EP0250286B1 - Underground mining process using downwardly directed stoping and caving, and installation for carrying this out - Google Patents

Description

The invention relates to a new method of operating underground mines or quarries and a device for its implementation. It applies more particularly to heaps or ore veins of significant height.

For deposits of this type, the farms have a rising or falling slaughter front. With falling edges, slaughter conditions are easier while rising edges can pose safety concerns due to felling on the roof.

Several falling edge solutions have been proposed, but they are not entirely satisfactory.

This is how "flexible floor" operations have hardly developed because of the operating difficulties and the safety problems they pose. Extraction operations do not allow complete recovery of the ore and require significant preparation work.

It has also been proposed to constitute a fixed concrete slab anchored in the walls (that is to say the ground surrounding the ore vein) and to extract a slice of ore under this slab, then to repeat the operation at increasing depths with the formation, one after the other, of successive fixed slabs sheltered from which the ore is extracted: the slabs remain permanently and are abandoned as and when they are mined. Such a practice is expensive because of the making of successive slabs and is only applicable to veins of limited thickness; the holding of the walls in right of the exploitation site is compromised by the constraints induced by the slabs remained in place upstream of it.

There is therefore no process to date fully satisfactory for farms that have to grow to a certain height.

A distinction is also made between operations by backfilling and operations by caving.

Although it is not an operation with top-down removals, an example of slaughter with backfilling is given by the document FR-1.313.646, which describes a method of slaughter in a vein, in a platorium deposit. or by erecting, by means of slaughtering devices and a movable wall of embankments which follows slaughtering under the action for example of traction winches. The working face has an inclination of about 45 ° and the felling is done in the direction of the upper end by letting the ore descend by gravity.

The practice of caving, which consists in letting the lands which overhang the exploited ore collapse, is more economical than the practice of backfilling which consists in substituting a material for the exploited ore.

It therefore seems desirable to seek to combine top-down mining with the technique of caving.

The present invention aims to solve this problem by proposing, for heaps or ore seams of considerable height, a method of operating with a falling edge with caving, which is relatively simple and inexpensive, and which allows the felling and recovery full ore with great security.

To this end, it proposes a method of operating underground mines or quarries by descending cuts under a ceiling, characterized in that, this ceiling being substantially horizontal, it is divided into a plurality of ceiling zones supported independently of one another by a plurality of independent slabs juxtaposed side by side and supported by support means, so as to jointly form a protective roof against caving scree, and, as and when ore is extracted under this ceiling, we lightning strikes each of these zones step by step over a limited height by successively lowering each of the slabs from which ore has already been extracted, using for this purpose mechanical means of temporary support and lowering fixed on at least one removable chassis used successively for the different slabs.

This allows satisfactory lightning control which is compatible with safety requirements. The zones envisaged here are the portions of the vault individually supported by the aforementioned slabs (the latter are sized so that they can be lowered). It will be appreciated that the invention proposes to work under a blasted area, overcoming the prejudice of those skilled in the art as to what, a priori, safety standards allow.

It is important to note that, during this lowering, the mass of the resulting scree remains low due to the arch effect induced in the overall mass of the caving scree by the presence of the neighboring slabs which remain fixed. This property allows the choice, for the successive lowering of the slabs, of devices (preferably hydraulic) whose characteristics (structure and operation) allow industrial manufacture and application.

It will be appreciated that the operating method according to the invention leads to high productivity because it makes it possible to mechanize all of the operating operations. On the other hand, investments are kept at a reasonable level since the slabs descend with the operating site.

According to a first embodiment of the invention, the slabs are supported on walls or pillars of ore and the ore is extracted, alternately, between the walls or pillars and at the top thereof (while supporting artificially these slabs).

According to another embodiment of the invention, the slabs rest on artificial pillars and the ore is extracted alternately, between these pillars and under them. These artificial pillars are in practice linked to the slabs; they are advantageously movable transversely to the operating direction.

In narrow sites, slabs are placed end to end or side by side. For larger worksites, the tiles are preferably aligned in rows and rows; the progression of slabs removal and lowering is preferably carried out either row by row or row by row.

The spacing of the walls or pillars is, at least in certain places, greater than the width of operating machines so as to allow circulation.

