JP7142282B2 - Drain mat damage prevention method and bulletproof sheet integrated drain mat - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for preventing damage to a drain mat and a bulletproof sheet-integrated drain mat used in tunnel construction.

As a construction method for mountain tunnels, the NATM construction method (New Austrian Tunneling Method) is known. In this construction method, ready-mixed concrete is sprayed on the wall of the ground hole formed by excavation. Rock bolts are driven into the concrete wall formed by this spraying. After that, a waterproof sheet is installed and the tunnel wall is finished with lining concrete.

The ground contains water. For this reason, spring water is an integral part of tunnel construction. Until the waterproof sheet is attached, the working environment will deteriorate depending on the degree of spring water. Therefore, various studies have been conducted to prevent deterioration of the working environment due to spring water and to improve the working environment (for example, Patent Literature 1).

In Patent Document 1, a drain mat including a non-water-permeable sheet material (hereinafter also referred to as a water-blocking sheet) made of a resin material such as polypropylene resin or polyvinyl chloride resin is studied. This drain mat guides the spring water from the top to the side wall, preventing the water from dripping down and preventing the deterioration of the working environment due to the water.

Japanese Patent Application Laid-Open No. 2002-054396

In tunnel construction, rock fragments are scattered by blasting excavation. If scattered pieces of rock or the like (hereinafter referred to as "flying stones") hit the drain mat, the drain mat may be damaged. If the drain mat is damaged, water leaks from the damaged portion, which deteriorates the work environment that should have been prepared by the drain mat. Since the drain mat may lose its original function due to flying stones, the actual situation is that the drain mat cannot be actively installed in the vicinity of the face.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for preventing damage to a drain mat and a bulletproof sheet-integrated drain mat that can prevent damage to the drain mat due to flying stones that accompany blasting excavation. and

A method for preventing damage to a drain mat according to the present invention includes: a water receiving portion covering the head of a rock bolt driven from the inside to the outside into a concrete wall formed inside a rock pit wall; and the water receiving portion A method for preventing damage to a drain mat having a waterproof sheet that further covers the inside of the drain mat,
A ballistic sheet made of aramid fibers is superimposed on the impermeable sheet inside the water receiving portion.

According to the present invention, a tough bulletproof sheet made of aramid fibers is arranged inside the impermeable sheet. Flying stones in blasting excavation hit the bulletproof sheet, and this bulletproof sheet catches the flying stones. Since flying stones do not hit the impermeable sheet directly, the impermeable sheet is prevented from being damaged by flying stones. Since this drain mat damage prevention method can prevent water leakage from the drain mat due to damage of the impervious sheet, the work environment prepared by the installation of this drain mat can be properly maintained. According to this drain mat damage prevention method, the drain mat can be installed near the working face.

Aramid fibers are difficult to process. For this reason, it is not easy to apply aramid fibers to, for example, a waterproof sheet of a drain mat. In the drain mat damage prevention method of the present invention, a configuration is adopted in which a bulletproof sheet is arranged inside the drain mat. Therefore, the method for preventing breakage of the drain mat of the present invention can easily apply aramid fibers. The drain mat damage prevention method of the present invention can also reduce the initial investment for implementation.

Preferably, in this method for preventing damage to a drain mat, the rock bolts driven into the concrete wall are arranged in a lattice, and when a group of rock bolts arranged in the circumferential direction of the tunnel is defined as a bolt line, a plurality of bolts are arranged. The lines are spaced apart in the tunnel extension direction. And the damage prevention method of this drain mat,
- fixing the drain mat to the concrete wall such that the water receiving part covers part or all of the bolt line;
- A step of fixing the bulletproof sheet to the concrete wall by overlapping the bulletproof sheet with the drain mat from the inside so that the bulletproof sheet covers the entire water receiving part.
In this drain mat damage prevention method, since the water receiving portion is arranged along the bolt line, spring water can be guided from the top end of the concrete wall toward the side end. Moreover, since the drain mat is prevented from being damaged by flying stones that accompany blast excavation, the drain mat can continue to guide spring water. In this drain mat damage prevention method, it is possible to maintain a working environment prepared by installing the drain mat.

