EP0145540A2 - Method of cutting a solid compact material - Google Patents

Abstract

1. A process for creating a substantially plane cut in a mass or compact solid material such as a rock block or mass, this process including the drilling, in the plane of the cut which it is desired to create, of at least two holes (101, 110), the sealing (3, 6) of these holes, and the placing under pressure of a fluid contained in their sealed parts, characterised in that these holes (101, 110) are disposed in such a manner that each hole, in a first zone of the plane, is situated at a distance from another hole less than about five times its diameter, or intersects the other hole, and is situated at a greater spacing from this other hole in a second zone of the plane, and that each of two holes (101, 110) is sealed (6) at least between the first zone or the plane and the free extremity or extremities of the said hole or at the level of these (3), in that a first pressure value P1 is determined which is capable of causing the appearance in the said first zone, but not in the second zone, of a fissure (2) into which some of the said fluid is forced, and a second pressure value P2 capable of resulting in the guidance, into the second zone, of a fissure having appeared in the first zone, and in that the pressure is raised simultaneously in both holes, at least in the first zone, to the value P1 and in that the pressure is maintained in the holes, at least in a part of the second zone, at the value P2 until the cut extends as far as desired.

Description

The present invention relates to a process for cutting a compact solid material.

The invention is the result of research concerning the extraction and rendering of blocks of ornamental rock, such as cut stone, granite, slate, marble, but it can find applications in very different fields and scales, for example the destruction of large masses of concrete or other, the cutting of precious or semi-precious stones, or certain works of surgery and biology, or the preparation of parts intended for electronics, such as quartz or silicon crystals, - it can also be used in the work of certain woods, synthetic materials, etc., whenever it is necessary to create in a mass a cut according to a plan defined in advance.

Currently, to make such a cut, the most common method consists in digging a groove in the chosen plane by removing material using a tool such as saw, wire, diamond disc, cutter. Such a technique has the advantage of providing surfaces very close to a plane, but it is slow and costly, and it results in a loss of material which constitutes a disadvantage if it is of great value.

• - création d'une fissure à l'aide d'ondes explosives partant simultanément de trous parallèles relativement rapprochés et situés dans le plan de coupure désiré, cette méthode exige le forage préalable de trous nombreux sur toute la surface de la coupure à obtenir,
• - propagation d'une fissure dans le plan choisi, préalablement affaibli par la foration de mines parallèles très rapprochées, fissure initiée sur l'un des bords libres du massif ou du bloc, cette méthode entraîne également des frais de forage importants, et n'exclut pas le risque de voir la fissure dévier et se propager dans une direction différente de celle qui est désirée,
• - dans certains cas, il arrive qu'on puisse employer un procédé consistant à développer une fissure dans une diaclase ou un joint plus ou moins recimenté à partir d'un trou recoupant cette diaclase ou ce joint, trou soigneusement bouché et dans lequel on injecte un fluide sous pression, ce procédé est d'application restreinte, car il est nécessaire que la diaclase ou le joint préexiste à l'endroit et avec l'orientation désirée pour le plan de coupure, en outre, il n'apporte pas de garantie contre une déviation au cas où la diaclase ou le joint s'arrêtent.

The rock extraction and preparation industry also uses faster methods involving explosives:

• - creation of a crack using explosive waves starting simultaneously from relatively close parallel holes located in the desired cutting plane, this method requires the prior drilling of numerous holes over the entire surface of the cutting to be obtained,
• - propagation of a crack in the chosen plane, previously weakened by the drilling of mines very close parallels, crack initiated on one of the free edges of the solid mass or block, this method also involves significant drilling costs, and does not exclude the risk of seeing the crack deviate and propagate in a direction different from that which is desired,
• - in some cases, we can use a process consisting in developing a crack in a joint or a joint more or less recimented from a hole cutting this joint or this joint, hole carefully plugged and into which we inject a pressurized fluid, this process is of restricted application, because it is necessary that the joint or the joint preexists at the place and with the desired orientation for the cutting plane, in addition, it does not provide any guarantee against a deviation in case the joint or the joint stops.

It was proposed, a long time ago (patent FR 405,498) to improve the control of the direction of the crack by drilling parallel holes in the plane of the desired cut and by practicing incipient ruptures in the wall of the hole, also directed in the plane of the desired cut. The certificate of addition FR 12.434 to the previous patent provided for improving the guidance using an explosive cartridge with split walls so that the expansion of the gas takes place towards the initiation of rupture and inside of it. This process did not have a practical application, undoubtedly because of the difficulty of controlling the direction of the crack when it progressed on a certain distance, which obliges to envisage close holes.

