Rock bolt structure and construction method thereof

Abstract

To save labor in connecting work for rock bolts and enable placing a long connected rock bolt into the natural ground with high construction efficiency, as well as eliminate a need for connecting work by man power at a high place in a tunnel space, thereby increasing construction safety.SOLUTION: A rock bolt structure 1 includes a coupler 4 connecting a leading rock bolt 2 and a subsequent rock bolt 3. A columnar insertion portion 32 is provided at a tip end portion of the subsequent rock bolt 3. A C-shaped ring 34 is engaged with and attached to an attachment groove 33 formed along an outer periphery of the columnar insertion portion 32, and an engagement groove 44 is formed along an inner periphery of an engagement hole 43 of the coupler 4. The columnar insertion portion 32 is inserted into the engagement hole 43 of the coupler 4 fixed to a rear end portion of the leading rock bolt, and the elastically restored C-shaped ring 34 is engaged with the engagement groove 44 to connect the leading rock bolt 2 and the subsequent rock bolt 3 via the coupler 4.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rock bolt structure that is driven into the ground of a tunnel to support the tunnel, and a construction method thereof. [Background technology]

[0002] Conventionally, rock bolts have been driven from the tunnel space into the surrounding ground to stabilize it. In recent years, there has been a demand for mechanization and labor savings in tunnel construction, and a rock bolt driving device such as that disclosed in Patent Document 1 has been proposed for driving rock bolts. This rock bolt driving device eliminates the need to use a special dedicated rock bolt driving machine after drilling the tunnel face with a jumbo drill, and enables rock bolt driving work simply by attaching it to the guide shell of the jumbo drill. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5090326 Summary of the Invention [Problem to be solved by the invention]

[0004] Rock bolts used as tunnel support materials have standard lengths set according to the size of the tunnel cross section and the ground grade. However, depending on the ground conditions, it may be difficult to provide stable support for the ground unless rock bolts longer than the size of the tunnel cross section are installed.

[0005] In such cases, it is conceivable to connect rock bolts of standard lengths corresponding to the tunnel cross section with couplers to install a long rock bolt structure of the desired length. However, since the connecting work of connecting rock bolts with couplers is a manual task, even if the rock bolt installation work itself is labor-saving by using a rock bolt installation device such as that described in Patent Document 1, it still requires manual work. In particular, the work of connecting rock bolts in the arch section of a tunnel is a dangerous and inefficient task because it is done manually at a high altitude.

[0006] The present invention has been proposed in view of the above-mentioned problems, and aims to provide a rock bolt structure that reduces the labor required for connecting rock bolts, enables long connected rock bolts to be driven into the ground with high construction efficiency, eliminates the need to connect rock bolts manually at high altitudes in tunnel spaces, and increases construction safety; a ground reinforcement structure in which this rock bolt structure is used; and a construction method for installing this rock bolt structure. [Means for solving the problem]

[0007] The rock bolt structure of the present invention comprises a first rock bolt that is driven from the tunnel space to the back of a hole drilled in the natural ground, a second rock bolt that is connected to the first rock bolt and driven into the hole, and a coupler that connects the first rock bolt and the second rock bolt, wherein a columnar insertion portion is provided at the tip end or the rear end of the first rock bolt, a C-ring is engaged and attached to an attachment groove formed along the outer periphery of the columnar insertion portion, an engagement groove is formed along the inner periphery of a locking hole in the coupler, the columnar insertion portion is inserted into the locking hole of the coupler that is fixedly attached to the rear end of the first rock bolt or the tip end of the second rock bolt, and the C-ring, which has elastically restored, engages in the engagement groove, thereby connecting the first rock bolt and the second rock bolt via the coupler. According to this method, the second rock bolt can be mechanically inserted into the first rock bolt driven into the natural ground using a rock bolt driving device, and the columnar insertion portion can be inserted relatively into the locking hole of the coupler, and the elastically restored C-shaped ring can engage with the engagement groove, thereby connecting the rock bolts. This reduces the labor required for connecting rock bolts, allowing long connected rock bolts to be driven into the natural ground with high construction efficiency. Furthermore, since manual connection work for rock bolts at high altitudes in tunnel spaces is no longer necessary, the safety of driving long rock bolt structures into the natural ground can be improved. The first rock bolt can be a standard rock bolt used alone without being connected, and no special processing is required for this method.

