Inner rod, and boring rod, as well as boring method for double pipe

Abstract

To provide boring technology capable of transporting and discharging excavated slime generated in the hole bottom to a hole mouth during air boring.SOLUTION: An inner rod of a boring rod using for double pile boring the ground with a boring bit arranged on the inner rod or a tip of the inner rod and a casing by applying impact and rotation on the inner rod by using a boring rod provided with the casing of an outer pipe and the inner rod inserted in the casing is configured to have no steps on a rod outside surface over from a base end to the tip. No steps makes a passage section area of a discharging passage is uniform over a whole passage and makes compressed air flow in a discharge passage flow uniformly without vortexes and congestion to prevent slime flowing by the compressed air flow from jamming through its congestion in the discharge passage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a double-pipe drilling technique for drilling holes in the ground using a boring rod of a double-pipe drilling method, which uses two rods, an outer pipe and an inner pipe, to drill holes in the ground. [Background technology]

[0002] As a drilling technique for drilling relatively soft ground or bedrock (hereinafter collectively referred to as "ground"), the "double pipe drilling method" is widely used, which uses an outer pipe (outer casing) with an outer bit at the tip and an inner pipe (inner rod) with an inner bit at the tip. In the double pipe drilling method, drilling is performed using two pipes, an outer pipe and an inner pipe, and after drilling, the outer pipe is left in place to protect the well hole from rockfall and only the inner pipe is removed, and drilling is completed by inserting steel and injecting grout as necessary. Examples of methods using the double pipe drilling method include the forepiling method, the injection type long-length forepiling method (AGF (All Ground Fasten) method, long-length steel pipe forepiling method), pipe roof method, and EP root pile method.

[0003] The "AGF method" is one of the reinforcement works for reinforcing loose ground in the case of excavating a tunnel in a special or poor ground where the ground at the excavation end or the ceiling surface is not self-supporting or where there is a risk of collapse. After a tubular reinforcement material (steel pipe or resin pipe) with many small through holes on the periphery is obliquely installed in the front outer periphery of the excavation end, a fast-hardening solidifying material (cement-based chemical solution, urethane resin, silica resin, etc.) is pressurized and injected from the inside of the tubular reinforcement material, and the solidifying material is allowed to seep into the ground around the tubular reinforcement material and expand and solidify, thereby increasing the ground pressure in the ground and reinforcing (improving) it (see Non-Patent Document 1). "Pre-supporting" refers to a method of supporting the ground above the excavation point prior to tunnel excavation. The AGF method was first applied to the entrance of the Futatsui Nishi Tunnel (Noshiro City, Akita Prefecture) in 1992, and has since been improved in various ways and has achieved many construction results. When driving the tubular reinforcement into the natural ground, a hydraulic drill jumbo, which is usually used in mountain tunnel construction, is used. Specifically, a rock drill mounted on the drill jumbo applies a rotational force, a propulsive force, and an impact force to the inner rod side of the drilling rod consisting of the above-mentioned double tube of the inner rod and the outer casing (tubular reinforcement), and the inner bit at the tip of the inner rod and the outer bit (ring bit) at the tip of the outer casing connected to the inner bit drill a hole in the natural ground at a predetermined inclination angle. As the hole is drilled, the tubular reinforcement, which is the outer casing, is inserted into the natural ground at a desired position. After that, the inner bit is separated from the outer bit, the inner rod is pulled out and collected, and only the tubular reinforcement (and the outer bit) is left in the natural ground. In this way, a plurality of tubular reinforcements are inserted at predetermined intervals in the circumferential direction of the tunnel to construct an arch-shaped pre-receiving reinforcement structure (umbrella arch) (see Patent Document 1).

[0004] Also, the lost bit method or wing bit method is known as a method for driving a tubular reinforcement material. The lost bit method is a one-use method in which an inner bit attached to the tip of an inner rod and a ring-shaped outer bit (ring bit) attached to the tip of an outer casing (tubular reinforcement material) are used as drilling bits, and after the outer casing is inserted into the ground, the inner rod and the inner bit are pulled out and retrieved, and the outer bit is left in the ground together with the outer casing (see, for example, Patent Document 2). The wing bit method is a method for drilling holes without using an outer bit (ring bit) by using a wing bit as an inner bit attached to the tip of an inner rod, which is expanded wider than the outer casing when drilling and is reduced in diameter when retrieved and stored in the tube of the outer casing (see, for example, Patent Document 3 and Non-Patent Document 2).

[0005] As such hole-drilling techniques used in the AGF method and other steel pipe driving work, the techniques described in Patent Documents 4 to 7 are known.

[0006] The drilling device of Patent Document 4 is a technique related to a lost-bit drilling device. This drilling device is configured such that a drill unit (3) is inserted into a tube of a tubular casing part (2) (see FIG. 1 of the document). A ring-shaped reaming drill (5) is attached to the tip of the casing part (2). A cylindrical drill head (4) is attached to the tip of the drill unit (3). The tip of the drill head (4) is stepped and is fitted detachably to the inner surface of the reaming drill (5). A bit (10b) is implanted at the tip of the reaming drill (5) so as to face outward toward the tip. A bit (10a) is implanted at the tip of the drill head (4). An ejection lumen (6a) is formed along the central axis of the drill head (4), and the tip of the ejection lumen (6a) is opened near the edge of the tip surface of the drill head (4) at an angle offset from the central axis. A discharge groove (6b) is formed on the outer surface of the enlarged tip portion of the drill head (4), and the drilling chips generated during drilling are discharged through the discharge groove (6b) into the pipe of the casing portion (2).

