Shaft lining structure and shaft construction method

Abstract

To propose a shaft lining structure capable of reducing stress generated in the lining concrete and improving the stability of the structure, and a shaft construction method utilizing this shaft lining structure.SOLUTION: The present invention relates to a shaft lining structure 2 consisting of a ring-shaped main body 3 made of hardened concrete, a collapsible part 4 interposed between the main body 3 and the ground surface, and an anchor 5 driven into the ground, and a shaft construction method using the shaft lining structure 2. The collapsible part 4 is made of a material with lower rigidity than the main body 3.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a shaft lining structure and a shaft construction method.

Background Art

[0002] When constructing a deep shaft, a short-step method may be adopted in which excavation and placement of lining concrete are repeated at predetermined depths. In the construction of underground structures, when the ground is excavated, the ground deforms. When the ground deforms, there is a risk that a large stress acts on the lining concrete due to the extrusion force accompanying the deformation. In tunnel construction, since there is a risk that buckling or the like may occur in the support due to the action of ground extrusion, in some cases, the deformation (extrusion) of the ground is absorbed by deforming a part of the support. For example, Patent Document 1 discloses a support structure in which a shrinkable member is provided in a tunnel support so as to cross an arch-shaped tunnel support, and even when the ground deforms, the shrinkable member absorbs the deformation to suppress buckling or the like from occurring in the support. In tunnel construction, it is common to close the ground exposed by excavation with a support at an early stage, and after the ground deformation has settled, install a formwork such as a slide center or the like and place lining concrete. On the other hand, in the construction of a shaft using a short-step method in which excavation of the ground and placement of lining concrete are repeated, it is necessary to install a formwork and place lining concrete before the ground deformation has settled, but the formwork and lining concrete may not be able to tolerate large deformations.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention aims to propose a shaft lining structure that can reduce the stress generated in the shaft lining concrete and ensure the improvement of the stability of the structure, and a shaft construction method using this shaft lining structure.

Means for Solving the Problem

[0005] In order to solve the above problems, the shaft lining structure of the present invention comprises a main body portion made of a hardened body of concrete, and a compressible portion interposed between the main body portion and the ground surface. The compressible portion is composed of a material having a lower rigidity than the main body portion (a material that is easily deformed). Further, the shaft construction method of the present invention includes an excavation step of excavating the ground downward, a compressible portion forming step of installing a compressible material on the ground surface exposed by the excavation of the ground, a formwork installation step of installing a ring-shaped formwork inside the compressible material, and a placing step of placing concrete between the formwork and the compressible material. According to such a shaft lining structure and shaft construction method, since it is provided with a compressible portion made of a material having a lower rigidity than the main body portion (lining concrete) (including a material having a compressive yield strength equal to or lower than that of the main body portion and a rigidity (modulus of deformation) in the plastic region lower than that of the main body portion), even when an extrusion force acts on the shaft lining structure due to the deformation of the ground after the concrete is placed, the stress acting on the lining concrete can be reduced by being absorbed by the compressible portion. Therefore, the stability of the shaft can be ensured. In addition, by reducing the stress generated in the lining concrete, the demolding time of the formwork can be advanced, and thus the construction cycle can be speeded up. Further, by reducing the stress, it is possible to reduce the cost associated with the reduction of the lining thickness.

[0006] The compressible portion may be a hardened body obtained by spraying a cementitious material or a resinous material containing cement, a porous material, and water onto the ground surface, or a resin sheet attached to the ground surface. If the compressible portion is formed by spraying the material or attaching the sheet material, early construction becomes possible. In addition, if the shaft lining structure further includes an anchor driven into the natural ground surface, integration with the natural ground can be achieved.

