Mirror bolts for tunnel construction

Abstract

To provide a mirror bolt providing required fixation strength without an injection material, and suppressed in resistance increase in driving.SOLUTION: A mirror bolt 10 is driven into natural ground 2 in front of the working face of a tunnel 1 under construction. A locking projection 20 is provided to project from the outer peripheral surface of a linearly extending pipe body 11 of the mirror bolt 10. The locking projection 20 is elastically deformable in a pipe axis direction of the pipe body 11. The locking projection 20 has a relatively small deformation resistance to the hand side in the pipe axis direction, and has a relatively large deformation resistance to the deep side in the pipe axis direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an auxiliary method for tunnel construction, and particularly to a mirror bolt driven into the ground in front of the face of a tunnel during construction.

Background Art

[0002] The long mirror bolt method is a method of integrating the ground and the mirror bolt by driving a mirror bolt such as a steel pipe substantially perpendicular to the excavation face and injecting an injection material such as a cement-based or urethane-based material. Effects such as suppressing the collapse of the face, reducing the extrusion amount of the face, and suppressing the prior displacement (suppressing ground surface settlement, ensuring slope stability) are expected (see Patent Document 1, etc.). In the mirror bolt of Patent Document 1, dimples (concave portions) are formed on the outer peripheral surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order for the above-described effects of the mirror bolt to be manifested, it is necessary for the mirror bolt to be firmly fixed to the ground. For this purpose, an injection material is injected around the mirror bolt to attach the mirror bolt to the ground, but in addition to the injection material, equipment and time for injection are required, leading to an increase in construction cost and a prolongation of the construction period.

[0005] By forming convex portions or concave portions such as those in Patent Document 1 on the outer peripheral surface of the mirror bolt, it is conceivable to ensure the fixing force of the mirror bolt without injecting an injection material. However, the convex portions on the outer peripheral surface usually become a resistance when driving the mirror bolt into the ground in front of the face. The concave portions on the outer peripheral surface become convex portions on the inner peripheral surface and are caught when passing a drilling rod through the inside of the mirror bolt, impairing workability. In view of these circumstances, the present invention aims to provide a mirror bolt that can achieve the required anchoring force without injection material, suppresses the increase in resistance during installation, and does not impair workability. [Means for solving the problem]

[0006] To solve the aforementioned problems, the present invention provides a mirror bolt that is driven into the ground ahead of the tunnel face during construction, A tube that extends in a straight line, A locking projection is provided so as to protrude from the outer surface of the tube, is elastically deformable in the axial direction of the tube, has relatively low resistance to deformation toward the front in the axial direction of the tube, and has relatively high resistance to deformation toward the back in the axial direction of the tube, It is characterized by having the following features.

[0007] With this type of head bolt, when driven into the face, the locking projection deforms toward the handle, reducing driving resistance. The locking projection then elastically returns to its original position. When the ground in front of the face loosens, the locking projection catches on the ground. This ensures that the required anchoring force of the head bolt to the ground is achieved without the need for grout. The locking projection on the outer surface does not cause any snagging when passing a drilling rod or the like through the inside of the head bolt, thus not impairing work efficiency.

[0008] Preferably, the locking projection is in the shape of a leaf spring, inclined toward the handle side from the base portion connected to the pipe body toward the protruding end. This makes it possible to reliably reduce the deformation resistance of the locking projection toward the hand side and reliably increase the deformation resistance toward the back side.

[0009] Preferably, the outer surface of the tube has a recess or an opening that penetrates to the inner surface, and the locking projection is obliquely positioned to cover the outer surface of the recess or opening in the radial direction of the tube. As a result, when the locking projection is deformed to tilt toward the handle side, the locking projection can enter the recess or opening. [Effects of the Invention]