[0007] The boring rod of Patent Document 5 is a technology related to a boring rod of the lost bit type. This boring rod (1) is configured to have a double-tube structure in which an inner rod (2) is inserted inside an outer rod (3), and each rod is connected in multiple stages to form a long rod (see Figures 1 to 4 of the document). A ring bit (5) is rotatably attached to the lower end of the outer rod (3) at the lowest stage of the boring rod (1). A bit (4) is attached to the lower end of the inner rod (2) at the lowest stage of the boring rod (1). A linking part (6) is provided between the lower end of the inner rod (2) and the ring bit (5), which is axially slidable and radially engaged with a locking pin (7) and an outer circumferential groove (8). The linking part (6) transmits the rotation of the inner rod (2) to the ring bit (5). A water injection channel having an injection port near the bit is formed inside the inner rod (2). In addition, a drainage channel (12) is formed between the inner rod (2) and the outer rod (3), and a screw blade (9) is provided around the outer circumference of the inner rod (2). When the inner rod (2) rotates at the top of the boring rod, the rotation is transmitted to the ring bit (5) at the bottom end of the outer rod (3) via the connecting part (6) at the bottom end of the lowest stage of the inner rod (2), and the bit at the bottom end of the inner rod (2) and the bit of the outer rod (3) rotate together, drilling the ground and soil. At this time, the outer rod (3) does not rotate. In addition, the cuttings (slime) drilled by the bit of the boring rod rise from the drainage channel between the inner rod (2) and the outer rod (3) together with muddy water, slime, soil, etc., and are discharged from the top to the ground. At this time, the discharge channel has a screw blade (9) that is attached to the outer circumference of the inner rod, so as the inner rod (2) rotates, the screw blade (9) rotates, forcing the slime, muddy water, soil, etc. near the bit to rise. At the same time, the soil, etc. that has clogged the drainage channel is forcibly removed, automatically clearing the blockage. After drilling, the inner rod (2) is removed from the outer rod (3), and the outer rod (3) and ring bit (5) are left in the wellbore.

[0008] The drilling bit in Patent Document 6 is also a lost-bit type drilling bit. This drilling bit is used in the AGF method and the like. This drilling bit is a drilling bit that penetrates a steel pipe or the like into the ground while drilling a hole, and is used by combining an inner bit, which is a pilot bit, with a lost bit (ring bit) that is left in the ground for enlarging the hole, inside and outside (see Patent Document Figures 1 and 2). A drifter is used as the boring machine, and the drill is excavated by rotating and simultaneously striking in the axial direction. It is said that air or water is used as the drilling fluid (see Patent Document Specifications

[0020] and

[0022] ). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2003-321992 A [Patent Document 2] JP 2003-166390 A [Patent Document 3] JP 2011-117126 A [Patent Document 4] Special Publication No. 8-504904 (Specification of Patent No. 2992344) [Patent Document 5] Japanese Utility Model Application Publication No. 7-034089 (Japanese Utility Model Application Publication No. 7-043264) [Patent Document 6] JP 2002-138786 A [Non-patent literature]

[0010] [Non-Patent Document 1] Japan Society of Civil Engineers, "Tunnel Standard Specifications [Mountain Construction Methods] and Commentary", p.233, May 1996. [Non-Patent Document 2] Toyo Kikaku Co., Ltd., "Product Information > Bits > Specifications and Structure Description", [online], [Searched on June 9, 2023], Internet,<URL:http: / / www.toyoplan.co.jp / product / bit / bit_structure.html> Summary of the Invention [Problem to be solved by the invention]

[0011] In the AGF method and other steel pipe installation works, drilling wells where insert pipes are inserted into the ground often uses pressurized water as the drilling fluid. However, when pressurized water is used as the drilling fluid, the water can loosen the ground around the insert pipe (loosening problem), and in weathered and less consolidated D-class rocks and fractured zones, the pressurized water can wash away fine particles and sand due to slaking (a phenomenon in which a lumpy substance absorbs water and crumbles into small pieces), causing localized irregular scour gaps in the ground around the insert pipe, which may prevent the grouting material from being injected and filled sufficiently.

[0012] On the other hand, if "air drilling" is used, which uses pressurized air as the drilling fluid, the aforementioned phenomena of loosening of the excavation and the formation of scouring gaps hardly occur. In addition, if pressurized air is used as the drilling fluid, the discharged drilling slime (cuttings: powder of rock, concrete, etc. that comes out when a hole is made with a rock drill. Rock powder discharged in powder or granular form by drilling. Cuttings.) can be visually observed, which is a very important advantage in natural ground excavation, as it allows the condition of the natural ground to be confirmed.

[0013] However, in the current drilling tools of tunnel boring machines as shown in the above prior art, it is difficult to use pressurized air as a drilling fluid to discharge the drilling slime generated at the borehole bottom to the borehole aperture. The reason is that the inner diameter of the insert pipe (outer pipe) is usually about 100 mm, while the rod diameter of the inner pipe rod is small at 38 mm, and the gap area is too large, which significantly reduces the discharge pressure of the compressor and causes jamming (a phenomenon in which drilling slime accumulates in the well hole, restricting the drilling part of the boring machine and making it impossible to excavate). Therefore, if an air drilling method is to be applied, it is necessary to use a large compressor with a higher discharge pressure than usual, which is a problem of high cost.

[0014] Therefore, the object of the present invention is to provide a drilling technology that enables the smooth transport and discharge of drilling slime generated at the end of a hole to the mouth of the hole when pressurized air is used as a drilling fluid in a drilling device for inserting a steel pipe or the like into the ground while drilling a hole. [Means for solving the problem]

[0015] The first configuration of the inner rod according to the present invention is an inner rod of a boring rod used in double pipe boring, which uses a boring rod including a casing forming an outer tube and an inner rod inserted into the casing and having an injection flow path for pressurized fluid formed therein, and strikes and rotates the inner rod while injecting pressurized fluid from the injection flow path, thereby boring a hole in the ground with a boring bit provided on the inner rod, or the tip of the casing, or the inner rod and the tip of the casing, The rod is characterized in that there is no step on the outer surface of the rod from the base end to the tip end, or the enlarged diameter portion of the outer surface of the rod end is formed in a tapered shape.

[0016] According to this configuration, since there is no step on the outer side surface of the rod from the base end to the tip end of the inner rod, the flow path cross-sectional area of ​​the discharge flow path between the inner rod and the casing is almost uniform throughout, and during air drilling, the compressed air flow in the discharge flow path flows uniformly without vortexes or stagnation, and slime caused by the compressed air flow is prevented from stagnation in the discharge flow path and causing jamming. Also, even if there is an expanded portion on the outer surface of the rod end, by forming the expanded portion on the outer surface of the rod end in a tapered shape, the resistance that the slime caused by the compressed air flow in the discharge flow path between the inner rod and the casing receives is reduced, and slime is prevented from stagnation in the discharge flow path and causing jamming.

