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Title:
METHOD AND APPARATUS FOR CONSTRUCTING UNDERWATER STRUCTURAL WALLS
Document Type and Number:
WIPO Patent Application WO/2002/016700
Kind Code:
A1
Abstract:
A domed shaped base (2) consisting of beams and struts has a number of anchoring points (5) by means of which it can be lowered by a crane (10) from a vessel (8) onto the seabed. A refrigeration plant (12) onboard the vessel has its evaporation coil (18) mounted on the structure to follow a sinuous path to be generally uniformly distributed over the base (2). A feed pipe (14) feeds liquid refrigerant under pressure from the plant (12) to a distribution unit (16) mounted on the base. The distribution unit (2) distributes the refrigerant to the coil (18) which then cools the surrounding water to form the required structural wall in ice.

Inventors:
Cuthbert, Anthony (Upper Brook Cottage Sarn Newtown Powys SY16 4HH, GB)
Application Number:
PCT/GB2001/003838
Publication Date:
February 28, 2002
Filing Date:
August 24, 2001
Export Citation:
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Assignee:
Cuthbert, Anthony (Upper Brook Cottage Sarn Newtown Powys SY16 4HH, GB)
International Classes:
B63C7/14; B63C11/44; B63G8/40; E02B1/00; B63B43/16; (IPC1-7): E02B17/02; B63C7/14; B63C11/44; B63G8/40; E02D29/00; E21B7/136; F16L1/26
Domestic Patent References:
WO1985001262A1
WO1986006771A1
Foreign References:
EP0009986A1
GB361292A
US1495310A
DE417599C1925-08-14
US4753552A
US3909992A
Attorney, Agent or Firm:
SAUNDERS & DOLLEYMORE (9 Rickmansworth Road Watford Hertfordshire WD18 0JU, GB)
Download PDF:
Claims:
CLAIMS
1. A method of forming a structural wall within a body of water comprising the steps of forming the evaporator of a refrigeration plant into a sinuous profile having an envelope defining the shape of the desired wall, lowering the coil into the required position for the wall below the surface of the body of water, operating the refrigeration plant to cool the evaporator and cause the adjacent water to freeze to form said wall.
2. A method according to Claim 1, including the step of introducing at least one tubular member to intersect the sinuous profile of the evaporator before it is lowered into the water so that the tubular member is locked into the wall as it is being formed.
3. A method according to Claim 2, wherein the wall defines a chamber on the bed of the body of water and including the step of pumping water out of the chamber through the tubular member and replacing it with air.
4. A method according to Claim 3, including the step of operating a second tubular member as an airlock to enable ingress and egress of personnel to the chamber.
5. Apparatus for constructing an underwater wall comprising a support structure having at least one anchoring point with which it can be lowered into the water, a refrigeration plant including an evaporation coil, said evaporation coil being supported by said support structure and following a sinuous path and being generally uniformly distributed between two complementary spaced surfaces defining the ultimate shape of the wall required, and at least one fluid tight tubular member supported by the support structure to traverse the spaced surfaces.
6. Apparatus according to Claim 5, wherein said tubular member comprises an airlock to allow personnel to enter and exit the chamber bounded by said wall.
7. Apparatus according to Claim 5, including distribution means for creating a suspension of aggregate in the region of said evaporation coil when submerged, so that the aggregate is locked into the ice wall as it is formed.
8. Apparatus according to Claim 7, wherein the distribution means comprises means for scouring the adjacent bed of the body of water where the wall is located, for said aggregate and pumping it into position.
9. Apparatus according to Claim 8, including at least one mesh bridging said coil to hold said suspension in position.
10. Apparatus according to any one of Claims 5 to 9, wherein said refrigeration plant is mounted on said structure in a sealed case, and is electrically operated through an electrical cable extending to the surface of the body of water.
11. Apparatus for constructing a fluid tight conduit between two underwater vessels comprising an axially expandable tubular member, refrigeration means having evaporation coil means extending around each axial end of the tubular member whereby to form an ice wall securing each axial end of the tubular member to an adjacent wall of a respective vessel.
12. Apparatus according to Claim 11, wherein the tubular member has a radially extending flange at each of its opposite ends supporting said evaporation coil.
13. Apparatus for constructing a repair patch on the ruptured wall of an underwater vessel, the apparatus comprising an axially extending tubular member having a radially extending flange, a refrigeration plant having an evaporation coil supported by said flange whereby when the flange is manoeuvred to lie adjacent that portion of the wall surrounding the rupture and the refrigeration plant is operated, an ice wall will be produced locking the flange to said portion of the wall in a hermetically sealed manner.
14. A method of effecting a repair on a ruptured underwater tubular member comprising the steps of providing a base support around the ruptured area of the tubular member, manipulating the evaporation coil of a refrigeration plant to surround the ruptured area of the tubular member supported by said support, and operating the refrigeration plant to create an ice sleeve around the ruptured area hermetically sealed thereon.
Description:
METHOD AND APPARATUS FOR CONSTRUCTING UNDERWATER STRUCTURAL WALLS The present invention relates to methods and apparatus for constructing underwater structural walls.

