JP4391549B2 - CUTTING METHOD AND CUTTING DEVICE FOR UNDERWATER STRUCTURE - Google Patents

Description

  The present invention provides an underwater structure capable of efficiently and safely cutting large-diameter piles and concrete structures, especially for cast-in-place piles and concrete piles that exist in water as the foundation of rivers and sea bridges and other large buildings. The present invention relates to an object cutting method and a cutting apparatus.

Foundation piles that have been used as foundations for railway tracks, etc. need to be cut and removed after being replaced with newly constructed foundations. At this time, it is required to cut a pile at a river or the sea especially at a position lower than the river bed. In such a case, it is necessary to excavate after retaining the soil around the pile, and the diver needs to cut the pile underwater with a wire saw or the like. However, such work is dangerous and requires a lot of man-hours. In addition, when there is a pile head restriction, the pile driving machine cannot approach the pile periphery, the ground around the pile is improved, or obstacles are buried, and earth retaining cannot be installed to the required depth There is also.

In view of such a problem, recently, as a method of cutting an existing pile, there is a method in which the target pile is cored, the cutting device itself is installed at a cutting position in the pile, and cut from the inside of the pile. It has been adopted.

As a method of cutting an existing pile, for example, (1) there is a method of installing a cutter disk inside the core and cutting it from the inside. Moreover, (2) As an apparatus which cuts an existing steel pipe pile, there exists a cutting apparatus which rotates and cuts the cutting machine by a plasma torch within the core which piled up (patent document 1).

On the other hand, as a method for cutting large structures other than underwater, for example, there is (3) a cutting method using an abrasive jet (Patent Document 2).
Japanese Patent Laid-Open No. 7-100654 JP 2000-2089 A

However, in the cutting method of (1), since the cutting thickness is limited by the diameter of the cutter disk and the core extraction diameter, it is difficult to cut a large diameter pile. There is a problem that it is difficult to confirm. In addition, the cutting device according to (2) can be applied to steel pipe piles, but cannot be applied to concrete piles or the like, and there is a problem that it is difficult to confirm whether or not cutting has been reliably completed. Further, the cutting method (3) has a problem that the cutting ability is remarkably deteriorated in water or in a water stream and cannot be applied to cutting a thick structure. Therefore, in any method, it is difficult to reliably cut a large-diameter pile or a concrete structure in water.

  The present invention has been made in view of such a problem, and particularly for cast-in-place piles and concrete piles existing underwater as the foundation of bridges and other large buildings on rivers and seas, particularly large-diameter piles and concrete. It is an object of the present invention to provide an underwater structure cutting method and a cutting apparatus capable of efficiently and safely cutting a structure.

  In order to achieve the above-mentioned object, a first invention is a method of cutting a structure in water, the step (a) of coring the inside of the structure, and a cutting machine using an abrasive jet. A step (b) of installing on the structure, a step (c) of maintaining the internal pressure of the structure at or above the water pressure received by the cutting site of the structure from the outside, and a step of cutting the structure with the cutting machine (D), and step (c) uses pressure adjusting means having air supply means to the inside of the structure, and the pressure adjusting means feeds back the pressure inside the structure. The method for cutting an underwater structure is characterized by adjusting an air supply amount to the inside of the structure.

The depth of core removal in the step (a) may be a depth at which a pool portion of the abrasive material injected by the abrasive jet is formed below the cut portion inside the structure.

You may further comprise the process (e) which confirms that the cutting | disconnection of the said structure was complete | finished after the said process (d). In the step (e), confirmation of completion of the cutting of the structure may be performed by confirming a change in the height of the structure, or may be performed by an underwater camera.

  According to the first invention, with respect to structures such as cast-in-place piles and concrete piles existing in water as the foundation of rivers and sea bridges and other large buildings, By maintaining the pressure above the surrounding water pressure at the cutting position, water can be prevented from flowing into the structure from the cutting position, so that cutting with an abrasive jet can be performed with high efficiency and the lower part of the structure. In addition, the abrasives sprayed by the abrasive jet can be stored, and the drainage pump is not worn by the abrasives. Further, the end of the cutting can be detected by the height change of the structure or the underwater camera. Therefore, it is possible to provide a method for cutting an underwater structure that can be efficiently and safely cut.

