Underwater concrete structure for preventing sinking at seabed soft foundation and construction method thereof

Abstract

The present invention has a concrete column formed along a vertical through-hole of a main concrete structure, a seabed soft foundation, and seabed rock, in which the concrete column formed on the seabed soft foundation supports the lower end of the main concrete structure while having a diameter larger than that of the concrete column formed in the vertical through-hole, and the main concrete structure can be prevented from sinking on the seabed soft foundation.

Description

Technical Field

[0001] The present disclosure relates to an underwater concrete structure capable of preventing sinking in a soft foundation of a seabed and a construction method thereof, and in particular to an underwater concrete structure and a construction method thereof, in which a concrete column can support the lower end of a main concrete structure to prevent the main concrete structure from sinking in a soft foundation of a seabed. Background Art

[0002] Underwater structures such as mooring facilities for ports, coastal wave dissipation 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 and an upper part, the lower part is immersed in water and the upper part may protrude above the water surface or be located below the water surface.

[0003] A well-known construction technique in the construction of underwater structures is a large caisson construction method. The large caisson construction method has the following advantages: it allows a very large caisson to withstand large waves, but it requires manufacturing a very large caisson on land, transporting the caisson to the installation site, and then installing the caisson underwater, so the large caisson construction method requires very high transportation and construction costs and has many limitations.

[0004] In order to solve the problems of this type of large caisson construction method, there is known a method of forming an underwater structure by stacking small concrete blocks in multiple layers according to the water depth.

[0005] The inventor proposed Korean Patent No. 10-1355805 “Construction method for underwater concrete block structure and underwater concrete block structure” (registered on January 15, 2014), and presented a technology that enables an underwater concrete block structure to have sufficient structural stability even against waves caused by a large typhoon, etc. by structurally integrating an upper concrete block and a lower concrete block with the help of concrete columns.

[0006] Meanwhile, soft foundations are widely distributed on the seabed, and when an underwater concrete structure is directly installed on the soft foundation, the underwater concrete structure sinks, thereby threatening its structural stability.

[0007] Therefore, before constructing an underwater concrete structure installed on a soft foundation, it is required to produce a foundation suitable for installing the underwater concrete structure through various soft foundation improvement methods (replacement riprap method and deep mixing treatment method, etc.).

[0008] However, in situations where the depth of the seabed is very great or the soft subsoil is very thick, it is difficult to create a suitable foundation.

[0009] When the water depth is very deep or the soft foundation layer is very thick, it is difficult to pass the soft foundation improving equipment located on the water surface through the soft foundation and reach the bedrock, and it is also difficult to accurately inject the material for improving the soft foundation.

[0010] For example, in the case of the southern coast of Korea, the water depth is 30m to 50m, and the thickness of the soft foundation is also about 30m to 50m, so in this case, the soft foundation improving equipment needs to be at least 60m to 100m long to reach the bedrock. Summary of the invention

[0011] Technical issues

[0012] The present disclosure is 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 thereof, in which the soft foundation concrete column portion as a part of the concrete column can support the lower end of the main concrete structure to prevent the main concrete structure from sinking in the soft foundation of the seabed.

[0013] Technical Solutions

[0014] In order to achieve the above-mentioned object, the present invention provides a method for constructing an underwater concrete structure for preventing sinking at a seabed soft foundation, the method comprising: installing a main concrete structure having a plurality of vertically extending vertical penetration holes on an upper portion of a seabed soft foundation located on top of a seabed rock; after installing the main concrete structure, forming a foundation penetration portion in the seabed soft foundation and the seabed rock by perforating the seabed soft foundation and the seabed rock located below each of the vertical penetration holes by means of the vertical penetration holes; and after forming the foundation penetration portion, forming a concrete column forming portion by A vertically extending concrete reinforcing member, a waterproof membrane covering the lower portion and the side portions of the concrete reinforcing member, and new concrete injected into the waterproof membrane are inserted into the vertical penetration hole and the foundation penetration portion to form a concrete column along the vertical penetration hole and the foundation penetration portion, wherein the concrete column is divided into a penetration hole concrete column portion located in the vertical penetration hole, a soft foundation concrete column portion located in the soft foundation of the seabed, and a rock concrete column portion located in the rock of the seabed, wherein the soft foundation concrete column portion is formed by having a diameter larger than that of the penetration hole concrete column portion to support the lower end of the main concrete structure.

