AP273A

AP273A - A method of fracturing rock or similar material.

Info

Publication number: AP273A
Application number: APAP/P/1991/000327A
Authority: AP
Inventors: Howard Dixon Bruce
Original assignee: Howard Dixon Bruce
Priority date: 1990-10-17
Filing date: 1991-10-16
Publication date: 1993-03-04
Also published as: CA2094729A1; YU167391A; MX9101573A; EP0559658A1; FI931744L; US5087100A; JPH06504335A; OA09397A; MC2328A1; EP0559658A4; HU9301118D0; NZ240242A; ZA918202B; BR9107048A; WO1992007169A1; MA22483A1; SK35893A3; AP9100327A0; HUT63911A; FI931744A0

Abstract

A method of fracturing a hard compact material such as

Description

λ METHOD OF FRACTURING ROCK OR SIMILAR MATERIAL

BACKGROUND

Iht present invention relates to a method and apparatus for fracturing rock or similar material, in a way so aj to achieve removal of large pieces of such material.

A conventional method of breaking rock is to drill into the rock and set explosive charges to blast away sections cf rock. Aside from the noise, flying rock frig-aunts and debris the drill-and-blast technique is somewhat unpredictable and frequently er.tails extra cost. Another technique is that of coring which involves drilling a haJe in the shape of a cylindrical sleeve and then inserting tools into the sleeve-like opening and by impacting the tools attempting to fracture the central core of i.clid material. Unfortunately, it is common for the tools to become jammed in the hole or, for the core to break lntc many snail pieces so that removal of the pieces becomes time consuming and inconvenient.

U. S. Patent No. 99,595 issued February 8, 1870 to Robt discloses a technique of filling a drilled hole with water cr ether liquids, and then inserting a plunger fitted to work as tightly as possible above the water, and subjectinc the plunger to impact forces such as by a hammer blow. The pressure transmission through the liquid imparts force over the side wall and causes fracturing. There is a practical .‘Limitation of the latter method due to the need to sea] the water at the side wall between the plunger and the hole. Any leaks reduce substantially the pressure developed in the liquid.

U. S. Patent No. 3,988,037 issued October 26, 1976 disclose» a method similar to Robb in that a pre-drilled hcl< is filled with hydraulic fluid. A piston is then dri·. e.i into the hole at speeds ranging up to several hundred meters per second by means of a gun to impact the fluid and

INAL d causa tensile stress cracks in the material by the estao.’.isbed pressure. Such techniques are not amenable to non-/nrtical holes. Moreover, the rapidly moving piston presents a potential hazard to a user.

U. S. Patent No. 3,507,540 issued to Silverman on April 21, 1970 uses an expandable packer filled with pressurized hydraulic fluid. A circular channel or kerf is drilled ard possibly a central hole drilled as well. The pa eke:* is .inserted into the bottom of the central hole and the fluid pressure increased until the core fractures. Alternatively, a pair of packers may be inserted into the circular channel at diametrically opposite locations and the pressure then increased until fracturing occurs. The Silverman method requires pumps, a tank and piping leading to and frem the pump to the packer. In addition, there is a 1 Lmit es to the forces the walls of the packer can withstand without rupturing.

Accordingly, it is an object of the invention to provide zir. improved method of and apparatus for fracturing rock. It. is a further object of the invention to provide a method of fracturing and removing large pieces of rock or other similar materials. It is yet another object of the invention to provide a method of fracturing rock which is simpler, more reliable and less expensive than predecessor methods.

SUMMARY OF THE INVENTION

According to the invention there is provided a roetloi of fracturing rock and other similar material in which a hole has been pre-drilled in the area to be fractared which includes inserting into the hole, to the bottom thereof, an outer slug of solid material and then

AP 0 0 0 2 7 3 fracture the rock.

Preferably, the outer slug and hole are cylindrical and the outer slug has a length approximately equal to the diair.ater of the hole.

Advantageously, the force of impact is sufficient to exceed the yield point of the outer slug material and cause at : east on upper portion of the outer slug to become flu: 1.:2 ed.

An annular kerf may be drilled using an annular drill bit which surrounds the central hole with a core of rock prioi' to insertion of and inpacting the top of the outer slug so that, upon fracturing at least a substantial portion cf the core defined by the kerf, a transverse plane at Ths bottom of the hole is fractured and freed from the under.Lyir.g formation.

Thu outer slug material may be a solid malleable material.

A pin may be used to transfer impact to the outer slug which pin extends at least from an opening of the hole down to a top of the outer slug when fully inserted and of a material harder than the outer slug and dimensioned to fit into the hole with a diameter not more than 10 I less than that of the hole.

An inner slug may be inserted betwee the outer slug and tie hole and be of a material harder than that of the outer slug.

