedding of the sinker.

As the present invention has been constructed as described above, it is effective in the following points: (1) Since dredging operations are no longer essential, there is no possibility of polluting the water area by the sinker embedding operations and also the cost needed for the dredging and other works related thereto (for example, filing of the dredged hole or the like) can be reduced or eliminated. In addition, it is to be noted that the embedding of the sinker can be completed within a very short period of time, making it possible to afford a margin for the corresponding work period.

Among a number of specific cases to be noted, it is not usual for a cost of more than several hundreds dollars to be saved by doing away with dredging and other works related thereto. In addition, the work period can be shortened almost to one half of the work period required for the conventional sinker embedding operations in which dredging is necessary.

(2) Since the sinker is provided with vertical plate portions, it is possible to increase the horizontal holding power. It is therefore possible to effectively moor structures on or in the water, such as a mooring buoy, a floating type lighthouse, or a radio communication tower, by such a strong holding power.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

Referring first to Figures 1(A) and 1(B), the sinker 1 shown in Figure 1(A) is composed of reinforced concrete and is designed to have a horizontal H-shaped section. Further, vertical plates 2 forming the Hshaped configuration are arranged to confront each other and are provided at the center of one outside surface thereof with a ring 3 for securing a mooring chain cable.

When the mooring chain cable C receives a tractive force f, the sinker 1 generates a drag (holding force) f against said tractive force f.

In the sinker 1 of Figure 1(A), the vertical plates 2 and 2 play the principal role in generating the horizontal holding force. Although most of the horizontal components (horizontal holding force) of f' are the drag formed by the side surface S at the side of the mooring chain cable C of the plates 2 and 2, the reaction force against the tractive force f in the horizontal direction which is caused at the bottom of the sinker 1 by its self-weight and the adhesion caused between the surface of the sinker 1 and the soil also contribute to said holding power f'.

Further, as shown in Figure 1(A), if the plates 2 and 2 are provided with a fluke-like protrusion N at the lower part of the side where the mooring chain cable C is secured, it is possible to greatly increase the strength of the holding power.

Since the sinker 1 is composed of vertical plates as a whole, it can easily sink into the soil at the water bottom by its self-weight or the weight of an additional load described below when laid on the bottom of the water.

Provided at the four corners of the upper side of the sinker 1 are wire fitting rings 4, which serve as an provisional fitting means for an additional load. These wire fitting rings are provided such as to be connected to each end of wires 43 which are passed through wire communicating holes 42 formed on an additional load 41 described below.

In addition, as shown in the same figure, there are provided slinging rings 5 which are used to move the sinker 1 to a desired place or to sink the latter to the bottom of the water. These rings may be formed at any suitable places (in this figure, they are formed at the center of the upper surface of each plate 2 and 2).

Figure 1(B) shows an additional load 41 which is adapted to be mounted on the sinker 1 of Fig. 1 and is provided with said wire communicating holes 42 which extend from the top four corners to the bottom surface of the sinker. As described above, the wires 43 pass through the respective communicating holes 42 to be secured to the wire fitting portion 4 of the sinker 1.

Also provided on the upper surface of the additional load 41 are slinging rings 44 in the same manner as the sinker 1.

Furthermore, the additional load 41 is provided with cutouts 45 and 46 which are located at positions corresponding to the wire fitting rings 4 and the slinging rings 5 of the sinker 1 to allow said additional load 41 to be mounted on the sinker 1.

The additional load is generally made of reinforced concrete in consideration of the production simplicity and economical efficiency, but it can also be made of other materials such as metals.

A specific design example for the sinker 1 and the additional load 41 is shown below in Table 1 for reference.

Table 1 Height of sinker (H) 3000 mm Length of sinker (L) 7000 mm Width of Sinker (W) 6000 mm Thickness of plate (T) 1500 mm Weight of sinker (M) 170 t Height of additional load (H') 3000 mm Weight of additional load (W') 260 t The weight, size, and shape of the sinker and additional load cannot be unconditionally determined.

They should depend on the scale of the mooring facilities, the nature of the soil at the bottom of the water, and the like. The sinker should be designed, for example, within the limits that it is not destroyed by the weight of the additional load.

Figures 2(A) and 2(B) are explanatory views showing a second embodiment of a sinker and an example of the additional load mountably disposed on said sinker, respectively, according to the present invention.

