JP4769961B2 - Mirror bolt and tunnel excavation method - Google Patents

Description

  The present invention relates to a mirror fixing bolt suitable for excavation of a tunnel in a soft ground composed of an unconsolidated layer such as sand or sandy soil or soft rock with high collapsibility, and tunnel excavation using this mirror fixing bolt. Regarding the method.

  When excavating a tunnel in a soft ground, a plurality of mirror retaining bolts are driven into the face of the tunnel at a predetermined pitch according to the ground condition so that the face does not collapse during excavation. Conventionally, using a glass fiber mirror locking bolt that is relatively easy to cut, a process of excavating the face with this mirror locking bolt and the mirror locking bolt is excavated, and a new one is added to the face with the mirror locking bolt remaining. A tunnel excavation method is known in which excavation is repeated by repeating the process of driving a simple mirror set bolt.

  However, this excavation method is disadvantageous in terms of cost because expensive glass fiber bolts are handled as consumables. Therefore, conventionally, a steel bolt is used as the mirror stop bolt, and after a plurality of mirror stop bolts are driven into the face of the tunnel, the face is excavated by avoiding the mirror stop bolt so that the rear part of the mirror stop bolt is exposed. There is also known a tunnel excavation method in which a mirror locking bolt is pushed into a face after excavation (for example, see Patent Document 1).

  According to this excavation method, since the excavation can be performed using the same mirror retaining bolt, there is an advantage that the construction cost is reduced. However, since the face is excavated while avoiding the mirror fixing bolt, the excavation work becomes troublesome and takes time, and the construction period is prolonged.

  Also known is a method of excavating a tunnel using a mirror retaining bolt in which a plate-like earth retaining member projecting radially outward of the bolt body is detachably attached to the rear end of the bolt body elongated in the front-rear direction. (For example, refer to Patent Document 2). In this case, remove the earth retaining member of some of the plurality of mirror fixing bolts driven into the face, and excavate the face avoiding the mirror fixing bolt so that the rear part of this mirror fixing bolt is exposed. After that, the mirror retaining bolt is pushed into the face after excavation, and the earth retaining member is attached to the rear end in order for all the mirror retaining bolts.

According to this, since the face is pressed by the earth retaining member at the rear end of the mirror fixing bolt other than the mirror fixing bolt during excavation, the face is prevented from collapsing more reliably. However, in this case, it is necessary to excavate the face by avoiding the mirror fixing bolt as in the above-described conventional example, and it is necessary to attach and detach the earth retaining member each time excavation, thereby shortening the construction period. I can't.
JP-A-7-127388 Japanese Patent Publication No.59-45074

  In view of the above points, the present invention provides a mirror fixing bolt capable of reliably preventing the face from collapsing by the earth retaining member and excavating the face efficiently, and tunnel excavation using the mirror fixing bolt. The challenge is to provide a method.

  In order to solve the above-mentioned problem, the first invention of the present application is a mirror retaining bolt that is driven into a face of a tunnel, and a bolt body that is long in the front-rear direction, and a bolt body at the rear end of the bolt body radially outward. What is provided with the earth retaining member provided so that it may protrude is characterized by attaching the blade part for excavating a face to the front surface of the earth retaining member.

The second invention of the present application is a tunnel excavation method using the mirror fixing bolt of the first invention, and after driving a plurality of the mirror fixing bolts into the face of the tunnel, each mirror fixing bolt is used as the face. By pushing in while rotating, the face is excavated by the blade portion of the earth retaining member, and the portion of the face where the mirror fixing bolt is not driven is excavated by excavating means .

  According to the present invention, the face is pressed by the earth retaining member at the rear end of the mirror fixing bolt, and the face is reliably prevented from collapsing. Moreover, the face is excavated by the blade portion of the earth retaining member by pushing the mirror stop bolt while rotating the mirror stop bolt. Therefore, the mirror set bolt does not interfere with excavation, and the face can be excavated efficiently. Furthermore, when excavating, it is not necessary to attach and detach the earth retaining members one by one, and coupled with the fact that the face can be efficiently excavated, the construction period can be shortened.

  In addition, in the mirror stop bolt of the present invention, it is basically unnecessary to attach or detach the earth retaining member. However, if the retaining member is detachable from the bolt body, it is advantageous that the retaining member can be replaced when the blade portion of the retaining member is worn.