Preferably, in this drain mat damage prevention method, in the bulletproof sheet fixing step, the bulletproof sheet is fixed to the concrete wall so as to cover the entire two or more drain mats fixed to the concrete wall. .
In this drain mat damage prevention method, the ballistic sheet can be installed efficiently. Moreover, in this case, since the bulletproof sheet is installed over a wide area, it is possible to prevent damage to parts other than the drain mat.

Preferably, in this method for preventing damage to a drain mat, the rock bolts driven into the concrete wall are arranged in a grid pattern, and when a group of rock bolts arranged in the circumferential direction of the tunnel are defined as bolt lines, a plurality of bolt lines are formed. are spaced apart along the length of the tunnel. And the damage prevention method of this drain mat,
a step of preparing a bulletproof sheet-integrated drain mat in which the bulletproof sheet is combined with the drain mat so as to overlap the water receiving portion via the waterproof sheet;
and fixing the bulletproof sheet-integrated drain mat to the concrete wall with the bulletproof sheet inside so that the water receiving part covers part or all of the bolt line.
In this drain mat damage prevention method, since the water receiving portion is arranged along the bolt line, spring water can be guided from the top end of the concrete wall toward the side end. Moreover, since the drain mat is prevented from being damaged by flying stones that accompany blast excavation, the drain mat can continue to guide spring water. In this drain mat damage prevention method, it is possible to maintain a working environment prepared by installing the drain mat.
In addition, in this drain mat damage prevention method, the bulletproof sheet integrated drain mat obtained by combining the drain mat with the bulletproof sheet is simply fixed to the concrete wall at a place other than the construction site. Installation of the bulletproof sheet is completed. This drain mat damage prevention method can contribute to the improvement of workability at construction sites.

The bulletproof sheet-integrated drain mat according to the present invention is used in the above-described method for preventing damage to a drain mat, and is configured by combining the bulletproof sheet with the drain mat so as to overlap the water receiving portion through the waterproof sheet. ing.
According to the present invention, the installation of the drain mat and the installation of the bulletproof sheet are completed simply by fixing the bulletproof sheet-integrated drain mat to the concrete wall. This bulletproof sheet-integrated drain mat can contribute to the improvement of workability at construction sites.
After the bulletproof sheet-integrated drain mat is fixed to the concrete wall, the drain mat guides spring water from the top end of the concrete wall toward the side end. Moreover, since the drain mat is prevented from being damaged by flying stones that accompany blast excavation, the drain mat can continue to guide spring water. This bulletproof sheet-integrated drain mat can contribute to maintaining a good working environment.
As previously mentioned, aramid fibers are difficult to process. For this reason, it is not easy to apply aramid fibers to, for example, a waterproof sheet of a drain mat. The bulletproof sheet-integrated drain mat of the present invention employs a structure in which the bulletproof sheet is arranged inside the drain mat. Therefore, the aramid fiber can be easily applied to the bulletproof sheet-integrated drain mat of the present invention. With the bulletproof sheet-integrated drain mat of the present invention, it is also possible to reduce the initial investment for implementation.

As is clear from the above description, according to the present invention, it is possible to prevent damage to the drain mat due to flying stones that accompany blast excavation. Since water leakage due to breakage can be prevented, this drain mat maintains a well-organized working environment. Moreover, the present invention enables installation of the drain mat near the face.

FIG. 1 is an explanatory diagram of a bulletproof sheet-integrated drain mat according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a tunnel in which the bulletproof sheet-integrated drain mat of FIG. 1 is installed. 3 is a cross-sectional view taken along line AA of FIG. 2. FIG. FIG. 4 is a cross-sectional view showing an example of construction of bulletproof sheets. FIG. 5 is a cross-sectional view showing another construction example of the ballistic sheet.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[First embodiment]
FIG. 1 shows a bulletproof sheet-integrated drain mat 2 according to one embodiment of the present invention. This bulletproof sheet-integrated drain mat 2 is constructed by combining a bulletproof sheet 6 with a drain mat 4 .