[0008] The rock bolt structure of the present invention is characterized by comprising: a first rock bolt that is driven from the tunnel space to the back of a hole drilled in the natural ground; a second rock bolt that is connected to the first rock bolt and driven into the hole; a columnar insertion portion provided at the tip end of the second rock bolt or the rear end of the first rock bolt; a C-ring that is engaged with and attached to an attachment groove formed along the outer periphery of the columnar insertion portion; a locking hole provided at the rear end of the first rock bolt or the tip end of the second rock bolt; an engagement groove formed along the inner periphery of the locking hole; the columnar insertion portion inserted into the locking hole; the C-ring that has elastically restored engages with the engagement groove, thereby connecting the first rock bolt and the second rock bolt. This allows the second rock bolt to be mechanically inserted into the first rock bolt driven into the natural ground using a rock bolt driving device, inserting the columnar insertion portion into the locking hole relative to the locking hole, and the elastically restored C-shaped ring engaging the engagement groove to connect the rock bolts. This reduces the labor required for connecting rock bolts, allowing long connected rock bolts to be driven into the natural ground with high construction efficiency. Furthermore, since manual rock bolt connection work at high altitudes in tunnel spaces is no longer necessary, the safety of driving long rock bolt structures into the natural ground can be improved. Furthermore, this method eliminates the need for the work of connecting the coupler to the first or second rock bolt, thereby further reducing the labor required for connecting rock bolts.

[0009] The lock bolt structure of the present invention is characterized in that a plurality of the C-shaped rings are arranged in the insertion direction of the columnar insertion portion, and the plurality of C-shaped rings are attached to the mounting groove in a juxtaposed state. According to this, when inserting the columnar insertion part into the locking hole relatively, if only one wide C-shaped ring is provided, the C-shaped ring may not contract to the desired diameter, making smooth insertion difficult, but by arranging multiple C-shaped rings side by side, the diameters of the multiple juxtaposed C-shaped rings are sequentially contracted during insertion, allowing the columnar insertion part provided with the C-shaped rings to be inserted smoothly into the locking hole. Also, the multiple juxtaposed C-shaped rings sequentially expand in diameter due to elastic recovery and engage with the engagement groove, allowing the multiple juxtaposed C-shaped rings to smoothly engage with the engagement groove.

[0010] The lock bolt structure of the present invention is characterized in that the C-rings are arranged side by side such that the circumferential positions of the openings of adjacent C-rings are different so that the openings do not overlap. This makes it possible to prevent the occurrence of large localized cross-sectional defects in the circumferential direction of the rock bolt structure, and when a tensile force is applied to the rock bolt structure, the C-ring can be reliably maintained in an engaged state with the engagement groove, thereby exerting the required resistance to the tensile force.

[0011] In the lock bolt structure of the present invention, the columnar insertion portion is formed in a tapered columnar shape, the mounting grooves include a first mounting groove formed on the tip side of the columnar insertion portion and a second mounting groove formed on the bolt body side, the C-rings include a first C-ring that engages with and is attached to the first mounting groove, and a second C-ring that engages with and is attached to the second mounting groove, and the engagement grooves include a first engagement groove formed on the back side of the tapered locking hole and a second engagement groove formed on the mouth side, and the first C-ring that has elastically restored is engaged with the first engagement groove, and the second C-ring that has elastically restored is engaged with the second engagement groove. With this, for example, when connecting and driving rock bolts diagonally upward in the arch section of a tunnel, it can be difficult to determine the axis of the rock bolts, but by forming the columnar insertion section as a tapered column and making the locking hole tapered, the axis of the first rock bolt and the second rock bolt naturally align, making it possible to more smoothly push the second rock bolt into the first rock bolt.In addition, the engagement states of both the first C-ring in the first engagement groove and the second C-ring in the second engagement groove can further increase the resistance of the rock bolt structure to tensile forces.

[0012] The natural ground reinforcement structure of the present invention is characterized in that a plurality of rock bolt structures of the present invention are driven radially into the natural ground of a tunnel and at intervals in the tunnel axial direction. This significantly improves the efficiency of driving long rock bolts into the ground in a tunnel, and also enables stable support of the ground even when the ground conditions in the tunnel are poor.

[0013] The method for constructing a rock bolt structure of the present invention is a method for constructing a rock bolt structure of the present invention, characterized in that it includes a step of inserting the columnar insertion portion relatively into the locking hole by pushing the second rock bolt into the first rock bolt that has been driven into the ground using a driving device provided in the guide cell of a drill jumbo, and engaging the C-shaped ring that has elastically restored into the engagement groove. This allows the second rock bolt to be mechanically pushed into the first rock bolt using a driving device installed in the guide cell of the drill jumbo, reducing the labor required for connecting the rock bolts.In addition, since construction can be done without using a special rock bolt driving machine, construction costs can be reduced and construction efficiency can be further improved. [Effects of the Invention]

