JPH0573876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shoring method for simply protecting the excavated ground surface to prevent it from collapsing when excavating a tunnel.

(Conventional technology) Conventionally, shoring for tunnel excavation involves placing plates on the inside of the ground surface inside the excavated tunnel.
A method of supporting this with pillars has been used for a long time, but this method creates a gap between the shoring plate and the excavated ground surface, so there is a risk that the loosening of the ground due to excavation will increase. There is.

Therefore, in recent years, as an alternative to conventional shoring, rapid-setting concrete is sprayed onto the ground surface early after tunnel excavation to provide a simple concrete covering on the ground surface, and this is used as shoring. There is a way (usually NATM) to do this.

This method includes a wet method in which quick-setting concrete is mixed with a water-cement quick-setting agent and aggregate in advance, which is pumped mechanically or with compressed air added thereto, and then sprayed with a nozzle. There is also a dry method in which water is added at the spray nozzle position when a mixture of aggregates is sprayed with compressed air.

This method of forming shoring by spraying concrete involves excavating and adhering the concrete to the ground surface early after excavation, so it is possible to minimize the loosening of the ground. It has the advantage of being possible.

(Problem to be solved by the invention) However, in both the wet method and the dry method, concrete is sprayed onto the ground surface using compressed air, so a large amount of concrete is used before hardening. There is a problem in that the concrete does not adhere to the ground surface and scatters as dust, significantly deteriorating the working environment and harming the health of workers.

Also, the return rate of concrete during spraying is 25
~40%, which is the concrete loss rate due to scattering without adhesion, and there was a problem that a large amount of expensive quick-setting concrete was wasted.

In view of these conventional problems, the present invention aims to provide a shoring method that can eliminate concrete loss and form shoring with a simple layer of quick-setting concrete without scattering concrete. It is something.

(Means for Solving the Problems) The gist of the present invention for solving the conventional problems as described above and achieving the intended purpose is to use an excavator to excavate a predetermined length at a time, and for each excavation. In the shoring method for tunnel excavation, in which concrete is poured inside the tunnel ground surface which is sequentially formed to form a shoring structure, the ground surface is sequentially formed after each excavation of a predetermined length. The shoring concrete is cast on the inside of the surface first to direct the back end side, and the tip side is filled with air to maintain the formation and supported with expandable tube material to form a sheet material. A method for shoring in tunnel excavation is provided, which comprises the steps of: placing a sheet of material in tension, and placing fluid, quick-setting concrete between the sheet material and the ground surface within the tunnel.

(Function) In this shoring method, after excavating a predetermined length with an excavator, the excavator is moved backwards, a sheet material is brought in and spread out, and its leading edge is fixed to the tube material. By filling the tube with air and expanding it in this state, the tip of the sheet material is held inside the ground surface at the tip of the tunnel excavation. Then, by fixing the rear end of the sheet material to the concrete surface of the inner surface of the ground previously formed using adhesive, a space for concrete placement is created between the sheet material and the ground surface. It is formed.

By pouring quick-setting concrete into this space, the concrete is deposited sequentially from the bottom of the space, hardens in a short time, and becomes a structural material that holds the concrete poured next, making it easy to move upwards one after another. A shoring structure consisting of a concrete covering layer is formed.

(Example) Next, an example of implementation of the present invention will be described with reference to the drawings.

First, an appropriate excavator (not shown) is used to excavate a certain length a within a range that will not collapse depending on the bearing strength of the ground in the tunnel excavation section. Thereafter, the excavation machine is moved backward, and the sheet material 1 and the tube material 2 are carried into the excavated area.

The sheet material 1 is made of a cloth material that is breathable but does not easily permeate concrete, and pipe connection ports 3, 3, . . . are formed at a plurality of locations. The tube material 2 is made of rubber and is formed into an arch-shaped elongated bag, which expands when filled with compressed air and maintains its Arts-like shape. Further, the arch shape is formed to match the cross-sectional shape of the inner vagina of the tunnel to be excavated, so that the outer circumferential surface is in close contact with the ground surface 4 on the inner circumference of the tunnel when inflated.

Next, the outer edge of the sheet material 1 carried into the tunnel is bonded with an adhesive to the inner surface of the concrete 5 previously placed in the tunnel. On the other hand, the tube material 2 is filled with compressed air and expanded, and the tube material 2 supports the inner edge of the sheet-like material 1. The sheet material 1 is stretched.

When tensioning the sheet material 1, if the excavation length a for one course is long and the central portion of the sheet material 1 sags greatly, tighten the lock bolts 6, 6, etc. as shown in Fig. 2. The intermediate portion of the sheet material 1 may be supported by driving into the ground surface 4, and lock bolts 8 may be driven into the face end surface 7 of the tube material 2 in the tunnel as shown in FIG. A large number of lock bolts 8 are placed along the inner circumferential surface of the concrete 5, and wire rods 10 are stretched between the lock bolts 8 and the anchors 9 on the inner circumferential surface of the concrete 5 placed earlier. The intermediate portion may be supported.

After the sheet material 1 is stretched in this way, concrete 12 is filled into the gap 11 between the sheet material 1 and the ground surface 4, as shown in FIG. This concrete 12 is mixed with water, cement, fine aggregate, coarse aggregate, quick-setting agent, and other admixtures for fluidity, and hardened in a short time.
3 and pour it through the concrete injection pipe 14 from the pipe connection ports 3, 3, . . . . At the time of pouring, concrete pouring pipes 13 are sequentially inserted from the bottom pipe connection port and successively raised upward so that the void 11 is filled from the bottom.

By pouring concrete in this way, the concrete hardens in order from the bottom along the pouring hole, and the lower hardened part supports the upper concrete that will be poured next. Therefore, the sheet material 1 does not need to have a proof strength to support all the concrete to be poured.

Furthermore, if the ground surface 3 is weak, after filling the void 11 with concrete, the tube material 2 may also be filled with concrete to form a concrete layer for shoring.

After a concrete layer is formed inside the ground surface 3 to form a shoring structure in this way, the face end surface 7 is excavated again, and concrete layers are sequentially formed in the same manner as described above.

(Effects of the Invention) The present invention is configured as described above, and a sheet-like material is supported and stretched inside the ground surface in a tunnel by a tube material that can be expanded and contracted, and the sheet-like material and the ground surface are stretched. By filling fluid and quick-setting concrete between the surface and the surface, it is possible to easily and quickly cover the ground surface with shoring consisting of a concrete layer, which is more effective than conventional spraying methods. There is no concrete scattering, there is no deterioration of the working environment, and there is no loss of concrete, making it possible to perform construction economically.

[Brief explanation of the drawing]

Figure 1 is a longitudinal side view of an example of a stretched state of sheet material, Figures 2 and 3 are longitudinal side views showing other examples of stretched sheet material, and Figure 4 is a vertical side view of an example of a stretched state of sheet material. It is a vertical front view showing a filling state. 1... Sheet material, 2... Tube material, 3...
Pipe connection port, 4...Mound surface, 5...Concrete, 11...Void.

Claims (1)

[Claims] 1. In a shoring method for tunnel excavation in which a predetermined length is excavated by an excavator and concrete is cast inside the tunnel ground surface formed sequentially with each excavation to form a shoring, the predetermined length excavation Shoring concrete is first cast on the inside of the ground surface in the tunnel, which is formed in each tunnel, to direct the shoring concrete toward the rear end, and the tip side is filled with air to maintain its shape. A sheet-like material is stretched by supporting it with an expandable and contractible tube material, and fluid, quick-setting concrete is placed between the sheet-like material and the ground surface in the tunnel. Shoring method for tunnel excavation.