JP2002047896A - Construction method for isolation layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method for an isolation layer easily constructed and attaining positive isolation. SOLUTION: Shotcrete 1 is sprayed onto the excavated natural ground, and spring water permeable unwoven fabric 3 is stuck as a permeation layer onto the shotcrete 1. Elastic mortar 4 with elasticity even after hardened is sprayed onto the unwoven fabric 3 to construct the isolation layer 2. Lining concrete 5 is placed on the isolation layer 2. The isolation layer 2 thereby isolates the shotcrete 1 from the lining concrete 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing an isolation (edge) layer in a NATM method or the like.

[0002]

2. Description of the Related Art NA mainly used in mountain tunnels
In the TM method, as shown in FIG. 4, after spraying concrete 20 (primary lining) on the excavated ground,
Lining concrete 2 using movable formwork (centre)
Pour 1 (secondary lining).

[0003] If the lining concrete 21 is cast directly on the shotcrete 20, the lining concrete 21 will crack. It is considered that the main cause of the occurrence of the cracks is tensile stress generated because the contraction strain of the concrete is externally restricted by shotcrete or the like. The main causes of shrinkage strain in lining concrete are as follows. Temperature shrinkage due to drop in concrete curing temperature. Temperature shrinkage due to a decrease in temperature in the tunnel. Drying shrinkage due to reduced humidity in the tunnel. Cracks in lining concrete can impair the durability of the structure, cause water leakage or icicles,
It is necessary to take appropriate crack measures. At present, cracks in lining concrete cannot be avoided, especially when lining concrete is directly applied to the shotcrete surface.

There are the following measures to prevent the crack. Edge cutting with shotcrete (reduction of external restraint). Improving concrete quality (reducing shrinkage strain or increasing tensile stress). Installation of crack induction joints (control of crack generation). Among them, the most effective method is edge cutting (isolation). As for isolation, the application of an isolation sheet to the entire surface of shotcrete is generally performed in many cases, but rubber asphalt emulsion, modified clay Attempts have also been made to spray edge-cutting materials such as type asphalt emulsions, ethylene vinyl acetate emulsions, acrylic copolymer emulsions, rock wool (rock wool), and foam mortar.

[0005] The isolation sheet must be excellent in durability, toughness, and flexibility, and must not be damaged at the time of pasting or lining concrete. Further, in the case of waterproofing, the rear surface of the seat must have sufficient water permeability. Therefore, as shown in FIG. 5, a sheet 22 for waterproofing is used in which a back cushioning material 23 is laminated. As the waterproof sheet 22, a sheet made of ethylene vinyl acetate (EVA) having a thickness of 0.4 mm is often used, and in addition, a sheet having a thickness of 1.5 to 3.0 mm is used.
Polyvinyl chloride (PVC) sheet or 1.
A polyethylene (PE) sheet of 0 to 1.5 mm is used. The back cushioning material 23 is made of polypropylene (PP) or polyester (P) having a thickness of about 3.0 mm.
What is called a nonwoven fabric manufactured by ET) is used,
It forms a buffer layer for contact between the sheet and the shotcrete surface and a water-permeable layer for water behind the sheet.

[0006] As described in Japanese Patent Application Laid-Open No. 07-097900, the construction of such an isolation sheet is performed by driving a concrete nail (pin) into a portion where the ends of the isolation sheet are overlapped. As shown in FIG.
A concrete nail 28 is driven into the portion of the nonwoven fabric 25 through a flat washer or a holding iron plate
After sticking to the sheet 9, the waterproof sheet 26 is welded for waterproofing.

[0007]

However, in this method, the sheet cannot follow the unevenness of the sprayed concrete surface at the time of attaching the sheet or placing the lining concrete.
Since the sheet is pulled, a gap may be formed between the rear surface of the sheet and the sprayed concrete surface, which may cause insufficient wrapping of the lining concrete. Further, since the isolation sheet is attached using a concrete nail (pin), there is a problem that the isolation sheet is easily broken. For this reason, various spraying materials as described above have been developed as a method to replace the isolation sheet. Not used much for such reasons.