[0010] The mirror bolt according to the present invention provides the required anchoring force without the need for injection material, and suppresses the increase in resistance during driving. Workability is also not compromised. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a side view showing a long mirror bolt, including a mirror bolt according to the first embodiment of the present invention, in a state where it has been driven into the ground in front of the tunnel face. [Figure 2] Figure 2 is a side view showing a portion of the mirror bolt in cross-section. [Figure 3] Figure 3 is a cross-sectional view taken along the line III-III in Figure 2. [Figure 4] Figure 4 is an enlarged cross-sectional view of circular section IV in Figure 2. [Figure 5] Figure 5 is a side view showing a mirror bolt according to a second embodiment of the present invention, with a portion of it in cross-section. [Figure 6] Figure 6 is a cross-sectional view along the line VI-VI in Figure 5. [Figure 7] Figure 7 is a side view showing a mirror bolt according to a third embodiment of the present invention, with a portion of it in cross-section. [Figure 8] Figure 8 is an enlarged side cross-sectional view showing a portion of a mirror bolt according to the fourth embodiment of the present invention. [Figure 9] Figure 9 is a side view showing a mirror bolt according to the fifth embodiment of the present invention, with a portion of it in cross-section. [Figure 10] Figures 10(a) to 10(d) are side cross-sectional views showing modified examples of the locking projection of the mirror bolt according to the present invention. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment (Figures 1-4)> As shown in FIG. 1, a long mirror bolt 3 is driven into the natural ground 2 in front of the face 1e of the tunnel 1 under construction. The long mirror bolt 3 is formed by connecting a plurality of mirror bolts 10 in a row to make it long.

[0013] As shown in FIG. 2, each mirror bolt 10 includes a tube body 11 and a plurality of locking protrusions 20. The tube body 11 is a steel pipe that extends linearly. The outer diameter of the steel pipe is, for example, about 2 inches to 8 inches. A female thread 12 is provided at one end of the tube body 11, and a male thread 13 is provided at the other end. The threads 12 and 13 of adjacent mirror bolts 10 are screwed together and connected. The length of the long mirror bolt 3 is, for example, about a dozen meters.

[0014] As shown in FIGS. 2 and 3, a plurality of locking protrusions 20 are provided on the tube body 11 at intervals from each other. Preferably, these locking protrusions 20 are aligned in the tube axis direction and the tube circumferential direction of the tube body 11. As shown in FIG. 3, here, four rows of locking protrusions 20 are arranged at 90° intervals, but it is not limited to this. Five or more rows of locking protrusions 20 may be arranged at intervals less than 90°, or three or two rows of locking protrusions 20 may be arranged at intervals greater than 90°. The locking protrusions 20 adjacent to each other in the tube axis direction may be offset in the tube circumferential direction. The locking protrusions 20 may be arranged in a staggered pattern or randomly.

[0015] As shown in FIG. 4, each locking protrusion 20 protrudes from the outer peripheral surface of the tube body 11 and is elastically deformable in the tube axis direction of the tube body 11. Specifically, the locking protrusion 20 is formed in a leaf spring shape that is inclined toward the near side in the tube axis direction (the right side in FIG. 4) from the attachment root portion 21 to the protruding end portion 22. The attachment root portion 21 of the locking protrusion 20 is continuously connected to the tube body 11. The protruding end portion 22 of the locking protrusion 20 is arranged on the outer side in the tube diameter direction and the near side in the tube axis direction than the attachment root portion 12.

[0016] As shown by the dashed line in Figure 4, the deformation resistance of the locking projection 20 toward the proximal end in the axial direction of the pipe is relatively small. As shown by the dashed line in Figure 4, the deformation resistance of the locking projection 20 toward the inward end in the axial direction of the pipe is relatively large.

[0017] As shown in Figure 2, the inclination θ of the locking projection 20 with respect to the tube axis of the tube body 11 is preferably θ = 5° to 45°.

[0018] As shown in Figures 2 and 3, the planar shape of the locking projection 20 is generally rectangular, but is not limited to this. The inner surface 23 of the locking projection 20 is angled toward the inside of the tube body 11 in the radial direction and toward the handle side in the axial direction of the tube (right side in Figure 2). The outer surface 24 of the locking projection 20 is connected to the outer circumferential surface of the tube body 11 on the side behind the locking projection 20 (left side in Figure 2) at an obtuse angle without any step difference.

[0019] The locking projection 20 is formed by cutting and bending the pipe body 11 and is integral to the pipe body 11. That is, a U-shaped notched groove is formed in the pipe body 11, and the inner pipe wall portion 11d of the notched groove is bent diagonally outward in the radial direction of the pipe to form the locking projection 20. The bent portion is the base portion 21.

