WO2024014729A1

WO2024014729A1 - Underwater concrete structure for preventing subsidence at seabed soft ground, and construction method therefor

Info

Publication number: WO2024014729A1
Application number: PCT/KR2023/008492
Authority: WO
Inventors: 김상기
Original assignee: (주)유주
Priority date: 2022-07-14
Filing date: 2023-06-20
Publication date: 2024-01-18
Also published as: KR102477117B1

Abstract

The present invention has concrete columns formed along a vertical penetration hole of a main concrete structure, seabed soft ground and seabed rock, wherein the concrete column formed on the seabed soft ground supports the lower end of the main concrete structure while having a diameter larger than the diameter of the concrete column formed in the vertical penetration hole, and thus can prevent the main concrete structure from subsiding on the seabed soft ground.

Description

Underwater concrete structures and construction methods to prevent subsidence in soft undersea ground

The present invention relates to an underwater concrete structure capable of preventing subsidence in soft ground on the sea floor and a construction method thereof. In particular, the underwater concrete structure is capable of preventing subsidence in soft ground on the sea floor by supporting the bottom of the main concrete structure with a concrete column. It relates to structures and their construction methods.

Underwater structures are installed underwater for various purposes, such as berthing facilities for ports, sofa structures installed on the coast, and breakwaters. In the above and below, an underwater structure refers to a structure installed with the lower part of the underwater structure submerged in water, and the upper part of the underwater structure may protrude above the water surface or be located below the water surface.

A widely known construction technique in the construction of underwater structures is the large caisson method. The large caisson construction method has the advantage of being able to withstand large waves, but because a very large caisson with a very large structure must be manufactured on land, transported to the installation point, and then installed underwater, transportation and construction costs are very high, and there are various constraints. There are a lot of these.

In order to solve the problems of such large caisson construction methods, there is a known method of forming an underwater structure by stacking small concrete blocks in several stages depending on the water depth.

The present inventor proposed Republic of Korea Patent Registration No. 10-1355805, “Construction method of underwater concrete block structure and underwater concrete block structure” (registered on January 15, 2014), which consists of an upper concrete block and a lower concrete block by concrete columns. By ensuring this structural integrity, we proposed a technology that allows underwater concrete block structures to have sufficient structural stability even in waves caused by large typhoons.

Meanwhile, soft ground is widely distributed on the seafloor, and if an underwater concrete structure is installed directly on soft ground, subsidence of the underwater concrete structure occurs, threatening its structural stability.

Therefore, the construction of an underwater concrete structure installed on soft ground must be preceded by creating a foundation suitable for the installation of the underwater concrete structure through various soft ground improvement methods (replacement riprap method, deep mixing treatment method, etc.).

However, in cases where the water depth is very deep or the soft ground layer is very thick, it is difficult to create an appropriate foundation ground.

If the depth of water is very deep or the stratum of the soft ground is very thick, it is very difficult for soft ground improvement equipment located on the water surface to pass through the soft ground and reach the bedrock, and there is also a problem that it is difficult to accurately inject materials for improving the soft ground. .

For example, in the case of the southern coast of Korea, the water depth is 30 to 50 m, and the thickness of the soft ground is also about 30 to 50 m, so in this case, soft ground improvement equipment must have a length of 60 to 100 m or more to reach the bedrock.

The present invention was developed to solve the problems of the prior art as described above, and prevents the main concrete structure from sinking in the soft ground on the sea floor by having the concrete column for soft ground, which is a part of the concrete column, support the bottom of the main concrete structure. The purpose is to provide an underwater concrete structure and its construction method.