Effecting constructions underwater is often both difficult and hazardous. It is difficult because one needs to create an environment in which construction personnel can work. It is hazardous because of the length of time needed to be spent at the site because of the great volume of materials and equipment that need to be transported to the site from a remote location. The longer one has to spend at the site, the more likely it is for the weather or sea conditions to change for the worse, and so cause problems and even possible abandonment of that stage of the project currently underway.

It is an object of the present invention to provide an improved method and apparatus for constructing underwater structural walls.

According to the present invention there is provided a method of forming a structural wall within a body of water comprising the steps of forming the evaporator of a refrigeration plant into a sinuous profile defining the shape of the desired wall, lowering the coil into the required position for the wall below the surface of the body of water, operating the refrigeration plant to cool the evaporator and cause the adjacent water to freeze to form said wall.

According to the present invention there is further provided apparatus for constructing an underwater wall comprising a support structure having at least one anchoring point with which it can be lowered into the water, a refrigeration plant including an evaporation coil, said evaporation coil being supported by said support structure and following a sinuous path and being generally uniformly distributed between two complementary spaced surfaces defining the ultimate shape of the wall required, and at

least one fluid tight tubular member supported by the support structure to traverse the spaced surfaces.

According to the present invention there is still further provided apparatus for constructing a fluid tight conduit between two underwater vessels comprising an axially expandable tubular member, a refrigeration means having an evaporation coil extending around each axial end of the tubular member whereby to form an ice wall securing each axial end of the tubular member to an adjacent wall of a respective vessel.

According to the present invention there is yet further provided apparatus for constructing a repair patch on the ruptured wall of an underwater vessel, the apparatus comprising an axially extending tubular member having a radially extending flange, a refrigeration plant having an evaporation coil supported by said flange whereby when the flange is manoeuvred to lie adjacent that portion of the wall surrounding the rupture and the refrigeration plant is operated, an ice wall will be produced locking the flange to said portion of the wall in a hermetically sealed manner.

According to the present invention there is again provided a method of effecting a repair on a ruptured underwater tubular member comprising the steps of providing a base support around the ruptured area of the tubular member, manipulating the evaporation coil of a refrigeration plant to surround the ruptured area of the tubular member supported by said base support, and operating the refrigeration plant to create an ice sleeve around the ruptured area hermetically sealed thereon.

Methods and apparatus for constructing underwater structural walls will now be described, by way of example, with reference to the accompany diagrammatic drawings, in which: Figure 1 is a front elevation of a domed shaped wall being created on the seabed from a ship; Figure 2 is fragmentary section taken through the base and evaporation tube to

illustrate the scouring unit; Figures 3 to 6 are vertical sections taken through the sea and seabed showing progressive stages in the construction process; Figure 7 is a partly cut away perspective view of a seabed structure containing an oil rig; Figure 8 is a front elevation of a coupling structure coupling two submarines; Figure 9 is a front elevation of apparatus repairing a rupture in a structural wall; and Figure 10 is a front elevation of apparatus for repairing a rupture in a cylindrical wall.

The apparatus shown in Figure 1 comprises a prefabricated support base 2 built up from an array of interconnected beams 4 generally in the shape of the dome shaped structure required to be created on the seabed. The base 2 has a three anchor points 5 which are coupled to a respective cable 6 so that the base 2 can be lowered onto the seabed from the deck of a boat 8 with the aid of a crane 10.

Also on the deck of the boat 8 is a refrigeration plant 12 which feeds liquefied gas under high pressure through a conduit 14 to a distribution unit 16 mounted on the base 2.

The base 2 supports the evaporator of the refrigeration plant 12 which evaporator is in the form of a tube 18 that follows a sinuous or tortuous path so that it is generally uniformly distributed between the inner and outer surfaces of the extent of the wall that is required to create.