[0017] A second configuration of the inner rod according to the present invention is the inner rod of the first configuration, further comprising: a central steel tube having the injection flow path for the pressurized fluid formed therein; A sound absorbing layer made of a sound absorbing material provided so as to cover the entire outer periphery of the central steel pipe; an outer steel pipe covering the outside of the sound absorbing layer; The present invention is characterized by comprising:

[0018] According to this configuration, by covering the entire outer periphery of the central steel tube of the inner rod with a sound-absorbing material, the loud noise generated during air drilling is absorbed, improving the working environment during drilling.

[0019] A third configuration of the inner rod of the present invention is characterized in that, in the inner rod of the first configuration, the sound-absorbing layer is any one of natural resin, synthetic resin, asphalt, expansive cement, other porous materials, or other consolidated powder materials.

[0020] According to this configuration, by covering the entire outer periphery of the central steel tube of the inner rod with either natural resin, synthetic resin, asphalt, expansive cement, other porous materials, or other consolidated powder materials, the loud noise generated during air drilling is absorbed, improving the working environment during drilling.

[0021] A fourth configuration of the inner rod according to the present invention is characterized in that a plurality of unit inner rods, which are the inner rods of the second configuration, are connected by joint sleeves, and the outer diameter of each unit inner rod is the same as the outer diameter of the joint sleeve.

[0022] According to this configuration, when drilling long holes using the injection type long-length pre-receiving method (AGF method) or the like, when drilling holes while connecting multiple inner rods (unit inner rods) with joint sleeves, the outer diameter of each unit inner rod is made the same as the outer diameter of the joint sleeve, so that the flow path cross-sectional area of ​​the discharge flow path between the inner rod (the connection between the unit inner rod and the joint sleeve) and the casing becomes almost uniform throughout, and during air drilling, the compressed air flow in the discharge flow path becomes a uniform flow without vortexes or stagnation, preventing slime moved by the compressed air flow from stagnating in the discharge flow path and causing jamming.

[0023] The first configuration of the boring rod according to the present invention is a boring rod used in a double-tube boring in which a boring rod is provided with a casing forming an outer tube and an inner rod inserted into the casing and having an injection flow path for a pressurized fluid formed therein, and a drilling bit is attached to the inner rod, or the tip of the casing, or the inner rod and the tip of the casing, by striking and rotating the inner rod while injecting pressurized fluid from the injection flow path, and boring a hole in the ground. The inner rod is an inner rod having any one of the first to fourth configurations, The cross-sectional area of ​​the discharge flow passage for drilling slime, which is the gap space between the inner rod and the casing, is 0.8 to 1.2 times the cross-sectional area of ​​the injection flow passage inside the central steel pipe.

[0024] According to this configuration, by making the cross-sectional area of ​​the discharge flow passage, which is the gap space between the inner rod and the casing, 0.8 times or more the cross-sectional area of ​​the injection flow passage, the flow passage width of the discharge flow passage is too narrow, and the hole drilling slime is prevented from clogging the discharge flow passage during air drilling. Also, by making the cross-sectional area of ​​the discharge flow passage 1.2 times or less the cross-sectional area of ​​the injection flow passage, the air pressure in the discharge flow passage is excessively reduced, and the flow is slowed, and the hole drilling slime is prevented from clogging the discharge flow passage during air drilling.

[0025] A second configuration of the boring rod according to the present invention is the first configuration, The drill bit is provided to close the tip of the casing; and A hammer piston is provided at the tip of the inner rod and fitted to the drill bit, and transmits impact and rotation of the inner rod to the drill bit; A plurality of cone-shaped button bit tips are implanted over the entire tip surface of the drill bit; A blowhole formed on a tip surface of the drill bit and communicating with the injection flow path; The drill bit is characterized by having a drain hole formed at the tip surface thereof and communicating with the drain flow path.

[0026] According to this configuration, by providing a hammer bit with many cone-shaped button bit tips planted over the entire tip surface, the grain size of rock fragments contained in the drilling slime during drilling can be reduced. This prevents problems such as large rock fragments contained in the drilling slime getting caught in the gap between the inner bit and the casing during air drilling, which increases the rotation load of the rock drill, and reduces the rotation load of the boring rod during drilling.

[0027] The first configuration of the double pipe drilling method according to the present invention is a double pipe drilling method using a boring rod having a casing forming an outer pipe and an inner rod inserted into the casing and having an injection flow path for a pressurized fluid formed therein, and boring a hole in the ground with a boring bit provided on the inner rod, or on the tip of the casing, or on the inner rod and the tip of the casing, The inner rod is the inner rod according to any one of claims 1 to 4, While injecting pressurized air into the injection passage of the inner rod, the inner rod is struck and rotated; The method is characterized in that the drilling slime generated at the end of the well hole when the ground is crushed by the drilling bit is transported to the discharge flow path, which is the gap space between the inner rod and the casing, by the flow of pressurized air injected from the injection flow path to the end of the hole, and is discharged to the mouth side of the well hole.

[0028] A second configuration of the double pipe drilling method according to the present invention is the double pipe drilling method of the first configuration, further comprising: The cross-sectional area of ​​the discharge passage, which is the gap space between the inner rod and the casing, is 0.8 to 1.2 times the cross-sectional area of ​​the injection passage inside the central steel tube. Effect of the Invention

[0029] As described above, according to the present invention, by configuring the outer surface of the rod from the base end to the tip end of the inner rod to have no steps or by configuring the expanded diameter portion of the outer surface of the rod end to be tapered, slime flowing due to the compressed air flow during air drilling is prevented from accumulating in the discharge flow path and causing jamming. This makes it unnecessary to increase the pressure of the compressed air for transporting slime to a level higher than normal in order to prevent clogging with slime, and it becomes possible to perform air drilling using a normal compressor. In addition, by covering the entire outer periphery of the central steel tube of the inner rod with a sound-absorbing material, the loud noise generated during air drilling is absorbed, improving the working environment during drilling.

