KR20170032917A

KR20170032917A - Installation method of jacket structure for supporting offshore structure

Info

Publication number: KR20170032917A
Application number: KR1020150130224A
Authority: KR
Inventors: 한윤수
Original assignee: 현대중공업 주식회사
Priority date: 2015-09-15
Filing date: 2015-09-15
Publication date: 2017-03-24

Abstract

An installation method of a jacket structure for supporting an offshore structure is disclosed. According to the present invention, a bottom cross section of a pile inserted into a leg for supporting the leg is disposed on excavated rock formation of a lower seabed, then drilling fluid inflows through an inner portion of the pile. Thus, the drilling fluid flows to an excavated soil level through the bottom cross section of the pile located at the lower seabed, thereby preventing the drilling fluid from leaking in between the support plate in contact with the seabed and the seabed. Therefore, an economic effect can be obtained by preventing expensive drilling fluid from being discharged.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a jacket structure for supporting an offshore structure,

The present invention relates to a method for installing a jacket structure supporting an offshore structure.

If offshore structures such as offshore wind power installations or marine drilling rigs are installed in the sea, they may be corroded or contaminated by seawater. As a result, a lower portion of the support structure is supported on an undersea layer, a platform is provided on the support structure exposed above the sea surface, and an offshore structure is installed on the platform.

The support structure includes a jacket structure wherein the jacket structure includes a plurality of legs of a hollow body and a foot plate formed at a lower end of the legs.

The pedestal plate is in contact with the seabed surface, and the upper part of the legs is exposed above the sea surface to form a platform. The mutually adjacent legs are interconnected by a connecting bar.

A method of installing a conventional jacket structure will be described.

After the jacket structure is lowered, the bottom plate of the jacket structure is brought into contact with the bottom surface of the jacket structure, and a reverse circulation drill (RCD) is inserted from the upper side to the lower side of the legs of the jacket structure.

Generally, the submarine strata consist of the upper rock layer and the lower soil layer, so the rock layer is first excavated and then the soil layer is excavated.

While the rock layer is excavated by the RCD, seawater flows into the legs. The seawater introduced into the legs and the rock pieces crushed by the RCD are pumped and discharged to the outside through the upper side of the legs.

After the rock layer is excavated, the soil layer is excavated. However, in the case of the soil layer, when the RCD is excavated, the excavated portion may be collapsed or settled by the pressure or the like. In order to prevent this, circulation water (circulating muddy water) flows into the legs while the soil layer is excavated by the RCD.

The recirculating water has a high viscosity and a high specific gravity, forming a mud wall on the inner surface of the excavated soil layer, which prevents the site of the excavated soil layer from collapsing or sinking.

The soil layer is excavated, the RCD is removed from the leg, and a tubular file is inserted into the interior of the leg. Grout material such as cement is supplied through the inside of the pile to provide a grout material between the pile and the inner surface of the excavated soil layer, between the pile and the inner surface of the rock layer excavated, and between the pile and the legs And cured by injection.

In the conventional method of installing the jacket structure, the number of the circulation water flowing into the excavated soil layer through the inside of the leg may leak through the contact portion between the support plate and the sea floor. As a result, the number of high-priced circulation pulses is discarded, which is an uneconomical disadvantage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of installing a jacket structure for supporting an offshore structure capable of solving all the problems of the prior art as described above.

Another object of the present invention is to provide an economical method of installing a jacket structure for supporting an offshore structure by preventing an expensive circulation water (circulating muddy water) from leaking.