The drain mat 4 is used at a tunnel construction site by the NATM construction method. In this construction method, ready-mixed concrete is sprayed on the wall of the ground hole formed by excavation. Rock bolts are driven into the concrete wall thus formed. This drain mat 4 is a member for receiving spring water that drips along the rock bolts driven into the concrete wall to improve the work environment at the construction site. The drain mat 4 includes a water receiving portion 8 for receiving spring water and a waterproof sheet 10 for supporting the water receiving portion 8. - 特許庁

The water receiving portion 8 is made of a resin-made elastic member having water permeability. The water receiving portion 8 includes a plurality of pipe-shaped support members 12 and a water-permeable nonwoven fabric 14 . The pipe-shaped support members 12 are arranged in parallel in the width direction of the drain mat 4 . The nonwoven fabric 14 surrounds the parallel pipe-shaped support members 12 . Thus, the plurality of pipe-shaped support members 12 and the nonwoven fabric 14 are integrated to form the water receiving portion 8 . The water receiving portion 8 is not particularly limited in its configuration as long as it has water permeability and can form a space capable of receiving spring water when configured as the drain mat 4 . The water receiving portion 8 may be composed of, for example, a mat formed by depositing a large number of filaments made of a resin such as polypropylene in a random loop shape.

The impervious sheet 10 is a non-permeable sheet. The waterproof sheet 10 is made of resin such as polypropylene or polyvinyl chloride. In this drain mat 4, the impervious sheet 10 prevents spring water from dripping down on the construction site.

In this drain mat 4 , a recess 16 is provided in the central portion in the width direction of the impermeable sheet 10 , and the water receiving portion 8 is fitted in this recess 16 . At each end portion of the drain mat 4, the impermeable sheet 10 is folded while winding the iron strip 18. - 特許庁A folded portion of the waterproof sheet 10 is a side end portion 20 of the drain mat 4 .

The bulletproof sheet 6 is a sheet constructed so as not to be torn by bullets or to be hard to be torn by bullets. The bulletproof sheet 6 may be made of a knitted or woven fabric made of the same material as the sheet so as not to be broken even by bullets, or to be hard to be broken even by bullets. In the present invention, bulletproof sheet 6 is made of aramid fiber.

The bulletproof sheet 6 is a tough sheet. Even if a flying stone caused by blasting excavation hits the bulletproof sheet 6 and damages the impervious sheet 10 of the drain mat 4, the flying stone does not penetrate the bulletproof sheet 6.例文帳に追加

In the bulletproof sheet-integrated drain mat 2 shown in FIG. 1 , the bulletproof sheet 6 is laminated on the waterproof sheet 10 . The ballistic sheet 6 is superimposed on the water receiving portion 8 with a waterproof sheet 10 interposed therebetween. This ballistic sheet 6 is folded back at the side edge 20 of the drain mat 4 . The ballistic sheet 6 covers the entire drain mat 4 from the waterproof sheet 10 side.

FIG. 2 shows a state in which the ballistic sheet-integrated drain mat 2 shown in FIG. The ballistic sheet-integrated drain mat 2 extends along the concrete wall 24 inside the concrete wall 24 and extending from the top end 26 toward the side end 28 along the arch-shaped concrete wall 24 .

Although not shown in FIG. 2, a large number of rock bolts 30 are driven into the concrete wall 24 . These rock bolts 30 are arranged in a grid on the concrete wall 24 . When a group of lock bolts 30 arranged in the tunnel circumferential direction is defined as a bolt line 32, a plurality of bolt lines 32 are arranged on the concrete wall 24 at intervals in the tunnel extending direction.

FIG. 3 shows a cross section along line AA of FIG. In FIG. 3, the horizontal direction is the extension direction of the tunnel. The bottom side of the paper is the inside of the tunnel, that is, the mine side, and the top side of the paper is the outside of the tunnel, that is, the ground side.

As shown in FIG. 3, the rock bolt 30 is driven into the concrete wall 24 formed inside the rock pit wall 22 from the inside to the outside. Located between one rock bolt 30 and another rock bolt 30 is a shoring 34 . In this concrete wall 24, rock bolts 30 and shorings 34 are alternately arranged in the tunnel extending direction.

Next, a method for preventing breakage of the drain mat 4 using the bulletproof sheet-integrated drain mat 2 will be described.

In this damage prevention method, first, the drain mat 4 is prepared. In this damage prevention method, if the spring water dripping along the rock bolt 30 can be received and the spring water can be guided from the top end 26 toward the side end 28 along the concrete wall 24, the drain mat used 4 is not particularly limited. This breakage prevention method also allows the use of commercially available drain mats.