  A second invention is an apparatus for cutting an underwater structure, the pressure adjusting means for holding the internal pressure of the structure higher than the water pressure received by the cutting site of the structure from the outside, and cutting the structure A cutting machine using an abrasive jet, and discharge means capable of discharging water and / or earth and sand inside the structure, wherein the pressure adjusting means is an air supply means to the inside of the structure; An underwater structure cutting apparatus comprising: means for feeding back pressure inside the structure; and adjusting an air supply amount into the structure according to the pressure inside the structure. .

  Further, an underwater camera may be further provided so that the cutting site can be observed.

  According to the second aspect of the invention, the pressure inside the structure after finishing the core removal for structures such as cast-in-place piles and concrete piles existing underwater as the foundation of bridges and other large buildings on rivers and seas, By maintaining the pressure above the surrounding water pressure at the cutting position, the inflow of water from the cutting position to the inside of the structure can be prevented, so that cutting with an abrasive jet can be performed with high efficiency. It is possible to discharge the earth and sand flowing into the water with a drain pump, and further, it is possible to know the end of cutting with an underwater camera, and it is possible to provide a cutting device for underwater structures that can be cut efficiently and safely.

  According to the present invention, it is possible to efficiently and safely cut large-diameter piles and concrete structures, especially for cast-in-place piles and concrete piles that exist in the water as the foundation of rivers and sea bridges and other large buildings. An underwater structure cutting method and a cutting apparatus can be provided.

Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a schematic diagram showing an appearance of a cutting machine 1 according to the present embodiment.

The cutting machine 1 is mainly composed of a cutting part 7, a drainage pump 9, a rotating shaft 21, a flange 27, an airtight lid 25, a rotating device 23, and the like. The flange 27 connects the underwater pile 3 and the hermetic lid 25 and can keep the pile interior 5 cored in advance airtight. The rotating shaft 21 penetrates the airtight lid 25 while keeping the pile interior 5 in an airtight state. The end of the rotating shaft 21 is connected to a rotating device 23 provided on a mount 26 on the hermetic lid 25. The cutting part 7 is connected to the other end of the rotating shaft 21 extending into the pile interior 5. Further, a drain pipe 13 is provided in the rotary shaft 21 and an end thereof is connected to a sand pump 9 as a drain pump.

The flange 27 is provided with an air supply pipe 15 and an exhaust pipe 17 and is connected to the pile interior 5. An exhaust valve 19 is provided in the exhaust pipe 17. The air supply pipe 15 is connected to a pressure adjusting device 40 which will be described later, and can adjust the pressure inside the pile 5 kept airtight by the flange 27 and the airtight cover 25. Various seals are applied to the flange 27 and the airtight lid 25 by packing, rotary seals, and the like to prevent air leakage from the site where the piping and the rotating shaft penetrate or are connected.

The high-pressure water hose 9 and the abrasive supply hose 11 pass through the hermetic lid 25 and are connected to the cutting unit 7, and supply high-pressure water and abrasive to the cutting unit 7, respectively. Although the high-pressure water hose 9 and the abrasive supply hose 11 are not specified, for example, a normal pressure-resistant hose can be used. The cutting part 7 can be rotated inside the pile 5 by the rotating device 23 via the rotating shaft 21. Details of the cutting unit 7 will be described later.

  The cutting machine 1 is installed in the underwater pile 3 whose upper part has been cut in advance and cored. The cutting of the underwater pile 3 by the cutting machine 1 is performed at a position deeper than the ground 31. Therefore, the cutting unit 7 of the cutting machine 1 is installed at a cutting position deeper than the ground 31. A sand pump 9 is provided below the cutting part 7. Since the water pressure corresponding to the depth from the water surface 29 is applied to the cutting position, even if the pressure inside the pile 5 is kept higher than the water pressure by using the pressure adjusting device 40 described later, the earth and sand slightly slightly from the outside at the time of cutting. There is a risk of inflow of water. Therefore, the sand pump 9 can discharge the earth and sand flowing into the pile interior 5 to the outside of the pile via the drain pipe 13.

The structure of the cutting part 7 is shown in FIG. FIG. 2A is a side view, and FIG. 2B is a bottom view. The cutting unit 7 includes a nozzle guide 33, a cutting nozzle 35, an underwater camera 37, and a guide roll 39.