In order to solve the above problem, the present invention includes a main concrete structure installation step of installing a main concrete structure having a plurality of vertical through holes extending in the vertical direction on the upper part of the soft submarine ground formed on the upper part of the submarine rock; After the main concrete structure installation step, a ground perforation forming step of forming a ground perforation in the submarine soft ground and seafloor rock by drilling the soft seabed ground and seabed rock located at the lower part of the vertical penetration hole through the vertical penetration hole. ; After the ground perforation forming step, a concrete column forming portion including a concrete reinforcing member extending in the vertical direction, a waterproofing membrane surrounding the lower and side portions of the concrete reinforcing member, and uncured concrete injected into the waterproofing membrane. A concrete pillar is formed along the vertical penetration hole and the ground drilling part by inserting the vertical penetration hole and the ground boring part, and the concrete pillar includes a concrete pillar portion for the penetration hole located in the vertical penetration hole and the sea bottom. It is divided into a concrete pillar for soft ground located in soft ground and a concrete pillar for bedrock located in the seabed rock, and the concrete pillar for soft ground has a diameter larger than the diameter of the concrete pillar for through-hole and the main concrete structure. Step of forming a concrete pillar formed to support the lower end of; It is characterized by including.

In the above, it is preferable that a cover for protecting the waterproofing membrane in the form of a tube or basket is provided on the outside of the waterproofing membrane, the upper end of which is located in the middle of the vertical direction of the waterproofing membrane.

In the above, the waterproof membrane protective cover is made of a net, and the waterproof membrane protective cover is preferably coupled to the outside of the waterproof membrane through a skirt member.

In the above: In the step of forming the ground drilling portion, a protection pipe extending in the vertical direction is inserted through the vertical penetration hole, and the inserted protection pipe is positioned across the vertical penetration hole and the ground drilling portion. and ; In the concrete pillar forming step, the waterproof membrane is inserted into the vertical penetration hole and the ground perforation along the inside of the protection pipe, and the protection pipe is removed after the waterproof membrane is inserted; This is desirable.

In another idea of the present invention, a main concrete structure is installed on the upper part of the soft undersea ground formed on the upper part of the seabed rock and is installed to be spaced upward from the seabed rock, and has a plurality of vertical through holes extending in the vertical direction; A plurality of concrete pillars formed continuously along the vertical penetration hole, soft ground on the sea floor located below the vertical penetration hole, and the sea floor rock; It includes, wherein the concrete pillar is divided into a concrete pillar part for a penetration hole located in the vertical penetration hole, a concrete pillar part for soft ground located in the soft ground on the sea floor, and a concrete pillar part for rock located in the seabed rock, The concrete column for soft ground has a larger diameter than the diameter of the concrete column for the through-hole and supports the lower end of the main concrete structure to prevent settlement of the main concrete structure.

In the above, the concrete column includes a concrete reinforcing member formed in the vertical direction and disposed across the vertical penetration hole, the soft ground on the sea floor, and the rock on the sea floor, and a waterproof membrane surrounding a lower portion and a side portion of the concrete reinforcing member, and Concrete poured and cured inside the waterproof membrane, and a waterproof membrane protective cover in the form of a tube or basket whose upper end is located in the middle of the vertical direction of the waterproof membrane on the outside of the waterproof membrane and protects the waterproof membrane located on the soft ground of the sea floor. It is desirable to do so.

As described above, the present invention can prevent the main concrete structure from sinking in the soft ground on the sea floor by allowing the concrete pillar for soft ground, which is a part of the concrete pillar, to support the lower end of the main concrete structure.

In addition, in the present invention, compared to the conventional soft ground improvement method, the work of forming concrete columns for soft ground is very simple, so the overall construction cost can be reduced.

Figure 1 is a perspective view of a concrete block used in the construction method of an underwater concrete structure to prevent subsidence in soft ground on the sea floor according to the first embodiment of the present invention;

Figure 2 is a plan conceptual diagram of a main concrete structure formed on the upper part of the seabed by installing the concrete blocks of Figure 1;

Figure 3 is a cross-sectional conceptual diagram of Figure 2;

Figure 4 is a view of a state in which a ground perforation part is formed after the main concrete structure of Figure 3 is formed;

Figures 5 to 8 are diagrams sequentially showing the process of forming a concrete column after forming the ground drilling part of Figure 4;

Figure 9 is a front view of the waterproof membrane combined with the waterproof membrane protective cover of Figure 5;

Figure 10 is a cross-sectional view of Figure 9 in a separated state;

Figure 11 is a perspective view of a concrete block used in the construction method of an underwater concrete structure to prevent subsidence in soft ground on the sea floor according to the second embodiment of the present invention;

Figure 12 is a cross-sectional view of the main concrete structure formed by the concrete block of Figure 11;

Figure 13 is a cross-sectional view of a state in which a ground perforation part is formed and a concrete pillar is formed after Figure 12;

Figure 14 is a cross-sectional view of the concrete placed after Figure 13.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part "includes" a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

First, a method of constructing an underwater concrete structure to prevent subsidence in soft ground under the sea according to the first embodiment of the present invention will be described.