In Figure 2(A), the sinker 21 is provided at its bottom with a protrusion which is designed to have a wedge shape in the section perpendicular to the longitudinal axis so that the sinker can therefore be easily embedded into the soil at the bottom of the water by its self-weight or the weight of the additional load.

Further, the sinker 21 is provided at one longitudinal end with a vertical plate 22, in the vicinity of the center of which is a mooring chain cable securing ring 3. The plate 22 is also designed to generate most of the horizontal holding power in the same manner as described for the embodiment of Figure 1 (A). Furthermore, the vertical plate 22 in Figure 2 is provided at its lower part with the same fluke-like protrusion N as that of the sinker of Figure 1(A) and this protrusion contributes considerably to an increase of the horizontal holding power.

Still further, in the same figure, the sinker 21 has at its upper surface a recessed portion 23 which serves as a provisional fitting means for an additional load and, for this purpose, is loosely engageable by a protrusion 52 formed at the lower part of additional load 51. There are further provided slinging rings 5 on the upper part of the sinker 21 in the same manner as in the case of the sinker 1 of Figure 1(A).

Figure 2(B) shows an additional load 51 which is mountable on the sinker 21 of Figure 2(A). As described above, provided at the lower surface of said additional load 51 is a protrusion 52. This protrusion 52 is formed to loosely engage, in the horizontal direction, with the recessed portion formed on the upper surface of the sinker 21.

In addition, on the upper surface portion of the additional load 51, there are provided slinging rings 53 in the same manner as in the case of the additional load 41 of Figure 1(B) and also a recessed portion 54 which has the same shape as that of the recess 23 of the sinker 21 so that additional loads can be further mounted thereon, if necessary. In this case, the recessed portion 54 is not necessarily made if no further additional load is to be piled up.

Figures 3(A) and 3(B) show explanatory views respectively of a third embodiment of the sinker and an example of an additional load which is mountable disposed on said sinker, according to the present invention.

In Figure 3(A), the sinker 31 is formed in a cylindrical shape, in this case in the form of a flat, thick cylinder. This sinker 31 is provided at its external surface with a plurality of axially disposed vertical plates 33 (three such plates 33 are provided in this example), each having the shape of an inverse triangle. These vertical plates 33 generate considerable horizontal holding power together with both of the inside and outside surfaces of the cylinder 32.

Further, the sinker 31 according to the present embodiment is provided at a plurality of upper cylindrical side portions (in this case, three side portions between the plates) with rings 34 used in common for the connection of the mooring chain cables and for slinging.

Figure 3(B) shows a cylindrical additional load 61 for mounting on the sinker 31 and which is provided at its bottom surface with a protrusion 62 which is loosely engageable with the hollow central portion 35 of the sinker 31. This hollow portion 35 forms a provisional fitting means for the additional load. Further, the upper portion of the additional load is provided with a recessed portion 63 for mounting other additional loads, and, at its side, with slinging rings 64 which are the same as the rings 34 adapted for use in slinging.

Figures 4(A) and 4(B) are explanatory views respectively showing a fourth embodiment of the sinker and an example of an additional load which is mountable disposed on said sinker according to the present invention.

The sinker 71 as shown in Figure 4(A) is also made of reinforced concrete as shown in the first to third embodiments (see Figures 1(A), 2(A) and 3(A)). Further, it is formed to have the same H-shaped horizontal section as the first embodiment, and a mooring chain cable securing ring 3 is attached to the center of the outside surface of one of vertical plates 72 and 72 which are arranged to confront each other.

In this sinker 71, the vertical plates 72 serve principally to achieve the horizontal holding power in the same manner as shown in the case of the sinker 1 of Figure 1(A). In addition, the horizontal reaction caused at the bottom of the water by the self-weight of the sinker 71, the so-called adhesion produced between the surface of the sinker 71 and the soil, and the like, also contribute to the horizontal holding power.

Further, since the sinker 71 is, on the whole, formed of vertical plates in the same manner as the sinker 1 of Figure 1(A), it can be, when laid at the bottom of the water, easily embedded into the soil at the water bottom by its self-weight or with the aid of the weight of the additional load described hereinafter.

The sinker 71 is provided, at its upper four corners, with recessed portions 73 to allow the additional load 81 described hereinafter to be mounted on the sinker 71 without hindrance and is provided further with wire fitting eye plates 4 (adapted to serve as a provisional securing means for the additional load) in said recessed portions. These wire fitting eye plates 4 are used to move the sinker 71 to a desired place and to sink the latter to the bottom of the water.