The nozzle guide 33 is a substantially rectangular parallelepiped, and the rotating shaft 21 is connected to the center of the upper surface. A drain pipe 13 passes through the rotary shaft 21 and is connected to a sand pump 9 (not shown). On both side surfaces of the nozzle guide 33, a pair of cutting nozzles 35 are respectively installed with the nozzles facing outward on the opposite side. A high pressure water hose 9 and an abrasive supply hose 11 are connected to the cutting nozzle 35, respectively.

On the upper surface of the nozzle guide 33, a pair of guide rolls 39 are installed facing outward in the same direction as the cutting nozzle 35. A pair of underwater cameras 37 are installed on the bottom surface of the nozzle guide 33 in the same direction as the cutting nozzle 35.

The nozzle guide 33 is rotated by the rotation shaft 21. By supplying high-pressure water and the abrasive to the cutting nozzle 35 by the high-pressure water hose 9 and the abrasive supply hose 11, the abrasive and water can be sprayed from the nozzle tip at high pressure. The target part is cut with these abrasives and high-pressure water. Although the abrasive is not specified, for example, garnet can be used.

The guide roll 39 is in contact with the inner surface of the pile interior 5 and plays a role of keeping the distance between the tip of the cutting nozzle 35 and the inner surface of the pile 5 constant and keeping the cutting distance properly. Therefore, it is desirable that the size of the nozzle guide 33 is slightly smaller than the core extraction diameter and that the cutting distance can be maintained by the guide roll 39. Moreover, although the material of the nozzle guide 33 is not specified, steel materials, an aluminum alloy, etc. can be used, for example.

The underwater camera 37 is connected to a monitor provided outside by a cable (not shown), and can monitor the cut portion in real time. Therefore, the cutting state can be grasped externally.

FIG. 3 is a schematic diagram showing the pressure adjusting device 40 connected to the cutting machine 1. The pressure adjusting device 40 mainly includes a compressor 41, a reservoir tank 42, and a pressure regulator 43, and is connected to the cutting machine 1 by an air supply pipe 15 and a pile internal pressure connection hose 49.

The pressure regulator 43 includes an air supply valve 45 and is connected to the air supply pipe 15, the pile internal pressure connection hose 49, the original pressure connection hose 47, and the reservoir tank 42. The pile internal pressure connection hose 49 feeds back the pressure inside the pile 5 to the air supply valve 45, and when the pressure inside the pile 5 becomes equal to or lower than a predetermined pressure (for example, water pressure at the cutting position), the air supply valve 45 opens, Air is supplied to the inside 5 of the pile through the air pipe 15. As the cutting progresses, the amount of air leakage from the cutting position of the underwater pile 3 increases. Therefore, in order to keep the pressure inside the pile 5 constant, it is necessary to supply air according to the amount of air leakage. Therefore, the capacity of the compressor 41 and the reservoir tank 42 is assumed to be a capacity that can obtain an air supply amount larger than this, assuming a maximum amount of air leakage in advance. Moreover, when the pressure inside the pile 5 becomes a predetermined value or more, the exhaust valve 19 is opened, and it is possible to prevent the pressure inside the pile 5 from becoming too high.

Next, the underwater structure cutting step will be described. FIG. 4 is a flowchart showing the cutting process. In the present embodiment, the underwater pile 3 is cut as an underwater structure.

First, the upper part of the underwater pile 3 is cut (step 101). FIG. 5A shows a state where the upper surface of the water surface 29 of the underwater pile 3 is cut. In addition, since it is the cutting | disconnection in the water upper part, the method by a normal wire saw, a cutter disk, other water jets, etc. can be used for the cutting method.

Next, the core of the underwater pile 3 is removed (step 102). As shown in FIG. 5 (b), the underwater pile 3 is cored to form a pile interior 5. Here, the core extraction depth is set to be deeper than the cutting position under the ground surface 31 and a depth at which an abrasive pool portion described later is formed. Further, the diameter of the core is determined in consideration of the thickness of the structure that can be cut by the abrasive jet.

Next, the cutting machine 1 is installed in the underwater pile 3 (step 103). FIG. 5C is a diagram showing a state in which the cutting machine 1 is installed. Along with the installation of the cutting machine 1, a pressure adjusting device 40 connected to the cutting machine 1 is also installed. Note that the lengths of the rotary shaft 21 and the gantry 26 are adjusted in advance so that the cutting portion 7 is installed at the cutting depth.

