JP2012140821A - Double pipe drilling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double pipe drilling device which eliminates the need for leaving an outer pipe underground and separately providing a boring machine that is not for drilling, and to provide a method of retracting the casing up to the ground.SOLUTION: A ring bit (20) has a rotation transmission protrusion (N1) formed and a casing shoe (22) has a cutout part (N2) formed that allows the rotation transmission protrusion (N1) to enter. The rotation transmission protrusion (N1) has a function of entering the cutout part (N2) in retraction and coming into contact with the cutout part (N2) to transmit rotation of the ring bit (20) to the casing shoe (22) and an outer pipe (casing 24).

Description

  The present invention relates to a double pipe drilling device used for drilling holes in the ground. More specifically, in the present invention, after drilling to a predetermined depth using a double-pipe drilling device, the outer pipe is retracted (pulled up or pulled out) to the ground side without remaining (buried) in the ground. ) Technology.

As a method of drilling holes in the ground during construction such as ground improvement work, rock grouting, ground anchor work, draining boring work, rotary boring is generally used.
In the rotary boring, the force (feeding force) and the rotational force that advance in the excavation direction are transmitted to the bit at the tip via a boring rod or the like to dig the ground.
Slime consisting of chips, crushed pieces, drilled scraps, etc. cut from the ground by the feed force and rotational force passes inside or outside the boring rod by water pressure, air pressure, etc. supplied from a pump or air compressor. Then, it is discharged out of the hole.

Rotary boring can be drilled with relatively simple equipment, but rotary percussion boring is widely adopted depending on the target ground and site conditions (especially when there is a need for shortening drilling time, etc.). Yes.
The rotary percussion type boring is a top hammer type in which a striking force is added to the rotary boring, and a boring machine is a source of the striking force.
With rotary percussion boring, a powerful striking force is added, so rapid drilling is possible even in gravel and boulder layers.
However, because of the top hammer method, there is a problem that noise is generated on the ground side where the boring machine is installed.
Moreover, when the drilling length becomes long and the boring rod becomes long, there is a problem that the striking force transmitted to the bit at the tip is reduced.

When the down-the-hole hammer method is employed for the above-described problems, the impact force generation source is located in front of the tip bit in the ground, so that noise on the ground side is reduced.
In addition, if the down-the-hole hammer method is used in which the source of impact force is located in front of the tip bit in the ground, the drilling length will be longer, and even if the boring rod is longer, the impact force transmitted to the tip bit will be reduced. do not do.

When drilling the ground using the down-the-hole hammer method, if the target ground is a hard rock or the like and the hole wall is completely “self-standing”, a single pipe drilling method is possible.
On the other hand, for the ground where the hole wall collapses, when the boring rod is retracted to insert the anchor body after drilling, the hole wall is collapsed, making it difficult to insert the anchor body or the like. In such a case (when the ground where the hole wall collapses is drilled using the down-the-hole hammer method), the double-pipe drilling method is adopted.

In the down-the-hole hammer method, a down-the-hole hammer is connected to the tip of a boring rod (inner pipe) connected to a swivel of a boring machine, and a pilot bit is connected to the tip of the down-the-hole hammer.
At the time of drilling, the feeding force and the rotational force transmitted from the boring machine are transmitted to the pilot bit, and the striking force is transmitted from the down-the-hole hammer to the pilot bit, so that the ground or rock can be dug.

In the double tube drilling method using the down-the-hole hammer, a casing (outer tube) is used in addition to the configuration in the down-the-hole hammer method (boring machine, boring rod or inner tube, down-the-hole hammer, pilot bit).
Here, for example, even if the casing (outer tube) is connected to the same swivel as the inner tube, the casing (outer tube) is transmitted from the boring machine only with the feeding force and the rotational force, and is an impact source connected to the inner tube. The striking force from a certain down-the-hole hammer is not transmitted. Therefore, when the drilling length is long or when the target ground is a hard rock, the drilling ability of the outer pipe is lowered, and there is a possibility that the drilling is impossible.
Therefore, by connecting a ring bit to the tip of the casing (outer tube) and connecting the pilot bit of the inner tube to the ring bit, the impact force from the down-the-hole hammer connected to the tip of the inner tube is applied to the casing (outer tube). It is common to transmit to the tip of the.

