WO2009066907A2

WO2009066907A2 - Drill body with air-hammer for inducing reverse circulation effectively and drilling method using the same

Info

Publication number: WO2009066907A2
Application number: PCT/KR2008/006743
Authority: WO
Inventors: Sun Keun Park
Original assignee: Core Geotechnics Co., Ltd.
Priority date: 2007-11-19
Filing date: 2008-11-17
Publication date: 2009-05-28
Also published as: WO2009066907A3

Abstract

The invention relates to a drill body equipped at the front end of a rod in a drill with a reverse circulation inducing air hammer and a method of using the drill body, the drill being proposed to use compressed air used in driving air hammers for discharging drill cuttings. More particularly, the invention concerns a drill body with a reverse circulation inducing air hammer in which primary initial reverse circulation of compressed air is induced by supplying compressed air without being involved in driving the air hammer in advance before driving it thereby to form a flow of discharging drill cuttings, and a method of drilling a hole in a reverse circulation manner. The drill body with a reverse circulation inducing air hammer equipped at the front end of a rod of a drill according to the invention comprises an air hammer; a discharge pipe; a first air supply pipe to which compressed air is supplied for driving the air hammer; and a second air supply pipe to which compressed air is supplied to be discharged to the discharge pipe, the bit at the front end of the air hammer being formed with air discharge holes.

Description

[DESCRIPTION]

[Invention Title]

DRILL BODY WITH AIR-HAMMER FOR INDUCING REVERSE CIRCULATION EFFECTIVELY AND DRILLING METHOD USING THE SAME

[Technical Field]

<i> The invention relates to a drill body equipped at the front end of a rod in a drill with a reverse circulating air hammer proposed to use compressed air in discharging drilled cuttings, the air having been used in driving the air hammer, and to a method of using the drill body and, more particularly, to a drill body with a reverse circulation inducing air hammer by inducing primary initial reverse circulation of compressed air by means of the compressed air supplied not involved in driving the air hammer before driving it in order to form a flow of discharging drill cuttings in advance before drilling.

<2>

[Background Art]

<3> In many cases, ground drilling is preceded in constructing a structure. The ground drilling is performed with a drill arrangement, and a special drill is required for hard ground, e.g., a rock mass, because it is not easy to carry out drilling thereon.

<4> Examples of the most general conventional method of drilling a rock mass include RCD (Reverse Circulation Drilling), PRD (Percussion Rotary Drilling) and MACH (Mud and Air Circulating Hammering).

<5> The method of RCD is to rotate a special roller bit at the front end to drill the ground to a designed depth, wherein drill cuttings (including drilled rock pieces, herein referred to as drill cuttings, collectively) produced during drilling are discharged through a reverse drill rod via compressed air on the ground together with circulating water. With such a method of RCD, it is possible to make holes in large diameter, e.g., from 1000mm to 3000mm in diameter and the method of RCD is thus applied to making a basis of a building or of a bridge pier with concrete-based piles site-laid for supporting ground structures.

<6> However, with the method of RCD, drilling is carried out only via rotation of bits, so that the drilling speed is very slow and special bits and large equipment should be used. With the method of RCD, a separate air compressor is required only for removing drill cuttings as well. Furthermore, slow speed of moving the circulating water hinders smooth removal of drill cuttings. In particular, in order to achieve efficient drilling of holes in large diameter, bits should be provided with a sufficient load in proportion to the large drilling diameter. In this case, production of drill collars and the like for supplying a sufficient load costs quite a lot, and large items of equipment should be employed for driving large bits as well.

<7> The method of PRD is for drilling holes with an air hammer by rotating the hammer bit equipped in a pile driver while percussing it by means of compressed air with a relatively small tool, in order to drill the ground and then to discharge drill cuttings with the compressed air. Since the method of PRD employs a single air hammer structure in which a single bit is used, it is hard to achieve drilling holes in large diameter. Therefore, as compared to the method of RCD, the method of PRD is applied to drilling holes of 600mm to 1000mm in diameter. Accordingly, it is an advantage that the method of PRD achieves fast speed of drilling in that the hammer bit is percussed while being rotated for drilling, but is a disadvantage that the method of PRD cannot be applied to drilling holes in large diameter, e.g., equal to or larger than 1000mm in diameter. In addition, with the method of PRD, the air hammer has a structure in which the compressed air used in driving the hammer is discharged through a narrow gap between the air hammer and the drilled hole together with the drill cuttings. Such a structure hinders smooth discharging of drill cuttings. That is, since the initial discharge path of the drill cuttings is made through a narrow gap between the air hammer and the drilled hole, initial discharging of large rock cuttings drilled is not easy. If the compressed air escapes above the ground, the whole amount of the compressed air is not used for discharging the drill cuttings, so that it is even harder to discharge drill cuttings. Difficulty in discharging drill cuttings results in the drilling speed to be lowered.

