Construction methods for mountain tunnels
The integration of semi-arch-shaped support structures with arch-shaped supports in tunnel construction addresses constructability, economic, and safety issues by reducing excess excavation and ensuring a smooth transition from enlarged to standard cross-section cavities, enhancing efficiency and safety.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KUMAGAI GUMI CO LTD
- Filing Date
- 2024-11-20
- Publication Date
- 2026-06-01
AI Technical Summary
Conventional tunnel construction methods face challenges in constructability, economy, quality, and safety when transitioning from enlarged cross-section cavities to standard cross-section cavities due to lack of precise reference points, excess excavation, difficult surface preparation, increased concrete usage, and prolonged working times with increased accident risks.
A method involving the use of a semi-arch-shaped support structure connected to the arch-shaped support at the end of the widened cross-section cavity to form the initial support at the standard cross-section cavity, reducing the need for additional excavation and enabling safer, more efficient construction by using pre-fabricated semi-arch structures.
Improves constructability, reduces construction costs and time, enhances safety by minimizing face-level accidents, and ensures a smooth finish by integrating semi-arch structures with arch structures for seamless transitions.
Smart Images
Figure 2026089157000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a construction method for mountain tunnels, and particularly to a method for constructing a support structure when transitioning from the construction of an enlarged cross-section cavity to the construction of a standard cross-section cavity.
Background Art
[0002] Conventionally, in the construction of mountain tunnels, the ground exposed by excavation is supported by a support structure to stabilize the ground. That is, steel support structures are arranged in an arch shape along the cross-sectional shape of the tunnel cavity formed by excavation. The support structures are arranged at predetermined intervals along the extension direction of the tunnel (see Patent Document 1). The tunnel cavity is configured such that a standard cross-section cavity having a standard cross-sectional diameter and an enlarged cross-section cavity having a larger cross-sectional diameter than the standard cross-section cavity are continuous. In the construction of a mountain tunnel, for example, when transitioning from the construction of a standard cross-section cavity to the construction of an enlarged cross-section cavity, a cavity larger in diameter than the cross-sectional diameter of the standard cross-section cavity is gradually excavated from the end face of the standard cross-section cavity, and arch-shaped support structures corresponding to the size of the cavity are built at predetermined intervals along the extension direction of the tunnel. At the same time, a lining is formed by rubbing concrete on the inner surface (ground) of the cavity. Also, when transitioning from the construction of an enlarged cross-section cavity to the construction of a standard cross-section cavity, as shown in FIGS. 3(a) and (b), excavation is advanced by a distance a from the position of the end face of the enlarged cross-section cavity 1 in the tunnel progress direction F, and an arch-shaped support structure 12SC corresponding to the size of the cross-sectional diameter of the standard cross-section cavity 2 is built at the position where the start end of the standard cross-section cavity 2 is located. Then, excavation of the standard cross-section cavity 2 is performed using the support structure 12SC as an index. Incidentally, the distance a is about several tens of cm, for example, 40 cm to 50 cm. That is, as shown in FIG. 3(b), in the construction of the enlarged cross-section cavity 1, arch-shaped support structures 11, 11... having a diameter corresponding to the cross-sectional diameter of the enlarged cross-section cavity 1 are built every time excavation is advanced by a predetermined distance. Then, after erecting the arch-shaped support structure 11E at the end of the widened section cavity 1, excavation is advanced by a distance a from the end face (end face) of the widened section cavity 1 toward the tunnel direction F, and an arch-shaped support structure 12SC with a diameter corresponding to the cross-sectional diameter of the standard section cavity 2 is erected at the position that will be the starting point of the standard section cavity 2. Subsequently, as shown in Figure 3(b), the construction of the standard cross-section cavity 2 involves sequentially erecting arch-shaped supports 12, 12… with a diameter corresponding to the cross-sectional diameter of the standard cross-section cavity 2, each time the excavation progresses a predetermined distance in the tunnel direction F. [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Japanese Patent Publication No. 2019-112863 [Overview of the Initiative] [Problems that the invention aims to solve]
[0004] However, in conventional tunnel construction methods, when transitioning from the construction of widened section cavities 1 to the construction of standard section cavities 2, there were challenges in terms of constructability, economy, quality, and safety, as shown in (1) to (5) below. (1) Since there is no precise reference point for the cross-section of the standard cross-section cavity 2, the amount of excess excavation required in the direction of tunnel travel F from the end of the widened cross-section cavity 1 increases. In other words, the workability is poor and construction costs increase. (2) The concrete spraying on the end face (end face) of the widened section cavity 1 results in a curved shape that rubs against the standard section cavity 2, making surface preparation difficult, resulting in poor workability and a poor finish. In other words, workability and quality are reduced. (3) The quantity of shoring will be greater than the design quantity, which will increase construction costs. (4) Because