[0015] In the above, a waterproof membrane protection cover having a tube or basket shape may be provided on the outer side of the waterproof membrane, wherein an upper end portion of the waterproof membrane protection cover is positioned on the vertical middle portion of the waterproof membrane.

[0016] In the above, the waterproof membrane protection cover may be formed as a mesh-like member, and coupled to the outer side of the waterproof membrane via a skirt-like member.

[0017] In the above, in the formation of the foundation perforated portion, a vertically extending protective pipe can be inserted through the vertical penetration hole, and the inserted protective pipe can be positioned to pass through the vertical penetration hole and the foundation perforated portion; and in the formation of the concrete column, a waterproof membrane can be inserted into the vertical penetration hole and the foundation perforated portion along the inside of the protective pipe, and the protective pipe can be removed after the waterproof membrane is inserted.

[0018] In another idea of ​​the present disclosure, an underwater concrete structure for preventing sinking at a seabed soft foundation includes: a main concrete structure, which is installed on an upper portion of a seabed soft foundation located on top of the seabed rock and is upwardly spaced apart from the seabed rock, and the main concrete structure has a plurality of vertical penetration holes extending vertically; and a plurality of concrete columns, which are continuously formed along the vertical penetration holes and the seabed soft foundation and seabed rock located below the vertical penetration holes, wherein each of the concrete columns is divided into a penetration hole concrete column portion located in each vertical penetration hole in the vertical penetration holes, a soft foundation concrete column portion located in the seabed soft foundation, and a rock concrete column portion located in the seabed rock, and the soft foundation concrete column portion supports the lower end of the main concrete structure by having a diameter larger than the diameter of the penetration hole concrete column portion to prevent the main concrete structure from sinking.

[0019] In the above, the concrete column may include: a concrete reinforcing member, which is vertically formed and arranged through a vertical penetration hole, a seabed soft foundation and a seabed rock; a waterproof membrane, which covers the lower part and the side part of the concrete reinforcing member; concrete, which is poured and cured inside the waterproof membrane; and a waterproof membrane protection cover, which has a tube or basket shape located on the outer side of the waterproof membrane and has an upper end portion positioned on the vertical middle part of the waterproof membrane to protect the waterproof membrane located in the seabed soft foundation.

[0020] In the above, the waterproof membrane protection cover may be formed as a mesh-like member, and coupled to the outer side of the waterproof membrane via a skirt-like member.

[0021] Beneficial effects

[0022] As described above, according to the present disclosure, the soft foundation concrete column portion as a part of the concrete column can support the lower end portion of the main concrete structure to prevent the main concrete structure from sinking in the soft foundation of the seabed.

[0023] Furthermore, according to the present disclosure, the work of forming the soft foundation concrete column portion is very simple compared to the conventional soft foundation improvement method, and thus the overall construction cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a perspective view of a concrete block used in a method for constructing an underwater concrete structure for preventing it from sinking on a soft foundation of a seabed according to a first embodiment of the present disclosure,

[0025] Figure 2 By installing Figure 1 The plan view of the main concrete structure formed on top of the seabed by concrete blocks,

[0026] Figure 3 yes Figure 2 A cross-sectional conceptual diagram of

[0027] Figure 4 is forming Figure 3 Figure 1. The perforated part of the foundation formed after the main concrete structure.

[0028] Figures 5 to 8 It is a diagram showing the formation of Figure 4 The process of forming concrete columns after the perforated parts of the foundation are shown in Figure 1.

[0029] Fig. 9 is with Figure 5 Front view of the waterproof membrane with the waterproof membrane protective cover attached,

[0030] Fig.10 yes Fig. 9 An exploded cross-sectional view of

[0031] Fig.11 is a perspective view of a concrete block used in a method for constructing an underwater concrete structure for preventing it from sinking on a soft foundation of a seabed according to a second embodiment of the present disclosure,

[0032] Fig.12 Is Fig.11 Cross-section of the main concrete structure formed by concrete blocks,

[0033] Fig.13 is Fig.12 The cross-sectional view of the perforated part of the foundation and the concrete column formed after the state of

[0034] Fig.14 is Fig.13 The cross-sectional view of the cap concrete in the state after formation. DETAILED DESCRIPTION

[0035] Hereinafter, the 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 implement the present disclosure. However, the present disclosure can be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the accompanying drawings, parts that are not related to the description of the present disclosure are omitted to facilitate a clear description of the present disclosure, and similar reference numerals are assigned to similar parts throughout the specification.