<s> The method of MACH was proposed to settle the problems in the method of PRD, as a method of providing a plurality of air hammers to one canister to carry out drilling with a multi-air hammer structure. However, it has a limit that it is not easy to apply the method of MACH to drilling holes in large diameter, e.g., equal to or larger than 1500mm in diameter, because of restriction on air hammers and the size of bits. The air hammers used in the method of MACH have a structure totally different from that of a general air hammer, so that the air hammers used in the method of MACH is relatively expensive to produce. Of course, the method of MACH requires a separate air compressor for discharging drill cuttings used in the method of RCD. <9> In order to address the problems in the methods of PRD and MACH by means of the aforementioned air hammers, the inventor has developed a method of drilling holes by means of a drill body with a reverse circulating air hammer as shown in Fig.l and the method was issued as a Korea patent registration No. 683909.

<io> However, it was seen that the drill cuttings could not be temporarily discharged through a discharge line and were discharged directly to the surface of drilled ground in a first step as shown in Fig.2 while applying the method to a field. I observed that, because drill cuttings were produced before a reverse circulation discharge flow via compressed air was formed, the drill cuttings were scattered on the surface of the ground before a reverse circulation discharge flow of drill cuttings was formed.

<π> Accordingly, the inventor devised the invention in order to address the aforementioned problems.

<I2>

[Disclosure] [Technical Problem] <i3> The invention was devised to address the aforementioned problems in the prior art. It is an object of the invention to provide a drill body with a reverse circulation inducing air hammer configured to carry out drilling holes with the air hammer while discharging the drill cuttings produced in drilling via compressed air used in driving the air hammer in a reverse circulation manner, the drill body with a reverse circulation inducing air hammer enabling initial reverse circulation to be inducted to allow the drill cuttings to be discharged smoothly.

<i4> It is another object of the invention to provide a drill body for economical drilling in that small equipment for driving air hammers used in drilling holes in small diameter can be used for drilling holes in large diameter and a method of drilling holes with the inventive drill body.

<15>

[Technical Solution]

<16> In order to achieve the aforementioned object of the invention, the invention provides a drill body equipped at the front end of a drill rod, characterized by comprising an air hammer driven by supplying compressed air and provided to percuss a front end bit; a discharge pipe member formed with a discharge passage running from an inlet at the front end to an outlet at the back end, to be clamped with the air hammer, while the inlet is located on the further inner side than the bit head at the front end of the air hammer and the discharge pipe receives the air hammer or is arranged in parallel and next to the air hammer; a first air supply pipe passing through the back end of the air hammer to communicate with the front end bit to which compressed air for driving the air hammer is supplied and a second air supply pipe arranged to communicate with the discharge passage of the discharge pipe to which compressed air to be discharged to the discharge pipe is supplied, characterized in that the front end bit of the air hammer is formed with air discharge holes extending from the first air supply pipe and toward the outer side of the bit .

<17> The invention also provides a method of drilling holes in a reverse circulation manner, characterized by comprising the steps of: (a) providing the drill with the inventive drill body to locate the front end bit of the air hammer on the surface of the ground to be drilled; (b) supplying compressed air to the first air supply pipe in the drill body in step (a); (c) supplying compressed air to the second air supply pipe to drive the air hammer and carrying out primary drilling at the same time in the drill body in step (a).

<i8> Also, the invention provides a method of drilling holes in a reverse circulation manner, characterized by comprising the steps of: (a) providing a drill with a drill body for drilling a pilot hole and locating the front end bit of an air hammer on the surface of the ground to be drilled; (b) supplying compressed air to a first air supply pipe in the drill body in step (a); (c) supplying compressed air to a second air supply pipe in the drill body in step (a) to drive the air hammer while carrying out primary drilling to form a pilot hole ; (d) providing a drill with a drill body for ream- drilling, placing a reaming support in the pilot hole and locating the front end bit oi the air hammer on the surface of the ground to be drilled around the pilot hole at the same time; (e) supplying compressed air to the first air supply pipe in the drill body in step (d); and (f) supplying compressed air to the second air supply pipe in the drill body in step (d) to drive the air hammer while carrying out secondary drilling to form a ream-drilled hole.

<19>

[Advantageous Effects]

<2i> It is expected that the invention will give the following effect.

<22> First, since compressed air can be supplied to the discharge passage through which drill cuttings are discharged without being involved in driving the air hammer, it is possible to form a reverse circulation discharge flow via the compressed air before drill cuttings are produced, so that it is possible smoothly to discharge drill cuttings through the discharge line at an early stage of drilling.

<23> Second, since the area around the pilot hole can be gradually expanded to be drilled after completing the primary drilling, it is possible to apply air hammers (bits) and driving equipment used in drilling holes in small diameter to drilling holes in large diameters. Therefore, economical drilling can be accomplished without restriction on the size of hole diameter to be drilled.

<24>

[Description of Drawings] <25> The features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments thereof illustrated with reference to the accompanying drawings, wherein: <26> Fig. 1 shows a conventional drill body with a reverse circulating air hammer ; <27> Fig.2 illustrates drilling with a drill equipped with a drill body shown in Fig.l; <28> Figs.3 to 8 illustrate examples of a drill body according to the invention, proposed for drilling a pilot hole! <29> Figs.9 to 13 illustrate another examples of a drill body according to the invention, proposed for ream-drilling holes; and <30> Figs.14 to 15 illustrate drilling holes by means of a drill equipped with a drill body according to the invention.

