JP2015025239A - Tunnel excavation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a tunnel excavation method capable of shortening a construction period, and capable of also restraining damage of the natural ground of the working face periphery.SOLUTION: The tunnel excavation method comprises a preparation process of loading sn explosive in these blast holes 2 by drilling the plurality blast holes 2 in a working face 1 and an excavation process of boring by initiating the explosive in the blast holes 2, and comprises a kerf process of forming a kerf 3 by cutting by a water jet along the outer periphery of a planned cross section of a tunnel before the excavation process.

Description

  The present invention relates to a tunnel excavation method.

  Tunnel excavation methods are broadly divided into mechanical excavation methods and blast excavation methods. Regardless of which excavation method is employed, the excavated surface is subjected to impact and vibration during excavation, and there is a concern that the skin may fall off from the raw excavated surface.

  In Patent Document 1, as an excavation method capable of suppressing vibration during excavation in a mechanical excavation method, a large number of kerfs are formed with a water jet on a tunnel excavation surface, and a wedge-like shape is formed in the kerf. The construction method which pushes in a destruction tool and destroys a bedrock sequentially is disclosed.

  Patent Document 2 discloses a smooth blasting method for adjusting the amount of explosive loaded in the outer blast hole for the purpose of suppressing the amount of surplus digging in the blast excavation method.

Japanese Patent Laid-Open No. 9-125867 JP 2009-168374 A

  Although the mechanical excavation method of patent document 1 has less damage of the natural ground around the face compared with the blast excavation method, the excavation speed is slow and hinders shortening of the construction period.

  The smooth blasting method of Patent Document 2 adjusts the amount of blasting installed on the outermost periphery to reduce the amount of overburden generation, but the influence on the outer periphery due to the effect of blasting is unavoidable, and around the face May cause damage to natural ground.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to propose a tunnel excavation method capable of suppressing damage to natural ground around the face while blasting. .

  In order to solve the above-mentioned problems, the present invention includes a preparation step of drilling a plurality of blast holes with respect to a face and loading an explosive in the blast hole, and an excavation step of detonating the explosive to advance A tunnel excavation method comprising: a kerf process for cutting a kerf along the outer periphery of the planned cross section of the tunnel before the excavation process.

  According to such a tunnel excavation method, since the outer periphery of the tunnel is preliminarily cut by a kerf, it is possible to suppress impacts and vibrations on the surface of the tunnel due to blasting, and as a result, the ground around the face Can prevent damage.

In addition, the amount of excessive digging can be reduced.
Moreover, since the blasting of the outer periphery of the tunnel is not required, the amount of explosive can be reduced, and the construction cost can be reduced.

If the cutting in the kerf process is performed with a water jet, vibrations and the like associated with the cutting can be reduced.
In addition, it is desirable that the water jet is selectively used for the hydro type and the abrasive shot type according to the type of the bedrock.

  In addition, it is desirable that the digging distance by the explosive loaded in at least the blast hole (outer blast hole) near the kerf is smaller than the depth of the kerf.

  According to the tunnel excavation method of the present invention, it is possible to suppress damage to natural ground around the face while blasting.

It is a front view which shows the face of the tunnel which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the tunnel shown in FIG. It is the support structure figure of the tunnel.

  The tunnel excavation method according to the present embodiment excavates a mountain tunnel, and includes a preparation process, a kerf process, and an excavation process.

As shown in FIG. 1, the preparation step is a step of drilling a plurality of blast holes 2 in the face 1 and loading explosives into the blast holes 2.
A rock drill (not shown) such as a drill jumbo is used for drilling the blast hole 2.

The depth, arrangement, and quantity of the blast hole 2 are appropriately set according to the type and strength of the rock mass, the cross-sectional shape of the tunnel, and the like.
The amount of explosive charged in the blast hole 2 is adjusted so that the digging distance by blasting is less than the depth of the kerf (1 m or less).

The kerf process is a process of cutting the kerf 3 along the outer periphery of the planned cross section of the tunnel.
In this embodiment, as shown in FIG. 2, the kerf 3 is cut with a water jet. In FIG. 2, reference numeral 8 denotes a water jet nozzle.

Depending on the natural conditions (such as the type of bedrock), the water jet should be selected from the water-only hydro type and the abrasive shot type in which abrasive is mixed in the water.
Note that the cutting with the water jet does not necessarily need to be performed using a plurality of types, and may be performed with only one type.

As shown in FIG. 1, the kerf 3 is formed along the outer peripheral surface (the top end and the side wall portion) other than the bottom (invert).
In the present embodiment, a groove having a depth of about 1 m is cut as the kerf 3. The depth of the kerf 3 is not limited and may be set as appropriate according to the natural ground conditions, but may be set to be equal to or greater than the excavation depth by blasting. Further, the width of the kerf 3 is not limited.