In this breakage prevention method, a ballistic sheet 6 is combined with the prepared drain mat 4 . As a result, the bulletproof sheet-integrated drain mat 2 is obtained. In this breakage prevention method, when combining the bulletproof sheet 6 with the drain mat 4 , the bulletproof sheet 6 is overlapped with at least the water receiving portion 8 through the impermeable sheet 10 . In this bulletproof sheet-integrated drain mat 2, the bulletproof sheet 6 and the drain mat 4 are combined so that the entire drain mat 4 is covered with the bulletproof sheet 6.例文帳に追加As shown in FIG. 1 , in this bulletproof sheet-integrated drain mat 2 , the bulletproof sheet 6 is folded so that the end portions of the bulletproof sheet 6 cover the side ends 20 of the drain mat 4 . Although not shown, the bulletproof sheet 6 may be adhered to the drain mat 4 so that only the water receiving portion 8 is covered with the bulletproof sheet 6 to form the bulletproof sheet integrated drain mat 2 . Furthermore, in order to prevent the bulletproof sheet 6 from being separated from the drain mat 4, the bulletproof sheet 6 and the drain mat 4 may be adhered using an adhesive.

In this breakage prevention method, the prepared bulletproof sheet-integrated drain mat 2 is fixed to the concrete wall 24 at the construction site.

In fixing the bulletproof sheet-integrated drain mat 2, the bulletproof sheet-integrated drain mat 2 is applied to the bolt line 32 so that the bulletproof sheet 6 is positioned inside. As a result, the water receiving portion 8 of the drain mat 4 is arranged so as to cover the bolt line 32 . In addition, when spring water is generated in all the lock bolts 30 forming the bolt line 32 , the bulletproof sheet integrated drain mat 2 is arranged so as to cover the entire bolt line 32 . When some of the lock bolts 30 forming the bolt lines 32 are springing water, the bulletproof sheet-integrated drain mat 2 is arranged so as to cover the part of the bolt lines 32 .

After placing the bulletproof sheet-integrated drain mat 2 at a predetermined position, concrete nails 38 are driven into the side ends 36 thereof. As a result, the ballistic sheet-integrated drain mat 2 is fixed to the concrete wall 24 . In the bulletproof sheet-integrated drain mat 2 fixed in this way, as shown in FIG. 8 is further covered from the inside. The impervious sheet 10 is covered with a ballistic sheet 6 from the inside.

In this damage prevention method, in the drain mat 4 having the water receiving portion 8 covering the head portion 40 of the lock bolt 30 and the water impervious sheet 10 further covering the water receiving portion 8 from the inside, the bulletproof sheet made of aramid fiber 6 is superimposed on the waterproof sheet 10 inside the water receiving portion 8 .

In this breakage prevention method, a tough ballistic sheet 6 made of aramid fiber is positioned inside the impervious sheet 10 . Flying stones in blasting excavation hit the bulletproof sheet 6, and this bulletproof sheet 6 receives the flying stones. Since the impermeable sheet 10 is not directly hit by flying stones, the impermeable sheet 10 is prevented from being damaged by the flying stones. Since this breakage prevention method can prevent water leakage from the drain mat 4 due to breakage of the impervious sheet 10, the working environment prepared by the installation of this drain mat 4 can be properly maintained. According to this breakage prevention method, it is possible to install the drain mat 4 near the face.

Aramid fibers are difficult to process. Therefore, for example, it is not easy to apply aramid fibers to the impermeable sheet 10 of the drain mat 4 and improve the impermeable sheet 10 itself. In this damage prevention method and bulletproof sheet-integrated drain mat 2 , a configuration in which the bulletproof sheet 6 is arranged inside the drain mat 4 is adopted. Therefore, this breakage prevention method can be easily applied to aramid fibers. This breakage prevention method does not require the introduction of equipment required for processing aramid fibers, and can reduce the initial investment for implementation.

Preferably, this anti-failure method comprises:
A step of preparing a bulletproof sheet-integrated drain mat 2 in which a bulletproof sheet 6 is combined with a drain mat 4 so as to overlap the water receiving part 8 via the impermeable sheet 10;
A step of fixing the bulletproof sheet-integrated drain mat 2 to the concrete wall 24 with the bulletproof sheet 6 inside so that the water receiving part 8 partially or entirely covers the bolt line 32 is included.

