JP2006016785A - Drilling bit for driven steel pipe for reinforcing natural ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drilling bit which is attached to a leading end of a driven steel pipe for reinforcing natural ground, stabilizing the natural ground by being driven into surrounding loose ground from inside a tunnel, and which enables the smooth driving of the steel pipe, while surely and efficiently taking in excavated matter so as to prevent the excavated matter from biting into a section between an outer peripheral surface of the steel pipe and the excavated ground. <P>SOLUTION: An annular wall part 2a2 is formed at the outer peripheral part of the front end surface of the drilling bit 2 which is attached to the leading end of the steel pipe 1; excavating tips 7a and 7b are protrusively provided in front of the front end surface of the annular wall part 2a2 and a recess 2a1 enclosed with the annular wall part 2a2; and an excavated matter intake hole 5, which communicates with the inside of the steel pipe 1 from the recess 2a1, is provided. Thus, the excavated matter excavated by means of the drilling bit 2 is taken into the recess 2a1, and discharged into the steel pipe 1 through the intake hole 5 from the recess 2a1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of a drill bit installed at the front end of a steel pipe for reinforcing natural ground which is driven into a natural ground where loose ground or the like exists to stabilize the natural ground.

  In tunnel construction, if the natural ground is soft, it is necessary to excavate the tunnel while stabilizing the natural ground. Therefore, every time a certain length of tunnel is excavated, A plurality of steel pipes fitted with perforated bits are driven radially in the circumferential direction of the tunnel, and through these steel pipes, a hard material such as cement milk or urethane resin liquid is injected and hardened in the ground, and in this state the steel pipe It has been attempted to stabilize the ground by leaving the ground with the perforated bit in the ground.

As such a ground-stabilized steel pipe, for example, as described in Patent Document 1, a slime feed groove and an air jet communicated from the front surface to a perforated bit attached to the tip of the steel pipe. An inner pipe is provided in the steel pipe via a down-the-hole hammer connected to the drill bit, and the drill bit is driven by the down-the-hole hammer while air is ejected from the air outlet of the drill bit through the inner pipe. There is known a structure in which a natural ground is excavated, and slime as excavated material is taken into the steel pipe through the slime feed groove and discharged from the rear end side.
JP-A-8-338191

  However, the perforated bit is formed in a conical shape with the tip pointed forward, and the slime feed groove is provided at a predetermined interval in the circumferential direction at the outer peripheral end portion so that the slime feed groove communicates with the steel pipe. Therefore, it is difficult to take all the excavated material excavated by the drill bit into the slime feed groove, and the inclined surface of the drill bit between adjacent slime feed grooves is used as a guide. The so-called jamming phenomenon, in which the excavated material enters the gap between the outer peripheral surface of the steel pipe and the drilling hole from the outer end of the inclined surface and clogs this gap, so that the advancement of the steel pipe is restricted and cannot be advanced. May occur.

  In particular, when the ground where the steel pipe is to be driven is a fragile rocky ground, the excavated material is easily cracked, and the large cracked excavated piece is a gap between the outer peripheral surface of the steel pipe and the borehole. It is difficult to penetrate the large-diameter slime feed groove at the outer peripheral end of the conical shape, and it is possible to take in the excavated piece that has been cracked. However, even if it can be taken in, there is a problem that the slime feed groove is clogged and the excavated material cannot be discharged thereafter.

  The present invention has been made in view of such problems, and the object of the present invention is to enable a steel pipe to be driven into a natural ground while taking in excavated material reliably and efficiently. It is an object of the present invention to provide a drill bit in a ground reinforcement steel pipe that can be surely discharged while smoothly discharging excavated material.

  In order to achieve the above object, the drill bit in the ground steel reinforcing driven steel pipe according to the present invention, as described in claim 1, is driven into the natural ground to stabilize the natural ground. A perforation bit attached to the front end of a steel pipe, and the perforation bit has an annular wall portion of a fixed height projecting forward from the front outer peripheral portion thereof, and a recess surrounded by the annular wall portion The structure is provided with a drilled material intake hole that penetrates from the back bottom surface to the rear surface of the steel pipe and communicates with the inside of the steel pipe.

  In the perforated bit in the ground-steel reinforcing driven steel pipe configured as described above, the invention according to claim 2 forms the projecting front end surface of the annular wall portion of the perforated bit into an inclined surface inclined rearward from the outer peripheral edge toward the concave portion. It is characterized by that.