[0008] An object of the present invention is to provide a method of constructing an isolation layer which can be easily constructed and can be reliably cut off.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 is, for example, as shown in FIG. A method for constructing an isolation layer (2) for cutting off with a lining concrete (5) to be constructed on a sprayed concrete, wherein a water-permeable permeation layer (for example, a nonwoven fabric 3) is provided on the shotcrete. An elastic mortar (4) is sprayed on the permeable layer.

Here, the elastic mortar is a mixture of a mortar and a polymer, and the aggregate is bonded with the cement and the polymer. The polymer used is desirably a water-soluble polymer containing no volatile solvent in consideration of the working environment such as the inside of a tunnel.

According to the first aspect of the present invention, a permeation layer through which water penetrates is provided on the shotcrete sprayed on the ground, and an elastic mortar is sprayed on the permeation layer to form a permeation layer. Since the spring water from the ground infiltrates, the water does not accumulate between the shotcrete and the elastic mortar, and the elastic mortar does not easily come off. In addition, by applying the elastic mortar by spraying, labor saving of the application can be achieved. Since the elastic mortar behaves very elastically even after hardening, it can absorb the shrinkage strain of the concrete and can prevent cracking of the lining concrete applied on the elastic mortar.
In addition, since the elastic mortar is excellent in waterproofness, it is possible to prevent seepage of spring water into lining concrete.

According to a second aspect of the present invention, there is provided a method for constructing an isolation layer according to the first aspect, wherein, for example, as shown in FIG. It is characterized by being formed by attaching.

According to the second aspect of the present invention, the nonwoven fabric is thinner and more flexible than the isolation sheet by forming the permeable layer by sticking the nonwoven fabric on the shotcrete. Adhered closely. Therefore, no gap is generated between the shotcrete and the infiltration layer, so that it is possible to prevent shortage of the lining concrete.

According to a third aspect of the present invention, there is provided a method for constructing an isolation layer according to the first aspect, wherein, as shown in FIG. 2, for example, the permeable layer is formed on a shotcrete by a permeable material such as urethane foam. It is characterized by being formed by spraying 7).

Here, urethane foam,
Examples include porous concrete and air mortar.

According to the third aspect of the present invention, the penetration of the infiltration material onto the shotcrete to form the infiltration layer can save labor for the construction of the infiltration layer. Further, since the penetrating material is sprayed and applied, no void is generated between the shot concrete and the penetrating layer. Therefore, the lining concrete can be cast at a specified thickness.

The invention according to claim 4 is, for example, as shown in FIG. 3, a shotcrete (1) sprayed on a ground without excavated spring water, and a lining concrete (5) constructed thereon. A method of constructing an isolation layer (10) for performing edge cutting with an elastic mortar (9) on the shotcrete.

According to the fourth aspect of the present invention, the elastic mortar is sprayed on the shotcrete sprayed on the ground without spring water, so that no void is formed between the shotcrete and the elastic mortar. Can be constructed. In addition, since elastic mortar shows elasticity even when hardened, it can absorb contraction strain of concrete,
Cracking of the lining concrete constructed on the elastic mortar can be prevented.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, a method of constructing an isolation layer when constructing a tunnel or the like in a mountain having a general spring will be described.

<First Embodiment> In the case of constructing a tunnel by the NATM method, excavation of a ground is first performed. Excavation of the ground includes a method of crushing the ground using dynamite, a method of digging by a machine, and the like. Primary lining (spraying concrete) before the excavated ground collapses
And stop. Next, a lock bolt (not shown) is driven into a necessary portion in a circumferential direction of the tunnel. After the installation of the rock bolts, the isolation layer 2 is constructed on the surface of the shotcrete layer 1 formed by the primary lining.

