Rock bolt extension method and rock bolt structure

Abstract

To efficiently add a rock bolt in tunnel construction in a short time.SOLUTION: Behind a leading rock bolt 11 driven into a ground 2, a succeeding rock bolt 12 to be driven next is arranged in a straight line. A joint sleeve 20 is arranged so as to straddle outer circumferences of th two rock bolts 11 and 12. After that, the joint sleeve 20 is crushed by a crushing device 40 and brought into close contact with the two rock bolts 11 and 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a rock bolt extension method and a rock bolt structure in a mountain tunnel constructed, for example, by the NATM (New Austrian Tunneling Method) method. [Background technology]

[0002] In general, in the construction of mountain tunnels, rock bolts are driven into the ground around the excavated tunnel to stabilize the ground. When the required length of the rock bolts is longer than the length of a single rock bolt, multiple rock bolts are added in a row in sequence to reach the required length in total (see Patent Document 1, etc.).

[0003] For example, Patent Document 1 discloses a cylindrical joint sleeve for extending a rock bolt. A female thread is engraved on the inner peripheral surface of the joint sleeve. The joint sleeve spans the outer periphery of the opposing ends of two fully threaded lock bolts. The male threads of each lock bolt are screwed into the female threads of the joint sleeve. As a result, the two lock bolts are joined in a straight line via the joint sleeve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 04-122808 Summary of the Invention [Problem to be solved by the invention]

[0005] To join two lock bolts by screw fastening as in Patent Document 1, it is necessary to rotate and screw a joint sleeve onto the previously driven lock bolt, and then rotate and screw the subsequent lock bolt into the joint sleeve. This makes the extension work complicated and time-consuming. In view of the above circumstances, the present invention aims to make it possible to add rock bolts efficiently in a short time during tunnel construction. [Means for solving the problem]

[0006] In order to solve the above problems, the method for adding a rock bolt according to the present invention comprises the steps of: The following rock bolt is driven into the ground in a straight line behind the preceding rock bolt that has been driven into the ground. A coupling sleeve is disposed so as to straddle the outer circumference of the two rock bolts, The joint sleeve is then crushed by a crushing device to be tightly attached to the two rock bolts. According to this method, two lock bolts can be joined together in a single operation by the crushing operation of the crushing device. There is no need to screw in the joint sleeve and the lock bolts to join them together.

[0007] The structure of the present invention is a rock bolt structure driven into the ground, The device is characterized by comprising a plurality of rock bolts arranged in a straight line and a joint sleeve that spans the outer circumference of two adjacent rock bolts, and the joint sleeve is crushed and tightly attached to the two rock bolts. As a result, the two rock bolts are connected to each other via the crushed joint sleeve. Crushed marks are formed on the joint sleeve.

[0008] It is preferable that a hook projection for hooking the joint sleeve before crushing is formed on the end of one of the two lock bolts facing the other lock bolt. With this, by hooking the joint sleeve on the hook projection of one lock bolt, the joint sleeve is supported by the one lock bolt, and in this state, the facing end of the other lock bolt can be inserted into the joint sleeve. Effect of the Invention

[0009] According to the present invention, rock bolts can be added efficiently in a short time during tunnel construction. [Brief description of the drawings]

[0010] [Figure 1] Figure 1 is a side cross-sectional view of a NATM tunnel under construction, showing the rock bolt driving process. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1, showing the connecting portion between the lock bolts in a state before the joint sleeve is crushed. [Diagram 5] FIG. 5 is a cross-sectional view showing one embodiment of a coupling sleeve. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 shows a second embodiment of the present invention, and is a cross-sectional view showing a connecting portion between lock bolts in a state before the joint sleeve is crushed. [Figure 8] FIG. 8 shows a third embodiment of the present invention, and is a cross-sectional view showing a connecting portion between lock bolts in a state where a subsequent lock bolt is inserted into a joint sleeve before being crushed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First Embodiment Figure 1 shows a NATM tunnel 1 being constructed using the NATM method. A number of long rock bolts 3 (rock bolt structure) (only one is shown in the figure) have been driven into the natural ground 2 around the excavated tunnel 1. Although not shown in the figure, the multiple long rock bolts 3 are spaced apart from one another in the circumferential and axial directions of the tunnel 1. Each long rock bolt 3 includes multiple rock bolts 10 (only two are shown in the figure) arranged in a straight line, and a joint sleeve 20. Hereinafter, when distinguishing adjacent rock bolts 10 from each other, the one driven in first will be referred to as the "leading rock bolt 11" and the one driven in next will be referred to as the "subsequent rock bolt 12."

