JPH0313689A - Construction method for tunnel - Google Patents

Abstract

PURPOSE:To construct a tunnel safely and efficiently by forming a strength augmentation area surrounding the whole periphery of an excavation section and a water stop area surrounding it by chemical injection at the portion along the excavation section where the tunnel is to be formed, and excavating the tunnel. CONSTITUTION:Working tunnels 4 are formed along an excavation section prior to a main tunnel T to be formed, and chemical injection pipes 5 injecting a chemical from the inside of tunnels 4 to improve the ground are buried in the ground G. A chemical is injected into the ground G through chemical injection pipes 5 by chemical injection devices installed in tunnels 4, and a water stop area 2 is formed by injection pipes 5A and a strength augmentation area 3 is formed by injection pipes 5B respectively. The second strength augmentation area 3 ' is formed by chemical injection pipes 5C inserted into the ground from a working face. The working face is stabilized, the safety at the time of excavation is improved, and lining processes can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for constructing a tunnel, and particularly to a method for constructing a tunnel accompanied by ground improvement.

[Conventional technology]

When excavating a tunnel, if the excavated ground is unconsolidated water-containing ground, in order to ensure the safety, economy, and construction period of the construction, it is necessary to i) stabilize the face, ii) prevent spring water, i)
ii) Efforts must always be made to prevent ground subsidence. These are particularly important factors in excavation using the NATM method.

As an effective ground reinforcement method for tunnel excavation using the NATM construction method, etc., the chemical grouting method (chemical injection method) has traditionally been widely used.In this method, for example, cement milk or cement bentonite was used as the injection agent. (commonly known as CB) is injected under pressure using a pressure device.

Furthermore, when improving the ground during tunnel excavation, such work has conventionally been carried out from the ground surface or inside the tunnel.

[Problem to be solved by the invention]

However, the above-mentioned conventional ground improvement method has caused the following problems.

In other words, when improving the ground by injecting chemicals as described above before excavating a tunnel, conventionally only an improved zone was formed in one layer, so both the water stopping effect and the ground stabilizing effect were achieved. It was not possible to be fully satisfied. In other words, in order to obtain water-stopping properties, it is necessary to use a chemical solution with relatively low viscosity and low thixotropy so that it can sufficiently penetrate into the fine gaps such as the fine sand that makes up the ground. On the other hand, if a chemical solution with high viscosity and high thixotropy is used to obtain a strong ground consolidation effect, sufficient water-stopping properties cannot be obtained due to low permeability. It is.

If emphasis is placed on water-stopping effects, problems will remain with the stability of the ground during tunnel excavation, while on the other hand, if emphasis is placed on consolidation effects, groundwater will flow in and problems will arise with the self-sustainability of the face. There is also the possibility of triggering a quicksand phenomenon.

For this reason, conventionally, if the excavated ground is unconsolidated water-containing ground (extremely soft), there has been a problem that excavation methods such as the NATM method cannot be applied.

In addition, when performing chemical injection work from the ground, it is necessary to set up a construction yard above ground, which may occupy various above-ground facilities such as traffic routes, and the depth of the tunnel increases. If it is large, there is a problem that the construction accuracy will decrease.On the other hand, if it is carried out from inside the main tunnel, the soil improvement process and the tunnel excavation process are carried out alternately, resulting in poor work efficiency and the need for soil improvement equipment. There was a problem in that the number of units was also limited, which required a long construction period.

The present invention was made in view of the above circumstances, and it is possible to reliably improve soft ground such as unconsolidated water-containing ground, which was previously considered difficult to construct with the NATM method, etc., and is therefore safe. and can build tunnels efficiently.
The purpose is to provide a method for constructing tunnels.

[Means to solve the problem]

In the method for constructing a tunnel according to claim 1 of the present invention, in constructing a tunnel, in advance, a portion of the ground along an excavated portion where a tunnel is to be formed is provided with a strength increasing material that surrounds the entire circumference of the excavated portion. The method is characterized in that a region and a clean water region surrounding the strength-increasing region are formed by injecting a chemical solution, and then a tunnel is excavated.