  Next, the pressure inside the pile 5 is adjusted by the pressure adjusting device 40 to obtain a predetermined pressure. The pressure needs to be higher than the external water pressure acting on the cutting position. Moreover, in order to leak from a cutting part, the air supply according to the amount of air leakage is performed, and the pressure of the pile inside 5 is adjusted in a fixed range. The pressure range inside the pile is, for example, not less than the hydrostatic pressure at the cutting position according to the cutting depth, and may be a range up to about 1.2 times the hydrostatic pressure. When it is confirmed that the pressure inside the pile 5 is within the specified value, the operation of the cutting machine 1 is started (steps 104 to 106).

FIG. 6 is a diagram illustrating a state in which the cutting machine 1 has started to operate, and FIG. 7 is a diagram illustrating details in the vicinity of the cutting unit 7. When the rotating device 23 rotates, the cutting part 7 rotates in the pile interior 5 via the rotating shaft 21. From the cutting nozzle 35 provided in the cutting part 7, the abrasive and the high-pressure water are jetted to cut the underwater pile 3 from the pile interior 5. The inside of the pile 5 is maintained at a pressure higher than the water pressure at the cutting position, but air from the inside of the pile 5 leaks from the cutting position, and there is little infiltration soil water 55 composed of earth and sand around the cutting position. Flows into the inside 5 of the pile. Further, the spray abrasive mixed water 57 which is a mixture of the abrasive and water sprayed from the cutting nozzle 35 is also accumulated in the pile interior 5.

As described above, the core is removed to the depth where the abrasive pool 53 is formed. Therefore, the abrasive having a large specific gravity contained in the jet abrasive mixture water 57 is deposited and accumulated in the abrasive reservoir 53. On the other hand, earth / sand mixed water 61 which is a mixed water of water contained in the infiltrated earth / sand water 55 and the jet abrasive mixed water 57 is discharged by the sand pump 9.

In addition, when cutting, heat is generated by the abrasive jet cutting, and the temperature inside the pile 5 may be increased. In this case, the sand pump 9 may stop due to a thermal trip, or evaporation of water inside the pile 5 may hinder internal confirmation by the underwater camera 37 described later. For this reason, if necessary, the pile interior 5 can be additionally supplied with water for cooling.

  The cutting part 7 cuts the underwater pile 3 from the inside 5 of the pile while rotating. When a pair of cutting nozzles 35 are installed in the opposite direction, the entire underwater pile 3 is rotated with the cutting part 7 rotated 180 degrees. Circumferential cutting ends. At this time, the cutting position is confirmed by the underwater camera 37 in order to know whether the cutting has been completed and there is no remaining cutting. The video by the underwater camera 37 can be confirmed even at the time of cutting, and it can be surely known whether there is any remaining cutting.

In addition, as a cutting confirmation method that can be used instead of or in combination with the underwater camera 37, there is a method by changing the height of the underwater pile. FIG. 8 is a diagram showing a change in the height of the underwater pile 3 at the end of cutting, FIG. 8 (a) is a diagram showing a state where cutting is completed, and FIG. 8 (b) is a diagram of FIG. 8 (a). It is an A section enlarged view.

When the entire circumference of the underwater pile 3 is cut, the height of the cut upper portion of the underwater pile 3 is lowered by a height corresponding to the cutting thickness 63. Therefore, by confirming the change in the height of the underwater pile 3 on the water, it is possible to reliably know that the cutting of the underwater pile 3 has been completed.

When the cutting of the underwater pile 3 is completed, the cutting machine 1 is removed. Fig.9 (a) is a figure which shows the state from which the cutting machine 1 was removed. When the cutting machine 1 is removed, if there is residual pressure in the pile interior 5, the cutting machine 1 can be safely removed by slowly opening the exhaust valve 19 and releasing the residual pressure.

Finally, the cutting of the underwater pile 3 is completed by removing the cut pile and refilling the ground 31.

As described above, according to the cutting method according to the present embodiment, it is possible to safely and reliably cut an underwater structure.

In particular, when an abrasive jet is used as the cutting nozzle 35, a structure having a cutting thickness such as a large-diameter pile or a large concrete structure can be easily cut. For this reason, it is not necessary to unnecessarily increase the core extraction diameter performed in advance.