In another aspect of the invention there may be provided apparatus for fracturing a hard unitary material such is rock and cement, having a hole formed in an area of the material to be broken, which includes an outer slug of

BAD original soli 1 material having an outer surface conforming to the inner surface of the hole, and mean? for impacting the outer slug when inserted into the hole eit a bottom thereof.

Preferably the impacting means includes an elongated pin oi material harder than the outer slug and extending from a top of the outer slug to a point exterior of the hole .

The foregoing method and epparatuB provides for a reliable, simple and predicatable method and apparatus for cr*iat:.ng rock fractures. The method and apparatus is a relatively convenient, inexpensive method of excavating rock or certent in difficult confined locations, of coring such mate-.ala and of making large slabs.

BRIE? DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof, will be best understood by reference to the detailed description which follows, read in conjunction with the accompanying drawings, wherein:

Figure l is a cross-sectional view of a rock formation showing an annular kerf and a central hole with a slug ind pin inserted into the hole/

Figure 2 is a croes-secticnal view as in Figure 1 but following impacting pin 14 with a vertical impact force;

Figure 3 is a cross-sectional view of a formation showing ar. impact pin and a composite slug assembly;

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Figure 4 is a cross-sectional view of a formation wirh a plurality of holes and a pin and elug in one of the holes;

Figure 5 is a plan view of a formation with a plin.'.ity of holes lying in a row in which a fracture in a plir.a joining the holes is formed by the method of a preferred embodiment of the invention;

Figure 6 is a plan view of a formation with a plurality of holes formed in an array;

Figure 7 cross sectional view of an excavation for a building using a preferred embodiment of the present invention;

Figure 8 is a perspective view partly in section shoeing fracturing and release of a slab of a material; and figure 9 is cross sectional view of a formation shotting the utilization of a plurality of separate balls of material rather than a single slug in which the pin is used to conprese the balls and form a slug in situ;

figure 10 is a cross-sectional view taken along line AA of Figure I, of a rock formation showing an annular kerf and a central nole with a slug and pin inserted into the hole; and ligure 11 is an elevation view partly in section of a drill and drill bit having a central drill bit and an ar.nxlir drill bit.

DETMLEC DESCRIPTION OF THE INVENTION

Referring to Figure l there is shown in cross sec:ion a rock formation 11 having an annular kerf 10 and

central hole 12 cut into the rock using a drill 66 (Figure 11) having a drill bit 61 composed of an annular drill bit 62 and a central drill bit 60 where the central drill bit drillr. to a depth substantially equal to the depth of the kerf 10. A cylindrical slug 16 of aluminum of a length approximately equal to its diameter and of a diameter slignxly loss than that of the hole 12 is inserted into the hole 12 down to the bottom thereof. It is unimportant whether the slug fits tightly into the hole or not. Next a long pin 14 is inserted into the hole until it contacts the pin 14. ihe tolerance of the pin 14 is such that its diameter ray be 5 to 10 I smaller than the diameter of the hole 12.

Finally, as shown in Figure 2 a large impact force is directed vertically down on the top of pin 14 so that it appli-ae ar impact force to slug 16 which exceeds the yield point of the latter at least in the upper region thereof. The iilug then acts as a hydraulic fluid and transmits pressure to the side walls of the hole 12. The high visco3ity of the fluid together with the small passageway around the pin 14 effectively prevents significant reduction in tho pressure due to leakage. The pressure created by the decelaration of the pin over a very short distance, which may fce of the order of one millineter, is transmitted as pressure against the side of the hole 12 in the region of the s'.ug If.. Some extrusion of the slug 16 around the aides of th2 pir 14 will occur but because of the relatively high viscoaity cf the material when extruded, this escape will not significantly reduce the impact pressure transferred to the sice» of the hole 12.

~ri most cases the impacting device (not shown) which is applied to pin 14 need develop only a relatively small velocity in the region of 2 to 5 meters per second as, for example, by a simple drop hammer. The slug 16 and pin 14 may te impacted several times until the rock fractures.

Ar 0 U Ο 2 / 3

Provided a sufficiently large impact is effected, the core fractures In a transverse plane 20 at its base. It may also fracture vertically but only to leave relatively large pi'Sceu of rock which can later be easily removed. By the foregoing method large cores of rock may be removed without blasting or without the difficult Job of attempting to fracture tne core from the annular kerf 10 with chieele and the l;.ke. If the slug 16 fits only loosely in the hole 12, it will be expanded radially following impact until it contacts the side wall of the hole 12 after which further impacting will cause the rock to fracture.