Furthermore, the tunnel construction method according to claim 2 of the present invention includes:
2. The method for constructing a tunnel according to claim 1, when forming the strength-increasing region and the water supply region, in advance of the main tunnel to be constructed, a working tunnel is constructed along the excavated portion where the main tunnel is to be formed. The method is characterized in that the process is carried out using a chemical injection pipe placed into the ground from inside the working tunnel.

Furthermore, the method for constructing a tunnel according to claim 3 of the present invention is characterized in that, in the method for constructing a tunnel according to claim 1, the strength-increasing region is configured in multiple layers by injecting the chemical solution a plurality of times. It is something.

[For production]

By forming a water-stop area and a strength-increasing area around the entire circumference of the excavated part, both the water-stop action and the ground stabilization action of the excavation part can be reliably obtained, making tunnel excavation efficient in a short period of time. It can be done quickly and safely.

In that case, by performing the water stop area and the strength increasing area from the working tunnel constructed prior to the main tunnel, ground improvement can be efficiently performed without being affected by the depth at which the tunnel is formed.

In addition, if the strength increasing region is formed in multiple layers,
The stability of the face during excavation can be further improved.

〔Example〕

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

FIG. 1 shows a first embodiment of the present invention, in which reference numeral T indicates a tunnel to be constructed, and reference numeral G indicates the ground on which the tunnel T is to be formed.

In this case, the ground G is unconsolidated water-containing ground.

When excavating the above-mentioned tunnel T, first, in the part of the ground G along the excavation part l where the tunnel T is to be formed,
By injecting the chemical solution, a water stop area 2 is formed to prevent spring water such as underground water. This water stop area 2 extends around the entire circumference of the excavation part 1 as shown in the figure, and also extends to the excavation part l.
Formed over the entire length of. Here, the water stop area 2 is formed to have a very large diameter compared to the diameter of the tunnel T to be formed, that is, to surround the excavated portion l over a wide range.

In order to form this water-stop region 2, a chemical solution having a relatively low viscosity and excellent permeability into the ground G is used. Further, when injecting a drug solution, it is possible to use a conventional drug solution injection method, but the method according to claim 2 of the present invention is more effective.

This will be discussed later.

Once the clean water area 2 has been formed as described above, the strength increasing area 3 is then formed by injecting a chemical into the inside or central part of the water stop area 2.

The chemical liquid injected here has a higher viscosity and a higher chicken tropism than the chemical liquid used to form the water stop area 2, and as a result, the strength increasing area 3 forms the water stop area 2. For example, the l-axis compressive strength is several times to several times higher than that of the water stop area 2.

The strength-increasing forehead region 3 can be formed by the conventional chemical injection method, similar to the water-stopping region 2, but it is preferable to use the method described below.

This strength-increasing region 3 is formed as described above (inside the water-stopping region 2), but here, the strength-increasing region 3 and the water-stopping region 2 may be formed in a completely separate state. Instead, both regions are formed by wrapping the inner part of the water-stopping region 2 and the outer part of the increasing-strength region 3, or alternatively, the increasing-strength region 3 is formed completely over and over the water-stopping region 2. In other words, this is because both regions are formed by injecting a chemical solution, and the chemical solution cannot create a clear boundary surface on the ground G.

Then, as described above (if the strength increasing region 3 and the water stop region 2 surrounding it are formed in the excavated portion 1), the tunnel T may be excavated along the excavated portion 1.

An increased strength region 3 is formed around the excavated portion 1 of the ground G, and the increased strength region 3 is surrounded by the water cutoff region 2. Therefore, even during excavation, the face and wall surface are not affected. Stability is sufficiently ensured, and spring water is reliably prevented.

In this way, according to the above method, even if the excavated ground is unconsolidated water-containing ground, solid consolidation stability of the ground and prevention of groundwater springing are achieved.
This makes it possible to apply the NΔTM construction method, which has been considered difficult in fl soft ground, and allows the construction of the tunnel T to be carried out economically and safely.