According to yet another embodiment, more particularly intended for narrow veins, the slabs are placed in lateral support against the wall, for example by bracing, which makes it possible to extract the ore on the ground over the entire width of the gallery .

The invention also proposes, for the implementation of the aforementioned method, a support installation for the exploitation of underground mines and quarries by descending descents under a ceiling, characterized in that it comprises a roof for protection against substantially horizontal caving-in scree formed of a plurality of independent elementary slabs juxtaposed side by side, provided with support means, as well as mechanical means of support and lowering at a controllable height, adapted to the individual lowering step by step of these slabs, these means for supporting and lowering slabs being fixed on one or more removable frames which are used successively for the different slabs
According to a first embodiment of the invention, the support means are pillars or walls made of ore to be exploited when the latter has sufficient strength.

According to another embodiment, the support means are artificial. These are fixed pillars integral with the slabs, or linked to the slabs with the possibility of translation along the latter. These pillars are in practice, like slabs, in reinforced concrete.

In the case of narrow veins, slabs can also be supported by a plurality of horizontal jacks bearing at their ends laterally against a vertical shoulder of the slabs and the walls themselves; these cylinders remain in practice in place while ore is extracted across their entire width.

In such narrow veins, instead of being a single piece, the slabs can also be formed from at least two articulated arch elements forming a variable angle arch, braced at the heels, advantageously supplemented by two lateral or extreme elements, articulated to the vault elements, and intended to go along the walls. Horizontal cylinders are provided for laterally pressing the end elements against the wall.

It will be appreciated that such slabs make it possible to take advantage of the weight of the caving scree to increase the safety of work under the slabs in the case of narrow veins while allowing variations in width of these narrow veins to be easily followed.

Spaces are maintained between the slabs as well as between the slabs and the side walls of the exploited cavity, so that the descent of each slab is carried out with ease. Devices prevent scree from passing through these spaces.

A flexible wire mesh is advantageously interposed between the roof formed by all of the slabs and the vault of caving scree which it supports. As a variant, shields supported by deformable triangles are arranged in interstices between adjacent slabs; preferably for a given gap between two slabs, the shield is carried by that of the slabs which is intended to be lowered first while the other carries a redent intended to press down on this shield when lowering this another slab.

Preferably, this plurality of elementary slabs comprises at least one alignment (row) whose support means are sufficiently spaced to allow the passage of operating machines.

The support and controlled lowering means preferably comprise hydraulic cylinders or cushions which act advantageously on the slabs by means of distribution plates, or on the pillars by means of fittings with which they are fitted. In the case of articulated slabs, the support and lowering means act on the extreme elements, for example by means of transverse rails coming under horizontal spans of these elements.

The thickness of the slabs and the geometry of the pillars are calculated so that the assembly can support the mass of the caving scree. Sensors are advantageously provided, either on the slabs (deflection measurement) or between slabs and pillars (pressure sensors) to enable the load supported by the slabs to be monitored so as to verify that it remains below the limits of use of slabs.

