Underwater Concrete Structure for Preventing Subsidence at Seabed Soft Ground, and Construction Method Therefor

This Application is a National Stage Patent Application of PCT International Application No. PCT/KR2023/008492 (filed on Jun. 20, 2023), which claims priority to Korean Patent Application No. 10-2022-0086653 (filed on Jul. 14, 2022), which are all hereby incorporated by reference in their entirety.

The present disclosure relates to an underwater concrete structure capable of preventing subsidence in seabed soft ground and a construction method therefor and, particularly, to an underwater concrete structure and a construction method thereof, in which concrete columns are capable of supporting the lower end of a main concrete structure to prevent the main concrete structure from subsiding in seabed soft ground.

An underwater structure, such as berthing facilities for ports, coastal wave-dissipating structures, and breakwaters, are installed underwater for various purposes. As used above and below, the term “underwater structure” refers to an underwater structure installed with a lower part thereof submerged in water, and an upper part thereof may protrude above the water surface or be located below the water surface.

A widely known construction technique in the construction of an underwater structure is the construction method of a large caisson. The large caisson construction method has the advantage of allowing a very large caisson to withstand large waves, but requires manufacturing the very large caisson on land, transporting it to an installation site, and then installing it underwater, so the large caisson construction method requires very high transportation and construction costs and has many restrictions.

In order to solve the problems of this type of large caisson construction method, a method of forming an underwater structure by stacking small concrete blocks in several layers according to the water depth is known.

The present inventor proposed Korean Patent No. 10-1355805 “CONSTRUCTION METHOD FOR UNDERWATER CONCRETE BLOCK STRUCTURE AND UNDERWATER CONCRETE BLOCK STRUCTURE” (registered on Jan. 15, 2014), and presented a technology for enabling an underwater concrete block structure to have sufficient structural stability even against waves caused by large typhoons, etc., by making an upper concrete block and a lower concrete block structurally integral by concrete columns.

Meanwhile, soft ground is widely distributed on the seabed, and when an underwater concrete structure is directly installed on the soft ground, the underwater concrete structure subsides, thereby threatening structural stability thereof.

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

However, it is difficult to create an appropriate foundation ground in a case in which the depth of the seabed is very deep or a soft ground layer is very thick.

When the water depth is very deep or the soft ground layer 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 bedrock, and it is also difficult to accurately inject materials for improving the soft ground.

For example, in the case of the southern coast of South 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, the soft ground improvement equipment is required to be at least 60 to 100 m long to reach the bedrock.

The present disclosure has been made to solve the problems in the prior art as described above, and is intended to propose an underwater concrete structure and a construction method therefor, in which a soft ground concrete column part, which is a portion of a concrete column, is capable of supporting the lower end of a main concrete structure to prevent the main concrete structure from subsiding in seabed soft ground.

In order to accomplish the above objectives, the present invention provides a construction method for an underwater concrete structure for preventing subsidence at seabed soft ground, the construction method including: installing a main concrete structure having a plurality of vertical penetration holes extending vertically on an upper part of seabed soft ground which is on a top of seabed rock; forming a ground perforated part in the seabed soft ground and the seabed rock by perforating the seabed soft ground and the seabed rock located under each of the vertical penetration holes through the vertical penetration hole after the installing of the main concrete structure; and forming a concrete column along the vertical penetration hole and the ground perforated part by inserting a concrete column formation part, which comprises a concrete reinforcing member extending vertically, a waterproof membrane covering lower and side portions of the concrete reinforcing member, and fresh concrete injected into the waterproof membrane, into the vertical penetration hole and the ground perforated part after the forming of the ground perforated part, wherein the concrete column is divided into a penetration hole concrete column part located in the vertical penetration hole, a soft ground concrete column part located in the seabed soft ground, and a rock concrete column part located in the seabed rock, wherein the soft ground concrete column part is formed to support a lower end of the main concrete structure by having a diameter larger than a diameter of the penetration hole concrete column part.

In the above, a waterproof membrane protective cover with a shape of a tube or a basket may be provided on an outer side of the waterproof membrane, with an upper end of the waterproof membrane protective cover positioned on a vertical middle of the waterproof membrane.

In the above, the waterproof membrane protective cover may be formed as a mesh and be coupled to the outer side of the waterproof membrane via a skirt member.

In the above, in the forming of the ground perforated part, a protection pipe extending vertically may be inserted through the vertical penetration hole, and the inserted protection pipe may be positioned across the vertical penetration hole and the ground perforated part; and in the forming of the concrete column, the waterproof membrane may be inserted into the vertical penetration hole and the ground perforated part along an interior of the protection pipe, and the protection pipe may be removed after the waterproof membrane is inserted.

In another idea of the present disclosure, an underwater concrete structure for preventing subsidence at seabed soft ground includes: a main concrete structure which is installed on an upper part of seabed soft ground which is on a top of seabed rock and is spaced apart upward from the seabed rock and has a plurality of vertical penetration holes extending vertically; and a plurality of concrete columns formed continuously along the vertical penetration holes and the seabed soft ground and the seabed rock located under the vertical penetration holes, wherein each of the concrete columns is divided into a penetration hole concrete column part located in each of the vertical penetration holes, a soft ground concrete column part located in the seabed soft ground, and a rock concrete column part located in the seabed rock, and the soft ground concrete column part supports a lower end of the main concrete structure by having a diameter larger than a diameter of the penetration hole concrete column part to prevent subsidence of the main concrete structure.

