JPH05263596A - Tunnel covering technique - Google Patents

Abstract

PURPOSE:To cut down introduction tension force impacted by PC cable. CONSTITUTION:An isolator 10, which isolates a concrete covering 6 and a base rock 8, is installed between the concrete covering 6 and the peripheral base rock 8 so as to stretch PC cable. Then, grout is poured in the rear surface of the contracted concrete covering 6. The tension force produced by prestress will not act on the neighboring base rock by the action of the isolator 10 during tension time, but every tension force will be introduced to the concrete covering 6. When design inner pressure is applied, both the concrete covering 6 and the base rock 8 will share the tensile force by way of the grout and the isolator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a concrete lining method for a tunnel which introduces prestress using a PC cable.

[0002]

[Prior art and its problems] Concrete lining for tunnels that introduces prestress with a PC cable (hereinafter P
Abbreviated as C lining. ) Has already been used in pressure channel tunnels, surge shafts and penstocks in Japan and overseas.
Has a track record of examples. For example, as shown in FIG. 7, this method uses the PC cable 2 and the jack 4 to apply the tension reaction force to the lining, and has an advantage that the tension force is surely introduced. However, since the concrete lining 6 is restrained by the surrounding bedrock 8, it is not always clear to which part the tension force is introduced.

As an example, as shown in FIGS. 6 (a) and 6 (b), a comparison will be made between the case where the concrete lining 6 is constrained by the surrounding bedrock 8 and the case where it is not constrained. The Young's modulus of concrete 6 is 2.5 × 10 ⁵ kgf / cm ² , and the Young's modulus of surrounding rock 8 is 1.0 × 10 ⁴ kgf / cm ² and 1.0 × 10 ⁵ kgf / cm ^2.
As a result, when the tension force shared by the concrete and the surrounding rock is calculated, the case of only the concrete lining 6 (Fig. 6
When (a)) is set to 100% and the surrounding bedrock 8 is constrained (Fig. 6 (b)), the Young's modulus is 1.0 × 10 ⁴ kgf /
86% at cm ² , Young's modulus 1.0 × 10 ⁵ kgf / cm ²
Is 37%. That is, the tension force introduced into the concrete lining 6 also flows into the surrounding bedrock 8, and becomes 37 to 86% of the given tension force depending on the mechanical properties of the surrounding bedrock.

On the other hand, it is considered that the tensile force generated by the design internal pressure due to the pressure water in the tunnel is also shared by the concrete lining 6 and the surrounding bedrock 8 in the same ratio. Therefore, if the PC cable 2 is tensioned with a compression force equal to the tension force due to the design internal pressure as the required tension force, no tension force is generated in the concrete lining 6.

This is the conventional way of thinking of the design of PC lining, but even if the tension force required for concrete lining is 50%, for this reason, the required tension force is 100%.
Therefore, the loss of tension is extremely large. In particular, in the case of a tunnel with a large design internal pressure, there is a problem that the required tension force becomes very large, the number of required PC cables increases, and the economical efficiency is significantly impaired.

[0006]

It is an object of the present invention to provide only 50% of the required tension for concrete lining directly to the concrete lining, even if the required tension is extremely large, to obtain the required tension. It seeks to reduce power.

[0007]

In order to achieve the above object, the present invention comprises:
In a concrete lining method for a tunnel in which prestress is introduced using a PC cable, an isolator is installed between the concrete lining and the surrounding bedrock to tension the PC cable, and then the concrete covering with a reduced diameter is used. It is characterized by injecting grout on the back of the work.

[0008]

The tension force due to the prestress is entirely introduced into the concrete lining due to the action of the isolator because the tension force does not flow to the surrounding rock mass at the time of tension. Further, when the design internal pressure is applied, the concrete lining and the surrounding bedrock share the tensile force together through the isolator and the grout.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. Example 1 FIG. 1 is a sectional view of an ideal tunnel for constructing a PC lining. As shown in the figure, if the excavated surface of the surrounding rock mass 8 is a perfect circle and is perfectly smooth, an isolator (isolator) is used. 1
When 0 is set, the ideal isolator 10 can be obtained by a simple edge cutting such as sandwiching one vinyl sheet or applying a release material to the rock surface.

When introducing the prestress, as shown in FIG.
As shown in, when tension is applied by using the PC cable 2 and the jack 4, etc., the concrete 6 is compressed and contracts inside the tunnel. Therefore, if the peripheral rock 8 and the concrete 6 are cut off from the peripheral rock 8, There is no restraint at all, and all the tension force is introduced into the concrete 6. If the gap created on the backside of the concrete lining after the tension is filled with grout, the concrete 6 will receive tension when the design internal pressure is applied and will spread to the outside of the tunnel.
Also, the internal pressure is transmitted, and the design internal pressure is shared by the PC lining 6 and the surrounding bedrock 8.

