JPH0823261B2 - Parallel tunnel construction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a parallel tunnel for excavating a leading tunnel and a trailing tunnel in parallel.

[0002]

2. Description of the Related Art When excavating tunnels in parallel, if the distance between adjacent tunnels is extremely short, the stress in the intermediate ground portion (hereinafter referred to as "pillar portion") between the tunnels increases and the stability thereof is impaired. Therefore, it is necessary to reinforce the pillar portion. Various methods have been used to reinforce the pillar portion.For example, in the middle wall type construction method and other auxiliary construction methods, the ground stress is reduced by dividing construction, and support members are used. Or, a method of using various reinforcing members such as reinforcing or replacing the pillar portion is also practiced. In addition, a method of reinforcing the ground of the pillar portion by driving a PC anchor into the pillar portion has also been implemented.

[0003]

However, for example, a method of reinforcing the ground of the pillar portion with a plurality of PC anchors is a reinforcing method performed after excavating both the leading tunnel and the trailing tunnel. Before excavating the tunnel, there was a problem that it was necessary to reinforce the pillar part by supporting work in preparation for the excavation of the trailing tunnel.

Further, in order to tighten the ground of the pillar portion, P
Since it is necessary to tension the C anchor to introduce prestress, there are problems such as extra work and equipment required. Furthermore, each of the construction methods has a problem that it takes a lot of time and labor, and the construction period is unavoidable, and the construction cost is high.

The present invention has been made in order to solve the above problems. When excavating a plurality of tunnels in parallel in close proximity to each other, the pillar portion can be surely reinforced, and It is an object of the present invention to provide a method for constructing a parallel tunnel that enables safe construction.

[0006]

According to a first aspect of the present invention, there is provided a method of constructing a parallel tunnel, wherein a side wall portion of the preceding tunnel is provided in an intermediate ground portion between the preceding tunnel and the following tunnel. A plurality of anchor holes are drilled on the trailing tunnel side, and an anchor bolt or an anchor steel pipe having a diameter-expanding pipe attached to the tip end is inserted into the anchor hole, and the diameter-increasing at the tip end of the anchor hole. Expand the pipe into the surrounding ground in the shape of an umbrella.

Further, a method for constructing a parallel tunnel according to a second aspect of the present invention is the same as the method for constructing a parallel tunnel according to the preceding paragraph, wherein the diameter-expanding pipe is double or more steel pipes having different diameters. And the elongated slits are formed on the side wall portions of the steel pipe so as to be circumferentially shifted so as not to overlap each other in the axial direction.

[0008]

[Operation] By the construction method as described above, the increase in the lateral (horizontal) strain of the pillar portion due to the Poisson effect of rock caused by the stress release during the backward tunnel excavation is applied to the anchor member such as the anchor bolt or the anchor steel pipe. Since the tension can be generated and the natural strength of the natural ground can be further increased, the pillar portion of the adjacent tunnel is reinforced.

This construction method is one of the conventional reinforced earth construction methods that applies the mechanism of tensile strength, and mainly improves the pseudo-shear strength by the internal friction angle (φ) of the natural ground. Is. Therefore, when φ is high, the reinforcing effect is increased.

In order to examine the applicability of this method,
Assuming an adjacent tunnel in soft rock and sediment, a trial calculation of the relationship between the compressive strength of the pillar and the safety factor and the required amount of reinforcing material is shown in Figs. 25 and 26 (here, the axis of the pillar is shown). Regarding the force, the stress concentration factor was set to 2 uniformly without considering the separation distance).

According to these figures, it is shown that the safety factor increases due to the increase in the cross-sectional area of the reinforcing material, and the reinforcing effect is produced (in this example, the effect of the tunnel lining is not taken into consideration). The graph shown in FIG. 25 is for soft rock and φ = 1.
It was assumed that 0 °, Young's modulus (E) = 1000 Kg / cm ² , and Poisson's ratio (υ) = 0.3. C (adhesive strength) = 50
tf / m ² is close to the physical properties of mudstone, and C = 30 tf / m ² is close to the properties of schist. In the case of mudstone, it can be seen that if one anchor member (φ = 25 mm) is placed per 1 m ² , the safety factor becomes close to 1.4 and the reinforcing effect appears. With schist, it can be seen that the safety factor becomes about 1.1 by placing four, and the reinforcing effect of the pillar part can be obtained.

The graph shown in FIG. 26 is an example of sandy ground, and φ = 30 °, E = 300 Kg / cm ² , υ = 0.4.
I assumed. In this figure, C = 10tf / ^{m 2} Narita sand, C = 0tf / ^{m 2} shows the physical properties close to scoria. It can be seen that the safety factor becomes 1.0 or more by inserting the reinforcing material, and the reinforcing effect can be obtained. In this result, the number of anchor members is determined from the allowable stress of the anchor members.