Among the techniques currently used to create a rupture by propagation of a crack we must mention those which replace the pressurized gases supplied by an explosive or by any other process by a liquid, such as water, pressurized by a pump. , possibly in an accumulator pressure, or even by the explosion of a slow explosive.

None of the techniques has brought a decisive improvement to the problem of controlling the direction in which the crack will develop, leading to the desired cut.

The object of the present invention is to provide a method making it possible to create a cut-off in any compact solid material, a method which is more economical in energy, investment and time than the techniques employed hitherto while ensuring excellent control of the direction in which the crack will develop whatever the position and orientation of the desired cutting plane.

The invention therefore provides a method for creating a substantially planar cut in a mass of compact solid material such as a block or a rock, this method comprising drilling, in the plane of the cut that it is desired to create, at least two holes, closing these holes and pressurizing a fluid contained in their closed part, characterized in that these holes are arranged so that. each hole in a first zone of the plane is at a distance from another hole less than five times its diameter, or intersects this other hole, and is more spaced from this other hole in a second zone of the plane, in that each of the two holes is closed at least between the first zone of the plane and the free end or ends of the said holes, in that a first pressure value P1 capable of cause the appearance, in the first zone, but not in the second zone of a crack in which said fluid is blown, and a second pressure value P2 capable of causing, even in the second zone, the guiding of a crack appeared in the first zone and in that the pressure in the two holes is raised simultaneously, at least in the first zone, up to the value PI and in that the pressure in the holes is maintained, at least in part of the second zone, at the value P2 until the cut has the desired extension.

As we said, in the first zone of the plane of the desired cut, the holes can be cut, they can also not be cut, either because one of the holes ends before having met the other , or because the two holes are not in the same plane due to a slight defect in orientation. In the latter case, the cut has a distortion in the region where the holes are brought together and will approach the substantially planar shape by moving away from this region.

By "appearance of a crack in which said fluid is blown" is meant either the formation of a discontinuity in the mass, followed by the penetration of the fluid from a hole in this discontinuity, or the penetration of the fluid into a pre-existing discontinuity, with in general widening of this discontinuity. The propagation of the crack to the desired extension requires the penetration, in this crack, of an additional quantity of fluid, which requires the maintenance, at least in a part of certain holes, of a pressure of insufflation In general the required insufflation pressure decreases sharply when the extension of the crack increases, and can drop well below the pressure P2. The pressure P1 capable of causing the appearance of a crack into which fluid is blown, is always at least equal to the pressure P2 necessary for guiding the further development of this crack. The determination of the values P1 and P2 can result from a calculation made from the mechanical characteristics of the mass, determined beforehand. It can also be done by means of preliminary tests, in particularly in the case of quarry materials or the like. According to an advantageous modality, before raising the pressure to the value Pl in the first zone, primers for ruptures are created in said first zone, these primers starting from the wall of at least one of the holes, in the plane of the cut to create this has the effect of lowering the value of Pl. As the formation of such a primer is costly, it is advantageous to limit its extension to the first zone. Such a primer differs from that described in FR-A-405,498. In this patent, in fact the initiation of rupture was intended for guiding the crack, and therefore had to have the greatest economic extension possible, both in the direction of the length of the hole as in a radial direction.

Advantageously, according to the invention, the initiation of rupture is created by the directed explosion of a very low charge of shattering explosive, which inexpensively creates a initiation of rupture of small extension.

When the surface of the desired cut has a certain extension, two holes are insufficient for correct guidance. We can then provide a suitable number of pairs of holes, implemented simultaneously or not. In order to limit the costs of starting a crack, of making break points for example, it is possible to provide in the said second zone additional holes which intersect at least one of the aforementioned holes or approach them, and the maintenance of the pressure in these additional holes to the value P2, which has the effect that they participate in guiding the crack that appeared in the first zone.

An important element of the invention resides in the control of the crack in progress. If the crack progresses more quickly in the plane at a distance from the holes than in the vicinity of these, its limit takes a convex shape in the direction of propagation. This can happen if the fluid used is a too viscous gas or liquid, the meeting of two streams halfway between the two holes leads to a faster progression of the crack in this region. It follows that the progression of the crack is no longer guided and can deviate from the chosen plane. If, on the contrary, the fluid has difficulty infiltrating into the crack, which can result from the use of a too viscous fluid, the limit of the crack takes an exaggeratedly concave shape and tends to progress from each hole as if the other did not exist and can therefore deviate, there too, from the chosen plane. The observation of the cut can inform a posteriori about the nature of the defects, which can result from an unsuitability of the fluid to the material to be cut. Among the possible remedies, it can be provided that in the first case, to control the insufflation of the fluid, the latter is constituted with a liquid of suitably chosen viscosity, it is pressurized with a gas or a liquid of lower viscosity, contained in deformable membrane placed inside the hole. In the second case, one can have along the walls of the hole a deformable membrane which extends essentially only in the second zone.

