JP3096643B2 - Tunnel widening 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 tunnel widening method, and more particularly, to a method for widening a tunnel in order to provide a branch / merge portion of a branch / merge tunnel or an emergency parking zone from an existing tunnel. This includes the case where the pit is widened to form the main pit.

[0002]

2. Description of the Related Art Widening an existing tunnel, for example, for branching
In the case of providing a branching / merging portion of a merging tunnel, a method of excavating while suppressing loosening of the ground with a lock bolt has been generally adopted.

[0003]

However, there is a problem that widening of a large space cannot be performed safely only by the support using the lock bolt.

Accordingly, it is an object of the present invention to provide a tunnel widening method capable of safely constructing a large space.

[0005]

The tunnel widening method (the present method) according to the present invention comprises a step A of placing a lock bolt in at least a widening direction of a surrounding ground from an existing tunnel; The wall corresponding to the area to be widened is left as a reinforcing middle wall, and the area to be widened is excavated while forming a ground arch in two directions, that is, in the transverse direction of the tunnel and in the longitudinal direction within a range where the effect of the lock bolt is not reduced. B, a step C of spraying concrete on the wall surface exposed in the step B, a step D of removing the reinforced middle wall, and the blown concrete wall obtained in the step C is left as a new reinforced middle wall to enlarge the width. And a step E of secondary excavation of the scheduled area, and thereafter, a step of excavating the newly exposed wall surface as a reinforcing middle wall is appropriately repeated.

Further, it is possible to increase the number of lock bolts prior to the step E.

Therefore, in this construction method, the area to be widened is excavated in order of primary, secondary, etc. while leaving the front wall as a reinforcing wall (center diaphragm). In addition, lock bolts (primary lock bolts) are also used to suppress the release of stress (looseness) in the ground, and after the second excavation, increase the number of lock bolts as necessary to expand the large space in the safety zone. It is made to work with. In addition,
The reinforced wall is partially broken as a working entrance. In addition, the steps after the third excavation are performed as necessary and are not essential.

“Putting a lock bolt at least in the widening direction” means that the rock bolt is driven radially at least in a direction in which digging is performed in all directions from inside the tunnel. The total length of the area to be excavated is included. In addition, the length of the lock bolt, the number of the bolts, or the pitch is appropriately set in accordance with the ground conditions (ground strength and ground pressure). In addition, since the primary lock bolts are radially driven and the pitch increases as they go deeper, when the lock bolts are additionally driven in secondary excavation, they are driven between the primary lock bolts.

[0009] The "range in which the operation effect of the lock bolt is not reduced" is a range in which the lock bolt can surely suppress the stress release (looseness) of the ground, and includes support by the reinforcing middle wall.

"Excavation while forming a ground mountain arch in two directions, that is, a tunnel cross direction and a longitudinal direction" means that the ground is excavated so as not to form a corner where stress concentration occurs in the ground. The walls on which the concrete is sprayed also have an arched cross section.

In the secondary excavation, excavation is performed in the same manner.

"Blowing concrete on the exposed wall surface" means that a new side wall is newly formed, the lining is closed once, and the stress is redistributed.

[0013] The shot concrete wall surface used as a rock bolt or a reinforcing middle wall has no stress at the time of construction, but exhibits a resisting force when subjected to a compressive force or the like from the ground as the excavation proceeds. Together with the surrounding ground, a resistance zone is formed that surrounds the work site in a vertical and horizontal cross section arch.

[0014]

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

FIG. 1 shows a branch to an existing tunnel 1.
FIG. 3 is a plan explanatory view for convenience showing a branching / merging portion 10 provided by partially widening the ground around the tunnel in order to merge the merging tunnel (single line) 2; As shown in FIG.

In the construction for obtaining the branching / merging portion 10, first, the primary lock bolts 11 a for all directions including the entire length of the area to be widened (branching / merging portion) 10 in the tunnel longitudinal direction from the tunnel 1. (See thick solid line and thick broken line).