[0030] Furthermore, according to the present invention, the outer surface of the inner rod from the base end to the tip end is configured to have no steps, or the enlarged portion of the outer surface of the rod end is formed in a tapered shape, and the cross-sectional area of ​​the discharge flow passage, which is the gap space between the inner rod and the casing, is 0.8 to 1.2 times the cross-sectional area of ​​the compressed air injection flow passage inside the central steel tube, thereby preventing slime clogging due to the flow passage width being too narrow or the air pressure in the discharge flow passage dropping excessively during air drilling. [Brief description of the drawings]

[0031] [Figure 1] FIG. 2 is an oblique view of a boring rod used for drilling a double pipe according to the first embodiment of the present invention. [Diagram 2] (a) Front view, (b) sectional view (vertical sectional view) taken along CC line, (c) sectional view (horizontal sectional view) taken along DD line, (d) left side view, (e) right side view, and (f) enlarged sectional view of part E of the boring rod in Figure 1. [Diagram 3] FIG. 3 is a perspective view of an inner rod 3 (inner rod assembly) to which an inner bit 5 of the boring rod of FIGS. 1 and 2 is screwed. [Figure 4] FIG. 4 is a front view of the inner rod assembly in FIG. 3, (b) a sectional view (vertical sectional view) taken along line CC, (c) a sectional view (horizontal sectional view) taken along line DD, (d) a side view (AA), (e) an enlarged sectional view (BB), and (f) an enlarged sectional view (E) of part E. [Diagram 5] 3 is a perspective view of an outer casing 2 (outer casing assembly) with an outer bit 4 of the boring rod of FIGS. 1 and 2 screwed thereto. FIG. [Figure 6] 6A is a front view of the outer casing assembly in FIG. 5, (b) a cross-sectional view (vertical cross-sectional view) taken along line CC, (c) a cross-sectional view (horizontal cross-sectional view) taken along line DD, (d) a side view (AA), (e) an enlarged cross-sectional view of part B, and (f) an enlarged cross-sectional view of part E. [Figure 7] 2 is a diagram showing the flow of compressed fluid during drilling using the boring rod 1 of the present embodiment. FIG. [Figure 8] 1 is a photograph showing test drilling using the boring rod 1 of this embodiment. [Figure 9] 11 is an oblique view and an exploded oblique view of a tip of a boring rod used for drilling a double pipe according to Example 2 of the present invention. FIG. [Figure 10] 11A and 11B are a plan view and a cross-sectional view of a tip of a boring rod used for drilling a double pipe in accordance with Example 2. [Figure 11] 11A and 11B are plan, side and bottom views of the drilling header and outer bit of the boring rod of FIGS. 9 and 10. [Figure 12] 11A and 11B are a perspective view and a side view of an inner rod according to a third embodiment. [Figure 13] FIG. 13 is a cross-sectional view of the inner rod of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0033] Fig. 1 is a perspective view of a boring rod used for drilling a double-walled pipe according to the first embodiment of the present invention. Fig. 1(a) is an overall perspective view, Fig. 1(b) is an enlarged perspective view of the tip of the boring rod, and Fig. 1(c) is an enlarged perspective view of the base end of the boring rod. Fig. 2 shows (a) a front view of the boring rod in Fig. 1, (b) a cross-sectional view (vertical cross-sectional view) taken along the line CC, (c) a cross-sectional view (horizontal cross-sectional view) taken along the line DD, (d) an enlarged side view of the line AA, (e) an enlarged cross-sectional view of the line BB, and (f) an enlarged cross-sectional view of part E.

[0034] In FIG. 1 and FIG. 2, the boring rod 1 includes an outer casing 2 forming an outer tube and an inner rod 3 forming an inner tube. The outer casing 2 is made of a steel pipe formed into a long cylindrical tube, and a crown-shaped outer bit 4 is screwed to the tip. The lumen in the outer casing 2 has a uniform circular cross section from the base end to the tip, and functions as a discharge flow path 2a for discharging the drilling slime generated by drilling while inserting the inner rod 3. The discharge flow path 2a is a gap space between the outer peripheral wall of the inner rod 3 and the inner peripheral wall of the outer casing 2. The cross-sectional area of ​​this discharge flow path 2a is 0.8 times or more and 1.2 times or less than the cross-sectional area of ​​the injection flow path 3b formed along the central axis of the inner rod 3. The outer casing 2 can be connected in any number by the screw grooves at the end depending on the length of the hole to be drilled. The inner rod 3 is made of a steel pipe formed into a long, thick cylindrical tube with an outer diameter smaller than the inner diameter of the outer casing 2, and an inner bit 5 is screwed to the tip of the inner rod 3. Any number of inner rods 3 can also be screwed together using joint sleeves 6 depending on the length of the hole to be drilled.

[0035] Figure 3 is a perspective view of the inner rod 3 (inner rod assembly) to which the inner bit 5 of the boring rod in Figures 1 and 2 is screwed. Figure 3(a) is an overall perspective view of the inner rod assembly, Figure 3(b) is an exploded perspective view of the inner rod 3, Figures 3(c) and (d) are enlarged perspective views of the tip portion, and Figure 3(e) is an enlarged perspective view of the base portion. Figure 4 shows (a) a front view of the inner rod assembly in Figure 3, (b) a cross-sectional view (vertical cross-sectional view) taken along the line CC, (c) a cross-sectional view (horizontal cross-sectional view) taken along the line DD, (d) a side view (AA), (e) an enlarged cross-sectional view of the cross-section BB, and (f) an enlarged cross-sectional view of part E.

[0036] 3 and 4 show an example in which the inner rod 3 is formed by connecting two unit inner rods 3a with a joint sleeve 6, but the number of unit inner rods 3a connected is adjusted appropriately depending on the depth of the hole to be drilled. As shown in FIG. 3(b), the inner rod 3 drills holes while extending its length by connecting a plurality of unit inner rods 3a with joint sleeves 6 as the hole drilling process progresses. In addition, when the unit inner rods 3a are connected with the joint sleeves 6, the unit inner rods 3a and the joint sleeves 6 are configured to have the same outer circumferential radius so that no step is generated at the connection point of the outer periphery of the unit inner rods 3a and the joint sleeves 6, as shown in FIG. 3(a) and FIG. 4(a)-(b),(f).