<3i> Description for reference numerals in the drawings <32> 100: air hammer 110: bit <33> 111: air discharge hole 130: front shoe

<34> 200: discharge pipe 210: inlet

<35> 310: first air supply pipe 320: second air supply pipe

<36> 410: cylindrical canister 420: disc-type flange

<37> 500: reaming support 510: inlet

<38> 530: insertion pipe 530: roller bit

<39> B: drill body R: rod

<4o> P: solid discharge line

<4i> Pl: unit pipe

<42> P2: connection string

<43>

[Best Mode]

<44> Hereinafter, the invention will be described in more detail with reference to the accompanying drawings and preferred embodiments of the invention for a drill body with a reverse circulating air hammer and for a method of drilling holes in a reverse circulation manner using the drill body, respectively.

<45>

<46> 1. Drill body with reverse circulation inducing air hammer

<47> Figs.3 to 10 illustrate various examples of a drill body with a reverse circulation inducing air hammer according to the invention. The invention is characterized in that a conventional drill body equipped at the front end of a rod of an air hammer drill is configured to supply separate compressed air for inducing primary reverse circulation in addition to the compressed air for driving the air hammer. To this end, the drill body according to the invention is configured to essentially comprise an air hammer 100, a discharge pipe 200 and an air supply pipe, wherein the air supply pipe is configured to comprise a first air supply pipe 310 for driving the air hammer 100 and a second air supply pipe 320 for inducing reverse circulation. <48> The air hammer 100 is configured to be driven by the supplied compressed air to percuss the bit 110 equipped at the front end, rotates and is propelled by propulsion of the rod at the same time to substantially realize ground drilling. The invention illustrates an exemplary embodiment in which a multi-air hammer structure, e.g., a plurality of air hammers 100 (two or four), is applied, but it is possible to apply a single air hammer therein.

<49> The air hammer 100 is provided with the first air supply pipe 310 to pass through the back end thereof and communicate with the front end bit 110. Compressed air is supplied through the first air supply pipe 310 to drive the air hammer 100. The front end bit 110 of the air hammer is formed with air discharge holes 111 extending from the first air supply pipe 310 and towards the outside of the bit 110. The compressed air used in driving the air hammer 100 is discharged through the air supply holes to the outside of the bit 110. The compressed air discharged as such acts to discharge drill cuttings in a reverse circulating manner.

<50> Also, in the invention, it is proposed further to equip a front shoe 130 for enclosing the head of the front bit 110 of the air hammer. In this case, the front shoe 130 should be equipped so that the inlet 210 at the front end of the discharge pipe to be described hereinafter is open. Such a front shoe 130 acts as a guide so that the drill cuttings can smoothly be introduced to the inlet 210 at the front end of the discharge pipe.

<5i> The discharge pipe 200 is a member formed with a discharge passage running from the inlet 210 at the front end thereof to the outlet at the back end thereof. The inlet 210 at the front is arranged to be positioned further inner than the front end bit 110 of the air hammer to receive or to be next to and in parallel to the air hammer 100 in order to be clamped with the air hammer 100. The embodiment of the invention illustrates that the discharge pipe 200 is arranged to be next to and in parallel to the air hammer 100 and clamped with the air hammer 100 by means of a cylindrical canister 410 or disc type flange 420. Although not illustrated, the discharge pipe 200 would be in the form that it acts as a cylindrical canister 410 as well if the discharge pipe 200 receives the air hammer 100. In particular, since the outer side of the cylindrical canister 410 can support the drilled side in the drilling process if the air hammer 100 is configured to be received in the cylindrical canister 410, the clamping structure by means of the cylindrical canister 410 is advantageous in achieving vertical drilling.

<52> The discharge pipe 200 acts as a passage for discharging drill cuttings produced in drilling a hole as the air hammer 100 is driven. The drill cuttings are introduced through the inlet 210 at the front end and discharged through the outlet at the back end. In the drill equipped with a drill body according to the invention, the rod is shaped a pipe for discharging drill cuttings. Since the discharge pipe 200 is combined with the rod to communicate therewith, the drill cuttings discharged through the discharge pipe 200 are discharged through the rod to the outside.

<53> The discharge pipe 200 is provided with a second air supply pipe 320 to communicate with the discharge passage. When compressed air is supplied through the second air supply pipe 320, the compressed air is discharged directly to the discharge pipe 200. As such, the second air supply pipe is provided to supply compressed air without being involved in driving the air hammer 100. As a result, while drilling is not carried out, e.g., the air hammer 100 is not driven, it is possible to form a reverse circulation discharge flow via compressed air in the discharge pipe 200. In other words, with the provision of the second air supply pipe 320, it is implemented that initial reverse circulation of compressed air is achieved through the discharge pipe 200 without being involved in drilling progress. Considering the role of the second air supply pipe 320 configured as such, it is preferred that the front end of the second air supply pipe 320 is formed to be bent toward the outlet of the discharge pipe 200 (see Fig.6). As such, after inducing initial reverse circulation of compressed air by supplying the compressed air to the second air supply pipe 320, supplying compressed air to the first air supply pipe 310 leads to the air hammer 100 to be driven for drilling progress. Since drill cuttings are produced while initial reverse circulation of the compressed air is already achieved by means of the second air supply pipe 320, the drill cuttings follows the initial reverse circulation flow of the compressed air smoothly to be discharged through the discharge pipe 200 in a reverse circulation manner. Of course, since the reverse circulation flow is formed while the compressed air used in driving the air hammer 100 is discharged through the air discharge holes 111 as well, discharging drill cuttings in a reverse circulation manner will be accelerated. Considering this, while the flow of discharging drill cuttings in a reverse circulation manner is formed, it is also possible to interrupt compressed air supply to the second air supply pipe 320. It is because the compressed air used in driving the air hammer 100 can keep the flow of discharging drill cuttings in a reverse circulation manner to be continued while continuously forming the flow of discharging drill cuttings in a reverse circulation manner.