Figure 1 is a perspective view of a concrete block used in the construction method of an underwater concrete structure to prevent subsidence in the soft ground of the sea floor according to the first embodiment of the present invention, and Figure 2 is a view of the concrete block of the sea floor by installing the concrete block of Figure 1. It is a plan conceptual diagram with the main concrete structure formed on the upper part, FIG. 3 is a cross-sectional conceptual diagram of FIG. 2, FIG. 4 is a diagram of a state in which a ground perforation part is formed after the main concrete structure of FIG. 3 is formed, and FIGS. 5 to FIG. 8 is a diagram sequentially showing the process of forming a concrete column after forming the ground perforation of Figure 4, Figure 9 is a front view of the waterproofing membrane combined with the waterproofing membrane protective cover of Figure 5, and Figure 10 is an separated cross-sectional view of Figure 9. am.

(1) Concrete block manufacturing steps

A concrete block 20 as shown in Figure 1 is manufactured.

The concrete block 20 may be formed in various shapes, but it is preferable that at least two through holes 21 for the block extending in the vertical direction are formed.

The block through hole 21 extends in the vertical direction with a first diameter.

Depending on the embodiment, a space for filling, a space for other purposes, or a shape for another purpose may be formed in the concrete block 20.

(2) Main concrete structure formation stage

Figure 2 is a plan view of the main concrete structure 100, and Figure 3 is a cross-sectional view of the main concrete structure 100.

A plurality of concrete blocks 20 manufactured in the concrete block manufacturing stage are installed on the upper part of the submarine soft ground 12 formed on the upper part of the seabed rock 11 as shown in FIG. 3, and a plurality of concrete blocks 20 are installed as shown in FIG. 2. ) are installed continuously in the horizontal direction to form the main concrete structure (100).

That is, in this embodiment, the main concrete structure 100 consists of a plurality of concrete blocks 20 arranged sequentially in the horizontal direction.

Depending on the embodiment, the main concrete structure 100 may be made of one concrete block 20.

As shown in FIG. 3, the main concrete structure 100 is installed spaced upward from the seabed rock 11.

The block penetration hole 21 of the concrete block 20 forming the main concrete structure 100 is a vertical penetration hole 101 extending in the vertical direction with the lower end blocked by the seabed soft ground 12 and the upper end open. ) to form.

That is, in this embodiment, the concrete blocks are manufactured in large sizes and installed in only one stage in the vertical direction, and the penetration holes 21 for each block of each concrete block 20 penetrate the main concrete structure 100 in the vertical direction. It functions as a sphere (101).

Accordingly, the vertical through hole 101 extends in the vertical direction with a first diameter.

(3) Ground perforation formation stage

After the main concrete structure formation step, the soft seabed ground 12 and the seabed rock 11 located at the lower part of the vertical penetration hole 101 are drilled through the vertical penetration hole 101 as shown in FIG. A ground drilling portion 102, which is a space continuous with the vertical penetration hole 101, is formed in the ground 12 and the seabed rock 11.

In this embodiment, when forming the ground perforation part 102 by drilling the soft seabed ground 12 and the seabed bedrock 11 located at the lower part of the vertical penetration hole 101, a protection pipe (a protective pipe in the form of extending in the vertical direction) 30) is inserted into the soft seabed ground 12 and the seabed rock 11 in the vertical direction through the vertical through hole 101.

The protection tube 30 inserted in this way is positioned across the vertical through hole 101 and the ground boring part 102, and the ground boring part 102 is formed inside the protection tube 30.

At this time, the protection pipe 30 prevents the surrounding soft seabed ground 12 from collapsing into the ground boring part 102 or various foreign substances from flowing into the ground boring part 102 during or after drilling.

In addition, the protective tube 30 serves to protect the waterproof membrane 112, which will be described later, when the waterproof membrane 112 is inserted into the protective tube 30.