FIG. 2 illustrates a method for forming the water-stop region 2 and the strength-increasing region 3.

First, the working tunnels 4, 4 are formed prior to the main tunnel T to be formed. These working tunnels 4 are constructed along the excavated portion 1 in which the main tunnel T is to be formed. This working tunnel 4 has an inner diameter of 3 to 5 m, for example, and is a shield tunnel in this embodiment.

That is, in this case, these working tunnels 4.4 are constructed using a shield excavator while performing segment lining, like ordinary shield tunnels. However, although some of the lining segments used here are not shown in the drawings, some of them are the chemical liquid injection pipes 5, 5, etc., which will be described later. ... can be buried in the surrounding ground G from inside this working tunnel 4,
An opening is formed that penetrates in the thickness direction.

Once the working tunnels 4, 4 have been constructed in advance along the excavated portion of the main tunnel T as described above, next, chemical solution injection for injecting a chemical solution for ground improvement from inside these working tunnels 4. Pipes 5゜5,... are buried in the ground G. This work of burying the chemical injection pipe 5 is carried out by drilling a hole in the ground from inside the working tunnel 4 through the opening of the segment using a drilling machine, and then similarly burying the segment opening from inside the working tunnel 4. Do it through.

Chemical solution injection tube 5,5. ... is buried, the chemical liquid is injected into the ground G by force-feeding the chemical liquid to each chemical liquid injection pipe 5 using a chemical liquid injection device (not shown) installed in the working tunnel 4.

In order to form the water supply region 2 and the strength-increasing region 3 by this method, as shown in FIG. A chemical solution for forming the water-stop region 2 and a chemical solution for forming the strength-increasing region 3 may be respectively injected using these chemical solution injection tubes.

FIGS. 3 to 6 respectively show cases in which the set position and number of the work tunnels 4 are changed in carrying out the above method.

The one in Fig. 3 is one in which one is provided above the main tunnel T where the working tunnel 4 is to be formed, and the one in Fig. 4 is
The one provided on both sides of the main tunnel T at a certain distance from the main tunnel T, the one in Figure 5 has the main tunnel T 2
In the example of parallel construction, one working tunnel 4 is provided between the main tunnels T and T to be formed, and the one in Figure 6 is one that is formed prior to the excavation part l. be. The working tunnel 4 in FIG. 6 will be demolished when the main tunnel T is formed.

In this way, the number and setting position of the work tunnels 4 are arbitrary, and even when the work tunnels 4 are not inverted, for example, the work tunnels 4 can be
Three pieces may be provided so as to form a triangle.

According to the above method, the ground improvement equipment etc. do not occupy the ground surface (in addition, it is possible to carry out efficient and highly accurate ground improvement, and it does not interfere with the excavation work of the main tunnel T. , construction work of the main tunnel T can be performed extremely efficiently.Furthermore, the work tunnel 4, which is constructed prior to the main tunnel T, is used as a material entry route and an excavated earth and sand transport route during construction of the main tunnel T. Moreover, after the completion of this tunnel T, it can not only be used as an I1m shaft, a ventilation shaft, or a common shaft as ancillary facilities of this tunnel T, but also the working tunnel 4 can be made sufficiently rigid so that multiple tunnels can be constructed. When constructed, these working tunnels 4, 4, etc. function as arch supports for the main tunnel T, which has the advantage of further strengthening the ground reinforcement effect (excluding the one in Figure 6). ).

Next, FIG. 7 shows another embodiment of the present invention. In this embodiment, after the water cutoff region 2 and the strength increasing region 3 are formed, a further center portion of the strength increasing region 3 is formed. A second strength-increasing area 3' is formed by further injecting a chemical solution for ground reinforcement into a nearer part, that is, a part closer to the excavation part l. Forming the water stop region 2 in a state surrounding the strength increasing region 3 is the same as in the above embodiment. Further, in this case, the means for forming the clean water region 2 and the strength increasing region 3 can be performed in the same manner as in the above embodiment.

The formation of the second strength-increasing region 3''
However, as shown in Fig. 7, for example, as the tunnel T is formed (excavation), chemical injection pipes 5C, 5C inserted into the excavated ground from the face in advance of the tunnel T are used. , . . .