[0020] As shown in Figures 2 and 3, an opening 14 is formed in the pipe body 11 by cutting and bending. The internal and external spaces of the pipe body 11 are connected through the opening 14. A locking projection 20 is positioned diagonally over the radially outer side of the opening 14. The locking projection 20 can enter the opening 14 when the pipe body 11 deforms toward the handle side in the axial direction of the pipe.

[0021] The material of the locking projection 20 is preferably high-tensile steel (spring steel). In other words, high-tensile steel is used as the material for the tube body 11, which is integrated with the locking projection 20, and consequently for the mirror bolt 10.

[0022] As shown in Figure 1, when using the mirror bolt method as an auxiliary method for tunnel construction, an excavation bit 4 is attached to the tip (back end) of the outermost (innermost) mirror bolt 10, and the mirror bolt 10 is driven in while excavating the ground 2 in front of the tunnel face. At this time, the locking projection 20 receives a force from the inner side to the outer side due to friction with the ground, and this force includes a component force from the outside to the inside in the diameter direction of the pipe. Due to this component force, the locking projection 20 retracts toward the opening 14 (see the dashed line in Figure 4). This reduces the resistance to driving in the mirror bolt 10. Furthermore, the locking projection 20 on the outer surface does not cause any snagging when passing a drilling rod (not shown) connected to the drilling bit 4 through the inside of the mirror bolt 10, thus not impairing work efficiency.

[0023] Multiple mirror bolts 10 are driven in sequentially in a line. This constructs a long mirror bolt 3 within the ground 2 in front of the tunnel face. The locking projection 20 is elastically returned to its original inclination angle θ. In particular, by making the drilling bit 4 slightly larger than the outer diameter of the pipe body 11, a small gap is created between the inner surface of the driving hole 2c and the outer surface of the pipe body 11, thereby ensuring that the locking projection 20 is reliably elastically returned.

[0024] In the mirror bolt method of this embodiment, the injection process of the grout material is unnecessary. That is, there is no need to inject the grout material into the surrounding ground through the inside of the mirror bolt 10. Therefore, the material and equipment costs required for injection can be reduced, and the construction period can be shortened.

[0025] The long mirror bolts 3 constructed in this manner can prevent collapse of the ground 2 in front of the tunnel face. Specifically, when the ground 2 in front of the tunnel face loosens, the amount of loosening is generally greater in the ground portion 2a on the near side than in the ground portion 2b on the far side. Therefore, the ground portion 2a tries to displace towards the near side (to the right in Figure 1) relative to the ground portion 2b. Consequently, the long mirror bolts 3 try to displace towards the near side (to the right in Figure 1) together with the ground portion 2a. Therefore, a force acts on the locking projection 20 of each mirror bolt 10 from the near side to the far side, and the locking projection 20 catches on the ground 2. As a result, the long mirror bolts 3 can be firmly fixed to the ground 2 without having to attach them to the ground 2 via injection material. The locking projection 20 exhibits a large resistance to the aforementioned force toward the far side (see the dashed line in Figure 4). As a result, the axial force acting on the long mirror bolt 3 can suppress or prevent the collapse of the ground 2.

[0026] With the ground 2 in front of the tunnel face stabilized by the long head bolts 3, the ground 2 is excavated sequentially from the near side. The head bolts 10 are crushed sequentially from the near side along with the ground. The mirror bolt 10 has no injection material filled inside, nor is any injection material attached to its outer surface. Therefore, the crushed mirror bolt 10 can be easily recycled as scrap iron without the need to separate it from the injection material.

[0027] Next, other embodiments of the present invention will be described. In the following embodiments, components that overlap with those described above are denoted by the same reference numerals in the drawings and their descriptions are omitted. <Second Embodiment (Figures 5-6)> As shown in Figures 5 and 6, the mirror bolt 10B according to the second embodiment of the present invention has a locking member 30 that is separate from the pipe body 11. The pipe body 11 in the second embodiment is preferably made of ordinary steel. A plurality of recesses 15 are formed on the outer circumferential surface of the pipe body 11, spaced apart from each other. The depth of the recesses 15 is less than the pipe thickness of the pipe body 11. The recesses 15 do not penetrate the inner circumferential surface of the pipe body 11. There is a one-to-one correspondence between the recesses 15 and the locking member 30.

