METHOD AND DEVICE FOR THE EXTRACTION OF BLOCKS FROM A ROCK FORMATION

Abstract: Extraction from rock formation of blocks of rock that are already of a paralellepiped shape and thus do not require final time consuming finishing operations involves cutting a long slot in the formation beneath a slice of rock to be removed and then drilling various orthogonal series of parallel aligned perforations to define cutting surfaces that are separated using metal plugs applied to the perforations. In this manner parallelepiped shaped small blocks are obtained directly and can be removed from the formation in a stage virtually ready for commercialisation. Equipment in the form of an extractor (1-28) permits the simultaneous formation of the slot and the perforations.

Description: Method and device for the extraction of blocks from a rock formation. The present invention refers to the extraction of parallelepiped shaped blocks of rock from a rock formation and to an extractor to be used for such purpose. The extraction of ornamental blocks of rock from rock formations, especially of granite, began to shows signs of advancement in recent years with the development of spe¬ cific explosives. Such explosives are placed in drill holes aligned along one or more cutting planes and then detonated simultaneously so as to make extraction more rapid. Figures 1 to 4 of the accompanying drawings illus- trate the most common method presently used for the extraction of blocks of rock from solid rock formations. Fundamentally, it comprises the following steps: Step 1: as shown in Figure 1, a large block of rock having, for example, a volume of 100 to 400 cubic meters is freed from the rock formation. Slots or channels are opened along the sides of the block of rock to be removed so as to relieve internal stresses. The slots or channels are normally opened by means of jet flame burners or slot-drills forming secant perforations. Rear, vertical and/or horizontal perforations are then drilled and the rock block is separated by the simultane¬ ous detonation of explosives placed in such perforations. One manner of carrying out this method is to take advantage of the natural separations found in many rock forma- tions. In order to extract the block, it is sufficient to drill the spaced aligned perforations suitably arranged in a plane normal to the plane defined by the natural separation in the rock formation and then to detonate the explosives placed in such perforations. Another manner is not to make the vertical perfo¬ rations, but rather to open a rear slot or channel and to drill perforations in the plane of the natural separation, then simultaneously detonating the explosives placed in such perforations. Stage 2: as shown in Figure 2, in this step the block of rock is sub-divided along the planes of separation defined by corresponding aligned drillings, separation being obtained by means of explosives or metal plugs driven into the drillings so as to produce smaller blocks of rock of commer¬ cial size. Stage 3: as shown in Figure 3, this stage concerns the finishing of the block of rock by squaring it perfectly using closely spaced aligned drillings, the block being cut by means of plugs driven into the drillings or alternatively cut¬ ting is effected by means of manual tools. Only then will the block be in condition for being passed for final processing in rock slicing machines. The following problems in the above method are to be noted: - low yield. When explosives are used, the block does not always separate from the rock formation in the manner intended, be it due to lack of precision in the calculations for the explosive, be it due to a misalignment of the rear perforations with respect to the cutting plane; - since the vertical and horizontal perforations are normally deep, it is necessary, as shown in Figure 4, to pro- vide for an angle greater than 90° between the planes formed therebetween so as to avoid jamming of the separated block. This makes it necessry to square the block of rock later which means loss of material and additional finishing work. • The purpose of the present invention is to overcome the majority of the above problems by means of a process that permits the extraction of effectively already finished blocks that do not have the cracks or microfissuras that usually ap¬ pear when conventional processes are used, thus ensuring an improved yield with less labour. A further object of the present invention is to pro- vide an extractor of blocks of rock for carrying out the proc¬ ess. According to the present invention, a process for preparing the exposed surface of a rock formation to permit the extraction of parallelepiped shaped