The construction procedure of this method follows the cycle time of a normal NATM tunnel, and a series of constructions can be carried out in the conventional work process. For example, after the excavation of one step of the preceding tunnel and the completion of the construction of auxiliary construction methods such as ordinary shotcrete and bolting, or in combination, in the direction of the trailing tunnel, the pillar width is equivalent to the pillar width, or The required number of bolts with a length exceeding this is placed horizontally. After the completion of such a series of preceding tunnel constructions, or the construction of a normal trailing tunnel with a predetermined face spacing.

As the fixing method of the anchor member, it is conceivable to use the whole surface attachment type bolt when the ground strength is high and to use the tip fixing type when the ground strength is low. In particular, the degree of fixation of the bolt tip is important for stability, and in the latter case, a diameter-expanding tube that expands in an umbrella shape in the ground is attached to the bolt tip. This expanded pipe also has a pseudo lining effect on the side wall of the trailing tunnel, and is expected to have a further effect on stability during excavation.

Further, the anchor member to be used can be used from a reinforcing bar to a steel pipe or the like according to a required cross-sectional area. Further, it is considered effective to use self-drilling bolts depending on the ground conditions or use FRP members (σ / E large) depending on the physical properties of the ground.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A parallel tunnel construction method according to the present invention will be described below with reference to an embodiment shown in the drawings. (1) First, the preceding tunnel 1 is excavated (see FIG. 1). The tunneling is performed by the most suitable method among the methods generally used in the past, considering the ground condition and the like. (2) Next, a plurality of anchor members 3 are horizontally installed from the side wall of the leading tunnel 1 toward the trailing tunnel 2 (see FIGS. 2 and 3). Anchor bolts and steel pipes having a length corresponding to the thickness of the pillar portion 5 are used for the anchor members 3, and the anchor members 3 are installed vertically and laterally at predetermined intervals. Moreover, the diameter of the anchor member 3 and the construction interval are appropriately determined in consideration of the type of the ground, the ground condition, and the like.

Next, a construction method when an anchor bolt is used as the anchor member 3 will be described. An anchor hole 4 is bored in the side wall of the preceding tunnel 1 (see FIG. 4). The anchor hole 4 is drilled up to substantially near the trailing tunnel 5 that is excavated after the anchor member 3 is constructed. Further, the anchor hole 4 is drilled by the most suitable drilling method generally used in the past, similarly to the tunnel excavation. Next, a hardening agent such as cement milk is injected and pressed into the tip of the anchor hole 4. This hardening agent is injected / press-fitted by using the rod 6a of the drill 6 as an injection tube (see FIG. 5), and the rod 6a is quickly pulled out after the hardening agent is injected. Next, the anchor bolt 3 is inserted into the anchor hole 4 (see FIG. 6). The anchor bolt 3 has a pillar portion A
Use bolts with a length corresponding to the thickness of the bolt or longer. A diameter-expanding tube 7 is attached to the tip of the anchor bolt 3 in advance (see FIGS. 8, 11, and 12). The diameter-expanding pipe 7 is formed of a steel pipe having a diameter substantially the same as that of the anchor hole 4 or a diameter slightly smaller than that of the anchor hole 4. Plates 8 and 8 are welded to both front and rear ends thereof, and a plurality of side walls are provided. Slits 9, 9 are formed at predetermined intervals in the circumferential direction. The slits 9 and 9 are formed in an elongated rectangular shape in the longitudinal direction of the expanded tube 7.

The expanded tube 7 formed in this manner penetrates the tip of the anchor bolt 3 in the substantially central portion of the front and rear plates 8, 8 and attaches the receiving plate 10 to the penetrating portion.
Further, it is attached by screwing a fixing nut 11 onto the external thread portion on the outside (see FIG. 8). Next, the center hole jack 12 is inserted into the anchor hole 4.
The drilling rod 13 is inserted, and its tip end is abutted against the rear end side plate 8 of the expanded tube 7. In addition, the center hole jack 12 is attached to the entrance of the anchor hole 4 to attach the attachment 12 of the center hole jack 12.
a is connected to the anchor bolt 3 (see FIGS. 8, 9, and 10). Next, the center hole jack 12 is operated to press-fit the drilling rod 13 into the anchor hole 4 and crush the diameter-expanding pipe 7 by the tip of the drilling rod 13 and the receiving plate 10. The part is expanded like an umbrella in the surrounding ground (see FIGS. 9 and 13). (3) When all the anchor members 3 have been constructed, the trailing tunnel 2 is constructed in the same manner as the leading tunnel 1. According to such a construction method, it is possible to prevent collapse of the surrounding natural ground portion during construction of the trailing tunnel, and it is possible to perform safe construction.