[0014] According to the present invention, the labor required for connecting rock bolts can be reduced, long connected rock bolts can be driven into the ground with high construction efficiency, and the need to connect rock bolts manually at high altitudes in the tunnel space is eliminated, thereby increasing the safety of construction. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1A is a front view of a lockbolt structure according to a first embodiment of the present invention, and FIG. 1B is an exploded explanatory view of the lockbolt structure according to the first embodiment. [Figure 2] 1A is a front view of the rear end portion of the leading rock bolt of the rock bolt structure of the first embodiment, FIG. 1B is a longitudinal cross-sectional view of the coupler, and FIG. 1C is a front view of the tip portion of the trailing rock bolt. [Figure 3] 1A is a front view of the vicinity of the tip of the trailing lock bolt in the lock bolt structure of the first embodiment with the C-ring removed from the tip of the trailing lock bolt, and FIG. 1B is a side view of the C-ring. [Figure 4]5(a) to 5(d) are explanatory views illustrating the operation of pushing a subsequent lock bolt into a coupler fixedly attached to a leading lock bolt in the lock bolt structure of the first embodiment. [Figure 5] (a) is an enlarged cross-sectional view taken along line AA in Figure 4(c), and (b) is an enlarged cross-sectional view taken along line BB in Figure 4(d). [Figure 6] (a) is a schematic diagram illustrating the contraction of the C-ring diameter when the subsequent rock bolt is pushed into the coupler, and (b) is a perspective view of C-rings arranged side by side so that the openings of adjacent C-rings do not overlap. [Figure 7] 5(a) to 5(f) are process explanatory diagrams showing the process of driving the rock bolt structure of the first embodiment. [Figure 8] FIG. 1 is an explanatory perspective view showing an example of a rock bolt driving device used to drive a rock bolt structure. [Figure 9] 1 is a schematic diagram showing the natural ground of a tunnel in which rock bolt structures of a first embodiment are installed radially. FIG. [Figure 10] 10A is a front view of the rear end portion of the leading rock bolt of the rock bolt structure of the second embodiment, FIG. 10B is a longitudinal cross-sectional view of the coupler, and FIG. 10C is a front view of the tip portion of the trailing rock bolt. [Figure 11] 10A is a front view of the vicinity of the tip of the trailing rock bolt in the rock bolt structure of the second embodiment with the C-shaped ring removed from the tip of the trailing rock bolt, FIG. 10B is a side view of the first C-shaped ring, and FIG. 10C is a side view of the second C-shaped ring. [Figure 12] 10(a) to 10(d) are explanatory views illustrating the operation of pushing a subsequent rock bolt into a coupler fixedly attached to a leading rock bolt in a rock bolt structure of a second embodiment. [Figure 13] (a) is an enlarged cross-sectional view of CC in Figure 12(d), and (b) is an enlarged cross-sectional view of DD in Figure 12(d). [Figure 14] 1(a) is a front view of the rear end portion and its periphery of the leading rock bolt in a modified example of the rock bolt structure of the first embodiment, FIG. 1(b) is a longitudinal cross-sectional view of the coupler, and FIG. 1(c) is a front view of the tip portion and its periphery of the trailing rock bolt. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Rock bolt structure of the first embodiment] 1 to 3, a rock bolt structure 1 according to a first embodiment of the present invention is composed of a lead rock bolt 2 corresponding to the first rock bolt to be driven from the tunnel space T to the back of a drilled hole 101 in the natural ground 100, a trailing rock bolt 3 corresponding to the second rock bolt to be connected to the first rock bolt and driven into the drilled hole 101, and a coupler 4 connecting the lead rock bolt 2 and the trailing rock bolt 3. The trailing rock bolt 3 in the illustrated example is a terminal rock bolt whose rear end is located at the opening of the drilled hole 101, but the rock bolt structure 1 may also be constructed by connecting multiple trailing rock bolts 3 using multiple couplers 4, such as connecting another trailing rock bolt 3 to the rear of the trailing rock bolt 3 via the coupler 4.

[0017] In the illustrated example, the lead rock bolt 2 is a twist bolt, with the main body 21 being a roughly cylindrical high-tensile deformed steel bar that has been twisted to form a predetermined knot shape. The tip of the lead rock bolt 2 is a pointed portion 22 that has been sharpened, and the rear end of the lead rock bolt 2 is a male thread portion 23. In other words, in this example, the lead rock bolt 2 can be a regular rock bolt that is used alone without being connected, and no special processing is required for the present invention.

[0018] In the illustrated example, the trailing lock bolt 3 is also a twist bolt, with the main body 31 being a roughly cylindrical high-tensile deformed steel bar with a predetermined knot shape formed in it. A columnar insertion portion 32 is provided at the tip of the trailing lock bolt 3, and its rear end is formed with a male thread portion 36. The columnar insertion portion 32 in the first embodiment is formed in a cylindrical shape with a diameter slightly smaller than the outer diameter of the main body 31, and a mounting groove 33 is formed in the middle along the outer periphery of the columnar insertion portion 32. A C-shaped ring 34 is engaged with and attached to the mounting groove 33.