blocks of rock ready for final processing, comprises the steps of: a) cutting into the surface of the rock formation a slot having a depth substantially equal to a width dimension of said blocks; b) drilling into said surface of the rock formation a first series of parallel aligned perforations orthogonal to said slot, said perforations terminating along the bottom of said slot and defining a first cutting surface orthogonal to the plane of said slot; c) drilling into said surface of the rock formation a plurality of parallel second series of parallel aligned per¬ forations, said perforations of each of said second series de¬ fining a second cutting surface orthogonal to the plane of said slot and to said first cutting surface; d) separating by the use of plugs applied in the perforations of said first and second series, the blocks de¬ fined by steps a) to c); and f) carrying out steps a) to d) repeatedly so the the slot of step a) is cut from the exposed surface of the rock formation, beginning along a line defined by the outer ends of the perforations of said first series of perforations, whereby the exposed surface of the rock formation, after extraction of the various blocks in steps d), acquires a stepped profile. Further according to the invention, a process for extracting parallelepiped shaped blocks of rock ready for final processing, from a rock formation having an exposed sur¬ face with a stepped profile, comprises the steps of: a) cutting orthogonally into a first surface of one step of said stepped profile a slot of a depth equal to that of the second surface of the same step, said slot being cut slightly above the plane of the second surface of the imme¬ diately previous step; b) cutting orthogonally into the second surface of the same step a first series of parallel aligned perforations along the junction between said second surface of the same step and the first surface of the immediately following step, the perforations of the first series extending to the bottom of said slot; c) cutting orthogonally into the second surface of the same step a plurality of parallel second series of parralel aligned perforations extending to said slot, said second series defining lines normal to said junction; d) separating by the use of plugs applied in the perforations of said first, and second series, the blocks de- fined by steps a) to c) ; and e) repeating steps a) to d) with respect to the fol¬ lowing steps of the profile of said rock formation, extracting the respective blocks of rock. Preferably, the slot is cut by means of secant per- forations and the first, second and third series of perfo¬ rations are effected by drilling hammers. The present invention also provides an extractor for extracting blocks of rock from a rock formation, that com¬ prises a structure formed by a front frame, a cental frame and a rear frame, said front and rear frames being perpendicular to said central frame, each said frame being associated with at least one respective perforation system. Each perforation system preferably includes at least one pair of rails and a support carriage mounted for displace- ment along said rails, the pairs of rails of the three perfo¬ ration systems being orthogonal with respect to each other. Moreover, the support carriage of each perforation system may include a pair of upright support guides perpendic¬ ular to its respective pair of rails, a perforation tool being displaceable along said support guides. The perforation system associated • with said front frame may be a slot-cutter whereas the perforation systems as¬ sociated with the central and rear frames may comprise hammer drills. The carriages of the extractor are preferably driven by electric motors and locking means may be provided for lock¬ ing each carriage in predetermined positions along their re¬ spective pairs of rails, adjustable support jacks being arranged under said central and rear frames for the correct positioning of said extractor on a rock formation. Auxiliary wheels on the central and rear frames -may be included for the support and displacement of the extractor over the rock formation. A process according to the present invention will now be described, by way of example, with reference to Figures 5 to 30 of the accompanying drawings, in which: Figura 5 shows a slice of rock displaced from the rock formation and having a width and height equal to the thickness (e) and length (c) of the blocks of rock to be ex¬ tracted. After the slice of rock is freed, it is chopped into blocks of rock having the desired width L of the blocks so that they can be extracted without requiring finishing. In this process the slot or channel is opened