[0028] The locking member 30 is preferably made of spring steel (high-tensile steel). The locking member 30 is formed by bending a rectangular (square) spring steel plate into a "V" shape in the middle of its longitudinal direction. The locking member 30 integrally has a mounting portion 31 and a locking projection 32, with the bent portion 33 in between. The mounting portion 31 is housed in the inner portion 15b of the corresponding recess 15 and joined to the pipe body 11. The means of joining the mounting portion 31 to the pipe body 11 may be welding, rivets, or screws. The thickness of the mounting portion 31 and thus the locking member 30 is equal to or less than the depth of the recess 15. Therefore, the outer surface of the mounting portion 31 is flush with the outer surface of the pipe body 11 or recessed below it.

[0029] A leaf-spring-shaped locking projection 32 protrudes diagonally outward in the diameter direction of the pipe and towards the user's side from the mounting portion 31. The locking projection 32 diagonally overlaps the open portion 15a on the user's side of the recess 15 from the outside in the diameter direction of the pipe.

[0030] In the second embodiment, since the pipe body 11 and the locking member 30 are separate components, the material of the locking member 30 and, consequently, the locking projection 32 can be different from that of the pipe body 11. This eliminates the need to construct the entire mirror bolt 10B from high-tensile steel, thus reducing material costs.

[0031] When the mirror bolt 10B is driven into the ground 2, the locking projection 32 can be tilted toward the handle side in the pipe axis direction (to the right in Figure 5). The tilted locking projection 32 can enter the open portion 15a of the recess 15. Subsequently, the locking projection 32 elastically returns to its original position and catches on the ground 2, thereby fixing the mirror bolt 10B to the ground 2 and suppressing or preventing the collapse of the ground 2.

[0032] <Third Embodiment (Figure 7)> As shown in Figure 7, in the mirror bolt 10C according to the third embodiment of the present invention, the elongated groove-shaped recess 15C is formed to extend for a long distance in the direction of the pipe axis of the pipe body 11. Multiple locking members 30 are arranged in the elongated groove-shaped recess 15C at intervals in the direction of the pipe axis.

[0033] An open portion 15d of the elongated groove-shaped recess 15C is provided between the mounting portions 31 of two adjacent locking members 30. The locking projection 33 of the innermost of the two adjacent locking members 30 is positioned diagonally over the open portion 15d from the outside in the diameter direction of the pipe.

[0034] <Fourth Embodiment (Figure 8)> As shown in Figure 8, in the mirror bolt 10D according to the fourth embodiment of the present invention, a locking hole 16 is formed at the inner end (left end in Figure 8) of the recess 15D of the pipe body 11. The locking hole 16 penetrates the pipe body 11 in the thickness direction.

[0035] A U-shaped engaging portion 34 is formed at the rear end (left end in Figure 8) of the mounting portion 31 of the locking member 30. The engaging portion 34 is inserted into the locking hole 16 and wraps around to the inner circumference (lower side in Figure 8) of the pipe body 11, fitting with the edge 16a on the near side (right side in Figure 8) of the locking hole 16. This makes the connection between the locking member 30 and the pipe body 11 stronger and reliably prevents the locking member 30 from coming off the pipe body 11 when driving in the mirror bolt 10 or performing other actions.

[0036] <Fifth Embodiment (Figure 9)> As shown in Figure 9, the mirror bolt 10E of the fifth embodiment comprises a pipe body 11 and a plurality (in this case, four) of elongated locking members 40. The four elongated locking members 40 are arranged at intervals, preferably at equal intervals, in the circumferential direction of the pipe body 11. Each elongated locking member 40 includes one elongated mounting portion 41 and a plurality of locking protrusions 42. The elongated mounting portion 41 is formed in the shape of an elongated plate extending in the axial direction of the pipe body 11.

[0037] A long groove-shaped recess 15E extending in the direction of the pipe axis is formed on the outer surface of the pipe body 11. The elongated mounting portion 41 is housed in this long groove-shaped recess 15E.