[0036] Throughout the specification, when a part “includes” specific components, it means that other components may also be included without being excluded, unless explicitly stated to the contrary.

[0037] First, a construction method of an underwater concrete structure that prevents sinking at a seabed soft foundation according to a first embodiment of the present disclosure will be described.

[0038] Figure 1 is a perspective view of a concrete block used in a method for constructing an underwater concrete structure for preventing it from sinking on a soft foundation of a seabed according to a first embodiment of the present disclosure, Figure 2 By installing Figure 1 The plan view of the main concrete structure formed on top of the seabed by concrete blocks, Figure 3 yes Figure 2 A cross-sectional conceptual diagram of Figure 4 is forming Figure 3 Figure 1. The perforated part of the foundation formed after the main concrete structure. Figures 5 to 8 It is a diagram showing the formation of Figure 4 The process of forming concrete columns after the perforated parts of the foundation are shown in Figure 1. Fig. 9 is with Figure 5 A front view of the waterproof membrane with the waterproof membrane protective cover attached, and Fig.10 yes Fig. 9 Exploded cross-sectional view of .

[0039] (1) Manufacturing concrete blocks

[0040] like Figure 1 In the process, a concrete block 20 is manufactured.

[0041] The concrete block 20 may be formed to have various shapes, but preferably includes at least two vertically extending block penetration holes 21 formed therein.

[0042] Each of the block penetration holes 21 extends vertically with a first diameter.

[0043] According to an embodiment, the concrete block 20 may have a shape formed to fill a space inside thereof, or a space for other purposes, or a shape for other purposes.

[0044] (2) Forming the main concrete structure

[0045] 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.

[0046] like Figure 3 As shown in FIG. 1 , a plurality of concrete blocks 20 manufactured during the manufacturing of the concrete blocks are installed on the upper portion of the seabed soft foundation 12 located on top of the seabed rock 11, and as shown in FIG. Figure 2 As shown in , a plurality of concrete blocks 20 are horizontally and continuously installed to form a main concrete structure 100 .

[0047] That is, in this embodiment, the main concrete structure 100 has a plurality of concrete blocks 20 arranged horizontally and continuously.

[0048] According to one embodiment, the main concrete structure 100 may be composed of one concrete block 20 .

[0049] like Figure 3 As shown in FIG. 1 , the main concrete structure 100 is installed spaced apart upward from the seabed rock 11 .

[0050] The block penetration holes 21 of the concrete blocks 20 constituting the main concrete structure 100 form vertically extending vertical penetration holes 101 , wherein the lower end portions of the vertical penetration holes 101 are blocked by the seabed soft foundation 12 and the upper end portions of the vertical penetration holes 101 are opened.

[0051] That is, in this embodiment, the concrete blocks are manufactured in a large size and vertically installed only at one level, and each of the block penetration holes 21 of each of the concrete blocks 20 serves as each of the vertical penetration holes 101 of the main concrete structure 100 .

[0052] Therefore, the vertical penetration hole 101 is in the form of extending vertically with a first diameter.

[0053] (3) Forming the perforated part of the foundation

[0054] After forming the main concrete structure, as Figure 4 As illustrated in FIG. 1 , the seabed soft foundation 12 and the seabed rock 11 located below the vertical penetration hole 101 are penetrated by means of the vertical penetration hole 101, and thus a foundation penetration portion 102 which is a space continuous with the vertical penetration hole 101 is formed in the seabed soft foundation 12 and the seabed rock 11.

[0055] In this embodiment, when the foundation perforated portion 102 is formed by perforating the seabed soft foundation 12 and the seabed rock 11 located below the vertical penetration hole 101, the vertically extending protective pipe 30 is vertically inserted into the seabed soft foundation 12 and the seabed rock 11 through the vertical penetration hole 101.

[0056] The protection pipe 30 inserted in this manner is positioned to pass through the vertical penetration hole 101 and the foundation penetration portion 102 , and the foundation penetration portion 102 is formed inside the protection pipe 30 .

[0057] In this case, the protection pipe 30 prevents the surrounding seabed soft foundation 12 from collapsing into the foundation perforated portion 102 , or prevents various types of foreign matter from being introduced into the foundation perforated portion 102 during or after the perforating operation.

[0058] In addition, the protection pipe 30 is used to protect the waterproof membrane 112 when the waterproof membrane 112 described later is inserted into the protection pipe 30 .

[0059] (4) Forming concrete columns

[0060] After the foundation penetration portion is formed, a concrete column 110 is formed along the vertical penetration hole 101 and the foundation penetration portion 102 .

