JPH11303592A - Multiple timbering construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple timbering construction method capable of constructing a tunnel timbering structure having a cross sectional performance suitable for a release ground pressure at the time of boring without necessitating replacing work of timbering dangerous in boring construction work of a mountain tunnel. SOLUTION: A closed structural body 4 is formed by an arch member 1 composed of sprayed concrete, a steel material, etc., a side wall member 2, and a temporary invert 3 immediately after the natural ground is digged by a predetermined length from a working face by a mini-bench construction method. when the closed structural body 4 reaches a fixed length due to the progress of the working face, a surface of the closed structural body 4 is reinforced by a steel material timbering 5 and sprayed concrete 6 to construct a tunnel timbering structure 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-support construction method for tunnel excavation.

[0002]

2. Description of the Related Art In tunnel excavation work, large deformation occurs after excavation, particularly in soft and low-strength grounds (ground strength ratio of 0.1 or less), in which initial ground pressure is high, and the required tunnel cross-section is Invading, the support structure becomes unstable and sometimes destroyed, and if nothing is done, the excavated tunnel will be crushed. Conventionally, tunnel excavation methods under such bad conditions include, for example, a method in which a tunnel is preceded in anticipation of an effect of excavation, excavation of the tunnel after releasing the ground pressure, and a large deformation margin and in-part A construction method and the like that take into account the cross-sectional closure by the construction are applied. In addition, in the places where the necessary tunnel cross section was damaged by the large deformation of the ground, reversing work, that is, dismantling and removing the existing shoring, and reconstructing the shoring after widening of the ground, reconstruct the tunnel cross section. Is secured.

[0003]

However, in the above-mentioned conventional tunnel excavation, although it depends on the nature of the ground, the reversing work involving dangerous work may be repeated several times. There is a problem that reliable stabilization between the tunnel and the tunnel cannot be expected. Furthermore, since the reversing work is a backward operation, there is a problem in that it is inefficient, causes a large loss of materials and the like, and requires a long construction time and cost.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and a support structure having a cross-sectional performance commensurate with the released ground pressure at the time of excavation can be constructed without the need for dangerous reversal work in tunnel excavation work. It is an object of the present invention to provide a multiple support construction method.

[0005]

As a specific means for achieving this object, the present invention is to excavate the ground by a mini-bench method or the like, and to reduce the tunnel diameter by about 1.0 mm from the face position.
Form a closed structure with a shape close to a circle within the double excavation area,
Within the length range of about 1 to 5 times the diameter of the tunnel with the progress of the face, by applying steel support and spraying concrete on the surface of the already-constructed closed structure, the support rigidity corresponding to the released ground pressure and The gist is a multi-support construction method in which tunnel support structures having support strength are sequentially constructed.

[0006]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an H-shaped steel arch member formed of a steel material or the like in a substantially semicircular arc shape and attached to an inner wall surface of an upper half excavated at a tunnel face. Then, concrete is sprayed between the steel supports.

After the arch member 1 is mounted, a lower half portion is excavated at the position of the tunnel face, and a side wall member 2 made of steel or the like is provided on the side wall surface so as to be connected to both lower ends of the arch member 1. On the bottom wall surface, a temporary invert 3 made of steel or the like is attached to both lower ends of the side wall member 2 to form a closed structure 4 having a shape close to a circle. After this, spray concrete is sprayed.

[0008] The excavation is performed by the mini-bench method, the forming operation of the closed structure 4 is performed within the excavation range of about 1.0 times the diameter of the tunnel from the upper and lower half face positions, and the supporting performance of the closed structure 4 is determined by the open ground pressure. Construction is to be carried out to have support rigidity and support strength suitable for. In this case, since the surrounding ground moves largely with the tunnel excavation, the deformation margin is set to be relatively large.

Here, when the support performance of the closed structure 4 corresponding to the released ground pressure is examined, the relationship between the support thickness and the stress generated in the circumferential direction of the tunnel is as shown in FIG.
Assuming that the support strength is 100 to 200 m, the supporting performance corresponding to this is a uniaxial compressive strength of about 2 cm with a supporting thickness of about 50 cm in a circular closed structure cross section.
30 to 460 kgf / cm ² is required.

If a supporting structure having such a supporting performance can be instantaneously constructed in the ground at the time of tunnel excavation, the inside of the tunnel will be stable. However, since the diameter of the tunnel is about 10 m and the excavation has a large cross section, In reality, construction is impossible. For this reason, the closed structure 4 is formed by excavating in the vertical half-cut method by the mini bench method.

Although stress is generated in the closed structure 4 as the tunnel face advances, if the length of the closed structure 4 is within the range of about 1 to 5 times the diameter of the tunnel, the support structure is kept healthy. Therefore, a reinforcing step is performed on the surface of the existing closed structure 4 when the sound is healthy. As shown in FIG.
The construction is carried out by spraying concrete 6, thereby constructing a tunnel support structure 7 having support rigidity and support strength corresponding to the released ground pressure. In this case, it becomes possible to increase the strength of the support structure according to the tunnel behavior characteristics after the formation of the closed structure 4, and it is possible to form a reasonable tunnel support structure.

By sequentially constructing the tunnel support structure 7 in this manner, the inside of the tunnel can be stabilized.
It is possible to secure an empty cross section in the tunnel, and to prevent the destruction of the shoring work due to the large deformation of the ground.
Therefore, it is not necessary to perform the conventional reversing work involving dangerous work.

Thereafter, a lining concrete 8 is cast inside the tunnel support structure 7, and a main invert 9 is cast on the temporary invert 3, so that the tunnel body 10
Is formed. At this time, a clearance S is provided between the tunnel support structure 7 and the lining concrete 8 in consideration of the deformation margin of the ground.
Is provided.

Incidentally, the tunnel excavation is based on the mini-bench method, but is not limited thereto, and may be another method. The mini-bench method is common, and based on this method, there are no technical difficulties, so excavation work can be performed smoothly.

[0015]

As described above, according to the present invention, the ground is excavated by the mini-bench method or the like, and a closed structure having a substantially circular shape is formed immediately after the ground is excavated for a predetermined length from the face, thereby reducing the deformation of the ground. At the same time, when the closed structure became a certain length, the surface was reinforced and a tunnel support structure with support rigidity and support strength corresponding to the released ground pressure was constructed.
Deformation and destruction of the tunnel support due to deformation of the ground can be prevented beforehand. As a result, the necessary cross section inside the tunnel can be ensured, and dangerous reversing work can be avoided.As a result, construction efficiency can be improved and materials can be saved, thereby shortening the construction period and reducing construction costs. When the method of the present invention is applied to excavation of a soft and low-strength ground tunnel with high ground pressure, the effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tunnel by a multiple support construction method according to the present invention.

FIG. 2 is a graph showing a relationship between a supporting thickness and a stress generated in a tunnel circumferential direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Arch member 2 ... Side wall member 3 ... Temporary invert 4 ... Closed structure 5 ... Steel material support 6 ... Shotcrete 7 ... Tunnel support structure 8 ... Lining concrete 9 ... Main invert 10 ... Tunnel body

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kosuke Kakimi 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Takahiro Ishii 2-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Tetsushi Akita Shimizu Corporation 1-3-2 Shibaura, Minato-ku, Tokyo

Claims (1)

[Claims] 1. Excavation of the ground by a mini bench method or the like, forming a closed structure having a nearly circular shape within an excavation area of about 1.0 times the tunnel diameter from the face position, and forming the tunnel diameter as the face progresses. Tunnel support structure having support rigidity and support strength corresponding to the released earth pressure by applying steel support and spraying concrete on the surface of the already-closed closed structure within a length range of about 1 to 5 times The multiple support construction method characterized by sequentially constructing.