with a slot-drill using secant perforations. The slot is opened on or near the rising or levant plane of the rock formation and has a depth equal to the depth of the block of rock to be ex¬ tracted. In the conventional processes, the slot is opened vertically or perpendicularly to natural separations, when there are any in the rock formation, and is normally deeper than that used in the present process. Since the depth of the slot is now limited to the thickness of the blocks, its opening is facilitated in a posi¬ tion where it is difficult to work, it being possible to make it horizontal or inclined to accompany the levant plane of the rock formation. Figure 6 shows the slice of rock with the bottom slot opened and still held to the rock formation by means of face B. When face B is cut by means of plugs, the weight of the block makes it displace itself by a few centimeters which assists in the freeing of the individual blocks at the time of their extraction. Since the height of the slice of rock is limited to the length of the blocks to be extracted, cutting face B, which is still part of the rock formation, by means of metal plugs is facilitated, there being no need for the use of ex- plosives. Figure 7 is a front view of the rock formation and preliminarily defines the most suitable position for ex¬ traction of the blocks of rock, taking the following into con¬ sideration: - the cutting planes of the rock. The closer the perforations are situated to such planes, the more spaced they may be, which makes extraction more economical; - the designs on the rock formation in relation to the finished blocks? and - the equipment to be used for manoeuvering the blocks of rock during extraction. Once the position of the slice of rock to be ex¬ tracted from the rock formation has been defined, a slot A is first opened in the surface of the rock formation by means of continuous cut drilling. Preferably, face A acompanies the levant plane of the formation and the corresponding slot A is opened using secant perforations. Face B, perpendicular to face A, is cut using metal plugs, in a plane of perforations made with hammer drills, the spacing between perforations being determined by the type of rock formation. As shown in Figure 7, axis YY' - which is the inter¬ section of faces A and B - should be positioned in such a way that it passes out of the exposed surface of the rock forma- tion at its two ends, it having an inclination (alpha) with respect to the horizontal that permits gravity assisted with¬ drawal of the blocks. As can be seen from Figure 8, after cut¬ ting of face A, the material (slice of rock) to be initially extracted will be held to the formation only by face B. It will be understood from Figures 9 and 9a that, if the rock formation does not fall away at the two ends of of axis YY', it will be necessary to open a slot with the slot drill using secant perforations at one of the ends of axis YY', depending on the case. Figure 10 is a perspective view of the reentrance opened in the rock formation during the first stage of removal of the initial slice of rock. The material extracted on forming faces A and B (see also Figure 12) does not provide blocks of rock at this stage. It will be cut into sizes that may be removed with the handl¬ ing equipment available at the site. Such cutting may be ef¬ fected using explosives in split perforations. Next, face A-^, parallel to face A, is cut using the same method of cutting as used for face A. The distance be¬ tween face A and face Ai will be the length (c) of the ex¬ tracted block plus an amount Z. Figure 13 shows the cutting of face B parallel to face B, using the same method as for cutting face B. The dis- tance between face B and face B-j_ will be the same as the thickness (e) of the block of rock to be extracted. The mass of rock between faces Ai and Bj will not produce a block and will be extracted precisely as was that between faces A and B. Figure 14 shows the sequential cutting of faces A2 and B2. Face A2 is parallel to face A^ with a spacing Z. The mass of rock delimited by faces A2 and B2 will be extracted just as in the case of the mass between faces A and B. As shown in Figure 15, faces A3 and B3 are then cut. Face A3 is parallel to face A2 and their spacing is equal to the distance between faces A and Aτ_. Face B3 is parallel to face B2 and their spacing is the same as the thickness (e) of the block of rock to be extracted. The mass of rock delimited by faces A3 and B3 is removed in the same manner as the mass between faces A and B, as shown in Figure 15. Whenever a new face A n is cut, it will be separated from face A n _ * L by (c+Z). If it does not attain this