The chemical solution for forming this second increased strength region 3° may be the same as the chemical solution used to form the increased strength region 3, or a chemical solution with a stronger ground consolidation effect may be used. may also be used.

Even in the former case, the soil strengthening effect is enhanced by repeated use of chemical solutions, but in the latter case, the ground strengthening effect is further enhanced.

According to this embodiment, the face part is further reinforced by the second strength-increasing region 3', so the face of the − layer is stabilized, further increasing safety during excavation. At the same time, the lining process can be simplified.

In addition, by the same operation as above, the third, fourth...
It is also possible to form a region of increased strength (not shown), and in this case, the ground in the excavated area can be further stabilized, and it can be applied effectively to particularly weak parts of the ground. It is.

It goes without saying that the present invention is not limited to tunnels using the NATM construction method, but can also be applied to other commonly practiced tunnel construction methods. Furthermore, the present invention is not limited to tunnels, but can be applied to the construction of other underground structures (underground spaces) that are constructed using a so-called excavation process.

Further, in the embodiment, the working tunnel 4 has been described as a shield tunnel, but the working tunnel according to the present invention is not necessarily limited to a shield tunnel. However, if the work tunnel is made into a shield tunnel in this way, it is extremely effective because its cross section can be made sufficiently thick, there is no restriction on the extension distance, and it can easily accommodate curved construction. be.

〔Effect of the invention〕

As explained above, according to the method for constructing a tunnel according to claim 1 of the present invention, both prevention of underground water springing and stabilization of the tunnel wall surface during excavation are reliably achieved, so that This makes it possible to construct tunnels safely, reliably, and economically.

・Furthermore, according to the method for constructing a tunnel according to claim 2, it is possible to carry out highly accurate ground improvement without occupying the ground surface, and also because it does not interfere with the excavation work of the main tunnel. construction work can be carried out extremely efficiently. Moreover, when multiple working tunnels are installed, these working tunnels function as arch supports and further strengthen the ground, making it easier to construct tunnels. It can be done more efficiently.

According to the tunnel construction method according to claim 3,
In addition to the above-mentioned effects, the stability of the face surface is further increased, making it possible to carry out more efficient and safe excavation work, especially on soft ground.

[Brief explanation of drawings]

FIG. 1 is a front vertical sectional view showing the ground of the tunnel construction part according to claim 1 of the present invention, and FIG. 2 is a front longitudinal sectional view showing the ground of the tunnel construction part according to claim 2 of the invention together with a working tunnel etc. The plan view and FIGS. 3 to 6 show other embodiments according to claim 2, and FIG. 7 is a front longitudinal cross-sectional view showing the ground of the tunnel construction part together with the working tunnel, and FIG. 7 is a claim of the present invention. FIG. 3 is a front vertical cross-sectional view showing the ground of the tunnel construction section according to item 3; G...ground, 'r...river/tunnel (heather tunnel), 1...excavation part, 2...
・Water stop area, 3... Strength increasing area, 3''... Second strength increasing area, 4...
Work tunnel, 5 (5A, 5 B, 5 G)... Chemical injection pipe.

Claims (1)

[Claims] 1) When constructing a tunnel, in advance, a region of increased strength surrounding the entire circumference of the excavated portion and an increased strength region are provided in a portion along the excavated portion in the ground where the tunnel is to be formed. A method for constructing a tunnel, characterized in that a water stop area surrounding the area is formed by injecting a chemical solution, and then a tunnel is excavated. 2) In the tunnel construction method according to claim 1, the strength-increasing region and the water stop region are formed in advance by carrying out work along an excavation section in which the main tunnel is to be formed, prior to the main tunnel to be constructed. 1. A method for constructing a tunnel, which comprises constructing a working tunnel and using a chemical injection pipe placed into the ground from inside the working tunnel. 3) The method for constructing a tunnel according to claim 1, wherein the strength-increasing region is constructed in multiple layers by injecting the chemical solution a plurality of times.