By the way, in FIGS. 14 and 15, as the anchor diameter D becomes larger, the space between the expanded blades becomes larger, and the steel material occupied area A _{2 with} respect to the cross-sectional area A ₁ of the expanded anchor portion increases significantly as the amount of expanded diameter increases. Fall to. Therefore, since the supporting force of the soil mass between the blades is not effectively utilized (scraping state), there is a possibility that the anchor supporting force corresponding to the anchor diameter (proportional to the square) cannot be sufficiently obtained.

FIGS. 16 to 20 show a diameter-expanding tube 7 developed to address such a problem, the details of which will be described below. The diameter expansion pipe 7 is composed of a plurality of steel pipes 7a having different diameters. The steel pipes 7a, 7a are overlapped in a double or multiple manner, and rectangular slits 9, 9 elongated in the axial direction are formed on the side wall portions of the steel pipes 7a, 7a so as to be shifted in the circumferential direction so as not to overlap each other. Further, the steel pipes 7a, 7a are respectively installed with the longest pipes on the outermost side so as to surely expand the diameter in a concentric shape.
The shorter ones are installed toward the inside. The other configurations are substantially the same as those of the radially expanded tube 7 described above.

21 to 24 show a construction method when a steel pipe is used as the anchor member 3 (hereinafter referred to as "anchor steel pipe"). The anchor steel pipe 3 used here is a steel pipe having a diameter substantially equal to or smaller than that of the anchor hole 4 and a length corresponding to the thickness of the pillar portion 5 or longer. . Further, a diameter-expanded pipe 7 is integrally formed at the tip of the anchor steel pipe 3. The expanded pipe 7 is formed by forming a plurality of slits 9, 9 each having an elongated rectangular shape in the longitudinal direction of the anchor steel pipe 3 on the side wall portion of the tip end portion of the anchor steel pipe 3 at predetermined intervals in the circumferential direction. A screw hole 14 that opens inward is formed at the tip of the screw hole 14. Thus, by forming the expanded diameter pipe 7 integrally with the anchor steel pipe 3, the attachment of the expanded diameter pipe 7 can be omitted.

Hereinafter, a construction method when the anchor steel pipe 3 is used will be described step by step. An anchor hole 4 is bored in the side wall portion of the preceding tunnel 1 in the same manner as the previous construction method, and a hardening agent such as cement milk is injected and pressed into the tip portion of the anchor hole 4. Next, the anchor steel pipe 3 is inserted into the anchor hole 4 (see FIG. 21). Next, insert the rod 15 into the anchor steel pipe 3,
A screw hole 14 formed at the tip of the expanded tube 7
Are connected by screwing (see FIG. 22). Further, the center hole jack 12 is installed at the entrance of the anchor hole 4 (see FIG. 22). Next, the center hole jack 12 strongly pushes the anchor steel pipe 3 into the anchor hole 4, so that the center hole jack 12 and the rod 15 crush the diameter expansion pipe 7 to expand it into an umbrella shape in the surrounding ground. (See Figure 23). Next, the anchor steel pipe 3 is filled with a hardening material such as concrete over its entire length (see FIG. 24). Note that the radially enlarged pipe 7 may not be integrally formed at the tip end portion of the anchor steel pipe 3, but may be separately formed as in the case of the anchor member 3 described above.

[0023]

Since the present invention is constructed as described above, it has the following effects. Since the so-called pillar portion is reinforced before the trailing tunnel is constructed, the pillar portion is already sufficiently reinforced when the trailing tunnel is constructed. For this reason, the construction of the trailing tunnel is only normal construction, and there is no problem in the construction cycle, and it is possible to proceed smoothly and extremely safely. Moreover, since the construction of the preceding tunnel can be carried out by the usual construction method, the construction is easy. Reinforcement of the pillar part is a tension introduction method that utilizes the inherent property of rock, which is the Poisson effect generated by rock excavation, and it is effective in redistributing the stress of the rock generated by bolting and rock excavation. It depends on the construction method used for. Therefore, unlike the PC anchor construction method, it is not necessary to introduce the prestress into the ground of the pillar portion to purposely compact it, which is extremely economical and the construction is very simple.

The effect is further doubled by using the so-called system bolt together. Expanded pipe is composed of multiple steel pipes with different diameters,
Each steel pipe is doubled or multi-layered, and its side wall is
The axially elongated rectangular slits are formed so as to be displaced in the circumferential direction so as not to overlap each other. Further, each steel pipe is installed such that the longest one is installed on the outermost side and the shorter one is installed on the inner side. Therefore, even if the anchor diameter is large and the space between the expanding blades is large, the steel pipes are expanded concentrically in the surrounding ground, so the steel material occupying area A _{2 with} respect to the cross-sectional area A ₁ of the expanding anchor portion is sufficient. Therefore, it is possible to secure the bearing capacity of the soil mass between the wings effectively.
Therefore, the anchor strength of the anchor member is extremely high. Furthermore, the anchor strength can be further increased by appropriately increasing the number of steel pipes as needed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a leading tunnel after excavation and a trailing tunnel before excavation.