value, then the latter will be only Z. Figure 16 shows the cutting of faces A4 and B4 in the same manner as faces A2 and B2 and the mass of rock therebetween will be removed as in the case of the mass be¬ tween faces A and B. Faces Ai' are B^' are cut, face A-i ' being spaced by Z from face A and face B^' following the direction of face Bi at the point where the perforatons in face Bi terminate. Figures 17 to 23 show the sequence of the continua¬ tion of the cutting of slices from faces A n and B n . As is shown in Figura 24, Z is the smallest dimen- sion in which the drill succeeds in cutting between two faces A n and A n -1, it being noted that, in order to cut a face B n of a slice, it has to has to have the continuity of face B n of the immediately following or upper block of rock. Figure 25 shows a plug F. In order to cut a face B n next to a step, one has to use a plug F having a body length greater than Z. Figure 26 shows a slice of rock when blocks are be ¬ ing produced. The slice formed by faces A n and B n is sliced during block extraction along faces C, C^, C2«..C n which are parallel to each other and perpendicular to axis YY 1 , being spaced from each other by a distance equal to the width L of the blocks of rock to be extracted. As shown in Figure 27, the cutting of faces C n is effected using metal plugs in drilling planes made with hammer drills, the perforation interspacings being determined by the type of rock. With reference to Figure 28, cutting of faces C n with plugs is only effected after removing the block of rock originating from face C n _ι. After cutting face C n with plugs, a larger diameter plug G is used at the lower region of of face C n to separate the block of rock at this point from the rest of the slice of rock by a further 1 or 2 centimeters, this avoiding jamming. After this procedure, a steel cable Q is tied to to the top of the block of rock and hauled in the direction of axis YY' . As can be seen from Figure 29, the block of rock which was at right angles to axis YY', turns about an axis formed by face A n with face C n so as to lie along axis YY'. This rotation is relatively smooth since the block of rock is supported and therefore will be dragged over face .B during the turn without damaging the block. Once it is lying in position, the block of rock will be further hauled until it leaves the rock formation. It will then be ready, without any need for squaring operations or other basic fin¬ ishing. It should be noted that, at this point, the first cuts C, Ci, C2... made in triangular parts of the rock slices will not produce blocks of rock and the distances between such cuts are determined as a function of the masses of rock to be removed. On removal of the last slice from faces A n and B n , a formation L-L1- 2 will appear, representing the total volume of worked rock, as can be seen from Figure 23. It wiil be observed that the last blocks of rock supported on face B n at the end of the formation will have a smaller thickness (e) due to the impossibility of maintaining the same alignment during cutting of such last face. When axis YY' perforates the rock at its lower end (Figure 9), the block of rock may be hauled off the rock for- mation with steel cables, it being possible to adjust angle alpha so as to make better use of gravity assistance during this manoeuver. Where there is no possibility of hauling along axis YY' (Figure 9a), the blocks of rock may be removed by strate- gically placed cranes. As shown in Figure 30, when fork lift loaders are used to handle the blocks of rock, they will require platforms on which they can be driven. For this purpose, axis YY' will be made close to horizontal with a small inclination suffi- cient to ensure suitable drainage of rain water, as seen in Figure 31. A layer of earth will then be spread over the tops of the blocks of rock (face A) so as to produce a platform having a regular surface where it is easy to operate the load¬ ers. This earth will be removed as the lower platform ad- vances. The process of the present invention provides for the slots or channels of secant perforations to be opened in an inclined, position varying from 45° to almost horizontal. Existing equipment for opening such slots have been designed to work vertically or nearly vertically and at depths of up to six meters, it being difficult to adapt them to surfaces with steep inclinations. An extractor for blocks of rock according to the present invention will now be described in detail with re- spect to an exemplary embodiment shown in Figures 32 to 40. Figures 32 and 33 show such an extractor which com¬ prises a metallic structure formed from a front frame R, a central