In the damage prevention method using this bulletproof sheet integrated drain mat 2, since the water receiving portion 8 is arranged along the bolt line 32, water springs from the top end portion 26 of the concrete wall 24 toward the side end 28. can be induced. Moreover, since the drain mat 4 is prevented from being damaged by flying stones accompanying blasting excavation, the drain mat 4 can continue to guide spring water. In this breakage prevention method, it is possible to maintain a working environment prepared by installing the drain mat 4 .

In this breakage preventing method, the drain mat 4 is installed only by fixing the bulletproof sheet integrated drain mat 2 obtained by combining the drain mat 4 and the bulletproof sheet 6 to the concrete wall 24 at a place other than the construction site. and installation of the bulletproof sheet 6 are completed. This breakage prevention method and the bulletproof sheet-integrated drain mat 2 can contribute to the improvement of workability at construction sites.

[Second embodiment]
FIG. 4 shows a construction example of a ballistic sheet 6 to which a damage prevention method for a drain mat 4 according to another embodiment of the present invention is applied. In this breakage prevention method, after fixing the drain mat 4 to the concrete wall 24 , the ballistic sheet 6 is fixed to this concrete wall 24 .

In this breakage prevention method, the drain mat 4 is fixed to the concrete wall 24 . In fixing the drain mat 4, the drain mat 4 is applied to the bolt line 32 so that the impervious sheet 10 is positioned inside. As a result, the water receiving portion 8 of the drain mat 4 is arranged so as to cover the bolt line 32 . In addition, when spring water is generated in all the lock bolts 30 forming the bolt line 32 , the drain mat 4 is arranged so as to cover the entire bolt line 32 . When some of the lock bolts 30 forming the bolt lines 32 are springing water, the drain mat 4 is arranged to cover the part of the bolt lines 32 .

After the drain mat 4 is in place, concrete nails 38 are driven into the side edges 20 thereof. The drain mat 4 is thereby fixed to the concrete wall 24 . In the drain mat 4 fixed in this way, as shown in FIG. covered from

In this breakage prevention method, the ballistic sheet 6 is fixed to the concrete wall 24 from the inside of the drain mat 4 . In fixing the bulletproof sheet 6 , the bulletproof sheet 6 is superimposed on the drain mat 4 from the inside so that the bulletproof sheet 6 covers the entire water receiving portion 8 . Then, a concrete nail 38 is driven into the side end portion 42 of the ballistic sheet 6 . The ballistic sheet 6 is thereby fixed to the concrete wall 24 . From the viewpoint of facilitating fixing of the bulletproof sheet 6, as shown in FIG. preferably. Furthermore, in this breakage prevention method, the bulletproof sheet 6 can be reliably fixed, and the bulletproof sheet 6 is superimposed after the adhesive is applied to the waterproof sheet 10 of the drain mat 4 from the viewpoint of ensuring good fixing workability. may

The damage prevention method according to the second embodiment described above preferably includes:
a step of fixing the drain mat 4 to the concrete wall 24 so that the water receiving portion 8 covers part or all of the bolt line 32;
A step of laying the bulletproof sheet 6 on the drain mat 4 from the inside so as to cover the entire water receiving part 8 and fixing the bulletproof sheet 6 to the concrete wall 24 is included.

In this breakage prevention method, as in the first embodiment, since the water receiving portion 8 is arranged along the bolt line 32, spring water flows from the top end portion 26 of the concrete wall 24 toward the side end 28. can be induced.

In this breakage prevention method, the drain mat 4 having the water receiving portion 8 covering the head portion 40 of the lock bolt 30 and the water impervious sheet 10 further covering the water receiving portion 8 from the inside is provided with a bulletproof sheet made of aramid fiber. 6 is superimposed on the waterproof sheet 10 inside the water receiving portion 8 .

In this damage prevention method, the bulletproof sheet 6 receives flying stones accompanying blasting excavation, so damage to the drain mat 4 due to flying stones is prevented. In this breakage prevention method, the drain mat 4 can continue to guide spring water. From this point of view, it is preferable that the ballistic sheet 6 covers the entire drain mat 4 as shown in FIG.

Since this breakage prevention method can prevent water leakage from the drain mat 4 due to breakage of the impervious sheet 10, the working environment prepared by the installation of this drain mat 4 can be properly maintained. This breakage prevention method also enables the installation of the drain mat 4 near the face.