Thus, when the ground is dug with the down-the-hole hammer double pipe drilling hole, the feed force, the rotational force and the striking force supplied to the pilot bit are the main excavation sources.
Then, by connecting the ring bit to the pilot bit and connecting the ring bit to the casing (outer pipe), the pilot bit entrains the casing (outer pipe) and, via the pilot bit, the ring bit and the casing (outer pipe). The striking force is transmitted to the tube.

Here, if the casing, which is the outer pipe connected through the ring bit on the ground side as described above, is further connected to the swivel on the ground side, the casing is restrained on the rear side on the ground side. The ring bit connected to the casing cannot move freely (in the excavation direction or vice versa). Therefore, even if the ring bit tries to move forward (excavation direction) by the striking force transmitted from the pilot bit, since the casing is connected to the swivel, such ring bit moves forward (excavation direction). Is also limited.
In addition, since movement of the pilot bit itself connected to the ring bit is also restricted, smooth drilling becomes impossible.
Furthermore, there is a possibility that the ring bit whose movement is restricted (forward or in the excavation direction) may be damaged if it is forced to move (forward or in the excavation direction).

Therefore, when excavating the ground by the double pipe drilling method using the down-the-hole hammer described above, the outer pipe (casing) is not connected to the swivel, and the outer pipe (casing) is entrained by the inner pipe. Adopted.
In such a method, in the method of directly connecting the inner tube and the outer tube, the rotational force transmitted to the inner tube is always transmitted to the outer tube (casing), so the outer tube (casing) and the ground (hole wall) ), The rotational force is lost or reduced, and the drilling accuracy is also reduced. Therefore, a structure is adopted in which a shoe is interposed between the inner tube and the outer tube (casing) so that the rotational force transmitted to the inner tube is not transmitted to the casing.

Here, when drilling the ground, the slime consisting of chips, crushed pieces, drilled scraps, etc. cut from the ground is clogged in the gap between the casing and the hole wall, the phenomenon that the casing does not move any more, So-called “jamming” may occur.
In order to prevent such jamming, fluid is ejected in the middle of drilling (flushing) to remove slime in the drilling hole, and at the same time, by rotating the outer tube (casing), the casing (outer tube) ) And the hole wall are generally prevented from being integrated (so-called “cutting edges”).

By the way, when drilling is performed by the above-described excavation method, that is, the down-the-hole hammer type double tube drilling, a shoe is interposed between the inner tube and the outer tube (casing) to the casing. Since the rotational force is not transmitted, the outer tube cannot be rotated to eliminate jamming.
For this reason, in the down-the-hole hammer type double pipe drilling in the prior art, a boring machine different from the boring machine for drilling is prepared and connected to the outer pipe (casing), and the outer pipe is connected by the other boring machine. By rotating the (casing), the casing (outer tube) and the hole wall are prevented from being integrated.
Or, without actively preventing the casing (outer pipe) and the hole wall from being integrated, the outer pipe (casing) was left behind in the ground or rock without retreating to the ground side (burial) )

However, the preparation of another boring machine (in contrast to the boring machine for drilling) leads to a situation where construction costs and facilities increase. Moreover, the operation | work which connects the said another boring machine and an outer tube | pipe (casing) must also be implemented by employ | adopting a special method.
On the other hand, if the outer pipe (casing) is left in the ground or rock, the cost increases at least by the amount of the outer pipe (casing) to be buried.
Furthermore, there are cases where the outer pipe (casing) cannot be left in the ground or rock.

As another conventional technique, for example, a double-pipe drilling bit used in a double-pipe drilling method that can minimize the number of ring bit drilling blades buried in the ground after excavation has been proposed (patented) Reference 1).
However, the related art is intended to reduce the number of ring bit excavating blades, and does not solve the various problems of the prior art described above.

JP 2010-121275 A

  The present invention has been proposed in view of the above-mentioned problems of the prior art, and is a double pipe drilling bit used in a double pipe drilling system using a down-the-hole hammer, and an outer pipe is left in the ground. The purpose of the present invention is to provide a double-pipe excavation bit that does not need to be provided and a boring machine that is not for drilling, and a method of retreating the casing to the ground side while rotating the casing.