[0012] As shown in Fig. 2, the joint sleeve 20 is formed in a cylindrical shape and spans the outer circumference of the opposing ends 11e, 12e of two adjacent lock bolts 11, 12. These opposing ends 11e, 12e are inserted into the inside of the corresponding portions of the joint sleeve 20, each of which has approximately half the length. The joint sleeve 20 is crushed and pressed against the outer circumference of the opposing ends 11e, 12e of the lock bolts 11, 12, so that the adjacent rock bolts 11, 12 are connected to each other via the crushed joint sleeve 20. As shown in Fig. 3, the joint sleeve 20 has an uneven crushed mark 28 formed thereon.

[0013] NATM tunnel 1 will be constructed as follows: Each time a predetermined length of the ground 2 is excavated, a primary lining (not shown) including arch supports and shotcrete is installed on the excavation surface, and long rock bolts 3 are driven into the surrounding ground 2. Before driving the bolts, driving holes are drilled and grout material is injected into the driving holes. The driving is carried out before the grout material hardens.

[0014] As shown in Fig. 1, a drill jumbo 30 (driving machine) is used to drive the rock bolt 10. The leading rock bolt 11 is driven into the natural ground 2 by the drill jumbo 30. As shown in Fig. 4, the driving is stopped before the rear end 11e of the leading rock bolt 11 is embedded in the natural ground 2.

[0015] Separately, the joint sleeve 20A before crushing is prepared. The joint sleeve 20A before crushing is formed in a cylindrical shape, and naturally has no crushing marks 28. As shown in Fig. 5, the inner peripheral surface of the joint sleeve 20A may be formed with projections and recesses in order to increase the degree of contact with the lock bolt 10 when crushed.

[0016] 4, the trailing lock bolt 12 to be driven next is placed in a straight line behind the leading lock bolt 11, and the joint sleeve 20A is placed so as to straddle the outer periphery of the opposing ends 11e, 12e of these two lock bolts 11, 12. That is, the rear end 11e of the leading lock bolt 11 is inserted inside the tip portion of the joint sleeve 20A, and the tip end 12e of the trailing lock bolt 12 is inserted inside the rear end portion of the joint sleeve 20A.

[0017] The trailing rock bolt 12 is supported by a guide cell 31 of a drill jumbo 30 shown in Fig. 1. A crushing device 40 is provided at the tip of the guide cell 31. The crushing device 40 holds the joint sleeve 20A.

[0018] As shown in Fig. 6, the crushing device 40 includes a hydraulic clamp 41 and a drive mechanism 43. The clamp 41 includes a plurality of dies 42 arranged in a ring shape. Although the number of dies 42 is three in Fig. 6, the number is not limited to three, and may be two or four or more. A hydraulic drive mechanism 43 is connected to each die 42. The hydraulic drive mechanism 43 moves the plurality of dies 42 forward and backward in the radial direction in synchronization with each other. This causes the clamp 41 to contract and expand in diameter.

[0019] As shown by the solid lines in Fig. 6, when connecting the lock bolts 11, 12, the clamp 41 of the crushing device 40 is expanded in diameter and the joint sleeve 20A is inserted therein. Preferably, the joint sleeve 20A is set at the center of the clamp 41. Then, as shown by the two-dot chain lines in Fig. 6, the clamp 41 is contracted in diameter by the hydraulic drive mechanism 43. That is, the multiple dies 42 are pushed radially inward in synchronization with each other.

[0020] 2 and 3, the joint sleeve 20A is crushed radially inward. The crushed joint sleeve 20 is pressed against and tightly attached to the opposing ends 11e, 12e of the lock bolts 11, 12. As a result, the lock bolts 11, 12 are connected to each other via the joint sleeve 20. In other words, the trailing lock bolt 12 is added to the leading lock bolt 11. A crushed mark 28 is formed on the crushed joint sleeve 20.

[0021] According to this connection method, the two rock bolts 11, 12 can be connected in a single operation by the crushing operation using the crushing device 4. There is no need to screw the joint sleeve 20 and the rock bolts 11, 12. Therefore, the rock bolts 11, 12 can be connected efficiently in a short time during tunnel construction.

[0022] After the above-mentioned connecting operation, the hydraulic drive mechanism 43 moves the die 42 outward in the radial direction and opens the clamps 41. This releases the coupling sleeve 20 from the crushing device 40. Next, the driving of rock bolts will be resumed using Drill Jumbo 30. The above connecting and driving operations are repeated for the required number of rock bolts to drive the long rock bolts 3 into the natural ground 2. The multiple long rock bolts 3 are driven into the surrounding natural ground 2 at intervals in the circumferential and axial directions of the tunnel 1. This stabilizes the natural ground 2. Thereafter, a waterproof sheet is laid on the inner surface of the primary lining (not shown), and then a secondary lining is constructed.