  The kerf 3 is drilled from the face 1. The drilling direction is substantially parallel to the tunnel excavation direction, but is slightly inclined so as to spread outside the tunnel cross section. Therefore, the raw digging surface after tunnel excavation (the inner peripheral surface of the tunnel) is slightly larger at the distal end side (opposite the hole opening) of the kerf 3 than the proximal end side (hole opening side) of the kerf 3 It is formed and has a step along the longitudinal direction of the tunnel. The inclination angle of the kerf 3 is not limited.

The excavation process is a process in which explosives installed in the blasting hole 2 are detonated (blasted) for excavation.
When the face 1 is broken by blasting, the gap is removed from the pit. In addition, the carrying-out method of a slip is not limited, For example, a conveyance vehicle and the carrying trolley | bogie may be used, and a continuous belt conveyor may be utilized.

  Next, spray concrete 4 is sprayed on the tunnel excavation surface (side wall and top end), and, if necessary, a lock bolt 5 is placed and a steel support 6 is installed.

Hereinafter, the tunnel is further dug by repeating the preparation process, the kerf process and the excavation process.
When the tunnel excavation is completed or has progressed to a predetermined distance, lining concrete 7 is placed as shown in FIG.

The effects of the tunnel excavation method of this embodiment are as follows.
Since the edge of the outer periphery of the tunnel is preliminarily cut by the kerf 3, it is possible to suppress impact and vibration on the tunnel digging surface due to blasting. Therefore, damage to the natural ground around the face 1 can be suppressed, falling off of the bedrock and the like from the bare digging surface is suppressed, and safety during construction is improved.

Moreover, since the amount of over-digging can be reduced, the amount of unloading soil and the amount of concrete sprayed can be reduced compared with the conventional blasting method, which is economical.
In addition, by suppressing impact and vibration, there is little influence on the neighborhood.

  Furthermore, since the cutting groove is formed in advance, a smooth cutting surface can be ensured. Therefore, a support structure and the like can be constructed relatively easily.

Moreover, since the blasting method is adopted, the construction period can be shortened compared to the machine digging method.
In addition, since it is not necessary to blast the outer periphery of the tunnel, the amount of explosives can be reduced, and the construction cost can be reduced.

Since the cutting of the kerf 3 is performed with a water jet, it is possible to reduce dust scattering, vibration associated with the cutting, and the like.
Moreover, since the water jet uses the hydro type and the abrasive shot type properly according to the natural ground conditions (the type of bedrock, etc.), efficient construction is possible.

As mentioned above, although embodiment of this invention was described, this invention is not restricted to the said embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably.
For example, although a so-called horseshoe-shaped tunnel has been described in the above embodiment, the cross-sectional shape of the tunnel is not limited, and may be, for example, an egg-shaped cross section, a circular cross section, an elliptical cross section, or a rectangular cross section.

  In the above embodiment, the case where the kerf is cut using a water jet has been described, but the cutting means for the kerf is not limited, for example, by continuously forming a hole with a drill, A kerf may be formed.

  Although the said embodiment demonstrated the case where a kerf process was implemented after a preparation process, you may implement a kerf process before a preparation process.

  In the above embodiment, the kerf is formed at the top end and the side wall, and the bottom of the tunnel (inverted part) is not formed as a kerf. Good. Further, the kerf may be formed only in the upper part of the spring line or only in the top end part (above the shoulder part).

  In the above-described embodiment, the amount of explosive loaded in all the blast holes 2 is adjusted so that the digging distance by blasting is equal to or less than the depth of the kerf (1 m or less). The amount of explosive loaded in the blasting hole (peripheral blasting hole) 2 formed in the vicinity may be adjusted so that the digging distance by blasting is equal to or less than the depth of the kerf 3, and not all blasting holes are required. It is not necessary for the digging distance by blasting 2 to be less than the depth of the kerf 3. That is, the digging distance of blasting by the blasting hole 2 in the center of the tunnel may be larger than the depth of the kerf 3.

DESCRIPTION OF SYMBOLS 1 Face 2 Blast hole 3 Groove 4 Sprayed concrete 5 Rock bolt 6 Steel support 7 Covering concrete 8 Nozzle

Claims (3)

A preparation step of drilling a plurality of blast holes with respect to the face and loading explosives in the blast holes;
A tunnel excavation method comprising detonating and expelling the explosive,
A tunnel excavation method comprising a kerf process for cutting a kerf along an outer periphery of a planned cross section of a tunnel before the excavation process.   The tunnel excavation method according to claim 1, wherein the grooving step is performed by cutting with a water jet.   The tunnel excavation method according to claim 1 or 2, wherein a digging distance by the explosive loaded in at least the blast hole in the vicinity of the kerf is smaller than a depth of the kerf.

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