JPH0996184A - Underground drilling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underground drilling apparatus which has drilling efficiency equal to that of double tube drilling and also can keep a core from entering a drilling bit. SOLUTION: An underground drilling apparatus comprises a ring bit 12 having plural undercuts 16 and an inner bit 14 which is positioned inside the ring bit 12 in the radial direction and in which a jet hole 20 for drilling water is formed. A dimensional difference between the inside diameter ϕ of the ring bit and the outside diameter D of the inner bit is set small δ to such a degree that slurry produced in underground drilling does not enter from a space between the inner circumferential surface 121 of the ring bit and the outer peripheral surface of the inner bit.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a device for underground excavation. More specifically, it relates to a drill bit at the tip of a drilling rig.

[0002]

2. Description of the Related Art Conventional drilling methods using a drill bit are roughly classified into three types as shown in FIGS. FIG. 6 shows a type called a casing single pipe drilling hole or an inner rod single pipe drilling hole, which is a hollow tubular bit (casing single pipe) having a drilling tip C embedded at its tip or a single pipe 1 of an inner rod having only an inner bit. Drilling or excavating a boring hole in the ground.

FIG. 7 shows a type called double pipe drilling, which includes an outer bit (or ring bit) 2 in which a drilling tip C is buried at the tip of a casing, and an inner bit 3 inserted inward in the radial direction. To excavate.

FIG. 8 shows a type called a non-core single pipe drilling hole, and like the casing single pipe drilling hole (or inner rod single pipe drilling hole) shown in FIG. 6, a single bit 4 is used for drilling. The bit 4 is not a hollow tubular member. In addition, the reference numeral 5 in FIG. 8 indicates an injection hole for the drilling water.

Here, for example, when the drilling shown in FIG. 6 is performed,
Slurry or core penetrates into the hollow tubular bit 1 as indicated by symbol S. Similarly, in FIG. 7, the core also enters the annular space forming the gap between the outer bit 2 and the inner bit 3. If this core penetrates into the rod for excavation, it may cause clogging, jamming, and galling, which is not preferable.

On the other hand, in the type called non-core single pipe drilling shown in FIG. 8, the inconvenience caused by the intrusion of the core into the bit is prevented. However, as compared with the double pipe drilling as shown in FIG. 7, only the self-supporting stratum (hard rock) is limited.

[0007]

[Problems to be Solved by the Invention] Based on the above situation,
Conventionally, there has been a demand for a device for underground excavation that has excavation efficiency comparable to that of double pipe drilling, and that the core does not penetrate into the excavation bit, but a device that can respond to this has still been proposed. It has not been.

An object of the present invention is to provide a device for underground excavation which can meet the above-mentioned demands.

[0009]

SUMMARY OF THE INVENTION An underground excavation device of the present invention is provided with a ring bit provided at a tip portion of a casing and having a plurality of relief grooves, and a ring bit located radially inward of the ring bit. And an inner bit in which an injection hole for water for drilling is formed, the dimensional difference between the inner diameter of the ring bit and the outer diameter of the inner bit is such that the slurry generated during underground excavation is the inner peripheral surface of the ring bit and the inner bit. It is set so small that it does not enter from the outer peripheral surface.

According to the present invention having such a structure,
Since the ring bit and the inner bit are used in combination, excavation is performed in the same manner as in the case of double pipe drilling, and excavation efficiency comparable to double pipe drilling can be obtained. In addition to this, the dimensional difference between the inner diameter of the ring bit and the outer diameter of the inner bit (for example, 1 mm) is small enough that the slurry generated during underground excavation does not enter between the inner peripheral surface of the ring bit and the outer peripheral surface of the inner bit. Since it is set, the core or the slurry is prevented from entering from the annular space formed between the ring bit and the inner bit. Further, since the core or slurry does not enter the rod for excavation, clogging, jamming, galling, etc. are prevented.

Here, the dimensional difference is set to, for example, 1 mm, so that the radial thickness dimension of the annular space formed between the ring bit and the inner bit is 0.
5 mm. Further, it is impossible for slurry or the like to enter the annular space having a radial thickness of 0.5 mm.

During excavation by the underground excavation device of the present invention, the core or slurry is jetted by the water during the excavation to the ground side through the annular space formed between the ring bit and the inner bit. I can't go back. Therefore, the slurry or the like is returned from the outer circumference of the ring bit to the ground side through the plurality of escape grooves formed in the ring bit.