(4) Concrete column formation stage

After the ground perforation forming step, the concrete pillar 110 is formed along the vertical through hole 101 and the ground perforation 102.

The concrete pillar formation step of this embodiment is carried out step by step as shown in FIGS. 5 to 8.

A concrete reinforcing member 111 extending in the vertical direction, a waterproofing membrane 112 surrounding the lower and side parts of the concrete reinforcing member 111, and uncured concrete 113 injected into the waterproofing membrane 112, By inserting the concrete pillar formation including the waterproof membrane protective cover 114 coupled to the outside of the waterproof membrane 112 into the vertical through hole 101 and the ground drilling portion 102, the vertical through hole 101 and A concrete pillar 110 is formed along the ground perforation part 102.

First, as shown in FIGS. 5 and 6, a concrete reinforcing member 111 such as a reinforcing bar assembly extending in the vertical direction is inserted into the vertical penetration hole 101 and the ground boring portion 102.

In this embodiment, since the protection pipe 30 is already located in the vertical penetration hole 101 and the ground boring part 102, the concrete reinforcement member 111 is inserted into the protection pipe 30.

At this time, the lower and side portions of the concrete reinforcing member 111 are wrapped with a waterproof membrane 112 and inserted into the vertical penetration hole 101 and the ground boring portion 102.

Meanwhile, on the outside of the waterproof membrane 112, a cover 114 for protecting the waterproof membrane is provided via the skirt member 115.

The waterproof membrane protective cover 114 is in the form of a tube or basket whose upper end is located in the middle of the vertical direction of the waterproof membrane 112 (this embodiment is a basket shape), and has a waterproof membrane (in the present embodiment) inside the waterproof membrane protective cover 114. 112), the lower part (specifically, the area to be located on the soft ground on the sea floor) is located.

The waterproof membrane protective cover 114 may be a net made of wire or carbon fiber formed in the form of a tube or basket.

Here, the tube shape means a cylindrical shape with the top and bottom open, and the basket shape means a cylindrical shape with the top open and the bottom closed.

The skirt member 115 is provided between the waterproof membrane protective cover 114 and the waterproof membrane 112.

The upper end of the skirt member 115 is joined to the middle of the outer vertical direction of the waterproof membrane 112, and the upper end of the waterproof membrane protective cover 114 is joined to the lower end of the skirt member 115 by sewing or the like.

After the concrete reinforcing member 111 surrounded by the waterproof membrane 112 is inserted into the protection pipe 30, concrete 113 is poured inside the waterproof membrane 112 as shown in FIGS. 7 and 8 to form concrete. Forms a pillar 110.

FIG. 7 is a diagram showing a state in which the protection pipe 30 is slightly raised while a portion of uncured concrete 113 (fresh concrete) is poured inside the waterproof membrane 112.

That is, in FIG. 7, the lower end of the protection pipe 30 is raised so that it is just outside the ground drilling part 102, and the inside of the waterproof membrane 112 is in the ground drilling part 102 area. The necessary unhardened concrete 113 has been poured.

At this time, the diameter of the waterproof membrane 112 located on the soft ground 12 on the sea floor is expanded by the pressure of the uncured concrete 113.

In Figure 7, the extent to which the diameter of the waterproof membrane 112 located on the soft ground 12 on the sea floor is expanded is greatly exaggerated, and in reality, as the unhardened concrete 113 is gradually injected into the waterproof membrane 112, the diameter of the waterproof membrane 112 is expanded. The pressure of the uncured concrete 113 located on the soft ground 12 on the sea floor gradually increases, and as the pressure gradually increases, the diameter of the waterproof membrane 112 located on the soft ground 12 on the sea floor gradually expands, This expansion of the diameter of the waterproofing membrane 112 continues until the uncured concrete 113 is fully injected into the waterproofing membrane 112, as shown in FIG. 8.

In consideration of such diameter expansion, the waterproof membrane 112 must have a structure that allows diameter expansion structurally (e.g., a structure that unfolds from a folded state) or a material (e.g., stretchable elastic material) that allows diameter expansion. .

In addition, the waterproof membrane protective cover 114 prevents the waterproof membrane 112 from being damaged due to excessive diameter expansion by allowing the waterproof membrane 112 to expand in diameter only within a certain limit.