• Fig. 1 est une coupe schématique selon le plan dans lequel on désire faire la coupure, montrant un ensemble de deux trous pour la mise en oeuvre du procédé de l'invention,
• Fig. 2 est une coupe analogue à celle de la Fig. 1 mais où on a foré deux ensembles de deux trous chacun, couvrant le plan de coupure désiré A B C D,
• Fig. 3 est également une coupe analogue à celle de la Fig. 1 représentant un seul ensemble de quatre trous couvrant le plan de coupe désiré,
• Fig. 4, 5 et 6 sont des coupes longitudinales et transversales de détail d'un trou.

The invention will now be explained in more detail using nonlimiting examples, illustrated by the drawings, among which:

• Fig. 1 is a schematic section along the plane in which it is desired to make the cut, showing a set of two holes for implementing the method of the invention,
• Fig. 2 is a section similar to that of FIG. 1 but where two sets of two holes were each drilled, covering the desired cutting plane ABCD,
• Fig. 3 is also a section similar to that of FIG. 1 representing a single set of four holes covering the desired cutting plane,
• Fig. 4, 5 and 6 are longitudinal and cross sections of detail of a hole.

Figs. 1 to 3 relate to the case where it is desired to develop a crack inside the contour A B C D of any kind, situated in any plane of a mass of solid material such as a solid mass or any block of rock.

In the simplest application of this case, two holes are drilled 101, 102 (Fig. 1), in the plane P of the desired cut, or substantially in this plane. They are connected by an initial crack 2 and we proceed as indicated below to put them under pressure. The pressurization is done from the two holes, unless there has been sufficient communication between them, in which case it can be done from a single hole. The crack then develops by being strongly guided along the holes 101 and 102, because of the pressure existing in these holes, it develops more quickly along the latter than in the zone lying between them and therefore always tends to remain in the plane P even when the holes 101 and 102 are relatively distant from each other.

The limit of the crack progression at a given time has been represented by a dashed line 20. In the same figure, these traces 20a and 20b correspond to a defective progression of the crack: the trace 20a convex in the direction of progression, that is to say towards the top of the figure may result from the interaction of two flow of fluid coming from holes 101 and 102 and coming to meet at approximately equal distance from these holes. It is understood that the crack is likely to take the form of a fraction of cone limited by two generatrices corresponding to the two holes. The excessively concave line 20b is due to insufficient blowing of fluid at a certain distance from the holes. The crack can then take an aberrant orientation, in a helix for example, in the vicinity of each hole. Some guidance, but less important, also exists in the area of the plane located outside that is between holes 101 and 102. This guidance is less and less effective as one moves away from the holes.

The diagram in FIG. 2 comprises two sets of each two holes 102, 104 and 105, 106, with two initial crack initiators giving a guidance which extends to a larger area than in the case of FIG. 1.

In sets such as 101, 102 or 103, 104 where the holes do not overlap, it is generally preferable to create an artificial crack primer, it is enough to create this primer only in the area where the two holes are very close. It can be created mechanically with an appropriate tool, one can also detonate a very short length of detonating cord arranged along at least one generatrix of one of the holes contained in the plane P. It is preferable to give an effect directive to the explosion for example by placing the cord in the axis of a half metal tube of small diameter.

In an assembly such as 105, 106 of FIG. 2 where two holes cross, one can possibly initiate the development of the crack thanks to the only pressure P1 existing in the two holes, and creating a high concentration of stress at the crossing point This pressure is then higher than that necessary when an artificial crack is created, but as we will see later this increase in pressure can only take place in the area where the two holes intersect.

In Fig. 3 we assumed that we created a single initial crack 2 at the place where two holes 107 and 110 overlap or are very close to each other, the hole 110 extending beyond this place . This crack will then develop along hole 107 and on both sides, along the hole 110. From the point where two other holes 108 and 109, also kept under pressure P2, intersect or are very close to hole 110, the crack is guided by these holes 108 and 109 and finally the guide is strongly guided. crack along all the holes and in the space between these holes, the progression being indicated by the dashed lines 21 to 24. The crack is therefore guided over a very large area with a very small number of holes. Each of the holes has one of the means described below for exerting pressure on its walls, only one of the holes may include insufflation means in the initial crack 2 but all or part of the holes may include insufflation zones which only become active after the crack has passed through these areas.

Finally, diagrams identical to those of FIGS. 1, 2 and 3 can be created in planes P intersecting inside the massif or block, thus determining smaller blocks, all limited by substantially planar walls.