[0037] Each unit inner rod 3a is formed in a long, thick cylindrical tube shape, and an injection flow passage 3b (injection flow passage for pressurized fluid) with a circular cross section is formed along the central axis. The unit inner rod 3a has a three-layer structure consisting of a central steel tube 3c in which the injection flow passage 3b, which is an injection flow passage for pressurized fluid, is formed, a sound absorbing layer 3d made of a sound absorbing material provided so as to cover the entire outer circumference of the central steel tube 3c, and an outer steel tube 3e covering the outside 3d of the sound absorbing layer. The central steel tube 3c and the outer steel tube 3e are made of metal such as steel. The sound absorbing layer 3d is made of a sound absorbing material such as natural resin, synthetic resin, asphalt, expansive cement, other porous materials, or other solidified powder materials. Male threads 3f for connecting to the inner bit 5 and the joint sleeve 6 are formed protruding from both ends of the central steel tube 3c of the unit inner rod 3a. The joint sleeve 6 is a short cylindrical metal tube, and a screw groove 6a is formed on the inner peripheral surface of the tube so as to be capable of screwing with the male screw portion 3f of each unit inner rod 3a.

[0038] An inner bit 5 for drilling at the end of a wellbore is screwed to the tip of the inner rod 3. The inner bit 5 includes a bit body 5a screwed to the male threaded portion 3f at the tip of the inner rod 3 and a hard tip 5b planted on the tip surface of the bit body 5a. The hard tip 5b is a drilling blade for striking the end of the hole during drilling and breaking up the ground. On the side of the bit body 5a, two slime discharge grooves 5c, 5c are formed symmetrically with respect to the central axis of the bit body 5a in parallel with the central axis. The radius of the arc-shaped groove bottom of the slime discharge grooves 5c, 5c is configured to be the same as the outer circumferential radius of the inner rod 3, and when the inner bit 5 is screwed to the tip of the inner bit 5, the groove bottom of the slime discharge grooves 5c, 5c and the outer circumferential surface of the inner bit 5 are flush with each other. In addition, an elliptical recess 5d that opens toward the tip side is formed at the tip of each slime discharge groove 5c. The recess 5d is provided to guide the drilled slime generated by crushing the rock by the hard tip 5b to the slime discharge groove 5c. A locking groove 5e is formed along the circumferential direction of the side surface of the inner bit 5, slightly toward the tip side from the center of the side surface of the inner bit 5 outside the slime discharge grooves 5c, 5c, with which the locking claw 4f provided on the inner circumference of the outer bit 4 engages. In addition, a cavity 5i is formed inside the inner bit 5, opening toward the base end side of the inner bit 5 along the central axis. A screw groove is engraved near the mouth of the cavity 5i to screw with the male screw portion 3f at the tip of the inner rod 3. When the inner bit 5 is screwed to the tip of the inner rod 3, the cavity 5i is in communication with the injection flow path 3b in the inner rod 3. The tip surfaces 5f, 5f and the recesses 5d, 5d of the inner bit 5 are formed with spray injection holes 5g that communicate with the cavity 5i and open obliquely toward the tip of the inner bit 5. In addition, near the center of each slime discharge groove 5c, 5c, a return injection hole 5h that communicates with the cavity 5i and opens obliquely toward the base end of the inner bit 5 is formed.By injecting compressed fluid from each spray injection hole 5g toward the end of the drilled well hole, the drilling slime is transported from the end of the hole to the slime discharge groove 5c, and by injecting compressed fluid from the return injection hole 5h, the drilling slime sent into the slime discharge groove 5c is further pressurized to the discharge flow path 2a.

[0039] Figure 5 is a perspective view of the outer casing 2 (outer casing assembly) to which the outer bit 4 of the boring rod in Figures 1 and 2 is screwed. Figure 5(a) is a perspective view of the entire outer casing assembly, and Figures 5(b) and (c) are enlarged perspective views of the outer bit 4. Figure 6 shows (a) a front view of the outer casing assembly in Figure 5, (b) a cross-sectional view (vertical cross-sectional view) taken along the line CC, (c) a cross-sectional view (horizontal cross-sectional view) taken along the line DD, (d) a side view (AA), (e) an enlarged cross-sectional view of part B, and (f) an enlarged cross-sectional view of part E.

[0040] The outer casing 2 is a steel pipe formed into a long cylindrical shape. A screw groove is formed on the outer periphery of the tip end of the outer casing 2, and a screw groove (not shown) is formed on the inner periphery of the base end of the outer casing 2, so that the outer casing 2 can be connected to the outer bit 4 or another outer casing 2.

[0041] The outer bit 4 is a ring-shaped boring bit screwed to the tip of the outer casing 2. The outer bit 4 is provided with a short cylindrical outer ring 4a on the base end side. A screw groove 4b that screws with the screw groove on the outer periphery of the tip of the outer casing 2 is engraved on the base end side of the inner pipe surface of the outer ring 4a. A circular ring bit part 4c is formed at the tip of the outer ring 4a with a stepped diameter expansion, and six hard tips 4d are planted at equal intervals on the tip surface of the ring bit part 4c. The hard tips 4d are drilling blades for striking the bottom of the hole during drilling and fracturing the ground. In addition, a circular arc-shaped recess 4e is formed in the part adjacent to each hard tip 4d on the tip surface of the ring bit part 4c. This recess 4e is provided to guide the drilling slime generated by fracturing the rock by the hard tips 4d to the inside of the ring bit part 4c. In addition, two locking claws 4f, 4f are provided on the inner peripheral surface of the outer ring 4a, symmetrically with respect to the central axis, protruding inward. When the inner rod 3 is rotated in the forward direction (the direction of the arrow R shown in Fig. 3(c) and (d) in the direction in which rotational pressure is applied to the inner rod 3 during drilling) during drilling, the locking claws 4f, 4f engage with the locking groove 5e of the inner bit 5 described above, and the inner rod 3 and the outer bit 4 become one body, so that rotational pressure and impact pressure are applied evenly. When the inner rod 3 is rotated in the reverse direction after drilling is completed, the locking claws 4f, 4f come out of the locking groove 5e of the inner bit 5, and the inner rod 3 can be pulled out while leaving the outer bit 4 and the outer casing 2 in the wellbore.