In addition, the waterproof membrane protective cover 114 is made of mesh, and prevents air or water from remaining between the waterproof membrane protective cover 114 and the waterproof membrane 112.

In this way, the uncured concrete 113 is gradually poured into the inside of the waterproof membrane 112 and the protection pipe 30 is gradually raised, and finally the protection pipe 30 is completely removed as shown in FIG. 8. Meanwhile, the work of pouring uncured concrete 113 throughout the vertical penetration hole 101 and the ground boring part 102 is completed.

That is, the protection pipe 30 is removed before the poured unhardened concrete 113 hardens.

In this way, when the uncured concrete 113 is poured into the interior of the waterproofing membrane 112, the waterproofing membrane 112 is connected to the seabed rock 11 and the concrete block 20 (or the main concrete structure) by the pressure of the uncured concrete 113. (100)), while its diameter is greatly expanded in the soft undersea ground (12), and then becomes a concrete pillar (110) through a curing process.

In this way, the concrete pillar 110 is formed in the main concrete structure 100, and the underwater concrete structure 200 is completed.

That is, the concrete pillar 110 includes a penetration hole concrete pillar portion 110a located in the vertical penetration hole 101 and extending vertically with a first diameter, and a penetration hole concrete pillar portion 110a located in the soft ground 12 on the sea floor and extending in a second diameter. It includes a concrete pillar part 110b for soft ground extending in the vertical direction, and a concrete pillar part 110c for bedrock located in the seafloor rock 11 and extending in the vertical direction with a third diameter.

In addition, since the concrete pillar part 110b for soft ground has a larger diameter than the diameter of the concrete pillar part 110a for a through hole, the concrete pillar part 110b for soft ground supports the lower end of the main concrete structure 100. Subsidence of the main concrete structure 100 can be prevented.

That is, the present invention can prevent the main concrete structure 100 from sinking without carrying out separate soft ground improvement work on the seabed soft ground 12.

Hereinafter, a second embodiment according to the present invention will be described.

Figure 11 is a perspective view of a concrete block used in the construction method of an underwater concrete structure to prevent subsidence in soft ground on the sea floor according to the second embodiment of the present invention, and Figure 12 is a main concrete structure using the concrete block of Figure 11. It is a cross-sectional view in the formed state, and Figure 13 is a cross-sectional view in a state in which a ground drilling part is formed and a concrete pillar is formed after Figure 12, and Figure 14 is a cross-sectional view in a state in which the top concrete is formed after Figure 13.

Hereinafter, only the differences from the first embodiment will be mainly described, and descriptions of parts that are the same as those of the first embodiment will be omitted.

(1) Concrete block manufacturing steps

In this embodiment, a concrete block 20 as shown in FIG. 11 is manufactured.

The concrete block 20 of this embodiment is formed with a plurality of block through holes 21, and each block through hole 21 is in the form of a corrugated pipe extending in the vertical direction as shown in FIG. 12.

(2) Main concrete structure formation stage

Concrete blocks 20 are stacked up and down to form the main concrete structure 100 as shown in FIG. 12. Concrete blocks 20 are stacked in 7 layers.

Compared to the first embodiment, the water depth of the second embodiment is deeper, and the stratum thickness of the seafloor soft ground 12 is thicker.

At this time, since the block through hole 21 of the concrete block 20 is in the form of a corrugated pipe extending in the vertical direction, the vertical through hole 101 of the main concrete structure 100 also has the shape of a corrugated pipe extending in the vertical direction.

The vertical through hole 101 in the form of such a corrugated pipe increases the binding force with the concrete pillar 110.

As described above, the main concrete structure 100 may be formed by stacking a plurality of concrete blocks 20 vertically.

(3) Formation of ground perforations and concrete columns

After FIG. 12, a ground perforation is formed through the vertical through hole 101 of the main concrete structure 100, and a concrete pillar 110 is formed along the vertical through hole 101 and the ground perforation as shown in FIG. 13. It becomes the same state as

Since this step is substantially the same as the first embodiment, detailed description is omitted.