[0019] The C-ring 34 is formed in a C-shape with an opening 35, and when the opening 35 is expanded and placed on the outer periphery of the mounting groove 33, it elastically recovers and narrows the opening 35, thereby engaging with the mounting groove 33. The outer arc length La1 of the C-ring 34 excluding the opening 35 is shorter than the circumferential length of the inner lead-in surface 45 of the coupler 4, which will be described later. Furthermore, the outer diameter Da1 of the C-ring 34 in an unloaded state is longer than the inner diameter of the inner lead-in surface 45 of the coupler 4, and the inner diameter Da2 of the C-ring 34 in an unloaded state is approximately the same as or very slightly shorter than the outer diameter of the mounting groove 33.

[0020] The C-shaped ring 34 in the first embodiment is formed to have a narrow width, and a plurality of C-shaped rings 34 are arranged side by side in the insertion direction of the columnar insertion portion 32, and are attached by engaging with the attachment groove 33 while the plurality of C-shaped rings 34 are arranged side by side. In the illustrated example, five narrow C-shaped rings 34 are arranged side by side so as to be stacked. It is also possible to employ a configuration in which one C-shaped ring 34 is attached by engaging with the attachment groove 33.

[0021] When arranging multiple C-shaped rings 34 side by side, it is possible to align the circumferential positions of the openings 35 of each C-shaped ring 34, but it is preferable to align the C-shaped rings 34 side by side so that the circumferential positions of the openings 35 of adjacent C-shaped rings 34 are different and the openings 35 do not overlap, and it is even more preferable to align the C-shaped rings 34 side by side so that the circumferential positions of the openings 35 of all C-shaped rings 34 are different and all openings 35 do not overlap (see Figure 6(b)). This prevents cross-sectional defects from concentrating at the installation locations of the C-shaped rings 34 and increases the resistance when a tensile force is applied to the rock bolt structure 1.

[0022] The coupler 4 is generally cylindrical, with a partition wall 41 formed at the axially intermediate position, and a female threaded portion 42 provided in front of the partition wall 41. In the first embodiment, the female threaded portion 42 is threadedly engaged with the male threaded portion 23 at the rear end of the leading lock bolt 2, and the coupler 4 is fixed and attached to the rear end of the leading lock bolt 2.

[0023] A locking hole 43 is provided on the rear side of the partition wall 41 of the coupler 4, with the partition wall 41 as its bottom, and the columnar insertion portion 32 of the trailing lock bolt 3 is inserted into the locking hole 43. An engagement groove 44 is formed along the inner periphery of the locking hole 43 near the axial center of the locking hole 43, and the rear side of the engagement groove 44 of the locking hole 43 forms an introduction inner circumferential surface 45. At the rear end of the locking hole 43, a guide taper portion 46 that gradually increases in diameter toward the rear end edge is formed on the inner circumferential surface to improve smoothness of insertion of the columnar insertion portion 32.

[0024] When constructing the rock bolt structure 1 by inserting the columnar insertion portion 32 of the trailing lock bolt 3 into the locking hole 43 of the coupler 4, the columnar insertion portion 32 of the trailing lock bolt 3 is inserted into the locking hole 43 of the coupler 4 that is fixedly attached to the rear end of the leading lock bolt 2. When inserting the columnar insertion portion 32, the diameters of the multiple juxtaposed C-rings 34 are successively reduced by the guide tapered portion 46 of the locking hole 43, and the C-rings 34 are introduced into the introduction inner peripheral surface 45 (see Figures 4(a) to (c), Figure 5(a), and Figure 6(a)).

[0025] Furthermore, the C-rings 34 in the juxtaposed state that have reached the engagement grooves 44 of the locking holes 43 due to the insertion operation of the columnar insertion portions 32 gradually expand in diameter due to elastic recovery and engage with the engagement grooves 44 until all of the C-rings 34 in the juxtaposed state are engaged with the engagement grooves 44, and the trailing lock bolt 3 is attached to the coupler 4 (see Figures 4(d) and 5(b)). In other words, the leading rock bolt 2 and the trailing rock bolt 3 are connected via the coupler 4, and the rock bolt structure 1 of the first embodiment is constructed.

[0026] In a construction example in which the rock bolt structure 1 of the first embodiment is driven from a tunnel space T into the natural ground 100, as shown in Figure 7(a), a drilled hole 101 is formed in advance in the natural ground 100, and mortar (not shown) is poured into the drilled hole 101. Then, a lead rock bolt 2 having a coupler 4 screwed and attached to its rear end is supplied from a rock bolt supply device 201 to a guide cell 202 of a jumbo drill, and is attached to a driving device 203 that is provided on the guide cell 202 so as to be able to move forward and backward. The driving device 203 is then advanced on the guide cell 202, and the lead rock bolt 2 is inserted into the drilled hole 101 up to the position of the rear end of the lead rock bolt 2 or the position of the coupler 4 (see Figures 7(b) and 8).