  Further, in the invention according to claim 3, the water injection hole is provided in the center part of the steel pipe over the entire length while the water injection hole penetrating the back surface of the perforation bit from the back bottom surface of the recess is provided in the perforation bit. The front end of the water supply pipe is connected to and communicated with the rear end of the water injection hole, and a gap between the outer peripheral surface of the water supply pipe and the inner peripheral surface of the steel pipe is formed in the excavated material discharge passage. The front end of the discharge passage is connected to and communicated with the rear end of the drilled material intake hole provided in the drill bit.

  According to the first aspect of the present invention, the annular wall portion having a constant height projects from the front outer peripheral portion of the drilling bit toward the front, and the drilling is performed from the bottom surface of the recess surrounded by the annular wall portion. Since the drilling material intake hole that penetrates to the rear surface of the bit and communicates with the steel pipe is provided, the drilled material drilled by this drilling bit can be once taken into the recess surrounded by the annular wall, The excavated material discharge passage in the steel pipe through the excavated material intake hole opened from the inside of the recessed portion to the back bottom surface of the recessed portion while reliably preventing the excavated material in the recessed portion from leaking out of the recessed portion by the annular wall portion. Can be efficiently and reliably discharged. Therefore, there is almost no possibility that the drilled material enters the gap between the outer peripheral surface of the ground reinforcement steel pipe and the excavation hole to which the drill bit is attached, and the gap is clogged. Can be carried out smoothly and reliably.

  In addition, since the drilling material intake hole is provided on the bottom surface of the recess surrounded by the outer peripheral annular wall portion of the drill bit, it may be formed in a relatively large diameter drilling material intake hole communicating with the steel pipe. Therefore, even if a large cracked excavation occurs when excavating a fragile rocky ground, the excavated material intake hole can be circulated and reliably discharged into the steel pipe without clogging. Can do.

  Furthermore, according to the invention according to claim 2, since the projecting front end surface of the annular wall portion of the drill bit is formed on the inclined surface inclined backward from the outer peripheral edge toward the concave portion, The excavated material excavated by the front end surface can be surely taken into the concave portion while being gathered to the concave portion on the central portion side along the inclined surface, and the clearance between the outer peripheral surface of the ground steel reinforcing driven steel pipe and the excavation hole Therefore, the excavated material can be efficiently discharged while suppressing the excavated material from flowing around.

  According to the third aspect of the present invention, the water drilling hole is provided in the center portion of the steel pipe over the entire length while the water drilling hole penetrating the back surface of the drilling bit from the back bottom surface of the recess is provided in the drilling bit. Since the front end of this water pipe is connected to and communicated with the rear end of the water injection hole, the pressure water supplied into the water pipe is jetted from the water injection hole provided in the perforation bit and excavated by this perforation bit. The drilled material can smoothly flow into the drilled material intake hole from the recess of the drill bit by the flow of water.

  In addition, the water supply pipe only needs to have a function of supplying pressure water from the rear end side of the steel pipe to the water injection hole of the drilling bit. Therefore, a small diameter water supply pipe is adopted and the inner circumference of the steel pipe is adopted. The cross-sectional space of the excavated material discharge passage formed by the gap between the surface and the outer peripheral surface of the water pipe can be widened over the entire length of the steel pipe, and the front end of the excavated material discharge passage communicates Combined with the fact that the drill bit intake hole on the drill bit side can be formed with a large diameter, the drill bit can be efficiently and reliably discharged from the drill bit through the drill bit discharge passage. The steel tube can be driven efficiently.

  Next, a specific embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a natural steel reinforcing driven steel pipe, which is a steel pipe 1 having a certain length. The perforation bit 2 is integrally fixed to the front end of the steel pipe 1 and the small diameter water supply pipe 3 is disposed at the center of the steel pipe 1 over the substantially entire length of the perforation bit 2. Are provided with several (two in the figure) water injection holes 4 and four (four in the figure) drilled material intake holes 5 penetrating between the front and rear surfaces. The front end of the water pipe 3 is connected to and communicated with the rear end of the water injection hole 4, and the excavated material discharge passage 6 is formed by an annular gap between the inner peripheral surface of the steel pipe 1 and the outer peripheral surface of the water supply pipe 3. There is a structure in which the front end of the excavated material discharge passage 6 is communicated with the rear end of the excavated material intake hole 5. There. And this excavated material discharge passage 6 formed between the inner peripheral surface of the steel pipe 1 and the outer peripheral surface of the water supply pipe 3 has its annular space part continuous with a substantially constant area over the entire length.