In the above, the concrete column may include a concrete reinforcing member formed vertically and arranged across the vertical penetration hole, the seabed soft ground, and the seabed rock, a waterproof membrane covering lower and side portions of the concrete reinforcing member, concrete poured and cured inside the waterproof membrane, and a waterproof membrane protective cover with a shape of a tube or a basket located on an outer side of the waterproof membrane and having an upper end positioned on a vertical middle of the waterproof membrane to protect the waterproof membrane located in the seabed soft ground.

In the above, the waterproof membrane protective cover may be formed as a mesh and be coupled to the outer side of the waterproof membrane via a skirt member.

As described above, according to the present disclosure, the soft ground concrete column part, which is a portion of the concrete column, is capable of supporting the lower end of the main concrete structure to prevent the main concrete structure from subsiding in the seabed soft ground.

Furthermore, according to the present disclosure, the work of forming the soft ground concrete column part is very simple compared to a conventional soft ground improvement method, so it is possible to reduce an overall construction cost.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present disclosure belongs can easily embody the present disclosure. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description of the present disclosure are omitted in order to clearly describe the present disclosure, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part “includes” a certain component, it means that other components may be further included without being excluded unless specifically stated to the contrary.

First, a construction method for an underwater concrete structure for preventing subsidence at seabed soft ground according to a first embodiment of the present disclosure will be described.

is a perspective view of a concrete block used in a construction method for an underwater concrete structure for preventing subsidence at seabed soft ground according to a first embodiment of the present disclosure,is a plan view of a main concrete structure formed on the top of the seabed by installing the concrete blocks of,is a cross-sectional conceptual drawing of,is a drawing of a ground perforated part formed after forming the main concrete structure of,are drawings illustrating the process of forming a concrete column in sequence after forming the ground perforated part of,is a front view of a waterproof membrane to which a waterproof membrane protective cover ofis attached, andis an exploded cross-sectional view of.

As in, a concrete blockis manufactured.

The concrete blockmay be formed to have various shapes, but preferably includes at least two block penetration holesextending vertically formed therein.

Each of the block penetration holesextends vertically with a first diameter.

Depending on an embodiment, the concrete blockmay have a space formed for filling the inside thereof, or a space for other purposes or a shape for other purposes.

is a plan view of a main concrete structure, andis a cross-sectional view of the main concrete structure.

A plurality of concrete blocksmanufactured in the manufacturing of the concrete block is installed on the upper part of seabed soft groundwhich is on the top of seabed rockas in, and as in, the plurality of concrete blocksis installed horizontally and continuously to form the main concrete structure.

That is, in this embodiment, the main concrete structurehas a plurality of concrete blocksarranged horizontally and continuously.

According to an embodiment, the main concrete structuremay be composed of one concrete block.

As illustrated in, the main concrete structureis installed spaced apart upward from the seabed rock.

The block penetration holesof the concrete blocksconstituting the main concrete structureform vertical penetration holesextending vertically with lower end parts thereof blocked by the seabed soft groundand upper end parts thereof open.

That is, in this embodiment, the concrete blocks are manufactured in large sizes and installed in only one level vertically, and each of the block penetration holesof each of the concrete blocksfunctions as each of the vertical penetration holesof the main concrete structure.

Accordingly, the vertical penetration holeis in the form of extending vertically with the first diameter.

After the forming of the main concrete structure, as illustrated in, the seabed soft groundand the seabed rocklocated under the vertical penetration holeare perforated through the vertical penetration holeand thus a ground perforated part, which is a space continuous to the vertical penetration hole, is formed in the seabed soft groundand the seabed rock.

In this embodiment, when the ground perforated partis formed by perforating the seabed soft groundand the seabed rocklocated under the vertical penetration hole, a protection pipeextending vertically is vertically inserted into the seabed soft groundand the seabed rockthrough the vertical penetration hole.

The protection pipeinserted in this manner is positioned across the vertical penetration holeand the ground perforated part, and the ground perforated partis formed inside the protection pipe.

In this case, the protection pipeprevents the surrounding seabed soft groundfrom collapsing into the ground perforated partor prevents various types of foreign substances from being introduced into the ground perforated partduring or after the perforating operation.

In addition, the protection pipeserves to protect the waterproof membranewhen a waterproof membraneto be described later is inserted into the protection pipe.

After the forming of the ground perforated part, a concrete columnis formed along the vertical penetration holeand the ground perforated part.

The forming of the concrete column in this embodiment is performed step by step as illustrated in.

A concrete column formation part, which includes a concrete reinforcing memberextending vertically, the waterproof membranecovering lower and side portions of the concrete reinforcing member, fresh concreteinjected into the waterproof membrane, and a waterproof membrane protective covercoupled to the outer side of the waterproof membrane, is inserted into the vertical penetration holeand the ground perforated partso as to form the concrete columnalong the vertical penetration holeand the ground perforated part.

First, as illustrated in, the concrete reinforcing member, such as a reinforcing bar assembly extending vertically, is inserted into the vertical penetration holeand the ground perforated part.

In this embodiment, since the protection pipeis already positioned in the vertical penetration holeand the ground perforated part, the concrete reinforcing memberis inserted into the protection pipe.

In this case, while the lower and side portions of the concrete reinforcing memberis covered by the waterproof membrane, the concrete reinforcing memberis inserted into the vertical penetration holeand the ground perforated part.

Meanwhile, the waterproof membrane protective coveris provided on the outer side of the waterproof membranevia a skirt member.

The waterproof membrane protective coveris in the form of a tube or basket (the form of a basket in the present embodiment) with an upper end thereof positioned on the vertical middle of the waterproof membrane, and a lower end portion of the waterproof membrane(specifically, a portion to be positioned in the seabed soft ground) is positioned inside the waterproof membrane protective cover.