<54> As described above, both of the first and second air supply pipes are supplied with compressed air. In this case, the first and second air supply pipes can be configured as a separate line or be branched out of one air supply pipe. If the first and second air supply pipes are of branch type, it is possible to share one air compressor and is thus advantageous in that efficiency in using facilities would be improved. In this case, however, it is required to provide a switch valve at their branch point to prevent compressed air from being supplied to the first and second air supply pipes simultaneously. By means of the measure, it is possible to supply primary compressed air only to the second air supply pipe 320 thereby to form a flow of discharging drill cuttings in a reverse circulation manner before drill cuttings are produced.

<55> It is preferred to equip the second air supply pipe 320 with a check valve, in order to prevent the drill cuttings from being introduced to the second air supply pile 320, the drill cuttings being discharged in a reverse circulation manner to the discharge pipe 200 when compressed air is not supplied to the second air supply pipe 320 after finishing its role of inducing initial reverse circulation. In this case, a conventional check valve is employed. <56> Figs. 3 to 13 illustrate an embodiment of a drill body of a multi-air hammer structure provided with a plurality of air hammers 100 and a first air supply pipe 310. The invention proposes two types of the drill body of the multi-air hammer structure which can be used depending on its use, that is a drill body for drilling a pilot hole Sl and another drill body ream-drilling holes S2, S3, S4 and S5.

<57> For the multi-air hammer structure, it is preferred to provide an air compressor to each hammer, respectively. However, for the multi-air hammer structure, if the second air supply pipe 320 is branched from any one of the multiple first air supply pipes 310, it is desirable in that continuous supply of compressed air is implemented while sharing an air compressor. That is, it is possible to gradually perform three steps of a first step of supplying compressed air through the second air supply pipe 320, a second step of supplying compressed air to the first air supply pipe 310 which is not branched, and a third step of supplying compressed air to a different first air supply pipe 310 from which the second air supply pipe 320 is branched out, while interrupting compressed air supply to the second air supply pipe 320. Such a step-by-step progress implements continuous supply of compressed air. Continuous supply of compressed air leads to continuously discharging compressed air in a reverse circulation manner. This results in smoothly discharging drill cuttings that start to be produced in the second step or third step.

<58> Also, in addition to the multiple air hammers, a plurality of discharge pipes 200 can be provided as well. In this case, it is desirable that each back end of the plurality of discharge pipes 200 is connected each other to lead to an integrated discharge pipe 230. This aims to form a unified passage for discharging drill cuttings. If a plurality of discharge pipes 200 are provided, one thing needed is to connect the second air supply pipe 320 only to any one of the plurality of discharge pipes 200.

<59> Also, since, in the drill body according to the invention, the air hammer 100 is clamped with the discharge pipe 200 by means of a cylindrical canister 410 or disc-type flange 420 to form one finished assembly, it is possible to provide a drill body various in drilling diameter with one and the same air hammer 100. That is, if the air hammer 100 and the discharge pipe 200 are assembled with a cylindrical canister 410 or disc-type flange 420 which is various in size depending on the drilling diameter while properly adjusting the state of arrangement thereof, it is possible to complete a drill body various in drilling diameter.

<6o> Figs.3 to 8 show a drill arrangement of the multi-air hammer structure for drilling a pilot hole. As shown, the drill body of the multi-air hammer structure for drilling a pilot hole is configured so that a plurality of air hammers 100 are arranged to be adjacent to each other while being next to the plurality of discharge pipes 200 in parallel. It is preferred that two of the plurality of air hammers 100 are arranged in parallel or three thereof are arranged in a triangular structure in parallel. This is because it is possible to drill a pilot hole with the same plurality of air hammers 100 while achieving a given drilling diameter. Of course, it is possible to arrange 4 or more air hammers 100 properly.

<6i> Figs.3 to 5 show an embodiment of a drill body in which two air hammers 100 and iwo discharge pipes 200 arranged in parallel pass through the cylindrical canister 410 and are accepted therein to be clamped. Here, the air discharge holes 111 formed on the front end bit 110 of each of the air hammers is formed toward the outside of the bit 110, especially the inside of the cylindrical canister 410 (outside of the discharge pipe). In such a case that the air discharge holes 111 are formed toward the inside of the cylindrical canister 410 as such, through-holes 220 are formed in the discharge pipe 200 to enable the discharge pipe 200 to communicate with the cylindrical canister 410. The purpose of this structure is to enable the compressed air to be discharged to the outside of the discharge pipe 200 in the cylindrical canister 410 through the air discharge holes 111 and then to come into the discharge pipe 200 through the through-holes 220 of the discharge pipe again in order to be discharged while inducing reverse circulation of drill cuttings.