FIG. 2 is a cross-sectional view of an anchor member installed in a pillar portion between a leading tunnel after excavation and a trailing tunnel before excavation.

FIG. 3 is a cross-sectional view of an anchor member constructed on a leading tunnel after excavation, a trailing tunnel, and a pillar portion between the leading tunnel and the trailing tunnel.

FIG. 4 is a cross-sectional view showing a method of constructing an anchor member using anchor bolts.

FIG. 5 is a cross-sectional view showing a method of constructing an anchor member using anchor bolts.

FIG. 6 is a cross-sectional view showing a method of constructing an anchor member using anchor bolts.

FIG. 7 is a cross-sectional view showing a method of constructing an anchor member using anchor bolts.

FIG. 8 is a side view showing an installed state of a diameter-expanding pipe in a method of constructing an anchor member using anchor bolts.

FIG. 9 is a side view showing a diameter-expanded state of the diameter-expanded tube in the anchor member construction method using anchor bolts.

FIG. 10 is a partially cutaway side view showing a connecting portion between the anchor bolt and the attachment of the center hole jack in the method of constructing the anchor member with the anchor bolt.

FIG. 11 is a perspective view showing an installed state of a diameter-expanding pipe in a method of constructing an anchor member using anchor bolts.

FIG. 12 is a cross-sectional view showing an installed state of a diameter-expanding pipe in an anchor member construction method using anchor bolts.

FIG. 13 is a perspective view showing a diameter-expanded state of the diameter-expanded pipe in the method of constructing an anchor member using anchor bolts.

FIG. 14 is a graph showing the relationship between the diameter D of the expanded-diameter anchor portion and the cross-sectional area A ₁ of the expanded-diameter anchor portion of the steel material occupied area A ₂ .

FIG. 15 is a cross-sectional view showing an outline of a diameter expansion anchor portion.

FIG. 16 is a vertical cross-sectional view of a radially expanded tube.

FIG. 17 is a vertical cross-sectional view of a radially expanded tube.

FIG. 18 is a vertical cross-sectional view of a radially expanded tube.

FIG. 19 is a vertical cross-sectional view of a radially expanded tube.

FIG. 20 is a front view of the expanded tube.

FIG. 21 is a cross-sectional view showing a method of constructing an anchor member using an anchor steel pipe.

FIG. 22 is a cross-sectional view showing a method of constructing an anchor member using an anchor steel pipe.

FIG. 23 is a cross-sectional view showing a method of constructing an anchor member using an anchor steel pipe.

FIG. 24 is a cross-sectional view showing a method of constructing an anchor member using an anchor steel pipe.

FIG. 25 is a graph showing a relationship between a cross-sectional area of a reinforcing material and a safety factor in soft rock ground.

FIG. 26 is a graph showing the relationship between the reinforcing material cross-sectional area and the safety factor in sandy ground.

[Explanation of symbols]

1 ... Leading tunnel, 2 ... Trailing tunnel, 3 ... Anchor member (anchor bolt or anchor steel pipe), 4 ... Anchor hole, 5 ... Pillar part, 6 ... Drilling drill, 6a ... Rod, 7 ... Expanding tube, 8 ... Plate, 9 ... Slit, 10 ...
Support plate, 11 ... Fixing nut, 12 ... Center hole jack, 13 ... Drilling rod, 14 ... Screw hole,
15 ... Rod.

Claims (2)

[Claims] 1. A method for constructing a tunnel in which a preceding tunnel is excavated, and after the preceding tunnel is excavated, a trailing tunnel is excavated in parallel with the preceding tunnel, wherein an intermediate ground between the preceding tunnel and the following tunnel. Part, a plurality of anchor holes are drilled on the trailing tunnel side from the side wall part of the preceding tunnel, and an anchor bolt or an anchor steel pipe having a diameter-expanded pipe attached to the tip part is inserted into this anchor hole,
A method for constructing a parallel tunnel, wherein the diameter-expanding pipe is expanded like an umbrella in the surrounding ground at the tip of the anchor hole. 2. The expanded pipe comprises a plurality of steel pipes having different diameters, which are installed in double or more layers, and the side walls of the steel pipes are not overlapped with elongated slits in the axial direction. The parallel tunnel construction method according to claim 1, wherein the parallel tunnels are formed so as to be displaced in the circumferential direction.