  The structure of the perforated bit 2 will be described in more detail. As shown in FIGS. And has an external shape in which a short cylindrical portion 2b having an inner diameter equal to the outer diameter of the steel pipe 1 is projected rearward. The short cylindrical portion 2b is fitted on the front end portion of the steel pipe 1 and the steel pipe 1 is fixed by a fixing pin 9. It is fixed to the unit. Note that the short cylindrical portion 2b of the drill bit 2 may be integrally fixed to the front end portion of the steel pipe 1 by welding instead of the fixing pin 9. Further, a circular recess 2a1 having a constant depth is formed in the front half of the head portion 2a of the perforating bit 2 from the front surface to the rear, leaving the outer periphery of the head 2a. The outer peripheral portion forms an annular wall portion 2a2 having a constant height protruding forward from the outer periphery of the recess 2a1.

  The annular wall portion 2a2 has an inner diameter substantially equal to the inner diameter of the steel pipe 1, and a front surface of the annular wall portion 2a2 is used as a pedestal surface of the excavation tip 7a. The mountain-shaped drilling tip 7a is projected. Similarly, a plurality of semi-spherical inner tips 7b project from the base surface of the circular recess 2a1 with the inner bottom surface of the inner excavation tip 7b. Further, the above-mentioned several small-diameter water injection holes 4 and large-diameter drilled material intake holes 5 are provided from the chip seat surface of the recess 2a1 of the drill bit 2 to the rear end surface of the drill bit 2. .

  A mounting seat 2a3 for the water supply pipe 3 is projected rearward at the center of the rear surface of the drill bit 2, and a water passage hole 2a4 is formed at the center of the rear end surface of the mounting seat 2a3. While the rear ends of the holes 4 and 4 communicate with the water passage hole 2a4, the front end opening of the small-diameter water pipe 3 disposed at the center of the steel pipe 1 is the rear end surface of the mounting seat 2a3. It is brought into contact with the central portion and fixed integrally by welding or the like, and the open end communicates with the water hole portion 2a4. The water pipe 3 is supported on the inner peripheral surface of the steel pipe 1 by support brackets 8 at several locations in the length direction. Specifically, as shown in FIG. 5, the support bracket 8 has several pieces (three pieces in the figure) of support arms from the central portion 8a having a slightly larger diameter than the water supply pipe 3 toward the inner peripheral surface of the steel pipe 1. A piece 8b is projected radially, and the water supply pipe 3 is inserted into and fixed to the central portion 8a thereof, and the outer end surface of the support arm piece 8b is fixed to the inner peripheral surface of the steel pipe 1 so that the water supply pipe 3 is fixed. The steel pipe 1 is supported over the entire length at the center.

  The steel pipe 1 is provided with injection holes 10 of a curable material penetrating the inner and outer peripheral surfaces at a plurality of locations on the tube wall and projecting projections 11 having a rectangular planar shape on the outer peripheral surface of the rear end portion. Further, as shown in FIG. 1, a spiral or ring-shaped protrusion 12 is integrally projected on the outer peripheral surface of the steel pipe 1 to increase the pulling resistance of the steel pipe 1 after being driven into a natural ground. . It is not always necessary to provide such ridges 12.

  A striking / rotation transmitting member 20 connected to the rear end of the steel pipe 1 and transmitting a striking rotational force from the driving machine to the steel pipe 1 is formed in a cylindrical shape having a certain length as shown in FIG. The swivel body 20A and a steel pipe connecting cylinder 20B that is detachably screwed to the front end of the swivel body 20A. The swivel body 20A has a rear end portion of the small-diameter connecting pipe 30 at the center of the latter half thereof. The front screw hole 21 and the rear screw hole 22 whose rear end is opened rearward from the rear end surface of the impact / rotation transmission member 20 are screwed into the screw hole parts 21 and 22. On the other hand, the rear end of the steel pipe coupling cylinder 20B is detachably screwed to the front half of the front half of the front half through the water passage hole 23 having the front and rear ends communicated with each other. A large-diameter screw hole portion 24, and a rear end of the large-diameter screw hole portion 24 and the front screw hole portion 21. Drilling was receiving hole portion 25 is formed between, to form a drilling product discharge outlet 25a which opens to the outer peripheral surface of the swivel member 20A from the excavated material receiving hole portion within 24. The water passage hole 23 communicates with a water supply path (not shown) in the operating shaft 41 protruding from the front end surface of the drifter 40 described later, and is configured to receive water from this water supply path. .