<62> Figs.6 to 8 are an embodiment of a drill body in which two air hammers 100 and two discharge pipes 200 arranged in parallel are clamped while passing through the disc-type flange 420 and being inserted. In this embodiment, the air discharge holes 111 formed in the front end bit 110 of each of the air hammers are formed toward the front side of the bit 110 head while the second air supply pipe 320 is connected to either of the two discharge pipes 200. Once primary reverse circulating discharge flow is formed by means of the second air supply pipe 320, the compressed air used in driving the air hammers 100 follows the primary reverse circulating discharge flow to be induced to the discharge pipe 200. Accordingly, although the compressed air is discharged toward the front side of the bit 110 head, the drill cuttings are discharged in a reverse circulation manner. When the compressed air is discharged toward the front side of the bit 110 head, the compressed air will act directly on the drill cuttings. As a result, the drill cuttings will be discharged even more smoothly in a reverse circulation manner. Therefore, as shown in Figs.3 to 5, the configuration would be even more advantageous in which the air discharge holes 111 are formed toward the front side of the bit 110 head even in a drill body provided with the cylindrical canister 410. However, in this case, it is not needed to form through-holes 220 in the discharge pipe 200 (see Fig.12).

<63> Figs.9 to 13 show a drill body of the multi-air hammer structure for ream-drilling. As shown in the figures, the drill body of the multi-air hammer structure for ream-drilling (S2, S3, S4, S5) is configured so that the discharge pipe 200 is arranged in the center, and the plurality of air hammers 100 are arranged in parallel to the discharge pipe 200 while forming one circular track around the discharge pipe 200. As a result of such an arrangement, drilling can proceed only at the position where the air hammers 100 are arranged other than the hammer case center. As a result, if the drill arrangement is positioned so that the air hammers 100 are positioned around the pilot hole Sl where drilling has already finished, it is possible to expand and drill the area around the pilot hole Sl. It is preferred that the plurality of air hammers 100 are arranged at the positions where they balance each other, centering on the discharge pipe 200. This is because it is possible to carry out ream-drilling (S2, S3, S4, S5) while achieving a given drilling diameter with the plurality of air hammers 100 in balance.

<64> It is preferred to configure the drill body for ream-drilling so that a reaming support 500 is equipped at the front end of the discharge pipe 200. The reaming support 500 is positioned for its outer side to be next to the front end bit 110 of the air hammer while protruding further forward than the front end bit 110. This is intended for the reaming support 500 to be placed in the pilot hole Sl already drilled to support the drilled surface. In this case, however, the reaming support 500 should be formed with inlets 521 so that the outer side of the support 500 can communicate with the inlet 210 at the front end of the discharge pipe 200. With this measure, when the reaming support 500 protruding further forward than the front end bit 110 of the air hammer is placed in the pilot hole Sl already drilled to support the drilled surface and then the air hammers 100 are driven, the area surrounding the pilot hole Sl is ream-drilled (S2, S3, S4, S5) and the drill cuttings from ream-drilling are introduced into the inlet 210 of the front end of the discharge pipe 200 through the inlets 521 of the reaming support at the same time, and then discharged.

<65> On the other hand, since the reaming support 500 protrudes further forward than the front end bit 110 of each of the air hammers to be placed in the pilot hole Sl already drilled, it is natural a short step is formed between the pilot hole Sl and the reamed areas (S2, S3, S4, S5) which is not reamed as much as the protruding length if protrusion of the reaming support 500 is kept continuously. It is necessary to configure the state of protrusion of the reaming support 500 differently in the steps of ream- drilling and ream-drill-finishing in order to avoid such a short step to be formed. That is, while the reaming support 500 protrudes further forward than the front end bit 110 of the air hammer in ream-drilling (see Figs, lib and 12b), it is configured not to protrude further forward than the front end bit 110 of the air hammer in the step of ream-drill-finishing (see Figs. 12c and 13c). To this end, the reaming support 500 in the present invention comprises an insertion pipe 510 for insert-coupling it to the inlet 210 at the front end of the discharge pipe, an extended wing pipe 520 extending in a flare shape from the front end of the insertion pipe, and inlets 521 formed to communicate with the insertion pipe 510 from the outer side of the extended wing pipe 520. In addition, it is proposed that the state of protrusion of the extended wing pipe 520 is controlled in the reaming support 500 by adjusting the position of insertion coupling of the insertion pipe 510 in the reaming support 500. The extended wing pipe 520 is formed to have a front side to be inclined in a flare shape. The reaming support having such a configuration operates as follows: for ream-drilling, the insertion pipe 510 is coupled to the discharge pipe 200 for the extended wing pipe 520 to protrude further forward than the bit 110 head, and, for ream-drill finishing, the insertion pipe 510 is coupled to the discharge pipe 200 so that the extended wing pipe 520 does not protrude further forward than the bit 110 head. As a result, in ream-drilling, drill cuttings are introduced from the extended wing pipe 520 through the inlets 521 to the insertion pipe 510 and finally introduced to the inlet 210 of the discharge pipe and then discharged (see Figs. 12b and 13b). In ream-drill finishing, the drill cuttings are introduced to the insertion pipe 510 along the front side of the extended wing pipe 520 in a flare shape and finally introduced to the inlet 210 of the discharge pipe to be discharged (see Figs. 12c and 13c).