Referring to Figure 3 there is shown a formation in cross section with a pin 14 inserted into a hole 12 and contacting an outer slug 30 of relatively hard but malleable material . The outer slug 30 rests on an inner slug 29 of much softer material. The outer slug 30 can be copper or aluminum while the inner slug 29 can be lead or even rubber. Impacting the pin causes a transverse pressure to be created against ths sides of the hole 12 along the whole of the length of slug 29. By making slug 29 long, a tendency to fracture Che formation along a vertical plane will be created. The function of outer pin 3 0 is to seal the material of the inner slug 29 and prevent diminution of pressure through escape of material of slug 29 up the sides of the hole upon impact. The outer slug 30 upon impact has a reduced tendencey to escape between the sides of the slug 30 and the hole 12 because of its higher viscosity.

Another application of the invention is shown in Figure 4 in which an array of holes 22 are drilled in a rock formation. Next the rock is fractured using slug 16 and pin 14 Jn a plane transverse to the holes 22 at their base, as in Figure 2. If the holes 22 lie in a line as in Figure 5, and a configuration as in Figure 3 is used, then fractures 27 lying in the plane through the longitudinal axes of the holes will be created. However, if the array is as shown

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I in Fiqure ό, then a configuration with a ehorter inner slug could be used to fora transverse fractures 26 as in Figure 4, intercepting nearby adjacent holes proximate the bottom thor-ac.f, as well as fractures 36 through the holes 22 in orthxonal directions. Further application of the technique in these nearby holes extends the plane of fracturing transversely until large sections of rock are loosened from the fcreation and can be removed.

Clsarly there are many possible choices of materials for t.’ie slugs such as various plastics and harder metals such as iron and steel. The preferred choice of material deposes on both the length of hole over which pressure Is to be t.:e n»f erred and the characteristics of the material to be frac zi.red.

Referring to Figure 7, there is shown how an array of hx’.es drilled horizontally as in Figure 6 can be used to exca/iite a building site in a location where blasting is unacceptable. First a vertical excavation over a limited arsa is carried out down to a desired depth. Next the exca/iiticn is widened by drilling and impacting an array of horizontally directed holes until the boundary of the site is reached.

Another application of the invention is shown in Figure 3 in which a parallel series of holes 34 are drilled into a bench of rock 31 formed on a rock face 33. Such a beocn 31 is formed after several slabs have been removed fron trace 13 from the top down to the level of bench 31. A horizontal series of holes 32 are also drilled to that they pa is betwe en respective ones of holes 3 4 near the bottom thereof. A composite slug such as 29 and 30 shown in Figure 3 ire inserted into each of holes 32 and 34 and impacted as pnviously described with reference to Figure 3. The longitudinally extended pressure transferral results in a frictures. 34 and 35 not only in a transverse plane but also

t '0 2 7 5 a lor. j the plane passing through the set of parallel holes 32 and 34 being fractured, λ resultant slab is formed which is reli illy defined by the planes through the two sets of holes 32 a k, 34.

Relerring to Figure 9 there is shown an alternative meth xl cf fracturing rock utilizing individual pieces of slug material, in this case in the form of balls 50. Pin 14 is used tc compress the balls into a slug defined by the diweviions of the hole 12. Further impacting of the slug so form ad resu lts in fracturing of the rock formation.

Accordingly, while this invention has been described wi:h reference to illustrative embodiments, this description is net intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well <is other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this desc-..ption. It is therefore contemplated that the appended clur.n will cover any such modifications or embodiments as fall within the true scope of the invention.

Claims

1. A method of fracturing a hard compact material such ae rxk or concrete which has a hole pre-drilled in the area to fca fractured, comprising:

inserting a slug of solid material into said hole, to a bottom thereof; and impacting 3aid slug with a force sufficiently large to cause said slug to transfer the impact by hydraulic action to the sides and the bottom of said hole so as to fracture material surrounding said hole.

2. A method according to claim 1, wherein said hole and said slue are cylindrical.

3. A method according to claim 1, wherein the length of said slug :.3 approximately equal to its diameter.

4. A nethod according to claim 1, wherein the force of impact in sufficient to exceed the yield point of the slug material and cause at least an upper portion of said slug to beccma fluidized.

5. A method according to claim l, including drilling an annular kerf so as to surround the hole down to a depth appi oximately equal to the depth of the hole prior to insertion of and impacting the top of said slug so that at least a substantial portion of a core defined by the kerf and transversely by the bottom of the hole is fractured and free of the underlying formation.

6. A method according to claim 1, wherein said slug is a malleable solid material.

° Ο Ο Ο 2 7 3 11

7. A method according to claim l, Including a pin expending at least from an opening of said hole down to a top of said slug when fully Inserted, said pin composed of a net aria] harder than said slug and dimensioned to fit snugly in said hole.

8. A method according to claim 1, wherein said slug is in tie form of pieces of material.

9. A method of fracturing a hard compact material such as rock or concrete which has a hole pre-drilled in the area to fcj fractured,comprising:

inserting first an inner slug and then an outer slug into :said hole to a bottom thereof, wherein both slugs are of solid material and said outer slug of a harder material thir. oaid inner slug; and

Impacting said outer slug with a force sufficiently large to cause said inner and outer slugs to transfer the imoait by hydraulic action to the sides and the bottom of said hole «.o as to fracture material surrounding said hole.

