JPH0240835B2 - CHISHITSUFURYOCHINIOKERUTONNERUNOKOCHIKUKOHO - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for constructing a tunnel in a geologically poor land, and in particular to a method for constructing a tunnel in a geologically poor land in which collapse of the ground can be prevented by using double pipes. be.

Conventionally, when constructing tunnels, arch-shaped steel supports were constructed every time a predetermined distance was excavated to prevent the excavated tunnel ground from collapsing, except in cases where the geology was solid. Tunnel excavation work was carried out repeatedly through a cycle of blasting with dynamite or direct excavation with a machine, offsetting, and constructing the support.

Particularly when constructing in a location with poor geology, there is a risk that the tunnel ground may collapse before the shoring is constructed, so sheet piles are inserted between the already constructed shoring and the tunnel ground. In order to prevent this, the so-called sewn-up method and the feed sheet pile method were used to prevent this by driving in sheet piles to compensate for the amount of ground that had been cut down.

However, when this construction method is adopted,
When concrete is sprayed onto the tunnel ground as a primary lining, a gap is created between the back surface of the sheet pile and the tunnel ground, which has the disadvantage that the function as the primary lining cannot be fully demonstrated.

For this reason, the so-called pre-lock bolt method and pre-pipe method have been proposed, in which bolts and pipes are driven toward the outer circumference of the excavation, but in these methods, a large portion of the bolts and pipes fall within the excavation area. Not only is it uneconomical because the excavation is discarded, but the pouring work must be carried out using machinery and scaffolding at the face, and the excavation cycle time is extended because this work is incorporated into the series of excavation cycles described above. There was also this problem.

In addition, in the above-mentioned advanced lock bolt construction method, etc., bolts are driven diagonally upward from the face, so the ground beneath the bolts is likely to collapse, and furthermore, the bolts, etc. protrude from the tunnel surface after excavation. There was also the problem that the excavation remained in a serrated state, resulting in an increase in the amount of shotcrete.

This invention was made in view of these conventional problems, and its purpose is to make it possible to safely and economically construct tunnels in poor geological locations with a relatively simple configuration. The purpose is to provide a method for constructing tunnels in geologically poor areas.

In order to achieve this object, the present invention uses a double pipe, in which a small-diameter inner pipe is housed within a cylindrical outer pipe, between the shoring and the excavated tunnel ground in a tunnel construction method using shoring. After arranging a plurality of inner pipes along the excavation cross section and almost perpendicular thereto and fixing them to the shoring, each inner pipe is sequentially extended in the excavation direction along the excavation surface as the excavation progresses. It has the characteristic of preventing the collapse of the ground.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 to 3 show an embodiment of the method for constructing a tunnel in a geologically poor area according to the present invention.

The main construction method shown in the figure is to construct a predetermined tunnel by sequentially installing supports 10 and 10' made of arch-shaped H-shaped steel into an excavated tunnel. , which shows the case where the construction method of the present invention is employed as an aid only in areas with poor geology.

It is relatively easy to detect areas with poor geology in advance because a thorough geological survey is carried out when constructing a tunnel.When construction progresses to an area with poor geology, the preliminary shoring 10, 1
0' and the tunnel ground 12 after excavation, a double pipe 18 is placed between a cylindrical outer pipe 14 and a cylindrical inner pipe 16 having a smaller diameter than the outer pipe 14, as shown in FIGS. 1 and 2. As shown in the figure, a plurality of pipes are arranged along the excavation cross section and almost perpendicular to the excavation cross section so as to span between the preceding shorings 10 and 10', and both ends of the outer pipe 14 are formed into a U shape. Bolts 20 are also screwed and fixed to the ribs 10a of the preceding shoring 10, 10'.

In this case, preferably, a wedge-shaped camber 22 is inserted between the front preceding shoring 10 and the outer pipe 14, so that the double pipe 1
When the inner pipe 16 is extended toward the excavation surface side as the excavation progresses, as will be described later, screwing the U-shaped bolt 20 with the U-shaped bolt 20 in a state where the inner pipe 8 is inclined and follows the ground will cause the tunnel ground to fall. It can better adhere to the mountain 12 and prevent the rock 12 from collapsing more effectively.