frame T and a rear frame S. Front frame R and rear frame S are perpendicualar to central frame T, each having a respective perforation system. As can be seen in Figura 34, the front frame is com¬ prised of a two-rail track 1 supported on three bars 2. On track 1 runs a carriage 3 which is the support for an upright support guide 4 that carries a slot drill Pi that opens the slot or channel of secant perforations. Carriage 3 is dis- placeable by means of a chain 5 driven by electric motor Mτ_. The upper portion of track 1 is provided with orifices 18 with spacings equal to the spacings between the perforations made in opening the continuous slot. Carriage 3 has an orifice 19 that coincides with orifices 18 so that it may be locked dur¬ ing opening of the perforations by drill Pi (Figure 34). Figure 35 shows that rear frame S is comprised of a two-rail track 6 supported on three supports 7. A carriage 8 runs on this track and mounts support guide 9 that carries a hammer drill P2 which opens the face B perforations perpendic¬ ular to the continuous slot of face A. Carriage 8 is also moved by a chain 10 driven by an electric motor M2. The upper portion of track 6 is formed with orifices 20 with spacings equal to the spacing between the perforations made by hammer drill P2. Carriage 8 has an orifice 21 that will coincide with orifices 20, permitting locking during drilling by hammer drill P2. Figure 36 shows the central frame T that is com- prised of three two-rail tracks 11 supported on parts 12 and 13. Part 12 serves as a base for the three bars 2 of front frame R. In their turn, tracks 11 support the three bars 7 of the rear frame S. On each track 11 runs a carriage 14 mounting a support guide 15 that carries a hammer drill P3 for drilling the perforations parallel to the slot in the blocks of rock. Carriage 14 runs on a rack 16, being moved by a cooperating pinion driven by an electric motor M3. Each track 11 is pro¬ vided with orifices 22 with spacings equal to the spacing be¬ tween the perforations made by the corresponding hammer drill P3. Carriage 14 has an orifice 23 that coincides with orifices 22, permitting locking during drilling by hammer drill P3. Frames R, S and T are reinforced with auxiliary beams 17 to increase the rigidity of the structure. As shown in Figure 37, in order to change the work¬ ing position, the extractor may be displaced by a system of steel cables 24 operated by a winch 25. Figure 38 shows how the extractor is supported dur¬ ing displacement. This is effected by means of three guide wheels 26 positioned at the edge formed by faces A and B of the slice of rock that have already been cut, as well as of four auxiliary wheels 27. During drilling, the extractor is supported on four support jacks 28 that permit the correct positioniong of the extractor on the rock. Figure 39 shows how the rear frame S is displaced along tracks 11 so as to facilitate the initial phase of drilling. In this position, both the auxiliary wheels 27 and the support jacks 28 work in positions that are perpendicular to the rock. As shown in Figure 38, such wheels and jacks are pivotally mounted on the extractor. Finally, Figura 40 is a perspective view of the com¬ plete metal structure formed by frames R, S and T. The auxil¬ iary reinforcement beams and two of the perforation systems, however, are omitted for clarity of representation. It is believed that the advantages of the present invention when compared with the conventional techniques de¬ scribed at the beginning of this specification will be abundantly clear to a person versed in the art. This, how- ever, is further emphasised when one considers that, quite apart from the savings in labour costs and the convenience of not having to provide a site for the various finishing oper¬ ations of the prior art, an enormous increase in yield of the reserve of rock in the formation may be obtained. This can to a certain extent be estimated in numerical terms. For example, in a given rock formation, as little as 20% of the rock re¬ moved may be used for commercialisation. Using the method and preferred embodiment of extractor of the present invention, on the other hand, this yield may be increased to values exceeeding 60%. It will also be apreciated that the method of this invention does not depend exclusively on the use of the spe¬ cific extractor illustrated and described herein. Thus much of the benefit of the invention can still be obtained if the per¬ foration and cutting of each face B n is terminated before the perforation and cutting of the individual faces C * L to C n , this latter being done after the whole slice of rock has been sepa¬ rated from the rock formation.