Here, in the case of the conventional double pipe drilling in which the core, the slurry or the like is returned to the ground through the annular space formed between the ring bit and the inner bit, the ground pressure or more is applied. Since it is necessary to inject the drilling water at the pressure of 1, the amount of water used and the amount injected into the drill hole increase. However, if the amount of water injected into the drill hole increases, the ground near the drill hole tends to collapse, and there is a problem in terms of safety and the quality of the underground structure. On the other hand, according to the present invention, since the slurry or the like is returned to the ground side from the outer circumference of the ring bit through the plurality of relief grooves formed in the ring bit as described above, the pressure equal to or higher than the underground pressure is applied. There is no need to inject drilling water at. Therefore, the amount of water used and the amount of water injected into the excavation hole are small, and there is no fear of weakening the ground near the excavation hole.

In carrying out the present invention, the inner bit is detachably attached to the ring bit so that it is possible to collect only the inner bit during the boring work even though the casing is a single pipe drilling hole. You can

In implementing the present invention, it is also possible to connect an inner rod to the inner bit to form a double pipe drilling system. Even in this case, the amount of water to be injected is much smaller than that of the conventional double pipe drilling method.

Alternatively, it is also possible to fix the inner bit to the ring bit and perform excavation in the same manner as the non-core single pipe drilling. Also in this case, since the ring bit and the inner bit are used for excavation, the same efficiency as that of the double pipe drilling can be expected.

In the present invention, it is preferable to fit an O-ring for preventing backflow of slurry or the like into the main body of the inner bit (inner bit body).

Further, the difference in quenching hardness between the ring bit and the inner bit is made extremely large (for example, 1 in HRC).
0 points or more) is preferable. As described above, since the dimensional difference between the inner diameter of the ring bit and the outer diameter of the inner bit is set to be extremely small, the ring bit and the inner bit easily contact each other, and when they contact each other, they are damaged. Therefore, in the present invention, a hardness difference is provided between the ring bit and the inner bit to prevent the ring bit and the inner bit from being damaged.

Further, in the present invention, the finishing accuracy of the inner peripheral surface of the ring bit (outer bit) is determined by the Japanese Industrial Standard (J
2 mountain triangles (25-S: 25) with finishing code of IS standard)
It is preferable that the finish is more accurate than (micron or less). By finishing in this way, the O-ring is protected from being damaged by the so-called "galling" phenomenon.

In addition to this, in the present invention, the maximum outer diameter of the inner bit is the outer diameter of the bit body, and is the outer diameter of the tip (carbide tip) of the reference outer diameter (the maximum outer diameter in the prior art). However, it is preferable that the outer diameter of the bit body is smaller than the maximum outer diameter. With this configuration, O
It is possible to increase the clearance from the water hole formed on the bit tip side of the ring to the ground to secure the water passage for the injected water for excavation. As a result, an increase in the pressure inside the pipe for excavation water is suppressed.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows a first embodiment of the present invention. The device for underground excavation of the present invention, which is generally indicated by reference numeral 10,
It has a ring bit (outer bit) 12 and an inner bit 14 that form a tip portion of a casing (not shown). The ring bit 12 forms a tip portion of the casing, and a plurality of (in FIG. 1, Carbide tips 15 ... and escape grooves 16 ... are formed. On the other hand, the inner bit 14 is located in the hollow portion (inward in the radial direction) of the ring bit 12, and a plurality of (only one is shown in FIG. 1) cemented carbide tips 18 ... And a plurality of (only one is shown in FIG. 1) drilling water injection holes 20 ... Are formed. In the figure, O is an O-ring.

In FIG. 1, the inner diameter Φ of the ring bit 12
Is 60 mm and the tolerance is +0.05 mm to −0 mm
Then, the outer diameter D of the inner bit 14 is 59 mm, and the tolerance is +0 mm to -0.05 mm. In this case, the inner peripheral surface of the ring bit 12 and 12I, and the inner bit 1
The width δ of the annular gap AS existing between the outer peripheral surface 14 and the outer peripheral surface 14O of No. 4 is about 0.5 mm. And this dimension δ (=
About 0.5 mm), the slurry (or core, water, etc.) S etc. generated during underground excavation by the device 10 has a gap A
Small enough to prevent entry into the device 10 through S.

The ring bit 12 is shown in detail in FIG. In FIG. 2, the angle of the escape groove 16 is indicated by the symbol α, and is, for example, 30 °. Further, the inner peripheral surface 12I of the ring bit 12 has a finish of two mountain triangles (25-S: 25 microns or less) according to the JIS standard finish symbol. It protects the mating O-ring (not shown). Further, the inner peripheral surface 12I is tapered at the portion of the ring bit main body portion 12B in the direction in which the wall thickness becomes thinner, as indicated by reference sign β. In the illustrated example, the taper β has an angle of 1 with respect to the line L parallel to the center line.
It has become °.

3 and 4 show the inner bit 14. In FIG. 3, the injection holes 20 for drilling water have an inner diameter of 8 mm (the outer diameter D of the inner bit 14 is 59 mm).
Is set). And inner bit 1
The angle of the injection holes 20 ... with respect to the water supply pipe 22 for excavation in 4 is 3 when the injection holes do not overlap the tip 18 (in the case where the injection holes 20 are shown in FIG. 4).
The angle is 0 °, and the position overlapping with the tip 18 (in the case where the injection hole 20 is not shown in FIG. 4) is 45 °.