(4) Formation of concrete on top

After Figure 13, the upper concrete 120 is formed on the upper part of the main concrete structure 100.

The reinforcing bar assembly of the concrete 120 is connected to the concrete reinforcing member 111 of the concrete column 110.

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as unitary may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

The present invention can be used as an underwater concrete structure installed underwater for various purposes, such as berthing facilities for ports, etc., sofa structures installed on the coast, and breakwaters.

Claims

A main concrete structure installation step of installing a main concrete structure having a plurality of vertical through holes extending in the vertical direction on the upper part of the soft submarine ground formed on the upper part of the seafloor rock;

After the main concrete structure installation step, a ground perforation forming step of forming a ground perforation in the seafloor soft ground and seafloor rock by drilling the seafloor soft ground and seabed rock located at the lower part of the vertical penetration hole through the vertical penetration hole. ;

After the ground perforation forming step, a concrete column forming portion including a concrete reinforcing member extending in the vertical direction, a waterproofing membrane surrounding the lower and side portions of the concrete reinforcing member, and uncured concrete injected into the waterproofing membrane. A concrete pillar is formed along the vertical penetration hole and the ground drilling part by inserting the vertical penetration hole and the ground boring part, and the concrete pillar includes a concrete pillar portion for the penetration hole located in the vertical penetration hole and the sea bottom. It is divided into a concrete pillar for soft ground located in soft ground and a concrete pillar for bedrock located in the seabed rock, and the concrete pillar for soft ground has a diameter larger than the diameter of the concrete pillar for through-hole and the main concrete structure. Step of forming a concrete pillar formed to support the lower end of;

A method of constructing an underwater concrete structure to prevent subsidence in soft undersea ground, comprising:
According to claim 1,

A method of constructing an underwater concrete structure to prevent subsidence in soft undersea ground, characterized in that a waterproof membrane protective cover in the form of a tube or basket is provided on the outside of the waterproof membrane, the upper end of which is located in the middle of the vertical direction of the waterproof membrane.
According to claim 2,

The waterproof membrane protective cover is made of a net, and the waterproof membrane protective cover is coupled to the outside of the waterproof membrane through a skirt member.
According to clause 1:

In the step of forming the ground drilling portion, a protection pipe extending in the vertical direction is inserted through the vertical penetration hole, and the inserted protection pipe is positioned across the vertical penetration hole and the ground drilling portion;

In the concrete pillar forming step, the waterproof membrane is inserted into the vertical penetration hole and the ground perforation along the inside of the protection pipe, and the protection pipe is removed after the waterproof membrane is inserted;

A method of constructing an underwater concrete structure to prevent subsidence in soft undersea ground, characterized by:
A main concrete structure installed on the upper part of the submarine soft ground formed on the upper part of the seafloor rock and spaced upward from the seafloor rock, and having a plurality of vertical through holes extending in the vertical direction;

A plurality of concrete pillars formed continuously along the vertical penetration hole, soft ground on the sea floor located below the vertical penetration hole, and the sea floor rock;

Includes,

The concrete pillar is divided into a concrete pillar part for a penetration hole located in the vertical penetration hole, a concrete pillar part for soft ground located in the soft ground on the seafloor, and a concrete pillar part for rock located in the seabed rock,

The concrete pillar for soft ground has a diameter larger than the diameter of the concrete pillar for the through-hole and supports the lower end of the main concrete structure to prevent sinking of the main concrete structure. For underwater concrete structures.
According to claim 5,

The concrete column includes a concrete reinforcing member formed in the vertical direction and disposed across the vertical penetration hole, the soft ground on the sea floor, and the rock on the sea floor, a waterproofing membrane surrounding the lower and side portions of the concrete reinforcing member, and an interior of the waterproofing membrane. Characterized by comprising concrete poured and cured, and a waterproof membrane protective cover in the form of a tube or basket, the top of which is located on the outside of the waterproof membrane in the middle of the vertical direction of the waterproof membrane to protect the waterproof membrane located on the soft ground of the sea floor. An underwater concrete structure to prevent subsidence in soft undersea ground.
According to claim 6,

The waterproof membrane protective cover is made of a net, and the waterproof membrane protective cover is coupled to the outside of the waterproof membrane through a skirt member.