The isolation layer 2 is composed of a nonwoven fabric 3 and an elastic mortar 4, as shown in FIG. First, the nonwoven fabric 3 is attached to the surface of the sprayed concrete layer 1. The non-woven fabric 3 is attached using a concrete nail (not shown) so that the non-woven fabric 3 is closely attached to the ground. Then, the elastic mortar 4 is sprayed on the nonwoven fabric 3. The elastic mortar 4 is a mixture of a mortar and a polymer, and has elasticity even when cured. As the polymer to be mixed, a water-soluble polymer having low volatility is used in consideration of use in a tunnel.
By spraying the elastic mortar 4, the isolation layer 2
Is completed.

After the elastic mortar 4 of the isolation layer 2 has hardened, a second lining (placement of lining concrete 5) is performed on the four elastic mortars using a movable mold (not shown). The inner wall of the tunnel is completed.

As described above, according to the method of constructing the isolation layer of the above-described embodiment, the nonwoven fabric 3 serves as a permeable layer and allows the spring water from the ground to pass through, so that the back surface of the elastic mortar 4 that does not allow water to pass through. The elastic mortar 4 can be prevented from peeling off without accumulating spring water. Further, since the non-woven fabric 3 is in the form of a thin and flexible sheet, the non-woven fabric 3 can be adhered following the unevenness of the ground.
There is no gap between the ground and the ground. Therefore, it is possible to prevent the thickness of the lining concrete from becoming insufficient. Since the elastic mortar 4 exhibits elasticity even after hardening, the elastic mortar 4 can absorb the shrinkage strain of the lining concrete 5. be able to. Further, since the elastic mortar 4 is constructed by spraying, labor saving of construction can be achieved.

<Second Embodiment> First, similarly to the first embodiment, the ground is excavated and concrete is sprayed on the surface of the ground to form a sprayed concrete layer 1, A lock bolt (not shown) is driven in the circumferential direction of the tunnel. Then, an isolation layer 6 is constructed on the surface of the sprayed concrete layer 1.

The isolation layer 6 is composed of urethane foam (penetrating material) 7 and elastic mortar 8 as shown in FIG. Here, the elastic mortar 8 has the same properties as the elastic mortar 4 used in the first embodiment. First, the urethane foam 7 is sprayed on the surface of the sprayed concrete layer 1. Then, after the sprayed urethane foam 7 is sufficiently foamed, the elastic mortar 8 is sprayed on the foamed urethane 7 to complete the isolation layer 6.

After the elastic mortar 8 of the isolation layer 6 is completely hardened, the lining concrete 5 is applied using a movable formwork as in the first embodiment, and the inner wall of the tunnel is completed.

As described above, according to the method for constructing the isolation layer of the above-described embodiment, the urethane foam 7 serves as a permeation layer, and allows the spring water from the ground to pass through, thereby preventing the elastic mortar 8 from peeling off. be able to. Further, since the urethane foam 7 is applied by spraying, no gap is formed between the urethane foam 7 and the ground. Therefore, it is possible to prevent the thickness of the lining concrete 5 from becoming insufficient. Elastic mortar 7
Since it exhibits elasticity even after hardening and absorbs the shrinkage strain of the lining concrete 5, it is possible to prevent the lining concrete 5 from cracking due to the external constraint of the shotcrete 1. Further, since the application of the urethane foam 7 and the elastic mortar 8 is performed by spraying, the application can be performed more easily than in the case where an isolation sheet or the like is attached, and the labor can be saved.

Next, a method of constructing an isolation layer when a tunnel or the like is constructed in a mountain without spring water will be described.

<Third Embodiment> First, the ground is excavated. The excavation of the ground is similar to the excavation of the ground having a spring. After the excavation, the sprayed concrete layer 1 is formed on the surface of the ground and the rock bolts (shown in the drawings), as in the first embodiment. (Omitted).

Next, as shown in FIG. 3, an elastic mortar 9 is sprayed on the surface of the sprayed concrete layer 1. The elastic mortar 9 has the same properties as those used in the first and second embodiments. The elastic mortar 9 becomes the isolation layer 10. After the elastic mortar 9 has hardened, the lining concrete 5 is applied to the surface of the elastic mortar 9 as in the first embodiment.