  Further, the inside of the front half of the steel pipe connecting cylinder 20B is formed in the rear end receiving cylinder 26 of the steel pipe 1, and the inner diameter of the rear half of the steel pipe connecting cylinder 20B is set to the rear end receiving cylinder of the steel pipe 1. An annular receiving member that is smaller in diameter than the inner diameter of the portion 26 and substantially the same diameter as the excavated material receiving hole portion 25, and abuts and receives the rear end surface of the steel pipe 1 at the rear end of the receiving tube portion 26. It is formed on the end face 26a. Further, the rear end portion of the steel pipe connecting cylinder 20B is formed in a screw cylinder portion 27 that is screwed into the large-diameter screw hole portion 24 of the swivel body 20A, and the screw portion 27 is formed on the front end side of the screw portion 27. An annular receiving end surface 28 protruding in the outer diameter direction from the front end is formed, and the front end surface of the large-diameter screw hole portion 24 of the swivel body 20A is brought into contact with and received by the receiving end surface 28 and driven into the screw thread. The striking force is transmitted from the receiving end face 28 to the steel pipe connecting cylinder 20B with little transmission of the striking force from the machine side, and further, the steel pipe 1 is hit from the steel connecting cylinder 20B via the receiving end face 26a. It is configured to transmit force.

  Further, an L-shaped notch locking portion 29 having a front end opened forward is formed on a part of the peripheral wall of the steel pipe receiving tube portion 26 in the steel pipe connecting cylinder 20B. Engaging protrusions 11 projecting from the outer peripheral surface of the rear end of the steel pipe 1 are inserted and engaged to transmit the rotation of the striking / rotation transmitting member 20 to the steel pipe 1.

  The small-diameter connecting pipe 30 has an outer diameter smaller than the bore inner diameter of the drilled article receiving hole 25 of the swivel body 20A and the latter half of the steel pipe connecting cylinder 20B, and its outer peripheral surface and these drilled article receiving hole parts. 25 and the inside of the cylindrical portion of the rear half of the connecting cylinder 20B are formed in a drilled article discharge gap 6a communicating with the rear end of the drilled article discharge passage 6 in the steel pipe 1 and the small diameter connecting pipe 30. Is formed in the water passage hole 31 over its entire length, and further, a screw part 32 detachably screwed into the front screw hole 21 provided in the rear end part of the swivel body 20A. Is formed.

  Further, a cylindrical head 33 is fixed to the front end portion of the small diameter connecting pipe 30, and the cylindrical head 33 has a central hole 34a having the same diameter as the water passage hole 31 at the center. An annular buffer member 34 and a water-stop sealing material 35 having a center hole 35a into which the rear end of the water pipe 3 protruding rearward from the rear end of the steel pipe 1 is inserted in a watertight manner at the center. The interior is in a state where the water-stop seal 35 is superposed on the front and back. The rear portion of the cylindrical head 33 is attached to the outer peripheral surface of the front end portion of the small diameter connecting tube 30 with the buffer member 34 in contact with the front end surface of the small diameter connecting tube 30.

  Next, a method for driving the steel pipe 1 into the ground using the striking / rotation transmission member 20 in which the small diameter connecting pipe 30 is housed will be described. As shown in FIG. 7, the drifter 40 in the steel pipe driving machine disposed in the tunnel has a striking mechanism (not shown) for striking the rear end surface of the operating shaft 41 protruding from the front end surface of the drifter 40 and the operation. A rotating mechanism (not shown) for rotating the shaft 41 is provided. The operating shaft 41 is screwed into the rear screw hole portion 22 of the swivel body 20A, and the tip end surface of the screw hole portion 22 is engaged. The striking / rotation transmitting member 20 is connected to the operating shaft 41 by bringing it into contact with the bottom end surface.

  On the other hand, the rear end portion of the steel pipe 1 is inserted into the steel pipe receiving cylinder portion 26 in the steel pipe coupling cylinder 20B of the hammering / rotation transmission member 20, and the engaging projection protruding from the outer peripheral surface of the rear end portion of the steel pipe 1 11 is inserted into an L-shaped notch locking portion 29 formed at the front end of the steel pipe receiving tube 26, and the rear end surface of the steel pipe 1 is brought into contact with and received by the receiving end face 26a and the steel pipe 1 is surrounded. By rotating in the direction, the engaging protrusion 11 is engaged with the L-shaped notch engaging portion 29 in a retaining state. Further, as the rear end portion of the steel pipe 1 is inserted into the steel pipe receiving cylinder portion 26, the projecting end portion that protrudes from the rear end of the steel pipe 1 in the water supply pipe 3 disposed in the central portion in the steel pipe 1 is hit. Inserted into the center hole 35a of the water-stop sealing material 35 provided in the front end cylindrical head portion 33 of the small diameter connecting pipe 30 provided in the center of the rotation transmitting member 20 so as to be slidable back and forth, and thereafter The end surface is elastically pressed against the front end surface of the buffer member 34 to communicate the inside of the water supply pipe 3 with the front end of the water passage hole 31 of the small diameter connecting pipe 30.