  Referring to FIGS. 1 and 2, reference numeral 1 denotes a tunnel excavated in a soft ground consisting of an unconsolidated layer such as sand or sandy soil or soft rock with high collapsibility. A concrete invert 2 is constructed on the bottom of the excavated portion of the tunnel 1. Then, an arch-shaped steel support 3 is built along the inner surface of the tunnel 1, and the lower ends of the left and right sides of the steel support 3 are joined to the left and right sides of the invert 2 to close the tunnel cross section. is doing. Moreover, concrete is sprayed on the inner surface of the tunnel 1 to form a supporting concrete layer 4. Further, a plurality of rock bolts (not shown) for supporting the excavated peripheral wall surface are radially pierced through the supporting concrete layer 4 in the ground surrounding the tunnel 1 and a receiving steel pipe 5 extending obliquely forward is driven. Yes.

  By the way, in a soft ground, when the face 6 of the tunnel 1 is excavated, the face face 6 may slide on the sliding face a as shown by an imaginary line in FIG. Therefore, a plurality of roof lock bolts 7 'are driven into the face 6 at a relatively narrow interval along an arched line extending from the ceiling portion of the tunnel cross section to the left and right side portions, thereby forming a roof. A plurality of mirror fixing bolts 7 are driven into the inner face 6. According to this, pulling out of the mirror fixing bolt 7 is suppressed by the friction of the first half portion of the mirror fixing bolt 7 with respect to the ground behind the sliding surface a. Then, the face mountain is prevented from slipping by the frictional resistance between the latter half of the mirror retaining bolt 7 and the face mountain before the sliding surface a, and the face 6 is prevented from collapsing.

  Here, as shown in FIG. 3, the mirror retaining bolt 7 includes a bolt body 71 made of a steel pipe that is long in the front-rear direction, and a drill bit 72 that is fixed to the front end of the bolt body 71 and has a blade portion 72 a attached to the front surface. A water supply pipe 73 in the bolt main body 71 for supplying water to the water discharge hole 72b formed in the drill bit 72 and a male joint portion 74 fixed to the rear end of the bolt main body 71 are provided. A rod 8 that is moved back and forth and rotated by a drifter of a drilling machine (not shown) is detachably connected to the joint 74 at a female joint 81 at the front end thereof. The rod 8 is hollow, and a water supply pipe 82 communicating with the water supply pipe 73 of the mirror fixing bolt 7 is inserted through the joint portions 81 and 74 inside. In addition, the drill bit 72 is formed with a drain hole 72 c that communicates with the internal space of the bolt body 71. The internal space of the bolt main body 71 communicates with the internal space of the rod 8 via joint portions 74 and 81.

  When driving the mirror stop bolt 7 into the face 6, the joint portion 81 at the front end of the rod 8 is connected to the joint portion 74 at the rear end of the mirror stop bolt 7, and the rod 8 is advanced while rotating in this state. Thereby, the mirror set bolt 7 is driven into the face 6 while drilling with the drill bit 72. The soil in the drilling portion mixes with the water from the water discharge hole 72b of the drilling bit 72 to become muddy water, and passes through the internal space of the mirror fixing bolt 7 and the internal space of the rod 8 from the soil discharge hole 72c of the drilling bit 72. Discharged.

  The structure of the roof lock bolt 7 ′ is the same as the structure of the mirror fixing bolt 7 described above, and is driven into the face 6 using the rod 8.

  However, unlike the roof locking bolt 7 ′, the mirror fixing bolt 7 includes an earth retaining member 75 that is detachably screwed to the joint portion 74 at the rear end of the bolt main body 71. As shown in FIG. 2, the earth retaining member 75 is formed in a cross shape having four arm portions projecting radially outward in the radial direction of the bolt main body 71. Further, a blade portion 75a is attached to the front surface of the earth retaining member 75 as shown in FIG.

  As described above, the face mountain is prevented from slipping to some extent by the frictional resistance between the latter half of the mirror fixing bolt 7 and the face face mountain before the sliding surface a. The surface (the end surface of the face 6) is pressed by the earth retaining member 75, so that the face 6 can be more reliably prevented from collapsing. The mirror fixing bolt 7 is driven into the face 6 with an interval such that the earth retaining members 75 and 75 of the adjacent mirror fixing bolts 7 and 7 do not interfere with each other.