  The double-pipe drilling device of the present invention includes an inner pipe (boring rod 10) connected to a ground-side boring machine (not shown) via a swivel joint (12), and an underground pipe of the inner pipe (10). A down-the-hole hammer (14) connected to the side tip, a pilot bit (16: constituting a part of the inner pipe) connected to the down-the-hole hammer (14), and disposed radially outside the pilot bit (16); Rotational force (R) and feed force (BF: force that advances in the excavation direction) can be transmitted from the pilot bit (16) (by engaging the convex portion 16T and the groove 20R having a shape complementary to the convex portion 16T). An annular ring bit (20) connected to the ground side of the ring bit (20) and capable of transmitting a feeding force (BF) from the ring bit (20) (by engagement of the protrusion 20T and the groove 22R). Circle And a ring-shaped casing shoe (22), and an outer tube (casing 24) whose tip on the ground side is fixed (for example, welded) to the casing shoe (22). (N1) is formed, and the casing shoe (22) is formed with a notch (N2) into which the rotation transmission projection (N1) can enter, and the rotation transmission projection (N1) in the ring bit (20). ) Enters the notch (N2) when retreating, and the rotation transmission projection (N1) comes into contact with the side edge (N2S) in the notch (N2) to rotate the ring bit (20). (22) It has the function to transmit to an outer pipe (casing 24), It is characterized by the above-mentioned.

According to the double-pipe excavation device of the present invention having the above-described configuration, the rotation transmission projection (N1) in the ring bit (20) is formed in the notch portion formed in the casing shoe (22) when retreating. When the ring bit (20) rotates into the N2), the rotation transmission projection (N1) comes into contact with the side edge (N2S) in the notch (N2), and the rotation of the ring bit (20) is the casing. It is transmitted to the shoe (22) and the outer tube (casing 24).
Therefore, even if the slime is clogged between the outer tube (24) and the inner wall of the excavation hole, so-called "jamming" occurs, and the outer tube (24) does not move in the backward direction, the rotation transmission projection (N1) ), The rotation is transmitted from the ring bit (20) to the outer tube (24) through the notch (N2) and the casing shoe (22).
Then, when the outer pipe (24) is rotated, so-called “cutting the edge” is performed, and the outer peripheral surface of the outer pipe (24) and the surrounding slime are sheared, and the outer pipe (24) and the inner wall of the unillustrated drilling hole Integration with is released. The outer pipe (24) can be moved in the backward direction, and can be moved back to the ground side.

Thus, according to the present invention, when the outer pipe is retracted, the outer pipe (24) can be reliably retracted to the ground side without preparing a boring machine separate from the boring machine for drilling. I can do it. Therefore, it is possible to prevent an increase in construction costs and facilities. Further, a special work for connecting the outer pipe with a boring machine different from the boring machine for drilling is also unnecessary.
According to the present invention, since it is not necessary to leave the outer pipe in the ground or the rock when retreating, it is possible to save the cost by at least the outer pipe (casing) to be buried. And even if it is the site of the enforcement conditions which cannot leave an outer pipe | tube (24) in the ground or a bedrock, it can enforce.

  Further, according to the present invention, during excavation, the ground and the rock are removed by the pilot bit (16) and the ring bit (20) in the same manner as when drilling with the down-the-hole hammer type double pipe drilling in the prior art. The outer pipe (24) can be moved in the excavation direction while excavating.

It is a side view showing an excavation system in a down the hole hammer to which an embodiment of the present invention is applied. It is explanatory drawing which showed the double pipe drilling system using the double pipe drilling system shown in FIG. 1 in the state which decomposed | disassembled the member used. It is an expanded sectional view showing arrangement at the time of excavation in an embodiment. It is a side view of a ring bit used in an embodiment. It is a side view of a casing shoe used in an embodiment. It is the elements on larger scale which show the relative position of the ring bit and casing shoe at the time of excavation. It is the elements on larger scale which show the relative position of the ring bit and casing shoe at the time of reverse. It is the elements on larger scale which show the relative position of the protrusion N1 for rotation transmission at the time of reverse | retreat, and the notch part N2. It is the elements on larger scale which show the relative position of the rotation transmission protrusion N1 and the notch part N2 at the time of excavation.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, referring to FIG. 1 and FIG. 2, an example of a double pipe drilling method using a down-the-hole hammer to which the illustrated embodiment is applied is illustrated.
In FIG. 1, a boring rod 10 (inner pipe) is connected to a swivel joint 12 on the right side of FIG. 1, and the swivel joint 12 is connected to a boring machine (not shown).
On the other hand, a down-the-hole hammer 14 is connected to a tip of the boring rod 10 on the ground side (left side in FIG. 1), and the down-the-hole hammer 14 is connected to a pilot bit 16 (inner pipe). An excavation tip 18 is provided at the tip of the pilot bit 16 on the ground side (left end in FIG. 1).