An additional load 81 described below is provided with wire communicating holes 42 through which each end of the wires 43 extends to be connected to respective ones of said wire fitting eye plates 4.

Figure 4(B) shows the additional load 81 which is used for mounting on the sinker 71 of Figure 4(A). Thus the additional load 81 is provided with said wire communicating holes 42 extending downward from the upper four corners. As described above, the wires 43 pass through the communicating holes 42 to be connected to the wire fitting eye plates 4. Furthermore, provided on the upper surface of the additional load 81 are slinging rings 44.

The additional load 81 is further provided at its bottom with a cutout portion 82 which serves not to receive reaction from the soil at the bottom of the water when the sinker 71 is laid in the soil at the water bottom.

Figures 5(A) to 5(D) are views illustrating a method of embedding the sinker 1 shown in Figure 1(A).

In the case where the nature of the soil at the bottom of the water is soft and the sinker 1 is embedded into the soil at the water bottom only by its selfweight, it is not necessary to mount an additional load (in this case, the additional load 41 of Figure 1(B)) on the sinker 1.

On the other hand, if the nature of the soil at the water bottom is especially hard, it may be appropriate to carry out dredging operations in advance. Even if such dredging operations are required, it is to be noted that a large scale of operations as those conventionally done will not be required any more and, therefore, there is not such serious pollution of the water in the surrounding water area as experienced before.

The method of embedding the sinker in the case where the nature of the soil is not soft, but not so hard as to require dredging, will be described below in detail with reference to Figures 1(A) and 1(B).

As shown in Figure 5(A), the sinker 1 is firstly laid at a desired position by a floating crane (not shown). Since the sinker 1 is made of vertical plates, a portion thereof sinks into the soil E at the bottom of the water.

Secondly, a slinging wire is secured to the slinging ring 44 of the additional load 41 as shown in Figure 1(B) and the additional load 41 is gradually lowered by a floating crane to mount it on the sinker 1 as shown in Figure 5(B). In this mounting operation, the wire or wires 43 passing through the wire communicating holes 42 of the additional load 41 is/are connected to the wire fitting rings 4 and the additional load 41 is gradually sunken by extending said wire or wires until the load reaches and is mounted on the sinker 1. In the mounting process, the wire 43 and the wire communicating holes 42 also serve to guide the additional load 41 to a suitable position on the sinker 1. After such mounting operations, the wire 43 and the wire communicating holes 42 serve to provisionally secure the additional load 41 to the sinker 1 together with the wire fitting ring 4 of the sinker 1.

In this way, the sinker 1 is further embedded into the soil E of the water bottom by its self-weight and the weight of said additional load 41.

Figure 5(C) shows a situation where a further additional load 41 is mounted on the sinker 1. The position of the further additional load is the same as that of Figure 5(B) and the sinker 1 is further given the weight of the new additional load 41 to achieve further embedding in the soil E.

After this, the additional loads 41 are removed as shown in Figure 5(D).

With this removal of the additional loads 41, there is left a recess. It is possible to fill in the recess by sand and gravel. However, because such a recess is naturally filled in by water currents, even through left as is, it is not necessary to fill it in by sand or the like.

Figure 6 is an enlarged view in the vicinity of the sinker showing the embedded state of the sinker for mooring the mooring buoy in the mooring facility shown in Figure 9, using the above-described method.

In this figure, the sinker 1 of Figure 1(A) is used.

Although the mooring chain cable C connected to the sinker 1 is not shown here, it is connected to the mooring buoy 02 in the same manner as in Figure 9.

In the case where the tanker is caused to drift apart from the mooring buoy due to the current and wind and the mooring cable S of Figure 9 is subjected to a tractive force, this tractive force is transmitted via the mooring cable C to the sinker 1. Since the mooring cable C is connected to the mooring buoy and the sinker 1 by drawing a catenary curve, the sinker 1 receives the force in the horizontal direction.

In this case, a strong horizontal holding effect is generated especially by the two parallel plates 2 and 2 of the sinker defining the H-shaped configuration and the tanker is moored to the mooring buoy without hindrance.

Further, in the case where an underwater float is provided to secure the underbuoy hose pulled out of the mooring buoy, various sinkers of the type shown in Figure 1(A), Figure 2(A), Figure 3(A), and Figure 4(A) can be used to moor the underwater float.

Figure 7 is a view showing the case where a relatively small-sized floating type radio communication tower 08 is moored using the sinker 31 of Figure 3(A).