This breakage prevention method also employs a structure in which the bulletproof sheet 6 is arranged inside the drain mat 4 . Therefore, aramid fibers, which are difficult to process themselves, can be easily applied. This anti-failure method can also reduce the initial investment in implementation.

[Third embodiment]
FIG. 5 shows another construction example of the ballistic sheet 6 to which the damage prevention method for the drain mat 4 according to still another embodiment of the present invention is applied. Also in this damage prevention method, the bulletproof sheet 6 is fixed to the concrete wall 24 after the drain mat 4 is fixed to the concrete wall 24 .

In this breakage prevention method, the drain mat 4 is fixed to the concrete wall 24 in the same manner as in the above-described second embodiment. After fixing the drain mat 4, the bulletproof sheet 6 is fixed. In this damage prevention method, a bulletproof sheet 6 larger than the bulletproof sheet 6 used in the second embodiment is used. Thereby, two or more drain mats 4 fixed to the concrete wall 24 are covered with one ballistic sheet 6.例文帳に追加That is, this breakage prevention method preferably includes:
a step of fixing the drain mat 4 to the concrete wall 24 so that the water receiving portion 8 covers part or all of the bolt line 32;
A step of overlapping the bulletproof sheet 6 with the drain mat 4 from the inside so as to cover the entire water receiving part 8 and fixing the bulletproof sheet 6 to the concrete wall 24,
In this bulletproof sheet 6 fixing process, the bulletproof sheet 6 is fixed to the concrete wall 24 so as to entirely cover the two or more drain mats 4 fixed to the concrete wall 24 . In the construction example shown in FIG. 5, the ballistic sheet 6 is fixed to the concrete wall 24 so as to cover the entire two drain mats 4 fixed to the concrete wall 24 .

This breakage prevention method can shorten the time for fixing the ballistic sheet 6 . That is, the bulletproof sheet 6 can be installed efficiently. Moreover, in this case, since the ballistic sheet 6 is installed over a wide area, damage to parts other than the drain mat 4 can be prevented.

As is clear from the above description, according to the present invention, it is possible to prevent the drain mat 4 from being damaged by flying stones during blast excavation. Since water leakage due to breakage can be prevented, this drain mat 4 maintains a well-organized work environment. Moreover, the present invention enables installation of the drain mat 4 near the face.

According to the method for preventing damage to a drain mat and the bulletproof sheet-integrated drain mat described above, it is possible to improve the working environment at a construction site involving blasting excavation.

2 Bulletproof sheet-integrated drain mat 4 Drain mat 6 Bulletproof sheet 8 Water receiver 10 Waterproof sheet 12 Pipe-shaped support member 14 Nonwoven fabric 16 ... Hollow 18 ... Iron band 20 ... Side edge of drain mat 4 22 ... Ground pit wall 24 ... Concrete wall 26 ... Top edge 28 ... Side edge 30. Rock bolt 32 Bolt line 34 Shoring 36 Side end of bulletproof sheet-integrated drain mat 2 38 Concrete nail 40 Head of rock bolt 30 42・Side edge of bulletproof sheet 6

Claims (2)

A drain having a water receiving portion covering the head of a rock bolt driven from the inside to the outside into a concrete wall formed inside a rock pit wall, and a seepage control sheet covering the water receiving portion from the inside. A mat damage prevention method comprising:
The rock bolts driven into the concrete wall are arranged in a lattice,
When a group of lock bolts lined up in the circumferential direction of the tunnel is defined as a bolt line, multiple bolt lines are arranged at intervals in the tunnel extension direction,
fixing the drain mat to the concrete wall such that the water receiving portion covers part or all of the bolt line;
A bulletproof sheet made of aramid fiber is overlapped with the drain mat from the inside so as to cover the entire water receiving part, and fixing the bulletproof sheet to the concrete wall;
A method for preventing damage to a drain mat, wherein the ballistic sheet is superimposed on the impermeable sheet inside the water receiving portion. 2. The prevention of damage to the drain mat according to claim 1 , wherein in the step of fixing the bulletproof sheet, the bulletproof sheet is fixed to the concrete wall so as to cover the entirety of the two or more drain mats fixed to the concrete wall. Method.

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