An annular ring bit 20 is provided outside the pilot bit 16 in the radial direction. An excavation tip 21 is provided at the underground tip of the ring bit 20 (left end in FIGS. 1 and 2).
As shown in FIG. 2, a convex portion 16T such as a part of a spiral is provided at the ground side end portion (right end in FIG. 2) of the pilot bit 16, and the ground side end portion (in FIG. A groove 20R having a shape complementary to the convex portion 16T of the pilot bit 16 is formed at the right end). Then, when the convex portion 16T of the pilot bit 16 is inserted into the groove 20R of the ring bit 20, the pilot bit 16 and the ring bit 20 are connected, and the rotational force acting on the pilot bit 16, the feeding force, and the impact The force is transmitted to the pilot bit 20 through the convex portion 16T and the groove 20R.
By the way, when the fitting state between the convex portion 16T of the pilot bit 16 and the groove 20R of the ring bit 20 is maintained, the pilot bit 16 and the ring bit 20 operate integrally, but the fitting state is released. When the force in the direction to be applied is applied, the integrated state of the pilot bit 16 and the ring bit 20 is released. That is, in FIG. 2, when a counterclockwise rotational force KL acts on the excavation direction (the direction of arrow BF in FIG. 2), the convex portion 16T of the pilot bit 16 is released from the groove 20R of the ring bit 20, and the pilot bit 16 and the ring bit 20 are released.

1 and 2, an annular casing shoe 22 is disposed on the ground side of the ring bit 20 (the right end in FIGS. 1 and 2), and the casing shoe 22 has an end on the ground side (see FIG. 1). The right end of FIG. 2) is fixed to the casing 24 (outer tube) at the welded portion W.
In FIG. 1, a plurality of casings 24 are screw-connected to each other, and as shown in FIG. 1, the ground side end portion (in FIG. 1) of the casing 24 arranged on the most ground side (right side in FIG. 1). (Right end) 24E is separated from the swivel joint 12. That is, the casing 24 is in a “free” state with respect to the swivel joint 12.

In FIG. 2, a protrusion 20T is formed on the outer peripheral surface of the ring bit 20 so as to extend over the entire circumference. A groove 22 </ b> R extending over the entire circumference in the circumferential direction is formed on the inner peripheral surface of the casing shoe 22.
Here, referring to FIG. 6, the protrusion 20 </ b> T of the ring bit 20 is fitted in the groove 22 </ b> R of the casing shoe 22. When the ring bid 20 moves in the excavation direction (in the direction of arrow BF in FIG. 6), the underground side (left side in FIG. 6) end 20Tf of the protrusion 20T is in the ground side of the groove 22R of the casing shoe 22 ( In FIG. 6, the power is transmitted by contacting the left side end 22Rf.
Further, with respect to the rotation direction (arrow KR direction and KL direction in FIG. 6), the rotation of the ring bit 20 is performed on the casing shoe 22 except when a rotation transmission projection N1 described later in detail is fitted in the notch N2. It has a structure that cannot be transmitted. When the ring bit 20 in FIG. 6 moves in the excavation direction (in the direction of arrow BF in FIG. 6), the rotation transmission projection N1 and the underground side end (left end in FIG. 6) 22E of the casing shoe 22 Appropriate spacing is maintained.
Therefore, the ring bit 20 and the casing shoe 22 move integrally in the excavation direction (the direction of the arrow BF in FIG. 6), but the rotation of the ring bit 20 is not transmitted to the casing shoe 22.

In the double pipe drilling method using the double pipe drill bit shown in FIGS. 1 and 2, the pilot bit 16 is connected to the down-the-hole hammer 14 and transmitted from the down-the-hole hammer 14. The striking force is transmitted to the pilot bit 16 and the ring bit 20, and the ground (including the rock) is drilled.
When moving while excavating to the underground side (left side in FIGS. 1 and 2), the down-the-hole hammer 14 and the pilot bit 16 are connected, and the pilot bit 16 and the ring bit 20 are connected via the convex portion 16T and the groove 20R. Move together.
The movement of the ring bit 20 in the direction of the arrow BF and the arrow BR (FIG. 1) is transmitted to the casing shoe 22 by the projection 20T of the ring bit 20 and the groove 22 of the casing shoe 22 (the casing shoe 22 and the casing). Since 24 is fixed at the weld W, it is transmitted to the casing 24).
Thereby, when moving while excavating to the underground side (left side of FIGS. 1 and 2), the casing 24 is also taken to the underground side.
Here, the projection 20T of the ring bit 20 and the groove 22R of the casing shoe 22 do not transmit the rotational force in the directions of the arrows KR and KL (FIG. 1), so the rotation of the ring bit 20 is not transmitted to the casing shoe 22. Therefore, the torque of the pilot bit 16 and the ring bit 20 is not lost due to the friction of the casing 24, and the drilling accuracy is not lowered.