A method for installing a jacket structure for supporting an offshore structure according to the present invention is a method for installing a jacket structure having a plurality of legs of a hollow body and a foot plate formed on a lower end of the legs, A step of sinking the rock layer of the seabed layer to a predetermined depth by inserting an RCD (Reverse Circulation Drill) into the inside of the leg in a state where the leg is submerged in the sea and the supporting plate is connected to the sea floor; Inserting a file in a tubular form into the legs, placing the lower end surface of the file in an excavated rock layer below the seabed surface, and then supporting the file on the legs; Excavating the soil layer under the rock layer and the rock layer remaining by the RCD to a predetermined depth while drilling the soil layer while introducing circulating muddy water into the pile; Removing a portion for supporting the file on the leg, and inserting a lower end of the pile to the excavated soil layer; Grout material is injected through the inside of the file between the outer circumferential surface of the file and the inner surface of the excavated soil side, between the inner circumferential surface of the file and the inner surface of the excavated rock layer, and between the outer circumferential surface of the pile and the inner circumferential surface of the leg Step can be performed.

A method of installing a jacket structure for supporting an offshore structure according to an embodiment of the present invention is characterized in that a lower end face of a pile to be inserted and supported in the leg is placed on an excavated rock layer below the sea floor, (Circulating muddy water: Drilling Fluid). That is, the circulating water flows into the soil layer excavated through the bottom surface of the pile located on the lower side of the sea floor, so that the circulation water is prevented from leaking through the space between the bottom plate and the sea floor in contact with the sea floor. Therefore, it is possible to prevent discarding of the expensive circulating fluid, which can be economically effective.

1 is a schematic perspective view of a jacket structure for supporting an offshore structure.
FIGS. 2A to 2E are views showing a method of installing a jacket structure for supporting an offshore structure according to an embodiment of the present invention.

It should be noted that, in the specification of the present invention, the same reference numerals as in the drawings denote the same elements, but they are numbered as much as possible even if they are shown in different drawings.

Meanwhile, the meaning of the terms described in the present specification should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

The term "above" means not only when a configuration is formed directly on top of another configuration, but also when a third configuration is interposed between these configurations.

First, a jacket structure for supporting an offshore structure will be described with reference to Fig. 1 is a schematic perspective view of a jacket structure for supporting an offshore structure.

As shown, the jacket structure 100 may include a plurality of legs 110 of a hollow body, and the mutually adjacent legs 110 and legs 110 may be connected to each other by a connecting bar 115).

A support plate 130 may be formed on the lower end surface of each leg 110. The support plate 130 may be formed on the bottom surface (see FIG. 2A) when the leg 110 is submerged in the sea, . When the leg 110 is submerged in the sea, the upper portion of the leg 110 is exposed above the sea surface, and a platform for installing an offshore structure is formed on the upper portion of the leg 110 exposed above the sea surface.

Since the area of the support plate 130 in contact with the sea floor is relatively wide, the jacket structure 100 can be stably installed.

Next, a method of installing a jacket structure for supporting an offshore structure according to an embodiment of the present invention on a seabed layer will be described with reference to Figs. 1 to 2E. FIGS. 2A to 2E are views showing a method of installing a jacket structure for supporting an offshore structure according to an embodiment of the present invention.

As shown in FIG. 2A, the leg 110 of the jacket structure 100 is submerged in the sea so that the support plate 130 is brought into contact with the sea floor. At this time, it is natural that the upper end side of the leg 110 should be exposed above the sea level.

2B, when the support plate 130 is brought into contact with the sea floor, an RCD (Reverse Circulation Drill) 50 is inserted into the upper end of the leg 110, The rock layer 61 is excavated to a predetermined depth. More specifically, it is preferable to excavate the rock layer 61 so that the rock layer 61 is not completely excavated but the lower rock layer 61 is slightly left.

The seawater introduced into the legs 110 and the crushed rock fragments are pumped and discharged to the outside through the upper side of the legs 110, do.

In the case of the rock layer 61, even if it is excavated with the RCD 50, most of it is not collapsed or settled.

Thereafter, as shown in FIG. 2C, the tubular file 150 is inserted into the leg 110, and then the file 150 is supported on the leg 110 so that the file 150 does not descend . At this time, the lower end surface of the file 150 should be located in the excavated rock layer 61a below the sea floor, and when the lower end surface of the pile 150 is located in the excavated rock layer 61a , The file 150 is supported on the leg 110 so that the file 150 does not descend.