<66> Of course, when the drill cuttings are introduced to the discharge pipe 200, they are discharged in a reverse circulation manner by means of compressed air.

<67> The reaming support 500 as described above may be equipped with roller bits 530 on the front side of the extended wing pipe 520 as shown in Fig.10. In the process of ream-drilling after placing the reaming support 500 in the pilot hole Sl already drilled to support, the ground for ream-drilling would become soft and may collapse to relatively large masses to fall into the pilot hole Sl. The roller bits 530 then function to crush rock masses to small pieces which gather in the pilot hole Sl. The roller bits 530 should be equipped at a position not interrupting the flow of discharged drill cuttings (considering the case that drill cuttings are discharged through the front side of the reaming support as shown in Figs. 12c and 13c). Conventional roller bits are applied which are used in a general RCD arrangement. Of course, when crushed to small pieces by means of the roller bits 530, these small rock pieces are discharged the same as drilled mud in a reverse circulation manner.

<68> The embodiment shown in Figs.9 to 13 illustrates an example of a drill body in which one discharge pipe 200 and four air hammers 100 arranged in a cross shape therearound pass through and are accepted in the cylindrical canister 410 to be clamped. Of course, it is possible to arrange one discharge pipe 200 and two air hammers 100 therearound in parallel or three air hammers in a triangular structure. Furthermore, it is possible to arrange 5 or more air hammers 100 in balance. Also, not shown, it is possible to use a disc-type flange 420 instead of the cylindrical canister 410 for clamping (see Fig.6). As shown in Figs.9 to 13, however, if a cylindrical canister 410 is used, it is required to form the cylindrical canister 410 to have an indented part 411 in the center of the cylindrical canister 410, so that the reaming support 500 can smoothly enter and come out of the indented part when the reaming support 500 slides into the front end of the discharge pipe 200.

<69> In addition, Fig.11 illustrates examples of air discharge holes 111 in the drill body for ream-drilling depending on the position of the holes 111. In Fig.11a, the air discharge holes 111 are positioned inside of the cylindrical canister 410 and formed toward the outside of the discharge pipe 200. In Fig. ll(b), the air discharge holes 111 are positioned outside of the cylindrical canister 140 and formed toward the front side of the bit 110. The drill body shown in Fig.11a should be formed with through- holes 220 in the discharge pipe 200 to enable the discharge pipe 200 to communicate with the cylindrical canister 410 each other as in the drill body shown in Figs.3 to 5. Such a drill body operates when compressed air is supplied as in Fig.12. The drill body shown in Fig. lib does not need the through-holes 220 formed in the discharge pipe 200. Such a drill body operates when compressed air is supplied as in Fig.13.

<70>

<7i> 2. Method of drilling by means of a drill with a reverse circulation inducing air hammer

<72> Figs.14 and 15 illustrate the steps of drilling by means of a drill with a reverse circulation inducing air hammer according to the invention. The method of drilling a hole according to the invention comprises the steps of drilling a pilot hole and ream-drilling. Before carrying out drilling a hole, phases of drilling should be planned as in Fig.14a.

<73> The drill with a reverse-circulation inducing air hammer comprises a previously described drill body H with a reverse circulation inducing air hammer, a rod R coupled to communicate with the outlet in the discharge pipe 200 of the drill body; an air compressor for supplying compressed air to the first and second air supply pipes 310 and 320 of the drill body; and a solid discharge line P equipped to communicate with the rod R.

<74> In particular, in the invention, a solid discharge line is proposed which comprises a plurality of unit pipes and connection strings. Such a solid discharge line enables the compressed air discharged in a reverse circulation manner to be separated from solids in the drill cuttings and thus to achieve smooth discharging of the drill cuttings. The unit pipe Pl is a tubular member shaped a truncated cone or pyramid of which the width gets narrower and narrower in lower parts and a plurality of unit pipes Pl are superimposed one above the other. The connection strings P2 connect the lower part of one upper unit pipe to the upper part of the other lower unit pipe thereunder in the configuration of the plurality of unit pipes Pl superimposed one above the other. In this case, the length of the second connection string P2 is determined to form a gap between the lower part of the upper unit pipe and the upper part of the lower unit pipe when it is spread. With this measure, while drill cuttings are discharged through the inside of the superimposed unit pipes P (discharged by free falling) one above the other, the compressed air is discharged through the gap between the unit pipes (moved and discharged to the outside of the unit pipes by means of density difference). Since the compressed air is discharged in the middle together with the drill cuttings, the drill cuttings are discharged without being disturbed by the compressed air.

<75>

<76> (1) Primary drilling - drilling a pilot hole Sl (see Fig. 13b)

<77> (a)Arrange a drill body:

<78> The drill body for drilling a pilot hole shown in Fig. 3 or 6 is first equipped in a drill. The front end bit 110 of each of the air hammers in the drill body is positioned on the surface of the ground to be drilled.