Embodiment 2 However, in reality, it is almost impossible to excavate a rock in a perfect circle and in a completely smooth manner. Due to the unevenness of the surrounding rock, it is possible to avoid restraining the concrete lining during tension. Can not. Therefore, the following structure can be considered as the structure of the isolator that makes this constraint as small as possible and can be ignored.

FIG. 2 is a sectional view of a tunnel in which a practical isolator 10 is installed. An elastic sheet 12 is installed between the surrounding rock 8 and the concrete lining 6. The elastic sheet 12 is made of rubber, PE, PVC, E
Resin-based sheets such as VA and PP are preferable. The thickness of the sheet should be the minimum thickness that can absorb the unevenness of the bedrock, generally 1
It is about 10 mm. FIG. 3 is a partially enlarged view of the isolator 10, and reference numeral 14 is a pipe for injecting grout on the back surface of the seat 12, which grouts the gap between the seat 12 and the rock 8 after tension.

The elastic sheet 12 is made of rock 8 and concrete 6
The edge of the rock is cut, and the unevenness of the bedrock 8 that restrains the movement of the concrete 6 is absorbed by the sheet thickness. Further, by grouting the back surface to eliminate the voids, when the concrete lining 6 expands due to the action of the design internal pressure, the reaction force can be transmitted to the surrounding bedrock 8 through the elastic sheet 12 and the internal pressure can be shared. it can.

Third Embodiment As another embodiment of the isolator 10, the elastic isolator 10 may be formed by spraying a rubber-based, asphalt-based, resin-based emulsion, urethane foam, or the like onto the surface of the rock 8. The layer thickness is about 1 to 10 mm, and grout is injected into the voids on the back side of the concrete lining 6 formed by tension in the same manner as in the second embodiment.

EXAMPLE 4 Concrete or mortar is placed by providing an inner formwork as a primary lining to form a perfect circle and a smooth surface, a peeling layer is provided and a rim is cut off, and then secondary concrete is placed. .. The primary lining may be ironed, and it needs to be thick enough to absorb all the unevenness of the bedrock.
The degree is enough.

Example 5 The primary lining of Example 4 is made of a resin or concrete precast panel. After tensing the space with the bedrock, grout is injected.

Embodiment 6 This embodiment uses the isolator itself as a space for grout injection in order to surely perform grout injection after tension. FIG. 4 is a partial sectional view of the isolator 10, and FIG. As shown in FIG. 5 as a partial perspective view, the spacers 20 are attached to the bedrock 8 and concrete 6 respectively.
Install between The spacer 20 includes a front plate 22 and a back plate 24.
The ribs 26 are connected and reinforced by ribs 26, and have strength enough to withstand the concrete pouring pressure. Further, a large number of through holes 28 are provided in the back plate 24 and the ribs 26 so that the supplied grout can flow freely.

If the grout is injected from the injection pipe 14 after the PC cable 2 is tensioned, the spacer 20 secures the grout injection space. Therefore, not only the inside of the spacer 20 but also the space between the back plate 24 and the bedrock 8 is secured. It is possible to fill the grout evenly in the narrow voids.

[0019]

The concrete lining method for a tunnel according to the present invention intervenes an isolator so that the tension force required for concrete lining does not flow to the surrounding rock.
Since it can be given only to the concrete lining, it is possible to reduce the tension of introduction, reduce the number of PC cables, and improve the economical efficiency. Further, since all of the introduced tension force is shared by the concrete lining and applied to the concrete as prestress, cracks do not occur and a highly water-tight and highly reliable lining can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an ideal tunnel for PC lining construction.

FIG. 2 is a sectional view of a tunnel in which an isolator made of an elastic sheet is installed.

3 is a partially enlarged view of the isolator 10 shown in FIG.

FIG. 4 is a partial cross-sectional view of a tunnel in which an isolator is installed using a spacer.

FIG. 5 is a partial perspective view of a spacer.

FIG. 6 is a tunnel cross-sectional view for a calculation model of tension sharing.

FIG. 7 is a tunnel cross-sectional view for explaining a conventional PC lining.

[Explanation of symbols]

 2 PC cable 4 Jack 6 Concrete (lining) 8 Peripheral rock 10 Isolator 12 Elastic sheet 20 Spacer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Tezuka 2-1 Tsukudocho, Shinjuku-ku, Tokyo Kumagai Gumi Tokyo Head Office (72) Inventor Tsutomu Matsuo 2-1 Tsukudo-cho, Shinjuku-ku, Tokyo Kumagai Gumi Tokyo Head Office

Claims (2)

[Claims] 1. In a concrete lining method for a tunnel in which a prestress is introduced by using a PC cable, an isolator is provided between the concrete lining and the surrounding bedrock to provide P
A concrete lining method for a tunnel, which comprises straining a C cable and then injecting grout into the back surface of the reduced diameter concrete lining. 2. The isolator comprises a spacer having a grout injection space.
The concrete lining method for the tunnels described.