[0061] The concrete column in this embodiment is formed as follows Figures 5 to 8 The step-by-step execution is shown in the figure.

[0062] A concrete column forming portion is inserted into the vertical penetration hole 101 and the foundation penetration portion 102, which includes a vertically extending concrete reinforcement member 111, a waterproof membrane 112 covering the lower and side portions of the concrete reinforcement member 111, new concrete 113 injected into the waterproof membrane 112, and a waterproof membrane protective cover 114 connected to the outer side of the waterproof membrane 112, so as to form a concrete column 110 along the vertical penetration hole 101 and the foundation penetration portion 102.

[0063] First, if Figure 5 and Figure 6 As shown in FIG. 1 , a concrete reinforcing member 111 , such as a vertically extending reinforcing bar assembly, is inserted into the vertical penetration hole 101 and the foundation penetration portion 102 .

[0064] In this embodiment, since the protection pipe 30 is already positioned in the vertical penetration hole 101 and the foundation penetration portion 102 , the concrete reinforcement member 111 is inserted into the protection pipe 30 .

[0065] In this case, the concrete reinforcing member 111 is inserted into the vertical penetration hole 101 and the foundation penetration portion 102 while the lower portion and the side portion of the concrete reinforcing member 111 are covered by the waterproof membrane 112 .

[0066] Meanwhile, the waterproof membrane protection cover 114 is provided on the outer side of the waterproof membrane 112 via the skirt member 115 .

[0067] The waterproof membrane protective cover 114 is in the form of a tube or a basket (in the present embodiment, in the form of a basket), wherein the upper end of the waterproof membrane protective cover is positioned on the vertical middle of the waterproof membrane 112, and the lower end portion of the waterproof membrane 112 (specifically, the portion to be positioned in the soft foundation of the seabed) is positioned inside the waterproof membrane protective cover 114.

[0068] The waterproof membrane protection cover 114 may be a mesh member woven from metal wires or carbon fibers and formed into a tube or basket shape.

[0069] Here, the tube shape is a cylindrical shape with the top and the bottom opened, and the basket shape is a cylindrical shape with the top opened and the bottom closed.

[0070] The skirt member 115 is provided between the waterproof membrane protection cover 114 and the waterproof membrane 112 .

[0071] The upper end portion of the skirt member 115 is joined to the vertical middle portion of the outer side portion of the waterproof membrane 112 , and the upper end portion of the waterproof membrane protection cover 114 is coupled to the lower end portion of the skirt member 115 by sewing or the like.

[0072] Therefore, after the concrete reinforcing member 111 covered by the waterproof membrane 112 is inserted into the protection pipe 30, the concrete 113 is poured into the inside of the waterproof membrane 112 to form a Figure 7 and Figure 8 The concrete column 110 is shown in FIG.

[0073] Figure 7 11 is a diagram showing a state in which the protection pipe 30 is slightly raised while some of the new concrete 113 is poured inside the waterproof membrane 112 .

[0074] That is to say, Figure 7 In the embodiment, the protective pipe 30 is raised so that the lower end of the protective pipe 30 is just outside the foundation penetration portion 102 , and new concrete 113 required for the foundation penetration portion 102 is poured into the inside of the waterproof membrane 112 .

[0075] In this case, the waterproof membrane 112 located in the seabed soft foundation 12 has a diameter increased by the pressure of the new concrete 113 .

[0076] exist Figure 7In the figure, the degree of increase in the diameter of the waterproof membrane 112 located in the seabed soft foundation 12 is greatly exaggerated, and in fact, as the new concrete 113 is gradually injected into the waterproof membrane 112, the pressure of the new concrete 113 located in the seabed soft foundation 12 gradually increases. As the pressure gradually increases, the diameter of the waterproof membrane 112 located in the seabed soft foundation 12 gradually increases, and this increase in the diameter of the waterproof membrane 112 continues until the new concrete 113 is completely injected into the waterproof membrane 112, as shown in FIG. Figure 8 As shown in the figure.

[0077] Considering the increase in diameter, the waterproof membrane 112 needs to have a structure that allows the diameter to be increased structurally (eg, a structure that is unfolded from a folded state) or by a material (eg, a stretchable elastic material).

[0078] In addition, the waterproof membrane protection cover 114 prevents the waterproof membrane 112 from being damaged due to an excessively large diameter by allowing the waterproof membrane 112 to expand in diameter only within a certain limit.