<79> (b) Induce reverse circulation-"

<8o> Compressed air is supplied to the second air supply pipe 320 in the drill body for drilling a pilot hole before driving the air hammer 100. When the compressed air is supplied to the second air supply pipe 320 by means of an air compressor, the very compressed air flows along the second air supply pipe 320 and then enters the discharge pipe 200. The compressed air which entered the discharge pipe 200 as such is discharged while forming a reverse circulation flow. Initial reverse circulation is thereby achieved through the discharge pipe 200.

<8i> (c) Proceed to drill:

<82> Drilling proceeds while supplying compressed air to the first air supply pipe 310 in the drill body thus to drive the air hammers 100. The compressed air used in having driven the air hammers 100 is discharged to the outside of the bit 110 (front side of the bit or the inside of the cylindrical canister) through the air discharge holes 111 in a reverse circulation manner. The compressed air discharged as such functions to induce the drill cuttings to the inlet 210 at the front end of the discharge pipe 200 while being discharged along the discharge pipe 200. Since initial reverse circulation proceeded in the above step (b) , however, the flow for discharging drill cuttings is easily induced, and the drill cuttings is thereby smoothly discharged without being lost as in Fig.14. The drilling process as described above may be applied with circulating water, etc., if required.

<83> Furthermore, in the process of drilling, it is possible to stop supplying compressed air through the second air supply pipe 320. It is because the initial reverse circulation induced by supplying compressed air through the second air supply pipe 320 can be kept with the compressed air used in having driven the air hammer 100. It can be realized by gradually supplying compressed air in the multi-air hammer structure as described above.

<84>

<85> (2) Secondary drilling- ream-drilling (S2, S3, S4, S5) (see Fig. lie)

<86> (d)Arrange drill arrangement •'

<87> The drill body for ream-drilling shown in Fig.9 is equipped in a drill. The reaming support 500 is inserted in the drill body and placed in the pilot hole Sl already drilled while the front end bit 110 of each of the air hammers is positioned on the surface of the ground to be drilled around the pilot hole.

<88> (e) Induce reverse circulation'-

<89> Initial reverse circulation is induced by supplying compressed air in the drill body for ream-drilling to the second air supply pipe 320 as for the primary drilling.

<9o> (f) Proceed to ream-drill:

<9i> As for the primary drilling, drilling proceeds by supplying compressed air to the first air supply pipe 310 in the drill body for ream-drilling while driving the air hammers 100. Since drilling proceeds while the ream support 500 is already positioned in the pilot hole already drilled, however, drilling proceeds while reaming the area around the pilot hole Sl.

<92> If secondary drilling comprising the steps of (d) to (f) is carried out repeatedly while increasing the diameter of reaming (S2, S3, S4, S5), it is possible to achieve drilling a hole in large diameter. That is, it is to repeat drilling with a drill body for ream-drilling while increasing the size of the reaming support 500 corresponding to a hole diameter of drilling.

<93>

[Industrial Applicability]

<94> The invention has been described in detail with reference to the embodiments in the above, but it will be apparent to those skilled in the art that various replacements, additions and modifications can be made thereto without departing from the scope of the invention described above. It should be understood that such modified embodiments belong to the scope of the invention as claimed in the accompanying claims of the invention.

<95> The invention resides in each and every novel characteristic feature and each and every combination of the features.

<96> Reference numerals in the claims do not limit the protective scope of these claims. The use of the verb "to comprise" and its conjugations does not exclude the presence of elements other than those stated in the claim. The use of the article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

<97>

Claims

[CLAIMS] [Claim 1] <99> A drill body with a reverse circulation inducing air hammer and equipped at the front end of a rod of a drill, comprising: <ioo> an air hammer (100) driven by compressed air supplied and provided to percuss a bit (110) at the front end thereof; <ioi> a discharge pipe member (200) formed with a discharge passage running from an inlet (210) at the front end thereof to an outlet at the back end thereof, to be clamped with the air hammer (100), while the inlet (210) is located on the further inner side than the front end bit (110) head of the air hammer (100) and the discharge pipe receives the air hammer (100) or is arranged next to and in parallel to the air hammer (100); <iO2> a first air supply pipe (310) passing through the back end of the air hammer (100) to communicate with the front end bit (110) to which compressed air is supplied for driving the air hammer (100); and <iO3> a second air supply pipe (320) arranged to communicate with the discharge passage of the discharge pipe (200) to which compressed air to be discharged to the discharge pipe (200) is supplied, <i04> characterized in that the front end bit (110) of the air hammer is formed with air discharge holes (111) extending from the first air supply pipe (310) and toward the outer side of the bit (110).

[Claim 2] <iO5> The drill body as claimed in claim 1, characterized in that the first air supply pipe (310) and the second air supply pipe (320) are formed to branch from one air supply pipe, and in that a switch valve is equipped at a point where they are branched from the one air supply pipe.

[Claim 3] <IO6> The drill body as claimed in claim 1, characterized in that a check valve is equipped in the second air supply pipe (320).

[Claim 4] <i07> The drill body as claimed in any one of claims 1 to 3, characterized in that it further comprises a front end shoe (130) for enclosing the front end bit (110) head of the air hammer while opening the inlet (210) at the front end of the discharge pipe (200). [Claim 5]

<iO8> The drill body as claimed in any one of claims 1 to 3, characterized in that a plurality of air hammers (100) and a plurality of first air supply pipes (310) consist of a multi-air hammer structure!