  In this state, the front end face of the drill bit 2 attached to the front end of the steel pipe 1 is brought into contact with the wall surface from the circumferential wall surface of the tunnel, and is then rotated against the operating shaft 41 of the drifter 40. When the drifter 40 is moved forward while applying force, the rotation of the operating shaft 41 is caused by the L-shaped notch formed in the steel pipe receiving cylinder portion 26 of the hammering / rotation transmission member 20 via the hammering / rotation transmission member 20. It is transmitted to the steel pipe 1 through the engaging projection 11 engaged with the stop portion 29, and the striking force of the operating shaft 41 is rearward in the striking / rotation transmitting member 20 receiving the front end surface of the operating shaft 41. The impact is transmitted to the swivel body 20A of the striking / rotation transmitting member 20 through the bottom end face of the side screw hole portion 22.

  Further, the swivel body 20A is transmitted to the steel pipe connection cylinder 20B via the receiving end face 28 on the outer peripheral surface side of the steel pipe connection cylinder 20B receiving the front end face of the swivel body 20A, and the steel pipe connection cylinder 20B. A drilling tip 7a projecting from the front end surface of the drill bit 2 is transmitted to the steel pipe 1 which is received by the rear end surface of the receiving end surface 26a via the inner end surface receiving end surface 26a. 7b, the steel pipe 1 is driven to a predetermined depth while excavating the natural ground.

  When the steel pipe 1 is placed, water is supplied to the water passage portion 23 in the swivel body 20A of the impact / rotation transmission member 20 through the water supply passage in the operation shaft 41, and the small diameter connecting pipe is supplied from the water passage portion 23. Through the 30 water holes 31, the water pipe 3 in the steel pipe 1 is circulated through the water pipe 3 to inject water from the water injection hole 4 of the drilling bit 2 onto the drilling surface of the drilling bit 2, and the drilling tips 7 a and 7 b of the drilling bit 2. The excavated material excavated by the pipe 2 is fed into the excavated material discharge passage 6 between the steel pipe 1 and the water supply pipe 3 through the excavated material intake hole 5 provided in the drill bit 2, and flows through the discharge passage 6 to It flows out from the rear end of the opening into the excavated material discharge gap 6a in the impact / rotation transmission member 20, and is discharged from the excavated material receiving hole 25 to the outside through the discharge port 25a.

  In this way, the steel pipe 1 is driven on the ground while applying a striking rotational force, but the front end of the drill bit 2 is provided with a circular recess 2a1 surrounded by an annular wall 2a2. There is provided a drilled material intake hole 5 communicating with the drilled material discharge passage 6 in the steel pipe 1 in the circular recess 2a1, and the drilled material discharge passage 6 is formed in a wide passage having substantially the same cross section over the entire length. Therefore, the excavated material excavated by the drill bit 2 is once taken into the circular concave portion 2a1, and then flows out of the circular concave portion 2a1 to the wide excavated material discharge passage 6 without flowing out to the outside by the annular wall portion 2a2. It is possible to smoothly and surely enter the excavated material discharge passage 6 in the steel pipe 1 from the excavated material intake hole 5 formed in the corresponding large-diameter hole, and accordingly, between the outer peripheral surface of the steel pipe 1 and the excavated hole. There is a risk that the excavated material will enter the gap and clog the gap. Throat eliminated, it is possible to implant steel pipe 1 is carried out efficiently and reliably.