In FIG. 2, the ring bit 20 is formed with a rotation transmission protrusion N1, and the casing shoe 22 is formed with a notch N2 at the underground end (left end in FIG. 2).
The rotation transmission protrusion N1 and the notch N2 will be described later with reference to FIGS.

Next, with reference to FIGS. 2-7, the principal part of embodiment of illustration and the aspect at the time of excavation are demonstrated.
FIG. 3 shows the pilot bit 16, the ring bit 20, the casing shoe 22, and the casing 24 during excavation (when the ring bit 16 advances to the ground side).
At the time of excavation, as described above, the protrusion 16T and the groove 20R are prevented from rotating in the direction in which the connection between the protrusion 16T of the pilot bit 16 and the groove 20R of the ring bit 20 is released (in the direction of the arrow KL in FIG. 2). When the excavation is performed while maintaining the connection to the pilot bit 16, the feed force transmitted to the pilot bit 16 (force to proceed in the excavation direction BF), the rotational force, the striking force, and the like are transmitted to the ring bit 20.

3 and 6, the ground side edge (front edge) 20Tf of the projection 20T of the ring bit 20 is in contact with the ground side edge (front edge) 22Rf of the groove 22R of the casing shoe 22. The feed force transmitted to the ring bit 20 is transmitted to the casing shoe 22 and the casing 24.
3 and 6, the ground side edge (rear edge) 20Tr of the projection 20T of the ring bit 20 contacts the ground side edge (rear edge) 22Rr of the groove 22R of the casing shoe 22 during excavation. For example, an interval of 9 mm is provided.
As described above, even if the rotational force is transmitted to the ring bit 20, the protrusion 20T of the ring bit 20 only rotates in the groove 22R of the casing shoe 22, so that the rotational force is transmitted via the protrusion 20T and the groove 22R. Is not transmitted to the casing shoe 22 and the casing 24.

The excavation tip 21 is welded to the front end surface of the ring bit 20, and a pin PN1 is embedded in a part of the rear region (ring bit front edge portion) 20F. And, in the annular space (for example, the interval in the arrow BR direction is 9 mm) between the ring bit front edge 20F and the underground side end (front end) 22E of the casing shoe 22, the ground side portion of the pin PN1 ( The right side portion in FIG. 3 protrudes as a rotation transmission protrusion N1 (for example, by 7 mm in the arrow BR direction).
At the time of excavation shown in FIGS. 3 and 6, the ground side end (tip) N1E of the rotation transmission projection N1 is not in contact with the ground side end (front end) 22E of the casing shoe 22. As shown in FIG. 6, there is a gap W between the ground side end (tip) N1E of the rotation transmission projection N1 and the casing shoe front end 22E (in the example of FIG. 3, the gap in the direction of the arrow BR is 2 mm). Exists.

Although not explicitly shown in FIG. 3, a notch N <b> 2 is formed at the front end 22 </ b> E of the casing shoe 22 as shown in FIGS. 1, 2, and 5 to 9.
As described above, during excavation, the rotation transmission projection N1 does not enter the notch N2. Therefore, during excavation, the rotational force is not transmitted to the casing shoe 22 due to the engagement between the rotation transmission protrusion N1 and the notch N2.

Next, the mode when the pilot bit 16 is retracted to the ground side (in the direction of the arrow BR in FIG. 3) (when retracting: when being pulled out) will be described.
Even when reversing, the pilot bit 16 and the ring bit 20 are integrated with each other as long as the rotational force in the direction for releasing the connection between the pilot pit 16 and the ring bit 20 (in the direction of the arrow KL in FIG. 2) is not generated. Operate.