[0027] The driving device 203 is detached from the rear end of the leading rock bolt 2 or from the coupler 4, and the driving device 203 is retracted on the guide cell 202. The subsequent rock bolt 3 is then supplied to the guide cell 202 from the rock bolt supply device 201. The subsequent rock bolt 3 is attached to the driving device 203, and the driving device 203 is advanced on the guide cell 202 to push and insert the columnar insertion portion 32 at the tip of the subsequent rock bolt 3 into the locking hole 43 of the coupler 4 (see Figures 7(c) to (e) and Figure 8). By inserting the columnar insertion portion 32 into the locking hole 43, the C-ring 34, which has elastically restored, engages with the engagement groove 44, and the subsequent rock bolt 3 is connected to the coupler 4.

[0028] Furthermore, the driving device 203 pushes the subsequent rock bolt 3 into the drilled hole 101, and the leading rock bolt 2 and the subsequent rock bolt 3 connected via the coupler 4 are inserted into the drilled hole 101, completing the driving of the rock bolt structure 1 of the first embodiment into the ground 100 (see Figures 7(e) and (f)).

[0029] As shown in Fig. 9, multiple rock bolt structures 1 like this are driven radially from the tunnel space T into the natural ground 100 of the tunnel, and are also driven at intervals in the tunnel axial direction as the tunnel is excavated, thereby constructing a natural ground reinforcement structure in which multiple rock bolt structures 1 of the first embodiment are driven in. Reference numeral 102 in Fig. 9 denotes a support area of ​​the natural ground 100 supported by the driven rock bolt structures 1.

[0030] According to the first embodiment, simply by mechanically pushing the trailing rock bolt 3 into the leading rock bolt 2 driven into the natural ground 100 using a rock bolt driving device 203 or the like, the columnar insertion portion 32 is relatively inserted into the locking hole 43 of the coupler 4, and the elastically restored C-ring 34 engages with the engagement groove 44, thereby connecting the rock bolts 2 and 3. This reduces the labor required for connecting the rock bolts 2 and 3, and allows long, connected rock bolts 2 and 3 to be driven into the natural ground 100 with high construction efficiency. Furthermore, because it is no longer necessary to manually connect the rock bolts 2 and 3 at a high altitude in the tunnel space T, the safety of the construction of driving the long rock bolt structure 1 into the natural ground 100 can be improved.

[0031] Furthermore, when inserting the columnar insertion portion 32 relatively into the locking hole 43, if only one wide C-shaped ring is provided, the diameter of the C-shaped ring may not be reduced to the desired state, making smooth insertion difficult. However, by arranging multiple C-shaped rings 34 side by side, the diameters of the multiple juxtaposed C-shaped rings 34 are sequentially reduced during insertion, allowing the columnar insertion portion 32 provided with the C-shaped rings 34 to be smoothly inserted into the locking hole 43. Furthermore, the multiple juxtaposed C-shaped rings 34 sequentially expand in diameter due to elastic recovery and engage with the engagement groove 44, allowing the multiple juxtaposed C-shaped rings 34 to be smoothly engaged with the engagement groove 44.

[0032] Furthermore, by arranging the C-rings 34 side by side so that the circumferential positions of the openings 35 of adjacent C-rings 34 are different and the openings 35 do not overlap, or more preferably by arranging the C-rings 34 side by side so that the circumferential positions of the openings 35 of all of the C-rings 34 are different and all of the openings 35 do not overlap, it is possible to prevent the occurrence of large localized cross-sectional defects in the circumferential direction of the rock bolt structure 1, and when a tensile force is applied to the rock bolt structure 1, the C-rings 34 can be reliably maintained in their engagement with the engagement grooves 44, and the required resistance to the tensile force can be exerted.

[0033] Furthermore, by forming a ground reinforcement structure in which multiple rock bolt structures 1 are driven radially into the tunnel ground 100 and spaced apart in the tunnel axial direction, the efficiency of the work of driving long rock bolts 2, 3 into the tunnel ground 100 can be significantly improved. Furthermore, the ground 100 can be stably supported even when the tunnel ground conditions are poor.

[0034] Furthermore, by using a driving device 203 provided in the guide cell 202 of the drill jumbo to drive the subsequent rock bolt 3 into the leading rock bolt 2 that has been driven into the natural ground 100, the columnar insertion part 32 is relatively inserted into the locking hole 43, and the elastically restored C-ring 34 is engaged with the engagement groove 44. This construction method allows the subsequent rock bolt 3 to be mechanically driven into the leading rock bolt 2 by the driving device 203 to perform the connecting work, thereby reducing the number of people required for the connecting work of the rock bolts 2 and 3. Furthermore, since construction can be done without using a special dedicated rock bolt driving machine, construction costs can be reduced and construction efficiency can be further improved.

[0035] [Rock bolt structure of second embodiment] 10 and 11, a rock bolt structure 1a according to a second embodiment of the present invention is composed of a leading rock bolt 2 corresponding to the first rock bolt having the same configuration as that of the first embodiment, a trailing rock bolt 3a corresponding to the second rock bolt connected to the first rock bolt and driven into the drilled hole 101, and a coupler 4a connecting the leading rock bolt 2 and the trailing rock bolt 3a. The trailing rock bolt 3a may be an end rock bolt, or a further trailing rock bolt 3a may be connected to the rear side of the trailing rock bolt 3a via the coupler 4a, and multiple trailing rock bolts 3a may be connected using multiple couplers 4a to form the rock bolt structure 1a.