Moreover, since the pressure inside the pile 5 is maintained at a pressure equal to or higher than the water pressure according to the cutting depth by using the pressure adjusting device 40, the inflow of the infiltrated soil sand water 55 from the cutting position can be suppressed, and the cutting ability of the abrasive jet can be suppressed. The high cutting ability can be maintained without being hindered. Moreover, since the infiltrated earth and sand water 55 slightly flowing into the pile and the water jetted from the nozzle can be discharged by the pump, the cutting is not adversely affected.

Further, if the abrasive material injected by the abrasive jet is discharged as it is with a drainage pump or the like, it may cause wear of impellers in the pump, etc. By forming, the abrasive is not discharged by the pump, and the pumping capacity can be maintained.

In addition, the underwater camera 37 can confirm the end of cutting of the underwater pile 3. Furthermore, the end of cutting can also be confirmed by a change in the height of the underwater pile 3 after cutting. Therefore, it is possible to know that the cutting has been completed without any remaining cutting, and the cutting operation can be performed efficiently without causing a reworking step due to the remaining cutting.

Next, the cutting unit 70 according to the second embodiment will be described. In the following description of the cutting unit 70, constituent elements that perform the same function as the cutting unit 7 are given the same numbers as in FIG.

The cutting unit 70 is used in the cutting machine 1 similarly to the cutting unit 7. FIG. 10 is a view showing the cutting unit 70, FIG. 10 (a) is a view of the cutting unit 70 as viewed from below, and FIG. 10 (b) is a view of the cutting unit 70 viewed from the direction of arrow A in FIG. 10 (a). 4 is a side view of a unit 70. FIG. The cutting unit 70 includes a nozzle guide 71, a cutting nozzle 35, an underwater camera 37, and the like. The nozzle guide 71 has a shape in which three substantially rectangular parallelepiped members are joined together at a center in a trifurcated shape at intervals of approximately 120 degrees. The rotating shaft 21 is connected to the center of the upper surface of the nozzle guide 71. A drain pipe 13 passes through the rotary shaft 21 and is connected to a sand pump 9 (not shown).

Three cutting nozzles 35 are provided on each side surface portion of the nozzle guide 71 extending in the three directions with the nozzles facing outward in the three directions. Underwater cameras 37 are installed on the bottom surface of the nozzle guide 71 in the same direction as the nozzle direction. A guide roll 39 is provided on the upper surface of the nozzle guide 71 in the same direction as the cutting portion 7, and the high pressure water hose 9 and the abrasive supply hose 11 are connected to the cutting nozzle 35.

The nozzle guide 71 is rotated by the rotation shaft 21. By supplying high-pressure water and the abrasive to the cutting nozzle 35 by the high-pressure water hose 9 and the abrasive supply hose 11, the abrasive and water can be sprayed from the nozzle tip at high pressure. The target part is cut with these abrasives and high-pressure water. Although the abrasive is not specified, for example, garnet can be used.

The guide roll 39 is in contact with the inner surface of the pile interior 5 and plays a role of keeping the distance between the tip of the cutting nozzle 35 and the inner surface of the pile 5 constant and keeping the cutting distance properly. Therefore, it is desirable that the size of the nozzle guide 33 is slightly smaller than the core extraction diameter and that the cutting distance can be maintained by the guide roll 39. Moreover, although the material of the nozzle guide 33 is not specified, steel materials and aluminum alloy can be used, for example.

The underwater camera 37 is connected to a monitor provided outside by a cable (not shown), and can monitor the cut portion in real time. Therefore, it is possible to grasp the cutting failure and the state where the cutting is completed outside.

According to the cutting machine 1 using the cutting unit 70 according to the second invention, the same effect as the cutting machine 1 using the cutting unit 7 can be obtained.

In addition, since the cutting nozzles 35 are installed at intervals of approximately 120 degrees, if the rotary shaft 21 rotates approximately 120 degrees at the time of cutting, the entire circumference of the pile can be cut, and therefore the cutting is completed in a short time. Can do.

As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

For example, the number of cutting nozzles 35 in the present invention may be one or four or more depending on the shape of the nozzle guide. In the cutting, water jet cutting that does not use an abrasive can be used instead of abrasive jet cutting. In the embodiment, the sand pump 9 is used. However, a normal drainage pump may be used, and depending on the amount of the infiltrating soil sand water 55 and the jet abrasive mixed water 57, there is no need to discharge the pump.