the sprayed concrete rubs against the arch-shaped support structure 12SC that is set back in the direction of travel, the thickness of the lining concrete increases, and the amount of concrete to be poured increases. In other words, construction costs increase. (5) It becomes difficult to reinforce the support structure 12SC at the starting end of the standard cross section cavity 2, and the working time inside the tunnel face where only primary spraying has been applied is prolonged. In other words, workability deteriorates, the risk of accidents from the top of the tunnel face increases, and safety issues arise. This invention has been made in view of the above-mentioned problems, and provides a method for constructing mountain tunnels that can improve constructability, economy, quality, and safety when transitioning from the construction of widened cross-section cavities to the construction of standard cross-section cavities. [Means for solving the problem]
[0005] The present invention relates to a method for constructing a mountain tunnel, which involves constructing a tunnel cavity consisting of a standard cross-sectional cavity with a standard cross-sectional diameter and a widened cross-sectional cavity with a larger cross-sectional diameter than the standard cross-sectional cavity. The method is characterized in that, when transitioning from the construction of the widened cross-sectional cavity to the construction of the standard cross-sectional cavity, a portion of the arch-shaped support structure at the end of the widened cross-sectional cavity is used as part of the support structure at the beginning of the standard cross-sectional cavity. Furthermore, the method is characterized by connecting a semi-arch-shaped support structure to the inside of the arch-shaped support structure at the end of the widened section cavity, and constructing the arch-shaped support structure at the beginning of the standard section cavity using the semi-arch-shaped support structure and a portion of the arch-shaped support structure at the end of the widened section cavity. Furthermore, the method is characterized by comprising the steps of: connecting the inner surface of the arch-shaped support at the end of the widened section cavity to the upper end of the semi-arch-shaped support corresponding to the cross-sectional diameter of the standard section cavity; and constructing the arch-shaped support at the beginning of the standard section cavity by erecting and fixing the leg portion of the semi-arch-shaped support connected to the inner surface of the arch-shaped support at the end of the widened section cavity at the same measurement point as the arch-shaped support at the end of the widened section cavity, thereby using the semi-arch-shaped support and a part of the arch-shaped support at the end of the widened section cavity to construct the arch-shaped support. According to the construction method for mountain tunnels of the present invention, when transitioning from the construction of widened cross-section cavities to the construction of standard cross-section cavities, constructability, economy, quality, and safety can be improved. [Brief explanation of the drawing]
[0006] [Figure 1] (a) is a perspective view showing the shoring at the starting end of a standard cross-section cavity, which is installed when transitioning from the construction of a widened cross-section cavity to the construction of a standard cross-section cavity, and (b) is a cross-sectional view of (a) (embodiment). [Figure 2] (a) is a front view showing the support structure at the end of the widened section cavity, (b) is a front view showing the semi-arched support structure, and (c) is a front view showing the support structure at the beginning of the standard section cavity, which is composed of the support structure at the end of the widened section cavity and the semi-arched support structure (embodiment). [Figure 3] (a) is a perspective view showing the shoring at the starting end of a standard cross-section cavity, which is installed when transitioning from the construction of a widened cross-section cavity to the construction of a standard cross-section cavity, and (b) is a cross-sectional view of (a) (conventional example). [Modes for carrying out the invention]
[0007] The construction method for a mountain tunnel according to the embodiment is a method for constructing a tunnel cavity in which a standard cross-sectional cavity with a standard cross-sectional diameter and a widened cross-sectional cavity with a larger cross-sectional diameter than the standard cross-sectional cavity are continuous. As shown in Figure 1, when transitioning from the construction of the widened cross-sectional cavity 1 to the construction of the standard cross-sectional cavity 2 with a smaller cross-sectional diameter than the widened cross-sectional cavity 1, a part 11a of the arch-shaped support structure 11E at the end of the widened cross-sectional cavity 1 is used as part of the support structure 12S at the beginning of the standard cross-sectional cavity 2.
[0008] In other words, conventionally, when transitioning from the construction of the widened section cavity 1 to the construction of the standard section cavity 2, as described above, an arch-shaped support structure 12SC corresponding to the cross-sectional diameter of the widened section cavity 1 was used as the support structure at the starting end of the standard section cavity 2. However, in this embodiment, a semi-arch-shaped support structure 13, as shown in Figure 2(b), is fabricated and used, which constitutes part of the initial support structure 12S of the standard section cavity 2.
[0009] Then, as shown in Figures 1(a) and 2(c), a semi-arch-shaped support structure 13 is connected to the inside of the arch-shaped support structure 11E at the end of the widened section cavity 1, and the semi-arch-shaped support structure 13 and a part 11a of the arch-shaped support structure 11E at the end of the widened section cavity 1 are used to construct the arch-shaped support structure 12S at the starting end of the standard section cavity 2.