[0079] In addition, the waterproof membrane protection cover 114 is made into a mesh-like member, and prevents air or water from remaining between the waterproof membrane protection cover 114 and the waterproof membrane 112 .

[0080] In this way, while the new concrete 113 is gradually poured into the interior of the waterproof membrane 112, the protective pipe 30 is gradually raised, and finally, as shown in FIG. Figure 8 As illustrated in FIG. 1 , the protective pipe 30 is completely removed, and the pouring of new concrete 113 through the vertical penetration hole 101 and the foundation penetration portion 102 is completed.

[0081] That is, the protection pipe 30 is removed before the poured new concrete 113 hardens.

[0082] When the new concrete 113 is poured into the waterproof membrane 112 in this way, the waterproof membrane 112 is in close contact with the seabed rock 11 and the concrete block 20 (or the main concrete structure 100) due to the pressure of the new concrete 113, and has a significantly increased diameter in the seabed soft foundation 12, and then undergoes a curing process to become a concrete column 110.

[0083] In this manner, the concrete column 110 is formed in the main concrete structure 100 , thereby completing the underwater concrete structure 200 .

[0084] That is, the concrete column 110 includes a penetration hole concrete column portion 110a located in the vertical penetration hole 101 and extending vertically with a first diameter, a soft foundation concrete column portion 110b located in the seabed soft foundation 12 and extending vertically with a second diameter, and a rock concrete column portion 110c located in the seabed rock 11 and extending vertically with a third diameter.

[0085] In addition, since the soft foundation concrete column portion 110b has a larger diameter than that of the penetration hole concrete column portion 110a, the soft foundation concrete column portion 110b supports the lower end portion of the main concrete structure 100, thereby preventing the main concrete structure 100 from sinking.

[0086] That is, according to the present disclosure, it is possible to prevent the main concrete structure 100 from sinking without performing a separate soft foundation improving work on the seabed soft foundation 12 .

[0087] Hereinafter, a second embodiment of the present disclosure will be described.

[0088] Fig.11 is a perspective view of a concrete block used in a method for constructing an underwater concrete structure for preventing it from sinking on a soft foundation of a seabed according to a second embodiment of the present disclosure, Fig.12 Is Fig.11 Cross-section of the main concrete structure formed by concrete blocks, Fig.13 is Fig.12 The cross-sectional view of the perforated part of the foundation and the concrete column formed after the state of Fig.14 is Fig.13 The cross-sectional view of the cap concrete in the state after formation.

[0089] In the following, only differences from the first embodiment are mainly described, and description of the same parts as the first embodiment is omitted.

[0090] (1) Manufacturing concrete blocks

[0091] In this embodiment, if Fig.11 The concrete block 20 shown in FIG. 1 is manufactured.

[0092] The concrete block 20 of the present embodiment has a plurality of block penetration holes 21 formed in the concrete block 20, and each of the block penetration holes 21 has a Fig.12 The shape of the vertically extending corrugated pipe shown in FIG.

[0093] (2) Forming the main concrete structure

[0094] Concrete blocks 20 are stacked vertically to form a main concrete structure 100, such as Fig.12 As shown in FIG. , the concrete blocks 20 are stacked into 7 layers.

[0095] Compared with the first embodiment, in the second embodiment, the water depth is greater and the layer of the seabed soft foundation 12 is thicker.

[0096] In this case, since the block penetration hole 21 of the concrete block 20 has the shape of a vertically extending corrugated pipe, the vertical penetration hole 101 of the main concrete structure 100 also has the shape of a vertically extending corrugated pipe.

[0097] The vertical penetration holes 101 in the form of corrugated pipes improve the bonding strength with the concrete column 110 .

[0098] As described above, the main concrete structure 100 may be formed by vertically stacking a plurality of concrete blocks 20 .

[0099] (3) Forming the perforated part of the foundation and forming the concrete column

[0100] exist Fig.12 After the state is obtained, the foundation penetration part is formed through the vertical penetration hole 101 of the main concrete structure 100, and the concrete column 110 is formed along the vertical penetration hole 101 and the foundation penetration part to obtain Fig.13 Status in.

[0101] This step is substantially the same as that of the first embodiment, and thus a detailed description of the step is omitted.

[0102] (4) Forming cap concrete

[0103] exist Fig.13 After the state of being formed, cap concrete 120 is formed on the top of the main concrete structure 100.