6 and 7, when the ring bit 20 moves to the ground side by the force BR for moving the ring bit 20 back to the ground side (right side in FIGS. 6 and 7), the ground of the protrusion 20 </ b> T of the ring bit 20 is grounded. The side edge (rear edge) 20Tr abuts on the ground side edge (rear edge) 22Rr of the groove 22R of the casing shoe 22. As a result, the force BR to be moved backward is transmitted to the casing shoe 22 and the casing 24.
At this time, the ring bit 20 is rotated so that the rotation transmission projection N1 enters the notch N2 so that the ground side end (tip) N1E of the rotation transmission projection N1 does not contact the casing shoe front end 22E. To adjust the position.
Thus, even when the pilot bit 16 is retracted, the protrusion 20T and the groove 22R are “contacted by a surface”, thereby enabling smooth movement, and the ground side end (tip) N1E of the rotation transmitting protrusion N1 is “One handedness” due to contact with the end of the casing shoe 22 is prevented.

Here, as described above, in the excavation mode, when the ring bit 20 rotates, the protrusion 20T of the ring bit 20 only idles in the groove 22R of the casing shoe 22, so the protrusion 20T and the groove 22R. The rotation of the ring bit 20 is not transmitted to the casing shoe 22 via.
However, referring to FIG. 7, when the rotational force KR is applied to the ring bit 20 with the rotation transmission projection N1 entering the notch N2 during retraction, the side surface N1S of the rotation transmission projection N1 The side edge N2S in the notch N2 abuts, and the rotation of the ring bit 20 is transmitted to the casing shoe 22 via the rotation transmission projection N1 and the notch N2.

In FIG. 3, when the rotational force KR is applied in the above-described backward mode, the rotation of the ring bit 20 is transmitted to the casing shoe 22 via the rotation transmission projection N1 and the cutout portion N2. The rotational force is transmitted to the casing 24 via the welded portion W.
Furthermore, referring to FIG. 6 and FIG. 7, when the pilot bit 16 retracted to an arbitrary distance is advanced in the same manner as in the excavation described above (moved in the direction of arrow BF in FIG. 6 and FIG. 7), Since the rotation transmission projection N1 is released from the notch N2, the rotational force applied to the ring bit 20 is not transmitted to the casing shoe 22, so that smooth excavation can be resumed.

In this manner, the casing 24 is rotated forward and backward by the rotational force transmitted from the ring bit 20 through the rotation transmission projection N1, the notch N2, and the casing shoe 22, and the liquid is ejected. "Flushing" becomes possible.
In addition, slime made of chips, crushed pieces, drilling scraps, and the like cut from the ground is clogged in the gap between the casing 24 and the inner wall of the drilling hole (not shown), so-called “jamming” occurs, and the casing 24 If the rotation force is transmitted from the ring bit 20 to the casing 24 via the rotation transmission protrusion N1, the cutout portion N2, and the casing shoe 22, and the casing 24 rotates, the so-called “cut edge” is generated. As a result, the integration of the casing 24 and the hole wall (not shown) is released, and the casing 24 can be retracted to the ground side.

In order to execute the excavation and retreating operations described with reference to FIGS. 1 to 9, various dimensions of the rotation transmission protrusion N1 of the ring bit 20 and the cutout portion N2 of the casing shoe 22 satisfy predetermined conditions. There is a need to.
Hereinafter, the specifications of the rotation transmission projection N1 and the notch N2 will be described with reference mainly to FIGS.

As described above with reference to FIG. 9, during excavation, a gap W (for example, a gap of 2 mm) exists between the tip N1E of the rotation transmission protrusion N1 and the front end 22E of the casing shoe 22.
If the dimension of the gap W is too large, a dimension δ (in the illustrated example, for example, between the ground side end portion (right end portion in FIG. 9) 20Fe of the ring bit front edge portion 20F and the front end 22E of the casing shoe 22 will be described. 9 mm) of the annular space becomes too large, and foreign matter may enter the annular space (width dimension δ).
On the other hand, if the size of the gap W is too small, the tip N1E of the rotation transmission projection N1 interferes with the front end 22E of the casing shoe 22 during excavation, and the tip N1E is worn.
According to the research by the applicant, the gap W is suitably in the range of 1 mm to 3 mm.