Schematic which shows the cutting machine 1 concerning this Embodiment. It is the figure which shows the cutting | disconnection part 7, (a) is the figure which looked at the nozzle guide 33 from the side, (b) is the figure which looked at the nozzle guide 33 from the downward direction. Schematic which shows the cutting machine 1 and the pressure adjustment apparatus 40. FIG. The flowchart which shows the cutting process of an underwater pile using the cutting machine 1. FIG. It is the figure which showed the cutting process of the underwater pile 3, (a) is the figure which cut | disconnected the upper part of the underwater pile 3, (b) is the figure which cored the underwater pile 3, (c) is the cutting machine 1 to the underwater pile 3 The figure which shows the state which installed. The figure which shows the state which rotates the cutting part 7 and cuts the underwater pile 3. FIG. The figure which shows the detail of the cutting part 7 vicinity at the time of a cutting | disconnection. The figure which shows the height change of the underwater pile 3 at the time of completion | finish of a cutting | disconnection. It is the figure which showed the cutting process of the underwater pile 3, (a) is a figure which shows the state which removed the cutting machine 1, (b) is a figure which shows the state which removed the cutting part. It is a figure which shows the cutting part 70 concerning 2nd Embodiment, (a) is the figure which looked at the nozzle guide 71 from the downward direction, (b) is the side surface of the nozzle guide 71 seen from the arrow A of (a). Figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ......... Cutting device 3 ...... Underwater pile 5 ......... Pile inside 7, 70 ......... Cutting part 9 ......... Sand pump 11 ......... High pressure water hose 13 ......... Abrasive supply hose 15 ... ... Air supply pipe 17 ... Exhaust pipe 19 ... Exhaust valve 21 ... Rotary shaft 23 ... Rotating device 25 ... Airtight cover 26 ... Fixture 27 ......... Flange 29 ......... Water surface 31 ......... Ground 33 ......... Nozzle Guide 35 ......... Cut Nozzle 37 ......... Underwater Camera 39 ......... Guide Roll 40 ......... Pressure Adjustment Device 41 ......... Compressor 42 ......... Reservoir Tank 43 ......... Pressure regulator 45 ... Air supply valve 47 ... Original pressure connection hose 49 ... Pile internal pressure connection hose 51 ... Exhaust valve connection hose 53 ... Abrasive material reservoir 55 ... Infiltration soil sand water 57 ......... Abrasive mixed with water 59 ......... Abrasive 61 ......... Sand Gosui 63 ......... cutting thickness 71 ......... nozzle guide

Claims (7)

A method for cutting an underwater structure,
A step (a) of coring the inside of the structure;
Installing a cutting machine using an abrasive jet in the structure (b);
Maintaining the internal pressure of the structure at or above the water pressure received by the cutting site of the structure from the outside (c);
A step (d) of cutting the structure with the cutting machine;
And the step (c) uses pressure adjusting means having air supply means to the inside of the structure, and the pressure adjusting means feeds back the pressure inside the structure, A method for cutting an underwater structure, characterized by adjusting an air supply amount to the inside . The depth of core removal in the step (a) is a depth at which a pool portion of the abrasive material injected by the abrasive jet is formed below the cut portion inside the structure. The method for cutting an underwater structure according to claim 1. After step (d)
The method for cutting an underwater structure according to claim 1, further comprising a step (e) of confirming that the cutting of the structure has been completed. 4. The method for cutting an underwater structure according to claim 3, wherein in the step (e), the completion of the cutting of the structure is confirmed by confirming a change in the height of the structure. The method for cutting an underwater structure according to claim 3, wherein in the step (e), confirmation of completion of cutting of the structure is performed by an underwater camera. An apparatus for cutting an underwater structure,
Pressure adjusting means for holding the internal pressure of the structure at or above the water pressure received by the cutting site of the structure from the outside ;
A cutting machine using an abrasive jet for cutting the structure;
Discharging means capable of discharging water and / or earth and sand inside the structure;
Comprising
The pressure adjusting means includes an air supply means to the inside of the structure and a means for feeding back the pressure inside the structure. An underwater structure cutting device characterized by adjusting a volume . The underwater structure cutting apparatus according to claim 6, further comprising an underwater camera and capable of observing a cutting site.

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