[0104] The reinforcement bar assembly of the cap concrete 120 is connected to the concrete reinforcement member 111 of the concrete column 110 .

[0105] The above description of the present disclosure is for illustrative purposes only, and those skilled in the art will appreciate that various modifications may be made without departing from the scope and spirit of the present disclosure. Therefore, it should be understood that the above embodiments are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a decentralized manner, and similarly, components described as decentralized may also be implemented in a combined form.

[0106] The scope of the present disclosure is indicated by the claims to be described later rather than the detailed description, and all changes or modifications 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 disclosure.

[0107] Industrial Applicability

[0108] The present disclosure may be used as an underwater concrete structure installed underwater for various purposes, such as a mooring facility for a port, a coastal wave dissipating structure, and a breakwater.

Claims

1. A method for constructing an underwater concrete structure to prevent it from sinking on a soft foundation on a seabed, the method comprising: installing a main concrete structure having a plurality of vertically extending vertical penetration holes on an upper portion of a seabed soft foundation located on top of seabed rock; After installing the main concrete structure, forming a foundation penetration portion in the seabed soft foundation and the seabed rock by perforating the seabed soft foundation and the seabed rock below each of the vertical penetration holes by means of the vertical penetration holes; as well as After forming the foundation penetration portion, a concrete column is formed along the vertical penetration hole and the foundation penetration portion by inserting a concrete column forming portion into the vertical penetration hole and the foundation penetration portion, the concrete column forming portion comprising a vertically extending concrete reinforcing member, a waterproof membrane covering a lower portion and a side portion of the concrete reinforcing member, and new concrete injected into the waterproof membrane, wherein the concrete column is divided into a penetration hole concrete column portion located in the vertical penetration hole, a soft foundation concrete column portion located in the seabed soft foundation, and a rock concrete column portion located in the seabed rock, wherein the soft foundation concrete column portion is formed by having a diameter larger than that of the penetration hole concrete column portion to support the lower end portion of the main concrete structure.

2. The construction method according to claim 1, wherein: A waterproof membrane protection cover having a tube or basket shape is provided on the outer side of the waterproof membrane, wherein an upper end portion of the waterproof membrane protection cover is positioned on the vertical middle portion of the waterproof membrane.

3. The construction method according to claim 2, wherein: The waterproof membrane protection cover is formed as a mesh-like member, and is coupled to the outer side of the waterproof membrane via a skirt-like member.

4. The construction method according to claim 1, wherein: In the forming of the foundation penetration portion, a vertically extending protective pipe is inserted through the vertical penetration hole, and the inserted protective pipe is positioned to pass through the vertical penetration hole and the foundation penetration portion; as well as In the formation of the concrete column, the waterproof membrane is inserted into the vertical penetration hole and the foundation perforated portion along the inside of the protection pipe, and the protection pipe is removed after the waterproof membrane is inserted.

5. An underwater concrete structure for preventing sinking on a soft foundation of a seabed, the underwater concrete structure comprising: a main concrete structure installed on an upper portion of a seabed soft foundation located on top of a seabed rock, wherein the main concrete structure is spaced upwardly from the seabed rock and has a plurality of vertically extending vertical penetration holes; and a plurality of concrete columns, wherein the plurality of concrete columns are continuously formed along the vertical penetration hole and the seabed soft foundation and the seabed rock located below the vertical penetration hole, wherein each of the concrete columns is divided into a penetration hole concrete column portion located in each of the vertical penetration holes, a soft foundation concrete column portion located in the seabed soft foundation, and a rock concrete column portion located in the seabed rock, and The soft foundation concrete column portion supports the lower end portion of the main concrete structure by having a diameter greater than that of the penetration hole concrete column portion to prevent the main concrete structure from sinking.

6. The underwater concrete structure according to claim 5, wherein: The concrete column includes: a concrete reinforcing member, which is vertically formed and arranged through the vertical penetration hole, the seabed soft foundation and the seabed rock; a waterproof membrane, which covers the lower part and the side part of the concrete reinforcing member; concrete, which is poured and cured inside the waterproof membrane; and a waterproof membrane protection cover, which has a tube or basket shape located on the outer side of the waterproof membrane and has an upper end portion positioned on the vertical middle part of the waterproof membrane to protect the waterproof membrane located in the seabed soft foundation.

7. The underwater concrete structure according to claim 6, wherein: The waterproof membrane protection cover is formed as a mesh-like member, and is coupled to the outer side of the waterproof membrane via a skirt-like member.

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