  When excavating the face 6, first, as shown in FIG. 1A, the uppermost mirror fixing bolt 7 driven into the face 6 is rotated to the face 6 by a rod 8 and is rotated to a predetermined position. Push in the stroke. According to this, the cutting face 6 is excavated by the blade part 75a of the earth retaining member 75, and the state shown in FIG. And the face 6 is excavated in order from the upper part to the lower part by pushing in while rotating the mirror stop bolt 7 to the face 6 in order from the upper one.

  Next, the lowermost part of the face 6 where the mirror fixing bolt 7 is not driven is excavated by appropriate excavating means. Then, as shown in FIG. 1 (c), the invert 2 is constructed by placing or spraying concrete on the bottom surface of the portion excavated this time, and on the left and right sides of the invert 2 on the left and right sides of the excavated portion. A rising wall 2a that rises to the same height as the lower ends of the left and right sides of the roof forming portion is formed. The rising wall 2a is formed by spraying concrete after planting a short steel support 3a on each side of the invert 2.

  Next, after excavating the roof forming portion of the face 6, the roof lock bolt 7 ′ is pushed into the face 6 after excavation. And as shown in FIG.1 (d), the arch-shaped steel support 3 is built over the right-and-left both sides from the ceiling surface of the part excavated this time, and the lower end of the right and left both sides of this steel support 3 is attached. The support concrete layer 4 is formed by spraying concrete while being coupled to the rising walls 2a on both the left and right sides of the invert 2. The tunnel 1 is excavated by repeating the above operations.

  Here, it is necessary to excavate the roof forming portion while avoiding the roof lock bolt 7 ', but since the cross-sectional area of the roof forming portion is small, excavation does not take much time. On the other hand, the face 6 inside the roof forming part has a large cross-sectional area, and if this part is excavated while avoiding the mirror stop bolt 7, the excavation takes much time. However, in the present embodiment, the face 6 is excavated by the blade portion 75 a of the earth retaining member 75 by pushing the mirror stop bolt 7 while rotating it on the face 6. Therefore, the mirror set bolt 7 does not interfere with excavation, and the face 6 can be excavated efficiently. Further, when excavating, it is not necessary to attach and remove the earth retaining member 75 one by one, and coupled with the fact that efficient excavation of the face 6 is possible, the construction period can be shortened.

  Moreover, since the earth retaining member 75 does not need to be attached or detached, it may be integrated with the bolt main body 71. However, if the earth retaining member 75 is detachable from the bolt body 71 as in the present embodiment, it is advantageous that the earth retaining member 75 can be replaced with a new one when the blade portion 75a is worn.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, in the above embodiment, the mirror locking bolt 7 with the drilling bit 72 is used, but a press-fit lock bolt having a sharp front end may be used. Further, in the above embodiment, the earth retaining member 75 is formed in a cross shape having four arm portions, but the number of arm portions may be three or more, and furthermore, the earth retaining member It is also possible to form the member 75 in a disc shape.

  Furthermore, in the said embodiment, although the steel pipe was used as the mirror stop bolt 7, a rod-shaped thing can also be used. The material is not limited to steel, and any material having a certain level of rigidity such as fiber reinforced plastic (FRP) can be used.

  In addition, a solidifying agent may be injected around the mirror fixing bolt according to the driving and pushing conditions to increase the frictional resistance between the bolt and the ground. In this case, it is desirable to select a material for the solidifying agent so that the bolt and the ground can be peeled well when the mirror fixing bolt is pushed.

The longitudinal cross-sectional view of the tunnel which shows the excavation method of embodiment of this invention. The cross-sectional view of a tunnel. The longitudinal cross-sectional view which shows the mirror stop bolt of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Tunnel, 6 ... Face, 7 ... Mirror stop bolt, 71 ... Bolt main body, 75 ... Earth retaining member, 75a ... Blade part.

Claims (3)

A mirror retaining bolt driven into the face of the tunnel, comprising a bolt body that is long in the front-rear direction, and a retaining member that is provided at the rear end of the bolt body so as to protrude outward in the radial direction of the bolt body.
A mirror retaining bolt, wherein a blade portion for excavating a face is attached to the front surface of the earth retaining member.   The mirror retaining bolt according to claim 1, wherein the earth retaining member is detachably attached to the bolt body. A tunnel excavation method using the mirror fixing bolt according to claim 1 or 2,
After driving a plurality of these mirror stop bolts into the face of the tunnel, each mirror stop bolt is pushed into the face while being rotated, so that the face is excavated by the blade portion of the earth retaining member, and the mirror stop bolt is driven. A tunnel excavation method characterized by excavating an uncut face portion by excavation means .

Images