[0042] Next, a double-pipe drilling method for drilling a hole in the ground using the boring rod 1 of this embodiment configured as described above will be described. In this double-pipe drilling method, as in the case of normal double-pipe drilling, the above-mentioned boring rod 1 is used, which is equipped with the outer casing 2 forming the outer pipe and the inner rod 3 inserted into the outer casing 2, and while injecting pressurized air from the base end side into the injection flow passage 3b of the inner rod 3 by a compressor, the inner rod 3 is struck and rotated by the drifter of the drill jumbo, and the ground is drilled by the inner bit 5 (drilling bit) provided at the tip of the inner rod 3 and the outer bit 4 (drilling bit) provided at the tip of the outer casing 2.

[0043] FIG. 7 is a diagram showing the flow of compressed fluid during drilling by the boring rod 1 of this embodiment. In FIG. 7, the flow of pressurized fluid for transporting drilling slime generated at the bottom of the well to the outside of the wellbore is indicated by arrows. The pressurized fluid is pressurized and fed into the injection passage 3b of the inner rod 3 by a compressor. The fed pressurized fluid flows from the injection passage 3b into the cavity 5i in the inner rod 3, and is injected from each blowing injection hole 5g and each return injection hole 5h into the tip of the inner bit 5 or into the slime discharge groove 5c of the inner bit 5. Rotational pressure and impact pressure are applied to the boring rod 1 by the drill jumbo's drifter, and the hard tip 5b of the inner bit 5 and the hard tip 4d of the outer bit 4 strike and crush the ground at the bottom of the wellbore, generating drilling slime at the bottom of the wellbore. The drilling slime at the bottom of the well is blown away from the bottom of the well by the pressurized fluid injected from each of the blowing injection holes 5g at the tip of the inner bit 5, and flows into the slime discharge groove 5c of the inner bit 5 in the outer bit 4. Furthermore, the slime is pressurized by the pressurized fluid injected from each of the return injection holes 5h in the slime discharge groove 5c into the discharge flow path 2a consisting of the gap space between the tube inner surface of the outer casing 2 and the outer circumferential surface of the inner rod 3, and is transported through the discharge flow path 2a from the mouth of the wellbore to the outside of the wellbore and discharged.

[0044] Here, in the boring rod 1 of this embodiment, the outer circumferential radius of the inner rod 3 is configured to be the same as the radius of the bottom surface of the arc-shaped groove of each slime discharge groove 5c, so there is no step at the connection part between the slime discharge groove 5c and the outer circumferential surface of the inner rod 3, and the drilling slime does not get caught and accumulate at this connection part to cause jamming. In addition, since the outer circumferential radius of the inner rod 3 is configured to be the same as the outer circumferential radius of the joint sleeve 6, there is no step at the connection part between the outer circumferential surface of the inner rod 3 and the outer circumferential surface of the joint sleeve 6, and the drilling slime does not get caught and accumulate at this connection part to cause jamming. Therefore, even in the case of air drilling using compressed air as the pressurized fluid, the drilling slime is smoothly discharged without jamming in the discharge flow path 2a.

[0045] In addition, in the boring rod 1 of this embodiment, the sound absorbing layer 3d is provided between the central steel pipe 3c and the outer steel pipe 3e of the inner rod 3, so that the noise generated in the discharge passage 2a during air drilling is absorbed to some extent by the sound absorbing layer 3d. This reduces the noise generated during drilling and improves the working environment.

[0046] In addition, as a result of actual test drilling, it was confirmed that by setting the cross-sectional area of ​​the discharge passage 2a, which is the gap space between the inner rod 3 and the outer casing 2, to 0.8 to 1.2 times the cross-sectional area of ​​the injection passage 3b inside the central steel tube 3c of the inner rod 3, it is possible to prevent the drilling slime from clogging the discharge passage 2a during air drilling. Figure 8 is a photograph showing the state of test drilling using the boring rod 1 of this embodiment. In air drilling, the cross-sectional area S of the injection passage 3b is 0.8 to 1.2 times the cross-sectional area S of the injection passage 3b inside the central steel tube 3c of the inner rod 3. in Cross-sectional area S of the exhaust flow passage 2a out Area ratio S out / S in When the area ratio S is set to 0.8 times or more and 1.2 times or less, the drilling slime is vigorously blown out from the discharge passage 2a as shown in FIG. 8(a). On the other hand, when the outer diameter of the inner rod 3 is increased and the area ratio S out / S inWhen the area ratio S is made smaller than 0.8, as shown in FIG. 8(b), the drilling slime is difficult to blow out of the discharge passage 2a, and the flow path width of the discharge passage 2a is too narrow, resulting in a phenomenon (jamming) in which the drilling slime clogs the discharge passage 2a. out / S in If the area ratio S is made larger than 1.2, the drilling slime will be biased toward the lower side of the discharge flow path 2a and will be weaker as shown in FIG. 8(b). out / S in As this increases, the flow rate of the pressurized air in the discharge flow path 2a decreases, the flow rate of the drilled slime decreases and gravity causes it to fall to the bottom of the discharge flow path 2a and concentrate there, and the pressurized air is discharged through the upper side of the discharge flow path 2a, so the flow separation between the pressurized air and the drilled slime increases, and it is thought that the overall transport efficiency of the drilled slime decreases. Since horizontal drilling was performed in the test drilling, jamming did not occur, but if drilling was performed downward or diagonally downward, it is expected that jamming would be more likely to occur locally because the force with which the drilled slime spurts out of the discharge flow path 2a is too weak. EXAMPLES

[0047] In the embodiment 2, another example will be described in which the tip portion of the boring rod 1 in the embodiment 1 is changed. The parts of the boring rod 1 other than the tip portion are the same as those in the embodiment 1.