<iO9> the plurality of air hammers (100) are arranged close to and in parallel to the discharge pipe (200); and the plurality of air hammers (100) and discharge pipes (200) pass through and are accepted in a cylindrical canister (410) or pass through and are inserted in a disc-type flange (420) then to be c1amped. [Claim 6]

<πo> The drill body as claimed in claim 5, the plurality of discharge pipes (200) being arranged to be next to and in parallel to the plurality of air hammers (100), characterized in that the back end of the plurality of discharge pipes (200) is connected each other to lead to an integrated discharge pipe (230) . [Claim 7]

<πi> The drill body as claimed in any one of claims 1 to 3, characterized in that a plurality of air hammers (100) and a plurality of first air supply pipes (310) consist of a multi-air hammer structure!

<ii2> the discharge pipe (200) is arranged in the center, and the plurality of air hammers (100) are arranged in parallel to the discharge pipe (200) while forming one and the same circular track around the discharge pipe (200); and

<ii3> the plurality of air hammers (100) and the discharge pipe (200) pass through the circular canister (410) and are accepted in the cylindrical canister (410) or pass through and are inserted in a disc-type flange (420) then to be clamped. [Claim 83

<ii4> The drill body as claimed in claim 7, characterized in that the front end of the discharge pipe (200) is equipped with a reaming support (500) of which the outer side is adjacent to the front end bit (110) of the air hammers and protrudes further forward than the front end bit, and the reaming support (500) is formed with inlets (521) to communicate from the outer side thereof to the inlet (210) at the front end of the discharge pipe (200). [Claim 9]

<ii5> The drill body as claimed in claim 8, characterized in that the reaming support (500) comprises an insertion pipe (510) for insert-coupling it to the inlet (210) at the front end of the discharge pipe, an extended wing pipe (520) extending in a flare shape from the front end of the insertion pipe, and inlets (521) formed to communicate with the insertion pipe (51) at the outer side of the extended wing pipe (520); and

<ii6> the extended wing pipe (520) protrudes or does not protrude further forward than the bit (110) at the front end of the air hammer in the reaming support (500) by adjusting the position of insertion coupling of the insertion pipe (510). [Claim 10]

<ii7> The drill body as claimed in claim 9, characterized in that the reaming support (500) comprises roller bits (530) equipped on the front side of the extended wing pipe (520). [Claim 11]

<ii8> A drill with a reverse circulation inducing air hammer comprising'-

<ii9> a drill body H as claimed in any one of claims 1 to 3;

<12O> a rod R coupled to communicate with an outlet of the discharge pipe (200) in the drill body!

<i2i> an air compressor for supplying compressed air to the first and second air supply pipes (310 and 320) in the drill body; and a solid discharge line P equipped to communicate with the rod R,

<122> characterized in that the solid discharge line (P) comprises a plurality of unit pipes (Pl) superimposed one above the other, shaped a truncated cone or pyramid of which the width gets narrower and narrower in the lower part thereof, and connection strings (P2) for connecting the lower part of one upper unit pipe to the upper part of the other lower unit pipe thereunder, and there is formed with a gap between the lower part of the upper unit pipe and the upper part of the lower unit pipe while the lower part of the upper unit pipe is superimposed on the upper part of the lower unit pipe when the strings (P2) are spread.

[Claim 12] <123> A method of drilling a hole in a reverse circulation inducing manner, characterized by comprising the steps of: <i24> positioning a front end bit (110) of the air hammer in a drill equipped with the drill body with the reverse circulation inducing air hammer as claimed in claim 1 on the surface of the ground to be drilled; <125> (b) supplying compressed air to the first air supply pipe (310) in the drill body in step (a); and <126> (c) carrying out primary drilling while driving the air hammer (100) by supplying compressed air to the second air supply pipe (320) in the drill body in step (a) .

[Claim 13]

<i27> A method of drilling a hole in a reverse circulation inducing manner, <128> (a) positioning the front end bit (110) of the air hammer in a drill equipped with the drill body with the reverse circulation inducing air hammer as claimed in claim 5 on the surface of the ground to be drilled; <129> (b) supplying compressed air to the first air supply pipe (310) in the drill body in step (a); <i3o> (c) forming a pilot hole (Sl) by carrying out primary drilling while supplying compressed air to the second air supply pipe (320) thereby to drive the air hammer (100) in the drill body in step (a); <i3i> (d) providing the drill with the reverse circulation inducing air hammer as claimed in claim 7, placing the reaming support (500) in the pilot hole (Sl), and then positioning the front end bit (110) of the air hammer on the surface of the ground to be drilled around the pilot hole (Sl); <132> (e) supplying compressed air to the first air supply pipe (310) in the drill body in step (d) ; and

<133> (f) carrying out secondary drilling thus to form holes by ream-drilling while supplying compressed air to the second air supply pipe (320) in the drill body in step (d) and thereby driving the air hammer (100). [Claim 14]

<134> The method as claimed in claim 13, characterized in that the steps of (d) to (f) are repeatedly carried out while increasing the diameter of ream- drilling thereby to achieve drilling a hole in larger diameter.