The file 150 and legs 110 should be spaced. That is, a gap should be formed between the outer circumferential surface of the file 150 and the outer circumferential surface of the leg 110, and the file 150 and the leg 110 are preferably concentric. A plurality of spacing members (not shown) may be formed on the outer circumferential surface of the pile 150 so that the pile 150 and the legs 110 may be concentrically installed.

The method of supporting the file 150 on the leg 110 includes welding the outer surface of the file 150 and the upper surface of the leg 110 or forming the stopper 152 on the outer surface of the file 150 , The stopper 152 may be hooked on the upper end surface of the leg 110. [

Thereafter, as shown in Fig. 2D, the rock layer 61 remaining in the RCD 50 and the soil layer 65 under the rock layer are excavated to a predetermined depth. In the case of the soil layer 65, the excavated soil layer 65a may collapse or sink. In order to prevent this, when the soil layer 65 is excavated, circulation water (circulating muddy water) having a high viscosity and specific gravity may be introduced into the pile 150.

The circulation water introduced through the inside of the file 150 is injected into the inner surface of the excavated soil layer 65a under the file 150 to form a mud wall or the like on the inner surface of the excavated soil layer 65a. As a result, the site of the excavated soil layer 65a can be prevented from collapsing or sinking.

In the method of installing the jacket structure for supporting an offshore structure according to the present embodiment, the lower end face of the pile 150 is positioned on the excavated rock layer 61a below the sea floor, and the circulation water is introduced through the inside of the pile 150 . That is, since the circulation water flows into the soil layer 65a excavated through the lower end surface of the pile 150 located below the seabed surface, the circulation water leaks through the contact portion between the seabed surface and the support plate 130 Is prevented.

Thereafter, as shown in Fig. 2E, the portion for supporting the file 150 to the leg 110 is removed, and then the lower end of the pile 150 is inserted to the excavated soil layer 65a. At this time, it is preferable that the bottom surface of the pile 150 does not touch the bottom surface of the excavated soil layer 65a. Grout material such as cement is supplied through the inside of the pile 150 to form a gap between the outer circumferential surface of the pile 150 and the inner circumferential surface of the excavated soil layer 65a and between the outer surface of the pile 150 and the excavated rock layer Grout material is injected between the inner circumferential surface of the leg portion 61a and between the outer circumferential surface of the pile 150 and the outer circumferential surface of the leg 110 to be cured. Then, the jacket structure 100 is installed on the seabed.

Thereafter, a platform is formed on the jacket structure 100 exposed above the sea level, and an offshore structure is installed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of. Therefore, the scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention.

100: jacket structure
110: Leg
130:
150: File

Claims

A method of installing a jacket structure having a plurality of legs of a hollow body and a foot plate formed at a lower end of each of the legs on a seabed layer,
Inserting an RCD (Reverse Circulation Drill) into the inside of the legs while the legs are submerged in the sea and connecting the footplate to the seabed surface;
Inserting a file in a tubular form into the legs, placing the lower end surface of the file in an excavated rock layer below the seabed surface, and then supporting the file on the legs;
Excavating the soil layer under the rock layer and the rock layer remaining by the RCD to a predetermined depth while drilling the soil layer while introducing circulating muddy water into the pile;
Removing a portion for supporting the file on the leg, and inserting a lower end of the pile to the excavated soil layer;
Grout material is injected through the inside of the file between the outer circumferential surface of the file and the inner surface of the excavated soil side, between the inner circumferential surface of the file and the inner surface of the excavated rock layer, and between the outer circumferential surface of the pile and the inner circumferential surface of the leg Wherein the step of attaching the jacket structure comprises the step of:

The method according to claim 1,
Wherein the file is welded to the leg or a stopper formed on an outer circumferential surface of the file is held by being hooked on an upper end surface of the leg.