In FIG. 4, the length of the rotation transmitting projection N1 (the length from the end 20Fe to the tip N1E) is indicated by reference symbol a, and the distance between the end 20Fe of the ring bit front edge 20F and the front edge 20Tf of the projection 20T is shown. The width CL of the protrusion 20T (the distance from the leading edge 20Tf to the trailing edge 20Tr) is denoted by the symbol b.
In FIG. 5, the depth of the notch N2 (the distance between the front end 22E of the casing shoe 22 and the bottom KAe of the notch N2) is indicated by a symbol D, and the bottom KAe of the notch N2 and the front edge 22Rf of the groove 22R The distance is indicated by a symbol L2, and the width dimension of the groove 22R (the distance from the front edge 22Rf to the rear edge 22Rr) is indicated by a symbol H2.
At the time of excavation, as shown in FIG. 6, the front edge 20Tf of the protrusion 20T of the ring bit 20 contacts the front edge 22Rf of the groove 22R of the casing shoe 22. As described above, a gap W (FIG. 6) exists between the tip N1E of the rotation transmission projection N1 and the front end 22E of the casing shoe 22.
Therefore, the following equation holds.
D + H2 = CL−a−W (1)

On the other hand, at the time of retraction, as shown in FIG. 7, the ring bit 20 is moved to the ground side (right side in FIG. 7), so that the rear edge 20Tr of the projection 20T becomes the rear edge 22Rr of the groove 22R of the casing shoe 22. Abut.
Since the front edge 20Tf of the protrusion 20T is in contact with the front edge 22Rf of the groove 22R of the casing shoe 22 during excavation, the protrusion 20T abuts on the front edge 22Rf of the groove 22R when moving from excavation to backward movement. It moves backward from the position where it contacts the rear edge 22Rr of the groove 22R (moves to the ground side). The movement amount m of the protrusion 20T at that time is m = H2-b.
If the length at which the rotation transmitting projection N1 enters the notch N2 during the reverse movement is denoted by X (see FIG. 8), m = X + W.
Further, if the clearance dimension between the tip N1E of the rotation transmitting projection N1 and the bottom portion KAe of the notch N2 at the time of reversal is Y (see FIG. 8), Y = W + D−m.
That is, the following relational expression holds for the movement amount m of the protrusion 20T.
m = H2−b = W + X = W + D−Y (2)

As shown in FIG. 8, the width dimension Y in the gap between the tip N1E of the rotation transmission projection N1 and the bottom (ground side end surface) KAe of the notch N2 is such that the tip N1E of the rotation transmission projection N1 is the same as the notch N2. It is a margin provided so as not to interfere with the bottom KAe.
When the width dimension Y of the gap is less than 0, before the rear edge 20Tr of the protrusion 20T comes into contact with the rear edge 22Rr of the groove 22R of the casing shoe 22, the tip N1E of the rotation transmission protrusion N1 is the bottom of the notch N2. Since it abuts against KAe, it becomes “one-sided” as described above, and even when the width dimension Y is too small, the gap between the tip N1E of the rotation transmission projection N1 and the bottom KAe of the notch N2 is excavated. There is a risk of interference with the slime that enters.
On the other hand, from the above equation (2), the width dimension Y is a value obtained by subtracting the movement amount m of the protrusion 20T from the depth D and the gap W of the notch N2. Since the movement amount m of the protrusion 20T is uniquely determined from the width dimension b of the protrusion 20T and the width dimension H2 of the groove 22R, if the width dimension Y is too large, the depth D of the notch N2 is increased. It is necessary to increase the risk of foreign matter entering the notch D.
According to the research by the applicant, it has been found that the gap dimension Y between the tip N1E of the rotation transmission projection N1 and the bottom KAe of the notch N2 is suitably in the range of 1 mm to 3 mm.

Here, at the time of “flushing” or “edge cutting” described above, the rotation transmitting projection N1 is in contact with the side edge N2S of the cutout portion N2, thereby transmitting a force for rotating the casing 24. If the length X at which the rotation transmission projection N1 enters the notch N2 is too small, the rotation transmission projection N1 may be damaged by the shearing force and fall off the ring bit 20.
According to the applicant's research, the length X at which the rotation transmitting projection N1 enters the notch N2 when retreating is 3 mm or more, and even if the force for rotating the casing 24 is transmitted, it is not damaged. It has been found.

Furthermore, if the cross-sectional area of the pin PN1 forming the rotation transmission protrusion N1 (the cross-sectional area of the rotation transmission protrusion N1) is denoted by A, it is expressed by the following formula: A ≧ P / (σS). Here, “P” is a force required to rotate the casing 24, “σ” is a limit stress of the material constituting the pin PN1, and “S” is a safety factor.
Since the cross-section of the pin PN1 is circular, the radial dimension r in the cross-section of the pin PN1 (rotation transmission projection N1) is expressed by the equation r ≧ (P / σSπ) ^1/2 . Here, “π” is a circumference ratio.