[0036] In the illustrated example, the trailing lock bolt 3a is a twist bolt, and its main body 31a is a substantially cylindrical high-tensile deformed steel bar with a predetermined knot shape. A columnar insertion portion 32a is provided at the tip of the trailing lock bolt 3a, and its rear end is male-threaded. The columnar insertion portion 32a is formed in a tapered column shape, tapering from a portion adjacent to the main body 31a that has approximately the same outer diameter as the main body 31a toward the tip. A first mounting groove 331a is formed along the outer periphery of the columnar insertion portion 32a at the tip side, and a second mounting groove 332a is formed along the outer periphery of the columnar insertion portion 32a on the main body 31a side. A first C-shaped ring 341a is engaged and attached to the first mounting groove 331a, and a second C-shaped ring 342a is engaged and attached to the second mounting groove 332a.

[0037] The first C-shaped ring 341a is C-shaped with an opening 351a. When the opening 351a is expanded and positioned around the outer periphery of the first mounting groove 331a, the first C-shaped ring 341a elastically recovers and narrows the opening 351a, thereby engaging with the first mounting groove 331a. The outer arc length Lb1 of the first C-shaped ring 341a excluding the opening 351a is shorter than the circumferential length of the lead-in inner circumferential surface 45a of the coupler 4a (described later) at a location immediately before the first engagement groove 441a. The outer diameter Db1 of the first C-shaped ring 341a in the unloaded state is longer than the inner diameter of the lead-in inner circumferential surface 45a of the coupler 4a at a location immediately before the first engagement groove 441a. The inner diameter Db2 of the first C-shaped ring 341a in the unloaded state is approximately the same as or slightly shorter than the outer diameter of the first mounting groove 331a.

[0038] The second C-shaped ring 342a is also C-shaped with an opening 352a. When the opening 352a is expanded and positioned around the outer periphery of the second mounting groove 332a, the second C-shaped ring 342a elastically recovers and narrows the opening 352a, thereby engaging with the second mounting groove 332a. The outer arc length Lc1 of the second C-shaped ring 342a excluding the opening 352a is shorter than the circumferential length of the lead-in inner circumferential surface 45a of the coupler 4a (described later) at a location immediately before the second engagement groove 442a. The outer diameter Dc1 of the second C-shaped ring 342a in the unloaded state is longer than the inner diameter of the lead-in inner circumferential surface 45a of the coupler 4a at a location immediately before the second engagement groove 442a. The inner diameter Dc2 of the second C-shaped ring 342a in the unloaded state is approximately the same as or slightly shorter than the outer diameter of the second mounting groove 332a.

[0039] The C-shaped rings 341a, 342a in the second embodiment are also narrow, and multiple C-shaped rings 341a, 342a are arranged side by side in the insertion direction of the columnar insertion portion 32a, and are attached by engaging with the mounting grooves 331a, 332a while juxtaposed. In the illustrated example, five narrow C-shaped rings 341a, 342a are arranged side by side in a stacked arrangement. Note that it is also possible to attach one C-shaped ring 341a, 342a by engaging with each mounting groove 331a, 332a.

[0040] When arranging a plurality of C-shaped rings 341a, 342a side by side, it is possible to align the circumferential positions of the openings 351a of the C-shaped rings 341a and the openings 352a of the C-shaped rings 342a. However, as with the C-shaped ring 34 of the first embodiment, it is also possible to align the circumferential positions of the openings 351a of the adjacent C-shaped rings 341a and the openings 352a of the adjacent C-shaped rings 342a. It is preferable to arrange the C-shaped rings 341a and 342a side by side so that the openings 351a and 351a and the openings 352a and 352a do not overlap, and it is even more preferable to arrange the C-shaped rings 341a and 342a side by side so that the circumferential positions of the openings 351a of all the C-shaped rings 341a and the openings 352a of all the C-shaped rings 342a are different and so that all the openings 351a and all the openings 352a do not overlap.

[0041] The coupler 4a is generally cylindrical and has a female thread 42a at its front end. In the second embodiment, the female thread 42a is threaded onto the male thread 23 at the rear end of the lead lock bolt 2, and the coupler 4a is fixed and attached to the rear end of the lead lock bolt 2.

[0042] A tapered locking hole 43a, which gradually reduces in diameter toward the front, is provided at the rear of the coupler 4a so as to communicate with the female threaded portion 42a, and the columnar insertion portion 32a of the trailing lock bolt 3a is inserted into the locking hole 43a. A guide tapered portion 46a, which gradually increases in diameter toward the rear edge, is also formed on the inner peripheral surface of the rear end of the locking hole 43a.