The reference numeral 24 in FIG. 3 indicates that
It is a groove into which an O-ring (not shown) fits.

In the embodiment shown in FIGS. 1-3, when excavating the ground, the inner bit 14 is responsible for excavating the central portion of the boring hole, and the ring bit 12 is responsible for the outer edge portion. Therefore, very efficient excavation is performed like conventional double pipe excavation.

At the time of excavation, the excavation water is injected through the excavation water supply hole 22 and the injection hole 20, but the excavation water is not injected at a high pressure against the underground pressure, and the excavation water is not injected. Acts as a lubricant for bit. Therefore, unlike the conventional double pipe excavation, the amount of injected water is relatively small.

The drilling water sprayed through the spray holes 20 acts as a lubricant during drilling, and then the escape groove 16
It is discharged to the outer peripheral side of the ring bit 12 via. And how the ground is absorbed into the ground being excavated,
Alternatively, it is not absorbed by the ground and is blown out to the ground side as a slurry.

In other words, in the case of ordinary double pipe excavation, the inside of the ring bit or the casing is grounded via the annular gap AS between the inner peripheral surface 12I of the ring bit and the outer peripheral surface 14D of the inner bit. However, in the present invention, the width AS of the gap AS is extremely small and there is no room for the slurry to enter. Therefore, excavation water, slurry, etc. do not enter the device as a core, and the excavation can be performed in a non-core state even though it has the same configuration as the double pipe.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, the outer shape of the portion where the injection holes 20 for excavation water are formed is made slightly smaller, and the maximum outer diameter is the portion indicated by the arrow D. With this configuration, the clearance from the injection hole 20 to the ground is increased to secure the water channel for the injected drilling water, and thus the increase in the pressure in the drilling water supply pipe 22 is suppressed.
The other configurations and operations are similar to those of the first embodiment, and therefore description thereof will be omitted.

In the illustrated excavator, if an inner rod is connected to the inner bit 14, double pipe excavation similar to that shown in FIG. 7 can be performed. Alternatively, if the inner bit 14 is fixed to the ring bit 12, as shown in FIG.
The same action as the non-core single pipe drilling shown in can be achieved.

[0033]

The effects of the present invention are listed below. (1) A so-called "non-core" drilling is possible in which slurry or the like does not enter the inside of the device. (2) Efficient excavation equivalent to double pipe drilling is performed. (3) The amount of drilling water used or injected can be reduced. As a result, the risk of borehole collapse is significantly reduced. (4) Double pipe drilling and non-core single pipe drilling are possible by combining with accessories.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of the present invention in a partial cross section.

FIG. 2 is a side view showing a partial cross section of the ring bit used in the first embodiment.

FIG. 3 is a side view showing a partial cross section of the inner bit used in the first embodiment.

FIG. 4 is an end view showing a tip portion of an inner bit used in the first embodiment.

FIG. 5 is a side sectional view of an inner bit used in the second embodiment of the present invention.

FIG. 6 is a front view showing a single pipe drilling hole.

FIG. 7 is a front view showing a double pipe drilling hole.

FIG. 8 is a front view showing a non-core single pipe drilling hole.

[Explanation of symbols]

 C, 15, 18 ... Drilling tip (carbide tip) 1 ... Tubular bit (2, 12 ... Ring bit (or outer bit) 3, 14, 14A ... Inner bit 4 ... Non-core single pipe drilling bit 5, 20 ... Drilling water injection hole S ... Slurry (or core) 12I ... Ring bit inner peripheral surface 14O ... Inner bit outer peripheral surface AS ... Ring bit Between the inner and inner bits δ ... Radial thickness of the space AS φ ... Ring bit inner diameter D ... Inner bit outer diameter (maximum outer diameter) 24 ... O-ring fitting groove

Claims (4)

[Claims] 1. A ring bit provided at a tip portion of a casing and having a plurality of escape grooves, and a ring of injection water, which is located radially inward of the ring bit and has a drilling water injection hole. The inner bit has an inner bit, and the dimensional difference between the inner diameter of the ring bit and the outer diameter of the inner bit is set so small that slurry generated during underground excavation does not enter from between the inner peripheral surface of the ring bit and the outer peripheral surface of the inner bit. Underground excavation equipment characterized by being 2. The underground excavation device according to claim 1, wherein the inner bit is configured to be detachable from the ring bit. 3. The underground excavation device according to claim 1, wherein an inner rod is connected to the inner bit. 4. The underground excavation device according to claim 1, wherein the inner bit is fixed to the ring bit.