10. A method according to claim 9, wherein said inner and outer slugs are of a malleable solid material.

11. A method of fracturing a hard unitary material such .13 rock and cement, comprising:

drilling a hole in said material:

Inserting a cylindrical slug of solid material into said hole;

inserting a pin into said hole which fits snugly intc uaii hole and extends from an exterior thereof down to a tcp cf said slug; and

BAD ORIGINAL &

impacting said pin with a force sufficiently large to cause said slug to transfer the impact by hydraulic action tc the sides and the bottom of said hole so as to fractvre material surrounding said hole.

12. A method according to claim ll, including drilling at annular kerf substantially concentric with said hole prior to inserting and impacting said elug so that after Impacting said slug a core of material within said kerf is fractured in at least a plane transverse to said hole between the kerf and the hole at a level of approximately a bottom of said hole.

13. A method according to claim 11 or 12, wherein said slug is cylindrical with an outer surface substantially conforming to the inner surface of the hole.

14. A method according to claim 11 or 12, wherein said slug is in the form of individual pieces which, upon impact become fused into a piece whose shape is substantially defined by the shape of said hole.

15. A method of fracturing a hard unitary material such as rock and cement, comprising:

drilling a hole in said material:

inserting first an inner cylindrical slug and then an outer cylindrical slug into said hole, wherein said slugs are of solid material, and said inner slug is longer than sale outer slug and has a substantially lower yield point than said outer slug;

inserting a pin into said hole which fits snugly intc said hole and extends from an exterior thereof down to a tep cf said outer slug; and badowg’N*¹· S

AP Ο Ο Ο 2 7 3 impacting said pin with a fore· sufficiently large to cajse at least a top portion of said outer elug to trar. der the in.pact by hydraulic action to the sides and the bottir. of said hole so as to fracture material surrounding sate hole.

16. A method of fracturing a hard unitary material such ts rotk and cement, comprising:

drilling a plurality of holes in said material de*i r.ng a preselected pattern;

Inserting a slug of solid material into each of said holes inserting a pin into each of said holes of a size whicn fits snugly into said holes and extends from an exte.-.or thereof down to a top of said slug; and impacting said pin with a force sufficiently large to cause said slug to transfer the impact by hydraulic action to the sides and the bottom of each of said hole so as to frecture material surrounding said hole.

17. A method of fracturing a hard unitary material such is rccX and cement, comprising:

drilling a plurality of holes in said material def.nlr.g a preselected pattern;

..rserting first an inner slug and then an outer slug intc each of 3aid holes, wherein said plugs are of solid material, said outer slug being of a material substantially harcer then said inner slug;

bad

ORIGINAL inserting a pin into each of said hoi·· of a size •vhich fits snugly into «aid holes and extends from an exterior thereof down to a top of said [outer] slug; and impacting said pin with a force sufficiently large to ctua slid inner and outer slugs to transfer the impact hy hydraulic action to the sides and the bottom of said hole so ai to fracture material surrounding said hole.

18. A method according to claim 17, wherein said pattirr. is a first set of vertically directed ones of said plursl.ixy :f holes forming a straight line and a second set horizontally directed ones of said plurality of holes forming a straight line and terminating proximate bottoms of said first set of holes so that following Impact said material i3 fractured in a vertical plane through said vertically directed holes and horizontally through eaid horizontally directed holes.

19. Apparatus for fracturing a hard unitary material such as rock and cement, having a hole formed in an area of the material to be broken, comprising:

a slug of solid material having an outer surface conforming to the inner surface of the hole; and means for impacting said slug when inserted into said hole at a bottom thereof so as to impart by hydraulic action the force of the impact upon the sides and the bottom of said hole.

20. Apparatus according to claim 19, wherein said impacting means includes an elongated pin of material harder than 3aid slug and extending from a top of said slug to a point exterior of said hole.

AP Ο Ο Ο 2 7 3

21. Apparatus according to claim 19, wherein the mate_-Jal of said slug is a solid malleable material.

22. Apparatus for fracturing a hard compact mate.-Jal such as rock and cement, comprising:

a drill having a central drill bit and an annular drill bit for forming a central hole and an annular kerf concn<tric with said hole down to approximately the eaid depti as said hole;

malleable material capable of being fused upon impact sc as to conform to the interior surface of a hole drilled ty said central hole drill bit;

an elongated pin of substantially the same diameter as si:.d central drill bit and extending from a top of said ma*:er:.al, vhen placed at a bottom of the central hole, to a polnc exterior to the hole; and means for impacting said pin vith sufficient force so as to exceed the yield point of said material and transfer impact pressure to the side of said hole so as to fracture said material.