[0048] Fig. 9 is a perspective view and an exploded perspective view of a boring rod tip used for drilling a double pipe according to Example 2 of the present invention. Fig. 10 is a plan view and a cross-sectional view of a boring rod tip used for drilling a double pipe according to Example 2. Fig. 11 is a plan view, a side view and a bottom view of a boring header and an outer bit of the boring rod of Figs. 9 and 10.

[0049] In Example 1, an outer bit 4 (hole-drilling bit) and an inner bit 5 (hole-drilling bit) are provided at the tip of the boring rod, and rock drilling is performed using a mountain-ridge (wedge-shaped) hard tip 4d on the outer bit 4 and a mountain-ridge hard tip 5b on the inner bit 5.However, in this example, a hammer bit 4' (hole-drilling bit) of a down-the-hole hammer is provided to close the tip of the outer casing 2 of the boring rod, and a large number of single-peaked (cone-shaped) button bit tips 4g are implanted over the entire tip surface of the hammer bit 4'.

[0050] The center of the tip face of the hammer bit 4' is recessed compared to the periphery, and three blowholes 4h that communicate with the injection flow passage 3b in the inner rod 3 are formed in the central surface of the circular tray-shaped recessed tip face at positions that are three-fold symmetrical about the center point O. Each blowhole 4h is formed so that the opening at the downstream end is inclined outward from the center point O of the tip face, and the upstream end communicates with a chamber formed inside the outer bit 4. The chamber inside this hammer bit 4' opens to the base end side of the hammer bit 4' (see Figures 9(a)(b1), 10(a)(c), and 11(a1)(a3)).

[0051] The side of the hammer bit 4' is formed with a cylindrical joint part 4k, the tip part of which is columnar with the same diameter as the outer casing 2, and the base part of which is stepped down in diameter. A screw thread is formed on the outer surface of this joint part 4k (see Fig. 9(b1), Fig. 11(a2)). Meanwhile, a cylindrical joint part 2b with a stepped up diameter is formed on the tip part of the outer casing 2, and a screw groove is formed on the inner surface of the joint part 2b (see Fig. 9(b3)). The joint part 4k of the hammer bit 4' is screwed into the joint part 2b of the outer casing 2 (see Fig. 9(a), Fig. 10).

[0052] A columnar hammer piston 7 having a diameter slightly smaller than the inner diameter of the discharge passage 2a in the outer casing 2 is provided at the tip of the inner rod 3. The tip of the hammer piston 7 is inserted and fitted into the internal chamber of the hammer bit 4', and transmits the impact vibration applied to the inner rod 3 to the hammer bit 4' from the inside. An injection passage 7a is formed through the hammer piston 7 along the central axis. With the hammer piston 7 fitted into the internal chamber of the hammer bit 4', the injection passage 7a communicates with the blowhole 4h of the hammer bit 4'.

[0053] On the side of the hammer piston 7, three groove-shaped discharge grooves 7d are formed in parallel with the central axis from the tip end to the base end of the hammer piston 7 at positions three times symmetrical with respect to the central axis of the hammer piston 7. When the hammer piston 7 is fitted into the inner space of the hammer bit 4', the three discharge grooves 7d are respectively connected to the three discharge holes 4i of the hammer bit 4' (see Fig. 9(b), Fig. 10(a)(b1)). In addition, inside the hammer piston 7, three blowholes 7b and four blowholes 7c are formed, which branch off from the injection flow passage 7a toward the side and open on the side. The downstream end of each blowhole 7b opens into the discharge groove 7d, and the opening of the downstream end is formed so as to be inclined toward the base end direction of the boring rod 1 (see Fig. 10(b)). As a result, the pressurized air injected from the injection passage 3b of the inner rod 3 through the injection passage 7a and the blower hole 7b into the discharge groove 7d is injected toward the base end of the boring rod 1 within the discharge groove 7d.

[0054] Next, a double-tube boring method for boring a hole in the ground using the boring rod 1 of this embodiment configured as described above will be described. Although it is basically the same as the first embodiment, in this embodiment, the impact vibration for drilling is applied to the hammer piston 7 via the inner rod 3, and the hammer piston 7 strikes the hammer bit 4' from the inside, and the resulting vibration causes the button bit tip 4g on the tip surface of the hammer bit 4' to break up the ground at the tip of the well hole.

[0055] Also, as in the first embodiment, pressurized air is injected from the injection flow passage 3b in the inner rod 3. The pressurized air is injected from the blowhole 4h on the tip surface of the hammer bit 4' to the ground excavation surface at the tip of the wellbore. As a result, the drilling slime generated by drilling is transported to the three discharge holes 4i by the flow of pressurized air, and is transported to the discharge flow passage 2a between the outer casing 2 and the inner rod 3 via the discharge groove 7d on the side of the hammer piston 7, and is discharged outside the wellbore. At this time, the pressurized air injected from the blowhole 7b into the discharge groove 7d prevents the drilling slime from clogging the discharge groove 7d. The following is as described in the first embodiment.

[0056] In this embodiment, a hammer bit 4' with a large number of single-peaked (cone-shaped) button bit tips 4g planted over the entire tip surface is used in the drilled rock at the tip of the wellbore, which reduces the grain size of the rock chips contained in the drilling slime compared to the case of Example 1. This prevents problems such as large rock chips contained in the drilling slime getting caught in the gap between the outer bit and the inner bit during air drilling, which increases the rotation load of the rock drill, and reduces the rotation load of the boring rod 1 during drilling. EXAMPLES

[0057] In the embodiment 3, another example will be described in which the inner rod 3 of the boring rod 1 of the embodiment 1 is changed. Note that the parts of the boring rod 1 other than the inner rod 3 are the same as those of the embodiment 1.

[0058] Fig. 12 is (a) a perspective view and (b) a side view of an inner rod according to Example 3. Fig. 13 is a cross-sectional view of the inner rod of Fig. 12. The inner rod 3 of this example is used in place of the inner rod of Example 1.