In operation, liquefied gas from the plant 12 reaching the distribution unit 16 is allowed to expand into the tube 18 where it draws in latent heat of evaporation and cools the surrounding water. The refrigerant is circulated through the tube to return to the distribution unit 16 from where it is released into the sea to bubble to the surface. As the water surrounding the tube 10 cools, it forms an ice wall in which the tube 18 is embedded.

Once the ice wall has been created, it will generally melt very slowly and so the energy required to keep the ice from melting is very considerably less than that needed to create it.

If the chamber defined between the ice wall and the seabed has the water pumped out and replaced by air, there is formed an environment in which construction personnel can work. In this environment a reinforced concrete structure can be created to replace the ice wall which can then be allowed to melt and removed. Melting can be expedited by feeding steam through the evaporation tube 18. The tube 18 may be integral with the beam structure of the base 2 so that both become embedded in, and reinforce, the ice wall.

Instead, the tube 18 may lie spaced from the beam structure of the base but secured to the base 2 with the aid of a plurality of releasable couplings (not shown) so that once the ice wall has formed, the base 2 can be decoupled and removed for reuse with another tube 18.

The distribution unit 16 will also need to be decoupled from the base and can be locked to the tube 18 by being at least partially embedded in the resulting ice wall that is formed.

The refrigeration plant 12 is shown as being mounted on the deck of the boat and so can be powered by various power sources such as a diesel or petrol engine or by electricity.

When the refrigeration plant 12 is driven by an electric motor, the motor may be encapsulated in a sealed casing and mounted alongside the distribution unit 16 on the base 2. All that is then needed is an electrical generator on the boat 8 to supply electrical current to the motor via an electrical cable extending between the boat 8 and the base 2. An appropriate condenser would need to be provided extending away from the plant 12 to allow the recycled gases from the tube 18 to give off heat away from the ice wall being found and so condense before being fed back to the compressor of the refrigeration plant for recycling.

As will be described in more detail hereinafter, one or more sealed hollow tubes are mounted on the base 2 so as to traverse the ice wall when it is being formed. The smaller diameter tubes can be used to convey fluids to and form the chamber while the larger diameter tubes can be adapted to form airlocks through which construction personnel can enter or leave the chamber.

In order to strengthen the structure of the ice wall, it needs to be reinforced with aggregate which can be collected from the adjacent seabed or supplied by the surface vessel.

Figure 2 shows an arrangement in which a suspension of aggregate is provided in the region in which the water is to be frozen to form the wall. Suspended between adjacent turns of the coil 14 are a series of spaced nets 20,22 and 24 of progressively diminishing size mesh with the largest mesh uppermost. A spray head 26 mounted on the base 2 collects aggregate from the sea bed and sprays it onto the nets. The finer aggregate passes through the courser mesh nets but is retained by the fine mesh nets, while the courser mesh nets retains the courser aggregate. In this way, a series of suspended layers of aggregate become loaded in the ice wall when it is formed. A scouring unit 26, including an impeller 30 stirs up aggregate from the sea bed and pumps it through a tube 32 to the spray head 26.

Either a series of fixed spray heads 26 and scouring units can be provided distributed over the base 2 or a single movable spray head 26 and scouring unit 28 can be provided but mounted to be progressively driven around the base 2 to ensure a generally uniform distribution of aggregate throughout the wall.

Figures 3 to 6 illustrate another method of creating a reinforced structure on the seabed. As can be seen from Figure 3, a diving bell 40 is lowered from a vessel 42 and construction personnel within the bell 42 drive a series of piles 44 into the seabed.

A lattice of support elements 46 are formed on the piles 44 (see Figure 4) and a sinuous evaporator tube (not shown) is suspended there from.

A refrigeration plant (not shown) is used to supply liquefied gas under pressure to the evaporation tube until an ice wall 50 (see Figure 5) has been built up. The chamber 52 within the ice wall then has the water then pumped out and is filled with air. An airlock 54 and feed tube 56 are formed in the ice wall and construction personnel are admitted to built

shuttering within the chamber evenly spaced from the ice wall. Concrete is then pumped into the space between the shuttering and the ice wall through the feed tube 56 to form a permanent structure.

It will be appreciated that if the evaporator tube is oriented so that it lies close to, or makes contact with, the sea bed then the adjacent portion of the sea bed will be frozen and locked to the ice wall to provide a liquid tight seal against ingress of the sea into the chamber and to anchor the structure to the sea bed so as to resist floatation.

The embodiment shown in Figure 7 shows an ice dome on the sea bed used to house an oil drilling rig.