If the circumferential length N2CL of the notch N2 is too small, it will be difficult for the rotation transmitting projection N1 to enter the notch N2 when retreating.
On the other hand, if the circumferential length N2CL of the notch portion N2 is too large, foreign matter easily enters the notch portion N2.
According to the applicant's research, the circumferential length N2CL of the notch N2 is not less than twice the diameter (= 2r) of the pin PN1 or the rotation transmission projection N1, and is 1 of the entire circumferential dimension of the casing shoe 22. / 4 or less is appropriate.

According to the illustrated embodiment described above, during excavation, the convex portion 16T of the pilot bit 16 abuts on the groove 20R of the ring bit 20, and the feed force transmitted to the pilot bit 16 is transmitted to the ring bit 20. . Here, since the convex portion 16T of the pilot bit 16 is engaged with the groove 20R of the ring bit 20, the rotational force R transmitted to the pilot bit 16 is also transmitted to the ring bit 20.
Since the front edge 20Tf of the protrusion 20T of the ring bit 20 is in contact with the front edge 22Rf of the groove 22R of the casing shoe 22, the feeding force transmitted to the ring bit 20 is transmitted to the casing shoe 22 and the casing 24. Is done.
Therefore, the pilot bit 16 and the ring bit 20 can move the casing 24 in the excavation direction while excavating the ground.

At the time of retreat, when power in the retreat direction BR is applied to the ring bit 20, the rear edge 20Tr of the protrusion 20T of the ring bit 20 comes into contact with the rear edge 22Rr of the groove 22R of the casing shoe 22, and the casing shoe 22 and The casing 24 can be moved to the ground side. Then, the rotation transmitting projection N1 at the ring bit front edge portion 20F enters the cutout portion N2 of the casing shoe front end 22E. Therefore, when the ring bit 20 rotates, the rotation transmission projection N1 becomes a side edge within the cutout portion N2. The rotation of the ring bit 20 is transmitted to the casing shoe 22 and the casing 24 in contact with N2S.
Therefore, even if the slime is clogged in the gap between the casing 24 and the inner wall of the excavation hole (not shown), so-called “jamming” occurs, or the casing 24 does not move in the excavation direction or the reverse direction, By rotating the casing 24 by transmitting a rotational force from the ring bit 20 to the casing 24 via the protrusion N1, the notch N2, and the casing shoe 22, so-called "cutting edges" are performed. The integration of the hole wall (not shown) is released, and the casing 24 can be retracted to the ground side.

  It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.

10 ... Boring rod 10
12 ... Swivel joint 14 ... Down-the-hole hammer 16 ... Pilot bit 16T ... Pilot bit projection 18 ... Drilling tip 20 ... Ring bit 20R ... Ring bit groove 20T .. Ring bit projection 21 ... excavation tip 22 ... casing shoe 22R ... casing shoe groove 24 ... casing N1 ... rotation transmission projection N1E ... rotation transmission projection tip PN1・ ・ ・ Pin N2 ・ ・ ・ Notch W ・ ・ ・ Gap between rotation transmission projection tip and casing shoe front end δ ・ ・ ・ Dimension between ring bit front edge end and casing shoe front end a ・ ・ ・ Ring bit Length from the edge of the front edge to the tip of the protrusion b ・ ・ ・ Width dimension of the protrusion of the ring bit CL ・ ・ ・ End of the edge of the ring bit and the front edge of the protrusion of the ring bit Interval D ... Depth L2 ... Distance H2 between the bottom of the notch and the groove front edge of the casing shoe ... Case shoe groove width m ... Ring bit projection movement amount X ... Length Y of rotation transmission protrusion entering into the notch when retreating ... Clearance dimension N2CL between tip of rotation transmission protrusion and bottom of notch ... Circumferential length of notch N2

Claims (1)

  An inner pipe connected to the ground boring machine via a swivel joint, a down-the-hole hammer connected to the ground-side tip of the inner pipe, a pilot bit connected to the down-the-hole hammer, and a pilot bit radially outward An annular ring bit arranged and capable of transmitting a rotational force and a feeding force from the pilot bit; an annular casing shoe connected to the ground side of the ring bit and capable of transmitting the feeding force from the ring bit; The inner end has an outer tube fixed to the casing shoe, the ring bit has a rotation transmission projection, and the casing shoe has a notch into which the rotation transmission projection can enter. The rotation transmission protrusion in the ring bit enters the notch when retreating, and the rotation transmission protrusion contacts the side edge in the notch. Double pipe drilling apparatus characterized by having a function of transmitting the rotation of the ring bit to the casing shoe and the outer tube.

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