Advantages of the Invention

[0007] According to the shaft lining structure and the shaft construction method of the present invention, it is possible to reduce the stress generated in the lining concrete and improve the stability of the structure.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the case of forming the shaft 1 will be described. The shaft 1 is shown in FIG. 1. As shown in FIGS. 1(a) and 1(b), the shaft 1 of the present embodiment is circular in plan view. The shaft 1 is formed by excavating the ground (natural ground G) downward and closing the natural ground surface exposed by the excavation with a shaft lining structure 2 formed in a ring shape. The shaft lining structure 2 is formed in a plurality of continuous stages vertically. At the bottom of the shaft 1, base concrete is placed as required. The shaft lining structure 2 is shown in FIG. 2. As shown in FIG. 2, the shaft lining structure 2 is formed by laminating a main body part 3 and a collapsible part 4. The main body portion 3 is made of a ring-shaped concrete hardened body. The main body portion 3 includes a general portion 31 with a rectangular cross-section and a reduced-thickness portion 32 formed below the general portion 31. The reduced-thickness portion 32 has a cross-sectional shape whose thickness decreases downward, and the main body portion 3 formed by connecting the general portion 31 and the reduced-thickness portion 32 has a pentagonal cross-section. Note that the cross-sectional shape of the main body portion 3 is not limited to a pentagon.

[0010] The compressible portion 4 is provided between the main body portion 3 and the ground surface. The compressible portion 4 is composed of a material (a material that is easy to deform) with lower rigidity than the main body portion 3. The compressible portion 4 of the present embodiment is composed of a plurality of strip-shaped resin sheets 41 pasted on the ground surface. When the ground G is excavated, the ground G is pushed out toward the center side of the space formed by the excavation. The compressible portion 4 functions as a buffer material that absorbs the pushing force caused by the deformation of the ground G. The thickness of the compressible portion 4 may be appropriately determined according to the strength of the material constituting the compressible portion 4 (resin sheet 41 in this embodiment), the assumed pushing force of the ground G, etc. The resin sheet 41 is continuously pasted on the ground surface in the circumferential direction. The resin sheet 41 is fixed by an anchor 5 driven into the ground surface. The compression rigidity of the resin sheet 41 is preferably about 1 / 100 to 1 / 10 of the compression rigidity (deformation coefficient) of the concrete hardened body at the time of demolding, and the compression yield strength is preferably equivalent to the compression strength of the concrete hardened body at the time of demolding. The material constituting the resin sheet 41 is not limited, but for example, it is made of high-strength polystyrene resin. The anchor 5 has a shaft portion 51 and a head portion 52 having an outer shape larger than that of the shaft portion 51. The anchor 5 is driven into the ground G with the head portion 52 locked to the surface of the resin sheet 41. Note that the fixing method of the resin sheet 41 is not limited, and for example, it may be fixed with pins or the like.

[0011] The shaft construction method of this embodiment will be described. The shaft construction method uses an excavation process, a collapsible part formation process, a formwork installation process, and a placing process as one construction cycle, and by repeating this construction cycle, a multi-stage shaft lining structure 2 is continuously provided to form a shaft 1 of a predetermined depth. That is, the shaft 1 is constructed by the so-called reverse winding method in which the shaft lining structure 2 is sequentially formed from top to bottom. In the excavation process, the natural ground G is excavated downward to a predetermined depth. The excavation process is shown in FIG. 3. As shown in FIG. 3, in the excavation process, the natural ground G is excavated to a predetermined depth in a circular shape in plan view. By excavating the natural ground G, a recess is formed from the ground surface or below the existing shaft lining structure 2. FIG. 3 shows the case where the area below the existing shaft lining structure 2 is excavated.

[0012] In the collapsible part formation process, a collapsible material (resin sheet 41) is installed on the natural ground surface exposed by the excavation of the natural ground G to form a collapsible part 4. The collapsible part formation process is shown in FIG. 4. In the collapsible part formation process, as shown in FIG. 4, a strip-shaped resin sheet 41 is attached to the natural ground surface, and the resin sheet 41 is fixed by driving an anchor 5 into the natural ground surface. By arranging a plurality of strip-shaped resin sheets 41 side by side in the circumferential direction, a ring-shaped collapsible part 4 is formed.

[0013] In the formwork installation process, a ring-shaped formwork 6 is installed inside the collapsible part 4. The formwork installation process is shown in FIG. 5. As shown in FIG. 5, the formwork 6 is installed at a predetermined interval (an interval equal to the thickness of the main body part) from the collapsible part 4. The formwork 6 has a retaining plate 61 in contact with the concrete and a support member 62 for supporting the retaining plate 61. The retaining plate 61 has a vertical part 63, an inclined part 64, and a bottom part 65 corresponding to the cross-sectional shape of the main body part 3. The upper end of the formwork 6 is open so that concrete can be poured. Since the thickness of the upper part of the main body part 3 is larger than the thickness of the lower part (thickened part 32), a gap (opening 66) is formed between the upper end part of the formwork 6 and the lower end of the main body part 3 of the existing shaft lining structure 2.