In the present embodiment, firstly the sinker 31 is embedded in the bottom of the sea in the same manner as Figure 4 and, secondly, the additional load 61 is mounted on the sinker 31, so that the sinker 31 is embedded into the soil E at the bottom of the water.

After this, the additional load 61 is removed therefrom and if necessary, the recessed area formed above the sinker 31 can be filled in by sand or the like to complete the sinker embedding operation.

After this, as shown in Figure 7, the radio communication tower 08 and the sinker 31 are connected via the mooring chain cable C. The radio commmunication tower 08 may be secured by a plurality of sinkers 31, but here is shown only one sinker.

In Figure 7, the mooring chain cable C is arranged to have such a length that the radio communication tower 08 can change its position while swaying on the surface of the water by the current and wind within a predetermined radius. With this, the mooring chain cable C draws a catenary curve between the radio communication tower 08 and the sinker 31 in the same manner as in Figure 6.

Accordingly, although the sinker 31 receives the force in every horizontal direction, the radio communication tower 08 is firmly secured to the sinker 31 since the sinker 31, as shown in Figure 3(A), can generate the horizontal holding force in every horizontal direction.

Figure 8 shows an embodiment in which the sinker is provided with an electric-powered vibrator for assisting in laying it in the soil at the water bottom.

The sinker 9 used in this figure is provided at its center with a hole for fitting the vibrator 10 and there are provided key-ways 91 (four key-ways provided in the figure) on the inside surface of the hole. Further, provided on the top of the sinker 9 are slinging rings 5.

On the side of the vibrator 10, there are provided key projections which engages with the key ways 91 of the sinker 9 and a slinging ring 101 is formed on the top of the vibrator 10. A power cable 102 extends from the vibrator 10.

The sinker 9 is usually equipped with the vibrator 10 and embedded at a desired site in the water by a floating crane. In this case, the sinker 9 sinks to a certain extent in the soil at the water bottom by its self-weight and the weight of the vibrator 10. After this, the sinking of the sinker 9 is accelerated by actuating the vibrator 10.

The vibrator 10 is lifted by the crane after the sinker 9 is fully embedded in the soil at the water bottom.

In this case, since it is not necessary to carry out a large scale operation, there is no pollution of the surrounding water area. Further, when this vibrator 10 is used, it is possible to reliably embed the sinker 9 at the water bottom, not only in the relatively soft ground such as sandy ground, but also in the hard ground such as a rock bed.

Claims (12)

1. A method of embedding a sinker for use in mooring a structure or apparatus on or in the water in which at least one third of the volume of the sinker is arranged to be embedded into the water bed by its selfweight.

2. A method of embedding a sinker as claimed in Claim 1, wherein said sinker and additional loads mounted thereon are embedded into the water bed by its self-weight and the weight of additional loads, and said additional loads are removed after embedding the sinker.

3. A method of embedding a sinker for use in mooring a mooring buoy attached to one end of a tanker, as claimed in Claim 1, wherein said sinker is firstly laid at the bottom of the water, secondly at least one additional load is mounted on said sinker to embed the sinker into the water bed, and thirdly said additional load is removed after embedding.

4. A sinker for use in mooring a structure on or in water having one or more vertical plates designed to generate a horizontal holding force and disposed so as to extend downwards in use.

5. A sinker for use in mooring a structure on or in water as claimed in Claim 4, wherein said sinker is provided at its upper or side portion with a temporary fitting means for one or more additional loads.

6. A sinker for use in mooring a structure on or in water as claimed in claim 4, wherein said sinker is provided with a vertical surface to generate the horizontal holding force, and, at its bottom, with a protrusion to be embedded.

7. A sinker as claimed in claim 4, having a plurality of said vertical plates which define an Hshaped configuration.

8. A sinker as claimed in claim 7, wherein the lower ends of two said vertical plates of the H are of triangularly shaped notch configuration.

9. A sinker as claimed in claim 4 of generally annular configuration, with a plurality of said vertical plates extending radially outwardly therefrom.

10. A sinker as claimed in claim 4, formed with a recess in an upper surface thereof which is adapted to receive a removable vibrator.

11. A method of embedding a sinker for use in mooring a structure on or in water, substantially as hereinbefore described, with reference to the accompanying drawings.

12. A sinker for use in mooring a structure or apparatus on or in water, substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 8 of the accompanying drawings.