After this, concrete 23 is sprayed to embed a part of the preceding shoring 10 and the double pipe 18, and these and the ground 1
2 is used as the primary lining to secure it, and then excavation is performed in areas with poor geology. In this case, as the excavation progresses, the inner pipe 16 of the double pipe 18 is moved in the excavation direction along the excavation surface. By proceeding with the excavation while extending the inner pipe 16, the outer circumferential surface of the inner pipe 16 comes into contact with the excavated tunnel earth 12, and acts as a cantilever supporting the preceding shoring 10, thereby preventing the earth 12 from collapsing. excavation can proceed while

Next, when the predetermined length of excavation is completed, a trailing shoring 24 is installed adjacent to the preceding shoring 10, and a primary lining is performed by spraying concrete.
In this case, disposing the gold steel 25 between the extended inner pipe 16 of the double pipe 18 and the tunnel ground 12 so as to cover the entire excavated surface means that small pieces of rock can be removed from the gap of the inner pipe 16. This is desirable because it prevents the outer pipe 14 and the inner pipe 16 from falling, and the connection between the outer pipe 14 and the inner pipe 16 is reinforced, increasing the strength against the collapse of the ground 12.

Further, in the above embodiment, after the double pipe 18 is screwed and fixed to the preceding shoring 10, 10' with U-shaped bolts 20, and after concrete 24 is sprayed, the inner pipe 16 is extended. Although we have shown the case where the concrete 24 is excavated, it is also possible to proceed with the excavation work by simply screwing and fixing the U-shaped bolts 20 without spraying the concrete 24.
Furthermore, the earth 12 after excavation is placed in the inner pipe 1 as described above.
6 is functioning as a cantilever beam, excavation progresses sequentially, and concrete 23 is added to several sections at once.
It is also possible to carry out the 11th lining by spraying.

Now, when a tunnel is constructed in a geologically poor area with the above-mentioned configuration, it is relatively easy to attach the double pipe 18 to the supports 10, 10', and In the conventional construction method, the double pipe 18 placed between the shoring 10, 10'
It is possible to replace the span pipe that was placed in between, and because the number of span pipes is reduced, the excavation cycle time will not be significantly extended as in the advance bolt method, but on the contrary, it will be shortened. can do.

Additionally, no special scaffolding or machinery is required to install the double pipe 18, and since the double pipe 18 is inexpensive, the economic effect is extremely large in addition to the shortened cycle time. .

Furthermore, even when concrete is sprayed as the primary lining, there is no risk of creating voids on the back of the sheet piles, unlike in conventional seamed or fed sheet pile construction methods, and the primary lining can be completed completely. In addition, unlike the conventional pre-lock bolt construction method, no additional excavation is required, so the amount of shotcrete does not increase.

Furthermore, since small collapses of the tunnel earth 12 can be prevented by providing the metal steel 25, the psychological effect of visual safety is added, and face work can be carried out with peace of mind.

In the above embodiments, a case has been described in which a tunnel to be constructed has a geological defect at a specific location, but the present invention is of course applicable even when the geological defect extends over the entire length of the tunnel.

As explained in detail in the embodiments above, the present invention is a tunnel construction method using shoring, in which a plurality of double pipes are arranged between the shoring and the tunnel ground, and as excavation progresses, the inner pipes By extending the length of the tunnel, tunnel excavation work can be carried out while preventing the collapse of the ground after excavation.
Since this can be effectively prevented without prolonging the excavation cycle time, tunnels can be constructed safely and economically.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, and FIG. 1 is an explanatory diagram showing the arrangement of double pipes;
2 is a sectional view of FIG. 1, and FIG. 3 is a partially enlarged view of FIG. 1. 10, 10'...Advanced shoring, 10a...Rib,
12...Tunnel ground, 14...Outer tube, 16...
Inner pipe, 18...Double pipe, 20...U-shaped bolt, 2
4... Trailing shoring.

Claims (1)

[Claims] 1. In a method of excavating a tunnel by sequentially installing supports inside the tunnel in order to prevent the tunnel ground from collapsing after excavation, there is a tunnel that falls between the support and the excavated tunnel ground within the cylindrical outer pipe. A plurality of double pipes containing inner pipes with a smaller diameter than the outer pipe are arranged along the excavation cross section so as to be almost perpendicular thereto, and are fixed to the shoring, and as the excavation progresses, each inner pipe is A method for constructing a tunnel in a geologically poor land, characterized in that the pipe is successively extended in the excavation direction along the excavation surface to prevent the collapse of the ground after excavation.