[0010] Furthermore, the shoring 11E and shoring 13 are constructed, for example, from steel materials with an H-shaped cross-section. As shown in Figure 2(a), the arched support structure 11E is an arched steel support structure formed with its upper part curved to correspond to the cross-sectional diameter of the widened cross-sectional cavity 1 and equipped with legs on both sides. For example, it is formed by connecting multiple steel members to create an arch. As shown in Figure 2(b), the semi-arched support structure 13 is a steel support structure with a curved shape at the top corresponding to the cross-sectional diameter of the standard cross-sectional cavity 2, and is equipped with only one leg portion 13F. For example, it can be formed by shaping a single steel member into a semi-arch, or by connecting multiple steel members to form a semi-arch.
[0011] In the construction method for a mountain tunnel according to the embodiment, the steps for transitioning from the construction of the widened section cavity 1 to the construction of the standard section cavity 2, which has a smaller cross-sectional diameter than the widened section cavity 1, include a semi-arch support structure fabrication step, a support structure connection step, a support structure construction step, and an end section lining step.
[0012] In the semi-arched support fabrication step, as described above, a semi-arched support structure 13 (see Figure 2(b)) is fabricated, which constitutes part of the first support structure 12S of the standard cross-sectional cavity 2. Furthermore, since the semi-arched support structure 13, together with a part 11a of the support structure 11E at the end of the widened section cavity 1, forms the arched support structure 12S at the starting end of the standard section cavity 2, for example, the semi-arched support structure 13, with dimensions corresponding to the cross-sectional diameter of the standard section cavity 2, is manufactured in advance at the factory and then transported to the site.
[0013] In the strut connection step, the inner surface of the arch-shaped strut 11E installed at the end of the widened cross-section cavity 1 is connected to the upper end 13e of the semi-arch-shaped strut 13 corresponding to the cross-sectional diameter of the standard cross-section cavity 2. For example, the upper end 13e of the semi-arch-shaped strut 13 and the inner surface of the strut 11E at the end of the widened cross-section cavity 1 are connected by welding (see Fig. 2(c)). In addition, the end face of the upper end 13e of the semi-arch-shaped strut that serves as the connection surface connected to the inner surface of the strut 11E at the end of the widened cross-section cavity 1 is formed as a curved surface that conforms to the curvature forming the inner surface of the strut 11E at the end of the widened cross-section cavity 1. Also, at the position of the inner surface of the strut 11E at the end of the widened cross-section cavity 1 to which the upper end 13e of the semi-arch-shaped strut 13 is connected, before performing the welding operation, markings or the like are made so that the alignment operation and the welding operation between the upper end 13e of the semi-arch-shaped strut 13 and the inner surface of the strut 11E at the end of the widened cross-section cavity 1 can be carried out smoothly.
[0014] In the strut construction step, the leg portion 13F of the semi-arch-shaped strut 13 connected to the inner surface of the arch-shaped strut 11E at the end of the widened cross-section cavity 1 is built into and fixed at the same measurement point MP as the arch-shaped strut 11E at the end of the widened cross-section cavity 1 as shown in Fig. 1(a), so that the semi-arch-shaped strut 13 and a part 11a of the arch-shaped strut 11E at the end of the widened cross-section cavity 1 construct the arch-shaped strut 12S at the start end of the standard cross-section cavity 2.
[0015] In the step of covering the end face of the widened cross-section cavity, as shown in Fig. 2(c), concrete is sprayed on the end face (end surface) of the widened cross-section cavity 1 located between the part 11b other than the part 11a of the strut 11E at the end of the widened cross-section cavity 1 and the semi-arch-shaped strut 13, as indicated by the hatching, to complete the end face covering work part 1EC.
[0016] From this point onward, using the arch-shaped support structure 12S at the starting end of the standard cross-section cavity 2 as a guide, the ground inside the arch-shaped support structure 12S is excavated in the direction of tunnel travel F to construct the standard cross-section cavity 2. In this case, every time the excavation progresses a predetermined distance, arch-shaped support structures 12, 12... with a diameter corresponding to the cross-sectional diameter of the standard cross-section cavity 2 are erected in sequence, and concrete is sprayed onto the ground to form a lining, thereby constructing the standard cross-section cavity 2.