[0043] A first engagement groove 441a is formed along the inner periphery of the tapered locking hole 43a at the back side where the diameter is small, and a second engagement groove 442a is formed along the inner periphery of the locking hole 43a at the opening side where the diameter is large. The area between the first engagement groove 441a and the second engagement groove 442a of the locking hole 43a and in front of the second engagement groove 442a forms an introduction inner periphery surface 45a. At the rear end of the locking hole 43a, a guide tapered portion 46a that gradually increases in diameter toward the rear edge is formed on the inner periphery to improve smooth insertion of the columnar insertion portion 32a.

[0044] When constructing the lock bolt structure 1a by inserting the columnar insertion portion 32a of the trailing lock bolt 3a into the locking hole 43a of the coupler 4a, as shown in Figures 12(a) and 12(b), the columnar insertion portion 32a of the trailing lock bolt 3a is inserted into the locking hole 43a of the coupler 4a that is fixedly attached to the rear end of the leading lock bolt 2. When inserting the columnar insertion portion 32a, the columnar insertion portion 32a is guided by the guide tapered portion 46a and introduced into the introduction inner circumferential surface 45a. Then, on the tapered surface of the introduction inner circumferential surface 45a just before the first engagement groove 441a, the multiple juxtaposed first C-shaped rings 341a with smaller diameters are successively reduced in diameter and introduced into the first engagement groove 441a, and on the tapered surface of the introduction inner circumferential surface 45a just before the second engagement groove 442a, the multiple juxtaposed second C-shaped rings 342a with larger diameters are successively reduced in diameter and introduced into the second engagement groove 442a (see Figure 12(c)).

[0045] Furthermore, by the insertion operation of the columnar insertion portion 32a, the first C-shaped ring 341a in the juxtaposed state that has reached the first engagement groove 441a of the locking hole 43a gradually expands in diameter due to elastic restoration and engages with the first engagement groove 441a, and the second C-shaped ring 342a in the juxtaposed state that has reached the second engagement groove 442a of the locking hole 43a gradually expands in diameter due to elastic restoration and engages with the second engagement groove 442a, and the trailing lock bolt 3a is attached to the coupler 4a (see Figures 12(d) and 13). In other words, the leading lock bolt 2 and the trailing lock bolt 3a are connected via the coupler 4a, and the lock bolt structure 1a of the second embodiment is constructed.

[0046] The other configurations of the rock bolt structure 1a of the second embodiment are the same as those of the first embodiment, and the rock bolt structure 1a of the second embodiment can also be constructed using the same construction example as the first embodiment, and a similar ground reinforcement structure can be constructed.

[0047] According to the second embodiment, for example, when driving a series of rock bolts diagonally upward into the arch of a tunnel, the axis of the rock bolts can be difficult to determine. However, by forming the columnar insertion portion 32a as a tapered column and making the locking hole 43a tapered, the axis of the leading rock bolt 2 and the trailing rock bolt 3a naturally align, making it possible to more smoothly insert the trailing rock bolt 3a into the leading rock bolt 2. Furthermore, the engagement of both the first C-shaped ring 341a with the first engagement groove 441a and the second C-shaped ring 342a with the second engagement groove 442a can further increase the resistance of the rock bolt structure 1a to tensile forces. Additionally, the second embodiment can achieve the same effects as the first embodiment due to the configuration corresponding to that of the first embodiment.

[0048] [Scope of the invention disclosed herein] The inventions disclosed in this specification include, in addition to the inventions, embodiments, and examples listed as inventions, those specified by changing partial contents of these to other contents disclosed in this specification, those specified by adding other contents disclosed in this specification to these contents, or those specified by deleting partial contents of these to the extent that partial effects are obtained and creating a generic concept.The inventions disclosed in this specification also include the following contents and further modifications described below.

[0049] For example, the shape of the main body 21 of the leading rock bolt 2 corresponding to the first rock bolt and the shape of the main body 31 of the trailing rock bolt 3 corresponding to the second rock bolt may be appropriate, and for example, the leading rock bolt 2t and the trailing rock bolt 3t may have main body parts 21t, 31t shaped as shown in Figure 14.

[0050] Furthermore, contrary to the first and second embodiments, a columnar insertion portion may be provided at the rear end of the leading lock bolt corresponding to the first lock bolt, and a coupler may be attached and fixed by screwing to the tip end of the following lock bolt corresponding to the second lock bolt. By pushing the following lock bolt in, the columnar insertion portion of the leading lock bolt is inserted relatively into the locking hole of the coupler, and the elastically restored C-shaped ring of the columnar insertion portion engages with the engagement groove of the coupler, thereby constructing the lock bolt structure of the present invention.