  Thus, after the steel pipe 1 is driven to a predetermined depth in the natural ground, the engaging projection 11 protruding from the rear end portion of the steel pipe 1 is formed by rotating the striking / rotation transmitting member 20 in the opposite direction. The hammering / rotation transmission member 20 is detached from the L-shaped notch locking portion 29 and the hammering / rotation transmission member 20 is removed from the steel pipe 1. FIG. 8 is a simplified side view showing a state in which the steel pipe 1 is driven into a natural ground. After that, the rear end portion of the steel pipe 1 protruding from the wall surface of the tunnel is sealed with a curable material injection cap (not shown), and curable such as cement milk or urethane resin liquid is supplied through the injection hose connected to this cap. When the material is supplied into the steel pipe 1, the hardenable material fills the steel pipe 1 and is injected into the ground around the steel pipe from the injection hole 10 provided in the pipe wall of the steel pipe 1 and the drilled bit 2 is excavated. It is also injected into the ground from the intake hole 5 and the ground is stabilized by hardening of the curable material.

  FIGS. 9 and 10 show a modification of the drill bit in the steel pipe for reinforcing natural ground according to the present invention. In the above embodiment, the drill bit 2 is protruded forward from the outer peripheral portion of the front end surface. The annular wall portion 2a2 has a projecting end surface (front end surface) formed on a vertical surface substantially perpendicular to the tube axis. In the perforated bit 2A, the peripheral wall of the annular wall portion 2a2 ′ is formed on the front end surface. An end surface between the excavation chips 7a and 7a adjacent to each other in the direction is formed as an inclined end surface 2a5 inclined rearward from the outer peripheral edge toward the concave portion 2a1 surrounded by the annular wall portion 2a2 ′. Since the other structure is the same as that of the piercing bit 2 of the above embodiment, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  In this way, if the front end surface of the annular wall portion 2a2 ′ of the drill bit 2A is formed on the inclined end surface 2a5 inclined rearward from the outer peripheral edge toward the recess 2a1 surrounded by the annular wall portion 2a2 ′, The excavated material excavated by the drill bit 2A can be taken into the recess 2a1 while gathering toward the center of the drill bit 2A, that is, the peripheral edge of the opening end of the recess 2a1, by the inclined end surface 2a5 of the annular wall 2a2 ′. In addition, it is possible to smoothly drive the steel pipe while further reliably preventing the excavated material from entering the gap between the outer peripheral surface of the ground reinforcement steel pipe and the excavation hole. In the above embodiment, the ground-steel-reinforcing steel pipe is formed from a single steel pipe 1 having a certain length. For example, the leading side in which the perforated bit 2 is fixed to the front end. A steel pipe, a rearmost steel pipe having an engagement projection 11 projectingly connected to an impact / rotation transmission member on the outer peripheral surface of the rear end portion, and interposed between the front steel pipe and the rearmost steel pipe Alternatively, a ground steel reinforcing driven steel pipe divided into a plurality of additional steel pipes to be connected may be used.

A partially omitted vertical side view of a cross section of the upper half of a steel pipe for reinforcing natural ground. The longitudinal side view of the perforated bit part. The front view of a drill bit. FIG. The longitudinal cross-sectional front view which shows the support structure of a water pipe. The vertical side view of a hit | damage and rotation transmission member. The some simple vertical side view which shows the steel pipe driving state by a drifter. The simplified side view which shows the state driven into the natural ground. The vertical side view of the drill bit part which shows another embodiment of this invention. The front view.

Explanation of symbols

1 Steel pipe 2 Drilling bit
2a1 recess
2a2 Annular wall
2a5 Inclined end face 3 Water pipe 4 Water injection hole 5 Drilled material intake hole 6 Drilled material discharge passage 8 Support bracket

Claims (3)

  A drill bit installed at the front end of a steel pipe for reinforcing natural ground that is placed in the natural ground to stabilize the natural ground, and this drill bit has an annular shape with a constant height toward the front outer periphery. A natural ground characterized in that it has a wall projecting and is provided with a drilled material intake hole that penetrates from the bottom to the rear of the recess surrounded by the annular wall and communicates with the inside of the steel pipe. Drilling bit in a reinforced steel pipe for reinforcement.   2. The drill bit in a ground reinforcement steel pipe according to claim 1, wherein the projecting front end surface of the annular wall portion of the drill bit is formed as an inclined surface inclined from the outer peripheral edge toward the recess.   The water drilling hole is provided in the perforated bit from the back bottom surface of the recess to the rear surface of the perforated bit. On the other hand, a water supply pipe is provided over the entire length in the center of the steel pipe. Further, a gap between the outer peripheral surface of the water pipe and the inner peripheral surface of the steel pipe is formed in the excavation discharge passage, and the front end of the excavation discharge passage is provided in the drill bit. 3. The drill bit in a ground reinforcement steel pipe according to claim 1 or 2, wherein the drill bit is connected to and communicated with a rear end of the drilled material intake hole.

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