[0023] Next, another embodiment of the present invention will be described. In the following embodiment, the same reference numerals are given to the same components as those in the above-described embodiment, and the description thereof will be omitted. <Second embodiment (FIG. 7)> As shown in Fig. 7, in the second embodiment, of two adjacent lock bolts 11, 12, a pair of hook projections 13 is formed on a rear end 11e (the end facing the other) of the leading (one) lock bolt 11. The hook projection 13 protrudes radially from the lock bolt 11. The pair of hook projections 13 are provided 180° apart in the circumferential direction of the lock bolt 11. The number of hook projections 13 may be one, or three or more. An engagement hole 24 is formed through the tip end portion of the joint sleeve 20A.

[0024] When connecting the leading lock bolt 11 to the trailing lock bolt 12, first, the rear end 11e is inserted into the tip end portion of the joint sleeve 20A, and the hooking projection 13 of 1 is passed through the locking hole 24, so that the joint sleeve 20A is hooked and supported by the rear end 11e of the leading lock bolt 11. This prevents the inserted joint sleeve 20A from falling, and the operator can release the joint sleeve 20A and move on to the insertion of the trailing lock bolt 12. This in turn makes the extension work even easier. By providing multiple hooking protrusions 13 spaced apart around the circumferential direction of the lead lock bolt 11, it is possible to select the hooking protrusion 13 on which the joint sleeve 20A will hook without falling off, depending on the rotation angle of the lead lock bolt 11.

[0025] <Third embodiment (FIG. 8)> 8, in the third embodiment, the rear end of the joint sleeve 20C before being crushed is an expanded end 25 that expands in a tapered shape toward the rear side. This makes it easier to insert the tip 12e of the trailing lock bolt 12 into the joint sleeve 20C.

[0026] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the present invention. For example, of two adjacent lock bolts 11, 12, the trailing (one) lock bolt 12 may have a hook projection 13 formed on a tip portion 12e (the end portion facing the other). Adjacent dies 42 at one or more predetermined circumferential positions of the clamp 41 of the crushing device 40 may be separable and joinable to each other, so that the clamp 41 can be opened and closed. In this case, the clamp 41 is opened and the joint sleeve 20A is placed inside the clamp 41, and then the clamp 41 is closed to form a closed ring and the crushing operation is performed. Thereafter, the clamp 41 is opened and separated from the outer periphery of the crushed joint sleeve 20, whereby the joint sleeve 20 can be released from the crushing device 40. [Industrial Applicability]

[0027] The present invention can be applied to, for example, the construction of NATM tunnels. [Explanation of symbols]

[0028] 1. Tunnel 2. Ground 3 Long rock bolts (rock bolt structure) 10 Rock Bolt 11 Pre-lock bolt 11e Rear end (opposite end) 12 Trailing rock bolt 12e Tip (opposite end) 13 Hook protrusion 20 Crushed joint sleeve 20A Joint sleeve before crushing 20C Fitting Sleeve 28 Crushed mark 24 Locking hole 25 Enlarged end 30 Drill Jumbo (Drilling Machine) 31 Guide Cell 40 Crushing Device 41 Clamp 42 Die 43 Drive mechanism

Claims

1. The following rock bolt is driven into the ground in a straight line behind the preceding rock bolt that has been driven into the ground. A joint sleeve is disposed so as to straddle the outer peripheries of the two lock bolts without performing a screw-turning operation, and an unevenness is formed on the inner periphery of the joint sleeve so as to face the outer peripheries of each of the lock bolts, and the inner diameter of the unevenness at the convex portion is larger than the outer diameter of each of the lock bolts, The method for extending a rock bolt comprises crushing the joint sleeve using a crushing device to bring the uneven portion of the inner surface of the joint sleeve into close contact with the two lock bolts, thereby forming uneven crushed marks on the outer periphery of the portion of the joint sleeve where one of the two lock bolts is inserted and on the outer periphery of the portion of the joint sleeve where the other lock bolt is inserted.

2. A rock bolt structure that is driven into the ground to stabilize the ground, a coupling sleeve that can be positioned so as to straddle the outer peripheries of two adjacent lock bolts without being screwed and that can be crushed by radial compression alone, wherein the inner surface of the coupling sleeve is formed with projections and recesses so as to face the outer peripheries of the lock bolts, the inner diameter of the coupling sleeve at the projections of the projections is larger than the outer diameter of the lock bolts, the coupling sleeve is crushed so that the portion of the inner surface of the coupling sleeve where the projections and recesses are formed is in close contact with the two lock bolts, and uneven crushing marks are formed on the outer periphery of the portion of the coupling sleeve where one of the two lock bolts is inserted and on the outer periphery of the portion of the coupling sleeve where the other lock bolt is inserted.

3. The lock bolt structure according to claim 2, characterized in that a hook protrusion is formed on the end of one of the two lock bolts facing the other, for hooking the joint sleeve before it is crushed.

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