Next, the area 10 to be widened in the main tunnel 1 will be described.
Wall (12a) corresponding to the work entrance (not shown)
, Except for the primary reinforcement middle wall 12a, and leave the area 10 to be widened with the primary lock bolt 11a and the primary reinforcement middle wall 12a.
The primary excavation is performed in a range in which the loosening of the ground can be reliably suppressed by a. At this time, the primary widening portion 10a is obtained by widening while forming a ground arch in two directions, that is, the tunnel cross direction and the longitudinal direction so that stress concentration does not occur.

Next, concrete is sprayed on the wall surface (12b) newly exposed by the primary excavation, the lining is closed once, and the stress is redistributed. Next, the primary reinforcing middle wall 12a is removed.

Next, the shot concrete wall surface (12b)
The secondary lock bolt 11b is additionally struck in the direction of widening or the like. At this time, the secondary lock bolts 11b are driven between the primary lock bolts 11a.

Next, the shotcrete wall surface (12b)
Is left as a secondary reinforcing middle wall 12b (excluding the work entrance), and secondary excavation is performed in the same manner as primary excavation to obtain a secondary widened portion 10b.

Thereafter, a predetermined lining or a secondary reinforcing middle wall 12b
The branching / merging section 10 is obtained through the removal of the above. If the area to be widened is even larger, the tertiary and quaternary excavations are repeated as appropriate.

In the above embodiment, the merging / branching unit 10
Although the case where the emergency parking zone is provided has been described as an example, the same construction can be applied when the emergency parking zone is provided.

[0023]

As described above, in the tunnel widening method according to the present invention, the area to be widened is primarily excavated by the rock bolts and the reinforcing middle wall while the loosening of the ground is suppressed, and thereafter, a new reinforcing middle wall is formed. Since the excavation is performed sequentially while obtaining the support, the widening of a large space can be performed safely, and the cost can be reduced as compared with the case where the support is obtained by a rigid body.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view showing an existing tunnel and a merging / branching portion for convenience.

FIG. 2 is a sectional view taken along the line II-II of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tunnel 2 Branching / merging tunnel 10 Branching / merging part (expected widening area) 10a Primary widening part 10b Secondary widening part 11a Primary lock bolt 11b Secondary lock bolt 12a Primary reinforcing middle wall (side wall of tunnel) 12b Secondary reinforcing wall

──────────────────────────────────────────────────続 き Continued on the front page (73) Patent holder 000172813 Sato Kogyo Co., Ltd. 1-11, Sakuragicho, Toyama City, Toyama Prefecture (73) Patent holder 000112668 Fujita Co., Ltd. 4-6-115 Sendagaya, Shibuya-ku, Tokyo ( 73) Patent Holder 000140292 Okumura Gumi Co., Ltd. 2-2-2 Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka (73) Patent Holder 390028015 Chizaki Kogyo Co., Ltd. 2- 23-1, Nishishinbashi, Minato-ku, Tokyo (73) Patent Authority 000146928 Morimoto Gumi Co., Ltd. 4-11, Yuyooka-cho, Tennoji-ku, Osaka-shi, Osaka (72) Inventor Minoru Yamamoto 1-15-2, Tamagawa Gakuen, Machida-shi, Tokyo (56) References JP-A-7-305589 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) E21D 9/00 E21D 9/04

Claims (2)

(57) [Claims] 1. A step A of placing a lock bolt in at least a widening direction of a surrounding ground from an existing tunnel.
And, the wall corresponding to the planned widening area of the tunnel is left as a reinforcing middle wall, and the ground widening arch is formed in two directions in the tunnel transverse direction and the longitudinal direction in a range in which the effect of the lock bolt is not reduced. Step B of excavating while forming, Step C of spraying concrete on the wall surface exposed in Step B, and Step D of removing the reinforcing middle wall
And exposing the shotcrete wall surface obtained in step C as a new reinforcing wall, and secondary excavating the area to be widened, and then excavating the newly exposed wall surface as a reinforcing intermediate wall. A tunnel widening method characterized by repeating as appropriate. 2. The tunnel widening method according to claim 1, wherein lock bolts are additionally driven before the step E.