As described above, according to the method for constructing the isolation layer of the above-described embodiment, since the ground does not have a spring, even if the elastic mortar 9 is constructed without passing through the permeation layer, the elastic mortar 9 Does not peel off. Elastic mortar 9
Exhibits elastic behavior even when hardened, so that the shrinkage strain of the lining concrete 5 can be absorbed. Therefore, cracking of the lining concrete 5 can be prevented.

In the above embodiment, urethane foam is used as the infiltration material. However, the present invention is not limited to this. Any material can be used as long as it can penetrate water. Alternatively, an air mortar or the like may be used. In addition, it goes without saying that other specific detailed structures and the like can be appropriately changed.

[0034]

According to the first aspect of the present invention, since the permeation layer is provided on the shotcrete sprayed on the ground, the spring water from the ground permeates without accumulating. The elastic mortar provided on the layer can be prevented from being peeled off by water. In addition, since elastic mortar has water blocking properties, it can prevent spring water from penetrating into the lining concrete, and also exhibits elasticity even when hardened, absorbing the shrinkage strain of the lining concrete. In addition, the lining concrete can be prevented from cracking. In addition, since the construction can be easily performed by spraying the elastic mortar, labor saving of the construction can be achieved.

According to the second aspect of the present invention, the thin and flexible non-woven fabric is applied as a permeation layer onto the shot concrete, so that the non-woven fabric can be stuck to the unevenness of the shot concrete. As a result, no void is formed between the shotcrete and the nonwoven fabric, so that the lining concrete can be reliably applied to the prescribed thickness.

According to the third aspect of the present invention, the permeation layer is sprayed to form the permeation layer, so that the permeation layer can be easily constructed and the labor of the permeation layer can be reduced. .

According to the fourth aspect of the present invention, the shrinkage strain of the lining concrete applied on the elastic mortar is absorbed by spraying the elastic mortar showing elasticity even when hardened on the shot concrete, Prevent cracks in lining concrete. Further, since the elastic mortar is applied by spraying, no void is formed between the sprayed concrete and the elastic mortar, and the lining concrete can be applied to a predetermined thickness.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of an isolation layer when a nonwoven fabric is used as a permeable layer as an example to which the present invention is applied.

FIG. 2 is a schematic cross-sectional view showing a structure of an isolation layer when urethane foam is used for a permeation layer.

FIG. 3 is a schematic sectional view showing a structure of an isolation layer using an elastic mortar.

FIG. 4 is a schematic sectional view of a tunnel showing a construction method of the NATM method.

FIG. 5 is a schematic sectional view showing the structure of a conventional isolation sheet.

FIG. 6 is a schematic cross-sectional view of an isolation sheet showing a conventional method of attaching the isolation sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shotcrete layer 2 Isolation layer 3 Nonwoven fabric 4 Elastic mortar 5 Lining concrete 6 Isolation layer 7 Urethane foam 8 Elastic mortar 9 Elastic mortar 10 Isolation layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kenichi Matsui 1-20-10 Toranomon, Minato-ku, Tokyo Nishimatsu Construction Co., Ltd. (72) Inventor Kazushi Shioda 1-20-10 Toranomon, Minato-ku, Tokyo Nishimatsu Construction Co., Ltd. F-term (reference) 2D055 BA06 BB02 CA02 DB00 KA00 KB10 KB16

Claims (4)

[Claims] 1. A method for constructing an isolation layer for cutting off a shotcrete sprayed on an excavated ground and a lining concrete applied thereon, wherein water is sprayed on the shotcast concrete. A method for constructing an isolation layer, comprising: providing a permeable layer that can penetrate; and spraying elastic mortar on the permeable layer. 2. The method for constructing an isolation layer according to claim 1, wherein said permeation layer is formed by sticking a nonwoven fabric on shotcrete. 3. The method according to claim 1, wherein the osmotic layer is formed by spraying an osmotic material onto shotcrete. 4. A method for constructing an isolation layer for cutting off a shotcrete sprayed to a ground without excavated spring water and a lining concrete applied thereon, wherein A method for constructing an isolation layer, characterized by spraying elastic mortar on the top.