Figs. 4 to 6 illustrate the various devices that can be fitted to each of the holes 1 with a pair of holes such as 101.102 to pressurize them. Each of the holes includes at least one plug obstructing its free end (s). It can be very short such as 3. This plug can also be constituted by a transversely elastic pipe element 5, described below.

The pressure P2 acting on the walls of the hole for guiding the crack can be exerted either uniformly over the entire perimeter of the hole, or mainly only on two opposite sectors of this perimeter, sectors arranged on either side of the plane P of the cut.

In the first case this pressure can be equal to the insufflation pressure over the entire length of the hole but the insufflation fluid can be isolated from the crack developing along the hole by a cladding 4 so that the insufflation takes place only in the initial cracking zone and possibly in certain zones that one wishes to privilege. Outside the initial cracking zone which is necessarily subjected to the pressure, variable in the insufflation time, a pressure P2 is exerted on the walls according to the invention for guiding the crack. To do this, one can for example introduce into the hole one or more pipe elements 5, transversely elastic, tightly closed at their ends and containing a fluid which is brought to the desired pressure P2. If this latter pressure is less than the insufflation pressure, these two zones are separated or different pressures prevail by a sealed intermediate plug 6.

In the case where the pressure is exerted only on two opposite sectors of the hole, in all or part of the length of the hole, it is possible inter alia to have the devices shown in FIGS. 5 and 6 showing the sections of the hole in the areas where such devices are installed. In Fig. 5 shows two rigid support pieces 7 of the desired length, exerting on opposite sectors 8, the force transmitted to them by an inflatable piping element 9. The sectors 8 are, of course, on either side of the plan P.

In Fig. 6 there is a single rigid part 10 and two inflatable pipe elements 11 are supported on one side on this rigid part 10, and on the other hand on the opposite sectors 8.

The pressurization of the blowing and guiding fluids can be carried out by numerous means known and not described here.

The insufflation fluid, under pressure, can either be brought in from the outside through the plug (s) 3, 6 as well as the constant pressure zone 5 from which it will remain isolated, or be supplied by the fluid initially- disposed in the hole and by gases from the deflagration of a slow explosive or powder, or any other means generating pressurized gas. It may be necessary for this deflagration to occur in more than one time so as to produce at the beginning only a small quantity of gas, then in one or more subsequent sequences, at the moment when part of the insufflation fluids escapes to the outside, a higher amount of gas.

Similarly, the fluid in the inflatable pipe element (s) 5, 9, 11 can be pressurized either by a pressurized fluid supplied from the outside, or by another method such as deflagration, the main thing being that pressure is exerted on the walls of the hole before the crack develops along these walls.

Claims (7)

1. A method for creating a substantially planar cut in a mass of compact solid material such as a block or a rock, this method comprising drilling, in the plane of the cut that it is desired to create, at least two holes , closing these holes and pressurizing a fluid contained in their closed part, characterized in that these holes are arranged so that each hole, in a first zone of the plane, is at a distance d '' another hole less than about five times its diameter, or intersects this other hole, and is more spaced from this other hole in a second zone of the plane, and in that each of two holes is closed at least between the first zone of the plane and the free end (s) of said holes, or at the level thereof, in that a first pressure value Pl capable of causing the appearance in the said first zone is determined, but not in the second zone, a crack in which said fluid is blown, and a second value pressure urine P2 capable of driving the guide, up to the second zone, of a crack which appeared in the first zone, and in that the pressure is simultaneously increased in the two holes, at least in the first zone, up to at the value Pl and in that the pressure is maintained in the holes, at least in part of the second zone, at the value P2 until the cut has the desired extension. 2. Method according to claim 1, characterized in that before raising the pressure to the value PI in the first zone, fracture primers are created in said first zone, these primers starting from the aproi of at least one holes in the plane of the cut to be created. 3. Method according to claim 2, characterized in that the initiation of rupture is created by the directed explosion of a very low charge of breaking explosive. 4. Method according to one of claims 1 to 3, characterized in that provision is made, in said second zone, for additional holes, which intersect or approach at least one of the above-mentioned holes, and in that the pressure in these additional holes is maintained at the value P2, which has the effect that they participate in guiding the crack that has appeared in the first zone. 5. Method according to one of claims 1 to 4, characterized in that the insufflation of the fluid in the crack is controlled so that the crack limit does not progress by taking, between the holes, a convex shape in the direction of its progression, or an exaggeratedly concave shape. 6. Method according to claim 5 characterized in that to control the insufflation of the fluid, it is constituted with a liquid of suitably chosen viscosity, which is pressurized with a gas or a liquid of lower viscosity, contained in a deformable membrane placed inside the hole. 7. Method according to claim 5, characterized in that, to control the insufflation of the fluid in the crack, is deposited along the walls of the hole a deformable membrane which extends essentially only in the second zone.

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