As can be seen, the domed ice wall 60 is formed by an embedded expansion tube array 62 to house an oil drilling rig 64. The chamber 66 formed by the ice wall may contain one or more floors 68,70 to provide different operating levels linked by steps 72 and/or elevators (not shown). Access to the chamber 66 can be gained through an air lock 74. Oil extracted from the rig 64 can be fed through a tube 76 traversing the well 60 to a sea container vessel (not shown) overhead. Instead, the oil can be pumped along a duct lying on the seabed to the nearest shoreline. Another tube 78 also traversing the wall 60 can be linked to the sea vessel to provide a conduit for air, electricity and other needs within the chamber 26.

Where a larger sea bed environment is required, another domed ice wall 60A can be built alongside the existing one and the two ice walls linked by a tunnel 80.

Underwater structures can also be built to link an incapacitated submarine vessel 82 with a rescue submarine vessel 84 (see Figure 8). As shown, an axially flexible bellows type linking tube 86 is provided with a respective radially extending flange 88 and 90 at opposite axial ends. These flanges 88 and 90 support a respective evaporation tube 92 and 94 of a refrigeration plant (not shown) housed in the rescue vessel 84.

The two tubes 92 and 94 may be different sections of the same tube or may be separate tubes of separate refrigeration plants. In operation, the tube 86 is supported on the rescue vessel 84 in a position in which the flange 88 surrounds a rescue hatch (not shown).

The rescue vessel 84 then positions itself in the vicinity of the incapacitated vessel 82 to bring the flange 90 to surround a rescue hatch on the incapacitated vessel 82. The refrigeration plant is then activated to cause an ice wall to form between each flange 88 and 90 and a respective vessel 84 and 82. As the ice contacts the exterior surface of each vessel, it adheres to the vessel to form an airtight seal. The sea water in the chamber defined by the tube 86 can now be pumped out and filled with air to allow both escape hatches to be opened and so provide an access path between vessels. The particular advantage of this arrangement is that it does not require the two vessels to have similar or interlocking hatch structures and so compatibility of escape hatches is generally not an issue.

When a submarine has suffered significant damage to the extent that one of its walls has been ruptured, the apparatus shown in Figure 9 can be used to effect a temporary repair.

As shown, a cylindrical airlock chamber 96 is provided with a radially extending flange 98.

The chamber 96 has a series of anchor points 100 by means of which it can be supported by a cable 102 from a crane (not shown) on the deck of a vessel. The flange 98 supports an expansion tube 104 of a refrigeration plant (not shown) on board the same vessel and feed and exhaust pipes 106 and 108 link the tube 104 to the refrigeration plant on the vessel. In operation, the airlock chamber 96 is lowered onto the damaged vessels so that the flange 98 surrounds the rupture. The refrigeration plant is then operated to create an ice wall which engages the wall of the vessel and envelopes the flange 98 so that the flange becomes sealed to the vessel in an airtight manner.

Water which has entered the vessel through the rupture can be extracted through the airlock chamber with the aid of compressed air supplied by the surface support vessel and once a breathing environment has been reached, rescue personnel can gain access to the damaged vessel in the usual way through the airlock chamber.

In some applications, the structured apparatus can be used to effect repair of damaged conduit located below the surface of the sea. As shown in Figure 10, a cylindrical leg 110 of an oil rig which extends from the seabed to above the surface of the sea, has been ruptured. Repair is effected with the use of repair kit but consisting of an axially split cylindrical support which can be clamped around the ruptured area of the leg 110 and a ductile expansion coil is wound around the base 112 and anchored thereto. The coil is then connected to a refrigeration plant on the oil rig to form an ice sleeve around the leg 110.

The ice sleeve becomes hermetically sealed to the leg to complete the repair. Refrigeration has to be maintained at a much lower level while the leg remains in commission.

As will be appreciated, the methods and apparatus for constructing underwater structural walls can be used in many different situations and do not always require the presence of personnel at the point at which the wall is being constructed. This is particularly useful where hazardous environments are involved. The wall can be built to any shape and few compatibility problems arise since ice will cleave to almost any surface to define a hermetic seal with that surface. Generally, there are no structural prerequisites such as one would find in other methods of construction.

The method and apparatus described particularly lend themselves to situations where sunken vessels are to be raised. The ice structures are formed to seal cargo hatches, and ruptures and can also be usefully employed to provide attachment points to enable lifting gear to be attached to the vessel. Such attachment points can readily be provided by freezing anchor loops or hooks into the ice structure at selected sites.