Claims: CLAIMS 1. Process for preparing the exposed surface of a rock formation to permit the extraction of parallelepiped shaped blocks of rock ready for final processing, comprising the steps of: a) cutting into the surface of the rock formation a slot having a depth substantially equal to a width dimension of said blocks; b) drilling into said surface of the rock formation a first series of parallel aligned perforations orthogonal to said slot, said perforations terminating along the bottom of said slot and defining a first cutting surface orthogonal to the plane of said slot; c) drilling into said surface of the rock formation a plurality of parallel second series of parallel aligned per¬ forations, said perforations of each of said second series de¬ fining a second cutting surface orthogonal to the plane of said slot and to said first cutting surface; d) separating by the use of plugs applied in the perforations of said first and second series, the blocks de¬ fined by steps a) to c); and e) carrying out steps a) to d) repeatedly so that the slot of step a) is cut from the exposed surface of the rock formation, beginning along a line defined by the outer ends of the perforations of said first series of perforations, whereby the exposed surface of the rock formation, after ex¬ traction of the various blocks in steps d), acquires a stepped profile. 2. Process for extracting parallelepiped shaped blocks of rock ready for final processing, from a rock forma¬ tion having an exposed surface with a stepped profile, com¬ prising the steps of: a) cutting orthogonally into a first surface of one step of said stepped profile a slot of a depth equal to that of the second surface of the same step, said slot being cut slightly above the plane of the second surface of the imme¬ diately previous step; b) cutting orthogonally into the second surface of the same step a first series of parallel aligned perforations along the junction between said second surface of the same step and the first surface of the immediately following step, the perforations of the first series extending to the bottom of said slot and defining a first cutting surface; c) cutting orthogonally into the second surface of the same step a plurality of parallel second series of paral¬ lel aligned perforations extending to said slot, said second series defining second cutting surfaces normal to said junc¬ tion; d) separating by the use of plugs applied in the perforations of said first, and second series, the blocks de¬ fined by steps a) to c); and e) repeating steps a) to d) with respect to the fol¬ lowing steps of the profile of said rock formation, extracting the respective blocks of rock. 3. Process according to claim 1 or 2, in which said slot or slots are cut by means of secant perforations. 4. Process according to claim 1 or 2, in which said first and second series of perforations are drilled with ham- mer drills. 5. Process according to any one of claims 1 to 4, in which steps a), b) and c) are carried out at substantially the same time. 6. Process according to any one of claims 1 to 5, in which step d) comprises first separating along said first cut¬ ting surface and then separating sequentially along said sec¬ ond cutting surfaces. 7. Extractor for extracting blocks of rock from a rock formation, comprising a structure formed by a front frame (R), a cental frame (T) and a rear frame (S), said front and rear frames (R,S) being perpendicular to said central frame (T) , each said frame being associated with at least one re¬ spective perforation system. 8. Extractor according to claim 7, in which each said perforation system includes at least one pair of rails and a support .carriage mounted for displacement along said rails, the pairs of rails of the three perforation systems be¬ ing orthogonal with respect to each other. 9. Extractor according to claim 7 or 8, in which the support carriage of each perforation system includes a pair of upright support guides perpendicular to its respective pair of rails, a perforation tool being displaceable along said sup¬ port guides. 10. Extractor according to claim 7, 8 or 9, in which the perforation system associated with said front frame (R) is a slot-cutter. 11. Extractor according to claim 7, 8, 9 or 10, in which each of said perforation systems associated with said central framel (T) and said rear frame (S) comprises a hammer drill. 12. Extractor according to any one of claims 8 to 11, in which said carriages are driven by electric motors. 13. Extractor according to any one of claims 8 to 12, including locking means for locking each carriage in predeter¬ mined positions along their respective pairs of rails. 14. Extractor according to any one of claims 7 to 12, comprising adjustable support jacks under said central and rear frames (T,S) for the correct positioning of said struc- ture on a rock formation. 15. Extractor according to any one of claims 7 to 13, comprising auxiliary wheels on siad central and rear frames (T,S) for the correct positioning of said structure on a rock formation.

Inventors: ANTUNES CACIQUE GERALDO, ANTUNES CACIQUE, GERALDO
Applicants: ANTUNES CACIQUE GERALDO, ANTUNES CACIQUE, GERALDO
Application year: 1992
Main classification: E21C41
IPC codes: B28D1, E21C41, E21C47