[0014] In the placing process, concrete is placed between the formwork 6 and the collapsible part 4 to form the main body part 3. The placing process is shown in Fig. 6. As shown in Fig. 6, concrete is poured from the opening 66 at the upper end of the formwork 6. After pouring the concrete, it is cured until a predetermined strength is developed. When the predetermined strength is developed in the concrete, the formwork 6 is removed.

[0015] According to the shaft lining structure 2 and the shaft construction method of the present embodiment, the collapsible part 4 made of a material having a lower rigidity than the main body part 3 (lining concrete) (including a material having a smaller compressive strength than the main body part and a lower rigidity (modulus of deformation) in the plastic region than the main body part) is interposed between the main body part 3 and the natural ground G. Therefore, even when a pushing force acts on the shaft lining structure 2 due to the deformation of the natural ground G, it is absorbed by the collapsible part 4. Therefore, the stress acting on the main body part 3 can be reduced, and thus the stability of the shaft 1 can be ensured. In addition, by reducing the stress generated in the lining concrete (main body part 3), the demolding time of the formwork 6 can be advanced, and thus the construction cycle can be speeded up. Further, by reducing the stress, it is possible to reduce the cost associated with reducing the lining thickness, and also to reduce the amount of concrete used and thus reduce the CO 2 emission. Since the collapsible part 4 is formed by pasting a sheet material, early construction is possible. In addition, by driving the anchor 5 into the natural ground G, the anchor 5 functions as a shear key, and the stability is further improved. In addition, the shaft lining structure 2 can be integrated with the natural ground G by the anchor 5 driven into the natural ground surface.

[0016] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately changed without departing from the spirit of the present invention. In the above-described embodiment, the strip-shaped resin sheet 41 is attached vertically (downward) to the natural ground surface, and the plurality of resin sheets 41 are connected in the circumferential direction of the shaft to form the collapsible portion 4. However, the method for forming the collapsible portion 4 is not limited. For example, the collapsible portion 4 may be formed by attaching a roll-shaped resin sheet 41 along the circumferential direction of the shaft 1. Further, the collapsible portion 4 may be formed by spraying a cementitious material containing cement, a porous material, and water onto the natural ground surface, or by spraying a resin material such as urethane onto the natural ground surface. Also, the collapsible portion 4 may be formed by installing a plate-shaped member (such as a resin material or a cementitious material). Also, the anchor 5 may be installed as needed. Steel materials or reinforcing bars may be embedded in the main body portion 3 as needed.

Explanation of Signs

[0017] 1 Shaft 2 Shaft lining structure 3 Main body portion 4 Collapsible portion 5 Anchor 6 Formwork G Natural ground

Claims

1. A ring-shaped main body made of hardened concrete; A shaft lining structure comprising a contractible portion interposed between the main body portion and a ground surface, A shaft lining structure, characterized in that the contractible portion is made of a material having lower rigidity than the main body portion.

2. The shaft lining structure according to claim 1, characterized in that the compressible portion is a hardened body formed by spraying a cement-based material containing cement, a porous material, and water onto the natural ground surface.

3. The shaft lining structure according to claim 1, wherein the shrinkable portion is a resin sheet attached to the natural ground surface.

4. The shaft lining structure according to claim 1, further comprising an anchor driven into the natural ground surface.

5. an excavation step of excavating the natural ground downward; a compressible portion forming step of installing a compressible material on the exposed natural ground surface by excavation of the natural ground; A form setting process of setting a ring-shaped form inside the compressible material; A shaft construction method comprising a pouring step of pouring concrete between the formwork and the compressible material.

6. The shaft construction method according to claim 5, wherein in the compressible portion forming step, a compressible material is sprayed onto the natural ground surface, and an anchor is driven into the natural ground surface.

7. The shaft construction method according to claim 5, characterized in that in the shrinkable portion forming step, a resin sheet is applied to the natural ground surface, and an anchor is driven into the natural ground surface.

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