[0051] Alternatively, instead of using separate couplers 4, 4a, the lock bolt structure of the present invention may be constructed by integrally providing a structure corresponding to the locking holes 43, 43a of the couplers 4, 4a of the first and second embodiments at the rear end of the leading lock bolt corresponding to the first lock bolt or at the front end of the following lock bolt corresponding to the second lock bolt, providing a columnar insertion portion at the front end of the following lock bolt or the rear end of the leading lock bolt, inserting the columnar insertion portion into the locking hole relatively, and engaging the elastically restored C-ring with the engaging groove of the locking hole. In this way, the work of connecting the couplers 4, 4a to the first or second lock bolt can be omitted, further reducing the labor required for connecting the rock bolts. [Industrial Applicability]

[0052] The present invention can be used when a long rock bolt structure is driven into the ground of a tunnel to support the tunnel. [Explanation of symbols]

[0053] 1, 1a... Rock bolt structure 2, 2t... Leading rock bolt 21, 21t... Main body 22... Point 23... Male thread 3, 3a, 3t... Subsequent rock bolt 31, 31a, 31t... Main body 32, 32a... Columnar insertion portion 33... Mounting groove 331a... First mounting groove 332a... Second mounting groove 34... C-shaped ring 341a... First C-shaped ring 342a... Second C-shaped ring 35, 351a, 352a... Opening 36... Male thread 4, 4a... Coupler 41... Partition wall 42, 42a... Female thread 43, 43a... Locking hole 44... Engagement groove 441a... First engagement groove 442a... Second engagement groove 45, 45a... Inner circumferential surface of introduction 46, 46a...guide tapered portion 100...natural ground 101...drilling 102...support area 201...rock bolt supply device 202...guide cell 203...concreting device T...tunnel space

Claims

1. a first rock bolt that is driven from the tunnel space to the back side of the drilled hole in the natural ground; A second rock bolt connected to the first rock bolt and driven into the drilled hole; a coupler that connects the first lock bolt and the second lock bolt; A columnar insertion portion is provided at the tip end of the second lock bolt or the rear end of the first lock bolt, A C-ring is fitted into a fitting groove formed along the outer periphery of the columnar insertion portion, An engagement groove is formed along the inner periphery of the locking hole of the coupler, The columnar insertion portion is inserted into the locking hole of the coupler fixedly attached to the rear end portion of the first lock bolt or the front end portion of the second lock bolt, The C-ring, which has elastically restored, is engaged with the engagement groove, and the first lock bolt and the second lock bolt are connected via the coupler. A lock bolt structure characterized in that a plurality of the C-shaped rings are arranged in the insertion direction of the columnar insertion portion, and the plurality of C-shaped rings are attached to the mounting groove in a juxtaposed state.

2. a first rock bolt that is driven from the tunnel space to the back side of the drilled hole in the natural ground; A second rock bolt connected to the first rock bolt and driven into the drilled hole; A columnar insertion portion is provided at the tip end of the second lock bolt or the rear end of the first lock bolt, A C-ring is fitted into a fitting groove formed along the outer periphery of the columnar insertion portion, A locking hole is provided at the rear end of the first lock bolt or the front end of the second lock bolt, An engagement groove is formed along the inner periphery of the locking hole, The columnar insertion portion is inserted into the locking hole, The C-ring, which has elastically restored, is engaged with the engagement groove, connecting the first lock bolt and the second lock bolt, A lock bolt structure characterized in that a plurality of the C-shaped rings are arranged in the insertion direction of the columnar insertion portion, and the plurality of C-shaped rings are attached to the mounting groove in a juxtaposed state.

3. 3. The lock bolt structure according to claim 1, wherein the C-rings are arranged side by side such that the circumferential positions of the openings of adjacent C-rings are different so that the openings do not overlap.

4. The columnar insertion portion is formed into a tapered columnar shape, As the mounting grooves, a first mounting groove is formed on the tip side of the columnar insertion portion and a second mounting groove is formed on the bolt body side, The C-shaped rings include a first C-shaped ring that is attached by engaging with the first mounting groove, and a second C-shaped ring that is attached by engaging with the second mounting groove, As the engagement grooves, a first engagement groove is formed on the inner side of the tapered locking hole, and a second engagement groove is formed on the opening side thereof, 4. A lock bolt structure according to claim 1, wherein the first C-ring, which has elastically restored, is engaged with the first engagement groove, and the second C-ring, which has elastically restored, is engaged with the second engagement groove.

5. A ground reinforcement structure characterized in that a plurality of rock bolt structures according to any one of claims 1 to 4 are driven radially into the ground of a tunnel and are driven at intervals in the axial direction of the tunnel.

6. A method for installing a rock bolt structure according to any one of claims 1 to 4, A method for constructing a rock bolt structure, comprising the steps of: pushing the second rock bolt into the first rock bolt that has been driven into the ground using a driving device provided in the guide cell of a drill jumbo, thereby inserting the columnar insertion portion relatively into the locking hole, and engaging the elastically restored C-ring with the engagement groove.

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