[0038] Multiple locking protrusions 42 are provided on the outer surface of the elongated mounting portion 41 at intervals in the longitudinal direction. Each locking protrusion 42 protrudes diagonally outward in the diameter direction of the pipe and toward the handle side (right side in Figure 9) in the direction of the pipe axis from the elongated mounting portion 41. The locking protrusions 42 are separate from the elongated mounting portion 41 and may be attached to the elongated mounting portion 41 by welding or the like, or they may be made of the same steel material as the elongated mounting portion 41. An elongated locking member 40 having the elongated mounting portion 41 and the multiple locking protrusions 42 may be formed by cutting or shaping the steel material.

[0039] <Other embodiments (Figure 10)> The locking projection only needs to be elastically deformable in the axial direction of the tube body 11, with relatively low resistance to deformation towards the front in the axial direction and relatively high resistance to deformation towards the back in the axial direction, and is not necessarily limited to a slanted leaf spring shape (Figures 1 to 9). The locking projection 51 shown in Figure 10(a) has a bag-shaped cross-section and protrudes diagonally from the mounting portion 50 toward the handle side (right side in the figure) in the direction of the pipe axis. The locking projection 52 shown in Figure 10(b) is formed in a triangular cross-section. The locking projection 53 shown in Figure 10(c) is formed in a trapezoidal (quadrilateral) cross-section. The locking projection 54 shown in Figure 10(d) is formed in an elliptical cross-section. As shown by the dashed lines in Figures 10(a) to 10(d), when the mirror bolt 50 is driven in, the locking projections 51 to 54 can be elastically deformed to tilt toward the handle side (right side in Figure 10) in the direction of the pipe axis. Along with the tilting, at least a portion of the locking projections 51 to 54 may stretch or contract. After being driven in, the locking protrusions 51 to 54 are elastically returned to their original position as shown by the solid lines in Figures 10(a) to 10(d).

[0040] The present invention is not limited to the embodiments described above, and various modifications can be made without departing from its spirit. For example, different types of locking protrusions may be provided on a single pipe 11. [Industrial applicability]

[0041] This invention can be applied to the mirror bolt method, which is one of the auxiliary construction methods for mountain tunnel construction. [Explanation of Symbols]

[0042] 1 Tunnel 1e slit 2. Natural terrain 2a The natural ground on the near side 2b The natural ground area at the back 2c drive hole 3. Long mirror bolts 4 drilling bits 10 Mirror bolts 10B~10E Mirror bolt 11. Body 11d Pipe wall part 12 Female thread 13 Male screw 14 Opening 15 recesses 15C Long groove-shaped recess 15D recess 15E Long groove-shaped recess 16 Attachment hole 20 Locking protrusion 21 Base 22 Projecting end 30 Locking member 33 Folding section 31 Mounting part 32 Locking protrusion 34 Engagement part 40 Long locking member 41 Long mounting section 42 Locking protrusion 50 Mounting part 51 Bag-shaped locking protrusion 52 Triangular locking protrusion 53 Trapezoidal locking protrusion 54 Elliptical locking projection

Claims

1. These are mirror bolts that are driven into the ground ahead of the tunnel face during construction. A tube that extends in a straight line, A locking projection is provided so as to protrude from the outer surface of the tube, is elastically deformable in the axial direction of the tube, has relatively low resistance to deformation toward the front in the axial direction of the tube, and has relatively high resistance to deformation toward the back in the axial direction of the tube, A mirror bolt characterized in that the locking projection is inclined toward the handle side from the base connected to the pipe body toward the protruding end, and is in the shape of a leaf spring that catches on the ground due to a force from the ground toward the back side that is trying to loosen.

2. The mirror bolt according to claim 1, characterized in that the base portion of the locking projection does not protrude inward in the radial direction from the inner circumferential surface of the pipe body, and the inner circumferential surface is located at the innermost part of the mirror bolt in the radial direction.

3. The mirror bolt according to claim 1 or 2, characterized in that a recess or an opening penetrating to the inner surface is formed on the outer surface of the pipe body, and the locking projection obliquely covers the outer surface of the recess or opening in the radial direction of the pipe.

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