[0017] When transitioning from the construction of the widened section cavity 1 to the construction of the standard section cavity 2, which has a smaller cross-sectional diameter than the widened section cavity 1, the series of operations described above—the support structure connection step, the support structure construction step, and the end lining step—are performed within the stable widened section cavity 1 after the secondary spraying (secondary lining) has been completed. This eliminates the risk of collapse from the top of the tunnel face, as was the case in the past. Furthermore, in the conventional construction method, where excavation proceeds for a distance a from the end face (terminal face) of the widened cross-section cavity 1 in the direction of tunnel travel F, excavation work and excavation work for this distance a are required. However, in this embodiment, this excavation work and excavation work for this distance a can be omitted, thus improving work efficiency and shortening the construction period. Furthermore, by providing the arch-shaped support structure 11E at the end of the widened section cavity 1 and the semi-arch-shaped support structure 13 at the same measurement point MP, the arch-shaped support structure 12S at the starting end of the standard section cavity 2 can be constructed. This reduces the working time at the excavation face for erecting the first support structure at the starting end of the standard section cavity 2, and also allows for the formation of a smooth and neat end lining section 1EC at the end face (end face) of the widened section cavity 1, thereby improving constructability, finish, and quality.
[0018] In other words, according to the tunnel construction method according to the embodiment, constructability, economy, quality, and safety can be improved, for example, as shown in (1) to (5) below. (1) The risk of face-level accidents can be reduced, and construction can be made safer (improved safety). (2) The support structure 12S at the starting end of the standard section cavity 2 is positioned on the end face of the widened section cavity 1, eliminating the need for extra excavation work, thus shortening the construction period (improvement in constructability and construction costs). (3) The arch-shaped support structure 12SC installed at the starting end of the conventional standard cross-section cavity section 2 is replaced with a semi-arch-shaped support structure 13 and a part 11a of the arch-shaped support structure 11E at the end of the widened cross-section cavity section 1, thereby reducing the cost of the support structure (improvement of construction costs). (4) The work of reinforcing the legs 13F of the semi-arch-shaped support structure 13 can be carried out safely and easily within the stable widened cross-sectional cavity 1 where the secondary spraying (secondary lining) has been completed, and the work time can also be reduced (improvement of safety and constructability).
[0019] As described above, the tunnel construction method according to the embodiment makes it possible to avoid the risk of face disasters (improved safety), shorten the construction period (improved constructability and cost-effectiveness), reduce material costs by using semi-arch-shaped support structures 13 (improved cost-effectiveness), form a smooth end lining section 1EC (improved quality), and reduce the amount of lining concrete (improved constructability and cost-effectiveness). In other words, according to the tunnel construction method of the embodiment, when transitioning from the construction of the widened section cavity 1 to the construction of the standard section cavity 2, constructability, economy, quality, and safety can be improved.
[0020] In the above-described embodiment, an example was given in which the upper end 13e of the semi-arch-shaped support structure 13 and the inner surface of the support structure 11E at the end of the widened cross-sectional cavity 1 were connected by welding. However, the upper end 13e of the semi-arch-shaped support structure 13 and the inner surface of the support structure 11E at the end of the widened cross-sectional cavity 1 may also be connected using connectors such as bolts and nuts. [Explanation of Symbols]
[0021] 1. Widened cross-sectional cavity section, 2. Standard cross-sectional cavity section, 11E Arch-shaped support structure at the end of the widened section cavity, 11a Part of the arch-shaped support structure at the end of the widened section cavity, 12S Standard cross section, arch-shaped support at the starting end of the cavity, 13. Half-arched support structure, 13e. Upper end of half-arched support structure, 13F The legs of the semi-arched scaffolding.
Claims
1. In a construction method for mountain tunnels in which a tunnel cavity is constructed in which a standard cross-sectional cavity with a standard cross-sectional diameter and a widened cross-sectional cavity with a larger cross-sectional diameter than the standard cross-sectional cavity are continuous, A method for constructing a mountain tunnel, characterized in that, when transitioning from the construction of a widened section cavity to the construction of a standard section cavity, a portion of the arch-shaped support structure at the end of the widened section cavity is used as part of the support structure at the beginning of the standard section cavity.
2. The method for constructing a mountain tunnel according to claim 1, characterized in that a semi-arch-shaped support structure is connected to the inside of the arch-shaped support structure at the end of the widened section cavity, and the semi-arch-shaped support structure and a part of the arch-shaped support structure at the end of the widened section cavity form the arch-shaped support structure at the beginning of the standard section cavity.
3. A step to connect the inner surface of the arch-shaped support at the end of the widened section cavity to the upper end of the semi-arch-shaped support corresponding to the cross-sectional diameter of the standard section cavity, The steps include: constructing the arch-shaped support at the beginning of the standard section cavity by erecting and fixing the legs of the semi-arch-shaped support connected to the inner surface of the arch-shaped support at the end of the widened section cavity at the same measurement point as the arch-shaped support at the end of the widened section cavity, and using the semi-arch-shaped support and a part of the arch-shaped support at the end of the widened section cavity; A method for constructing a mountain tunnel according to claim 1, characterized by comprising the following: