JPH0835391A - Preceding leg reinforcing type fore piling method by heading - Google Patents

Abstract

PURPOSE:To enhance the reliability of securing the holding force of a leg in a steel timbering even in a superlarge section of tunnel, and to facilitate the construction of the steel timbering, CONSTITUTION:In a superlarge section of tunnel, three headings 1, 2, and 3 are advanced at the positions at the upper side of a crown, and at the outer sides of a leg (two positions), and then, a timbering top plate metal 4 is provided to the top heading 1, while timbering receiving metals 5 and 6 are provided to the leg side headings 2 and 3, and at the same time, concrete 7 is placed to the three headings. By utilizing the metals 4, 5, and 6 buried and fixed in the concrete 7, a steel timbering 9 to which fore piles 8 are hit beforehand is held, and its construction is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fore-pile construction method for reinforcing leading legs by a tunnel.

[0002]

2. Description of the Related Art In recent years, a large number of large-section tunnels have been constructed in tunnel construction where a structure is standing on the top or collapsible ground with a small overburden, and it is desired to develop an auxiliary construction method for large excavators. There is.

Usually, in such collapsible ground, a long forepiling method is adopted. For example, a steel pipe having a large number of injection holes, a rod inserted through the steel pipe, and a steel pipe attached to the tip of the steel pipe are used. And a tip bit for excavation protruding from the tip of the injection pipe.
That is, the tip bit is rotated to insert the steel pipe into the ground while excavating the ground, and then the tip bit is removed from the steel pipe and recovered, and the steel pipe is left in the ground, and the ground hardening material is placed in the steel pipe. Is forcibly fed, and the ground hardening material is injected into the ground around the injection pipe to improve the ground, so that the fore piles are formed adjacent to each other in an arched shape one after another along the periphery of the pit opening. Then, the excavation method is carried out by repeating the steps of excavating and excavating by the length of the fore pile and carrying out support lining.

Conventionally, in such a construction method, as described above, after driving a large number of long fore piles into the ground so as to form an arch as a whole, the fore piles are supported from the inside of the arch by steel support work. Is going to hold. This steel support is located at the position specified by the design.
It is in the same plane at right angles to the tunnel axis and must be installed correctly so that it does not twist, fall or sink. Therefore, considering the shape of the excavated cross section and the magnitude of the cross sectional force, the steel support structure should have a strong structure that does not cause buckling or bending damage and be firmly supported by the surrounding ground. desired.

[0005]

However, in the case of a large-section tunnel, it becomes difficult to secure the supporting force at the leg portion of the steel supporting structure, and in the case of the steel supporting structure divided into a plurality of parts as appropriate. In addition, the joint portion of the member tends to be a structural weak point. In addition, it takes a lot of time to position the steel supporting members and to connect the members to each other, and it is relatively difficult to install the steel supporting members in the conventional forepiling method.

[0006] Therefore, an object of the present invention is to solve the above-mentioned problems and to secure the supporting force of the leg portion in the steel supporting work even in a large-section tunnel, so that the steel supporting work can be easily installed. An object of the present invention is to provide a leading leg reinforced forepiling method using such a tunnel.

[0007]

In order to achieve the above-mentioned object, the leading leg reinforced fore-piling method by the guide of the present invention is provided at a position above the crown of the arch and outside both legs of the arch in the large section tunnel. Advanced drilling process,
Fixing the support top plate metal in the guide at the top of the crown and the support brackets in the guides of both legs by placing concrete in each of the guides and burying it in the guide. At the time of, the process of holding and supporting the steel support work that supports the injection type steel pipe fore piling that has been driven in advance by holding the support support top metal plate above the crown and the support support receiving parts of both legs. It includes.

[0008]

[Operation] During excavation, the steel support work that supports the fore pile that was driven in advance is built using the metal embedded in the guide shaft when excavating the main pit. The retaining force of the arch legs is taken up by the concrete cast in advance. That is, since the arch leg portion of this portion is reinforced in advance, the reliability of securing the supporting force by the steel supporting work is enhanced. In addition, the concrete placed in the tunnel is a kind of front receiver in the axial direction of the tunnel.

[0009]

The present invention will be described below with reference to the illustrated embodiments. Here, we will explain the injection-type steel pipe fore-piling method for reinforcing the leading leg with a circular guideway, using the ultra-large section tunnel divided into the upper and lower halves as an example.

According to this method, injection type steel pipe fore piling is performed in an arch shape around the ground to be excavated in the ultra large section tunnel, more precisely, the peripheral portion of the upper half excavation ground, but prior to this, the position of the upper part of the crown of the arch is located. To one circular tunnel
, And one circular tunnel 2, 3 respectively outside the upper half leg of the arch (2 places) is advanced by, for example, a tunnel boring machine. After that, of these circular tunnels 1, 2 and 3, in the circular tunnel 1 above the crown,
As an embedded product, for example, the longitudinal length of the cross section is 400 mm
A support top plate 4 made of approximately I-type steel is installed, and support receiving brackets 5 and 6 are installed as embedded fittings in the circular guide pits 2 and 3 of the upper half legs. , 2 and 3 are assembled, and concrete 7 is poured so as to have a shape capable of obtaining a sufficient supporting reaction force. This allows
The support work top metal plate 4, the support work receiving metal parts 5, 6 are firmly embedded and supported by the concrete 7 and firmly fixed in the guide shaft.

Next, injection type steel pipe fore piling is applied in an arch shape around the ground to be excavated in the tunnel. The above-mentioned conventional technique can be applied to this. That is, an injection pipe including a steel pipe having a large number of injection holes, a rod inserted through the steel pipe, and a tip bit for excavation attached to the tip of the rod and protruding from the tip of the steel pipe is used. That is,
By rotating the rod, the tip bit is rotated at the tip of the steel pipe, and the steel pipe is inserted into the peripheral part of the ground to be excavated while excavating the ground in the main shaft excavation advancing direction. After that, when the steel pipe is inserted to a predetermined position, the tip bit is removed together with the rod from the steel pipe to be recovered, the steel pipe is left in the ground, and the ground hardening material is pressure-fed into the steel pipe, and the steel pipe is injected through the injection hole. Ground hardening material is injected into the ground around the injection pipe to improve the ground.
Thereby, the fore piles 8 which are the cylindrical hardened layers of the steel pipe and the improved ground are successively formed adjacent to each other along the periphery of the opening of the pit, and the fore piles 8 are driven in an arch shape.

For the insertion of the injection pipe, a double pipe rotary percussion drill type (top hammer system) in which the steel pipe as the injection pipe is used as the inner pipe drilling pipe, or down the hold in which the steel pipe is used as the casing You can use a drill type (casing entrainment type hole expansion bit type) or an auger drill type (double rotary type) with a steel pipe as an outer pipe, and pull out the steel pipe used for drilling when the drilling of the specified length is completed. Prepare for injection.

Next, excavation work is performed on the upper half portion of the main pit while constructing a steel support 9 for supporting the fore pile 8 driven in as described above from the inside of the arch. The steel shoring support 9 is installed by using the shoring support top sheet metal 4 and the shoring support receiving hardware 5, 6 embedded in the circular tunnels 1, 2, 3. That is, make the steel support 9 about 1 / about the crown of the arch.
By dividing it into steel support members 9a, 9b having a length of 2, one of which 9a holds the upper part by the flange portion of the support top sheet metal 4 and the lower part by the support support 5
Further, the other structure supporting member 9b is built by holding the upper portion by the flange portion of the supporting top metal plate 4 and the lower portion by the supporting bracket 6.

After the upper half excavation is completed, the lower half excavation is driven by, for example, driving in the lock bolt 10 and the like, and the invert 11 is also appropriately completed.

As described above, at the time of excavation in the upper half, the steel supports 9 that support the fore pile 8 that was previously driven are used by using the metal fittings 4, 5, 6 embedded in the circular guide holes 1, 2, 3. Since it is a construction method in which it is built in, the supporting force of the arch leg portion of the steel support structure 9 is firmly supported by the concrete 7 in the guide pit that has been placed beforehand. That is, since the arch leg portion of this portion is reinforced in advance, the reliability of securing the supporting force by the steel supporting member 9 is enhanced.

Further, the concrete 7 cast in the three tunnels 1, 2 and 3 is a kind of front receiver in the tunnel axial direction. Therefore, it is particularly effective when it is applied to the ultra-large section tunnel in soft rock and unconsolidated ground.

[0017]

In summary, according to the present invention, in the large-section tunnel, three tunnels are advanced at the positions of the crown upper part and the leg outer side (two places), and then the support tunnel top sheet metal is installed at the top tunnel. In addition, a support receiving metal fitting is installed in the leg tunnel, and this is rolled in to pour concrete, and the metal embedded in the concrete tunnel through the concrete is used to make the fore pile steel Since this is a construction method in which the construction and support work is held and the building is built, the holding force of the legs will be taken care of by the concrete cast in advance, and this is equivalent to the fact that the legs are reinforced in advance. , The reliability of securing bearing capacity when excavating the main pit will be increased.

Further, since the steel supporting work is held by the supporting top plate metal member on the upper part of the crown and the supporting support metal member on the legs,
Compared to the case where these holding members are not provided, the steel support work is positioned less easily and the members are connected to each other, and the steel support work can be easily installed even in the case of the ultra-large section tunnel.

Further, it is possible to obtain an advantage that the concrete cast in the three guide shafts serves as a kind of front receiving in the axial direction of the tunnel.

[Brief description of drawings]

FIG. 1 is a tunnel cross-sectional view showing a leading leg reinforced forepiling method using a tunnel of the present invention.

[Explanation of symbols]

 1,2,3 Circular guide 4 Supporting top plate metal 5,6 Supporting support 7 Concrete 8 Fore pile 9 Steel support 9a, 9b Constituent support member 10 Side pile 11 Invert

Claims (1)

[Claims] 1. A process of advanced excavation of a tunnel at a position above the crown upper portion and both legs of an arch in a large-section tunnel, and by placing concrete in each of the tunnels and burying the concrete in the tunnel, guiding the crown upper portion. The step of fixing the support top plate metal in the mine and the support support hardware to the guide pits of the both legs, and the steel support that supports the injection type steel pipe fore piling that was previously driven at the time of excavation of the main pit, A leading leg reinforced fore-pilling method using a guide shaft, which comprises a step of holding and supporting the supporting top metal plate on the top of the crown and the supporting support metal members on both legs.