[0059] The inner rod 3 of this embodiment includes a central steel tube 3c, a sound absorbing layer 3d, and an outer steel tube 3e, as in the first embodiment. In addition, joint parts 3g and 3h are formed at both ends of the central steel tube 3c of the inner rod 3. Here, if the hole mouth side of the inner rod 3 during drilling is called the "base end side" and the hole back side is called the "tip side", the joint part 3g on the base end side is formed so as to have a larger diameter than the pipe diameter of the central part of the central steel tube 3c, and a female thread 3g-1 is engraved in the pipe (see FIG. 13). In the connection region 32-2 (see FIG. 13) from the central part of the central steel tube 3c to the joint part 3g, a taper part 3i is formed in which the pipe diameter is continuously expanded in a sigmoid curve shape. On the other hand, the joint part 3h on the tip side is formed with a male thread 3h-1 of a size that can be screwed with the female thread 3g-1 of the joint part 3g on the base end side. By screwing the joint parts 3g and 3h of each inner rod 3 together and sequentially adding to the length, the inner rod 3 can be extended during boring work.

[0060] The sound absorbing layer 3d and the outer steel pipe 3e of the inner rod 3 are provided so as to cover the central steel pipe 3c except for the joints 3g and 3h. The outer diameter of the outer steel pipe 3e is slightly smaller than the outer diameter of the joint 3g, and the outer surface of the connection between the outer steel pipe 3e and the joint 3g is connected by a smooth tapered curved surface via the tapered portion 3i.

[0061] In this way, by forming the expanded diameter portion of the outer surface of the base end portion of the inner rod 3 into a smooth tapered curved surface, the resistance encountered by the flow of drilling slime caused by the compressed air flow in the discharge flow passage 2a between the inner rod 3 and the outer casing 2 is reduced, preventing the drilling slime from accumulating in the discharge flow passage 2a and causing jamming. [Explanation of symbols]

[0062] 1 Boring Rod 2 Outer casing 2a Discharge channel 2b Joint part 3 Inner Rod 3a unit inner rod 3b Injection channel 3c center steel pipe 3d sound absorption layer 3e outer steel pipe 3f Male thread 3g, 3h Joint 3i Tapered section 4 Outer Bit 4' Hammer Bit 4a Outer ring 4b Thread groove 4c Ring bit section 4d Hard Tip 4e recess 4f Locking claw 4g button bit chip 4h Fumarole 4i drain hole 4j drain groove 4k Joint 5 Inner Bit 5a Bit body 5b Hard Tip 5c Slime drain 5d recess 5e Locking groove 5f Tip surface 5g spray nozzle 5h Return nozzle 5i Cavity 6 Joint Sleeve 6a Thread groove 7 Hammer Piston 7a,7b,7c Fumarole 7d drain groove 7c Injection channel

Claims

1. The present invention relates to an inner rod of a boring rod used in a double-tube boring method, in which a boring rod is used that includes a casing that forms an outer tube, and an inner rod that is inserted into the casing and has an injection flow path for a pressurized fluid formed therein, and a drilling bit is attached to the inner rod, or the tip of the casing, or the inner rod and the tip of the casing, while striking and rotating the inner rod while injecting a pressurized fluid from the injection flow path, There is no step on the outer surface of the rod from the base end to the tip end, or the enlarged diameter part of the outer surface of the rod end is tapered. An inner rod characterized by:

2. a central steel tube having the injection passage for the pressurized fluid formed therein; A sound absorbing layer made of a sound absorbing material provided so as to cover the entire outer periphery of the central steel pipe; an outer steel pipe covering the outside of the sound absorbing layer; 2. The inner rod according to claim 1, further comprising:

3. 3. The inner rod according to claim 2, wherein the sound absorbing layer is any one of natural resin, synthetic resin, asphalt, expansive cement, other porous material, or other consolidated powder material.

4. 3. An inner rod according to claim 2, comprising a plurality of unit inner rods connected by joint sleeves, the outer diameter of each unit inner rod being the same as the outer diameter of the joint sleeve.

5. A boring rod is used in a double pipe boring process in which a boring rod is used that includes a casing that forms an outer pipe, and an inner rod that is inserted into the casing and has an injection flow path for a pressurized fluid formed therein, and a drilling bit is attached to the inner rod, or the tip of the casing, or the inner rod and the tip of the casing, by striking and rotating the inner rod while injecting a pressurized fluid from the injection flow path, The inner rod is the inner rod according to any one of claims 1 to 4, A boring rod characterized in that the cross-sectional area of ​​the discharge flow passage for drilling slime, which is the gap space between the inner rod and the casing, is 0.8 to 1.2 times the cross-sectional area of ​​the injection flow passage inside the central steel pipe.

6. The drill bit is provided to close the tip of the casing; and A hammer piston is provided at the tip of the inner rod and fitted to the drill bit, and transmits impact and rotation of the inner rod to the drill bit; A plurality of cone-shaped button bit tips are implanted over the entire tip surface of the drill bit; A blowhole formed on a tip surface of the drill bit and communicating with the injection flow path; A discharge hole formed on a tip surface of the drill bit and communicating with the discharge flow path; 6. The boring rod of claim 5, comprising:

7. A method for boring a double pipe, comprising: a boring rod including a casing forming an outer pipe and an inner rod inserted into the casing and having an injection flow path for a pressurized fluid formed therein; and a boring bit provided on the inner rod, or on the tip of the casing, or on the inner rod and the tip of the casing, boring a hole in the ground, The inner rod is the inner rod according to any one of claims 1 to 4, While injecting pressurized air into the injection passage of the inner rod, the inner rod is struck and rotated; A double-pipe drilling method characterized in that drilling slime generated at the end of a well hole when the ground is crushed by the drilling bit is transported to the discharge flow path, which is the gap space between the inner rod and the casing, by a flow of pressurized air injected from the injection flow path to the end of the hole, and discharged to the mouth side of the well hole.

8. A double pipe drilling method as described in claim 7, characterized in that the cross-sectional area of ​​the discharge flow passage, which is the gap space between the inner rod and the casing, is 0.8 to 1.2 times the cross-sectional area of ​​the injection flow passage inside the central steel pipe.

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