• la figure 1 est une vue en coupe longitudinale d'un chantier d'exploitation, selon l'invention, d'un filon vertical de minerai,
• la figure 2 est une vue en coupe transversale,
• les figures 3 et 4 sont des vues en coupe transversale et longitudinale d'un chantier analogue, au cours de l'exploitation selon le procédé de l'invention,
• les figures 5A à 5D sont des vues latérales d'une dalle à piliers latéralement déplaçables en 4 phases successives d'extraction,
• les figures 6A à 6D sont des vues en coupe longitudinale d'un chantier analogue à celui des figures 1 à 4 illustrant 4 phases successives d'exploitation selon une variante du procédé de l'invention,
• la figure 7 est une vue en coupe transversale d'un chantier de grande largeur,
• la figure 8 est une vue de dessus d'un autre chantier de grande largeur,
• la figure 9 est une vue en élévation latérale d'une dalle supportée par des piliers de minerai dans un chantier étroit,
• la figure 10 en est une vue simplifiée dans un stade intermédiaire d'extraction,
• la figure 11 est une vue en coupe longitudinale dans le stade intermédiaire de la figure 10,
• les figures 12 et 13 sont des variantes de la figure 9,
• les figures 14 et 15 sont des vues respectivement en coupe transversale, et en vue de dessus d'un chantier de grande largeur dans lequel les dalles reposent sur du minerai à exploiter,
• la figure 16 est une variante de la figure 14,
• la figure 17 est une vue en coupe transversale partielle de deux dalles adjacentes munies d'un bouclier de protection.
• la figure 18 est une vue éclatée de dessus des quatre éléments constitutifs d'une dalle articulée selon l'invention;
• la figure 19 est une vue de côté d'une telle dalle dans une veine de minerai fortement pentue;
• la figure 20 est une autre vue de côté de cette dalle, dans une veine analogue de plus grande puissance;
• la figure 21 est une vue schématique partielle en élévation d'un dispositif de soutien et de guidage en descente d'une dalle articulée selon une variante de réalisation;
• la figure 22 est une vue en perspective de ce dispositif de guidage en descente;
• la figure 23 est une vue de côté d'une autre dalle selon l'invention selon une configuration complètement aplatie;
• la figure 24 est une vue en coupe transversale d'une galerie étroite dont la voûte est formée de dalles planes munies de vérins de soutien latéral;
• la figure 25 est une vue en coupe longitudinale montrant un chariot élévateur de mise en place des vérins et de support et d'abaissement des dalles; et
• la figure 26 est une vue de cette galerie en coupe longitudinale à plus petite échelle montrant plusieurs dalles côte à côte.

Objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which:

• FIG. 1 is a view in longitudinal section of an operating site, according to the invention, of a vertical ore vein,
• FIG. 2 is a cross-sectional view,
• FIGS. 3 and 4 are views in transverse and longitudinal section of a similar site, during operation according to the method of the invention,
• FIGS. 5A to 5D are side views of a slab with pillars laterally displaceable in 4 successive extraction phases,
• FIGS. 6A to 6D are views in longitudinal section of a site analogous to that of FIGS. 1 to 4 illustrating 4 successive phases of operation according to a variant of the method of the invention,
• FIG. 7 is a cross-sectional view of a very wide site,
• FIG. 8 is a top view of another very large site,
• FIG. 9 is a side elevation view of a slab supported by ore pillars in a narrow site,
• FIG. 10 is a simplified view thereof in an intermediate stage of extraction,
• FIG. 11 is a view in longitudinal section in the intermediate stage of FIG. 10,
• FIGS. 12 and 13 are variants of FIG. 9,
• FIGS. 14 and 15 are views respectively in cross section, and in top view of a very wide site in which the slabs rest on ore to be mined,
• FIG. 16 is a variant of FIG. 14,
• Figure 17 is a partial cross-sectional view of two adjacent slabs provided with a protective shield.
• Figure 18 is an exploded top view of the four elements of a hinged slab according to the invention;
• FIG. 19 is a side view of such a slab in a steep ore vein;
• Figure 20 is another side view of this slab, in a similar vein of greater power;
• FIG. 21 is a partial schematic view in elevation of a support and guiding device in descent of an articulated slab according to an alternative embodiment;
• Figure 22 is a perspective view of this descent guide device;
• Figure 23 is a side view of another slab according to the invention in a completely flattened configuration;
• FIG. 24 is a cross-sectional view of a narrow gallery, the vault of which is formed of flat slabs provided with lateral support jacks;
• Figure 25 is a longitudinal sectional view showing a forklift for setting up the jacks and for supporting and lowering the slabs; and
• Figure 26 is a view of this gallery in longitudinal section on a smaller scale showing several tiles side by side.

Figures 1 to 26 show various alternative embodiments of a support installation for the exploitation of ore (coal, metallic ores ...) by descending removals and with progressive, controlled and localized caving. The extraction can be done by a classic technique (cutting, planing, shooting ...), the felling front progressing from one slab to another. The clearance height is an important parameter but the operator is completely in control of it as long as he has an appropriate slaughtering machine.

Figures 1 and 2 show an operating site according to the invention in which a plurality of tiles D1 ... are arranged side by side. It is a narrow site and the slabs, generally parallelepiped, are arranged transversely.

These calles D1 ... are supported by pillars P here arranged transversely to the slabs so as to release one or more corridors or rows C1, C2 ... These pillars rest on a pile 10 of ore to be exploited.

At the ends of the site are shown here two vertical galleries 11 and 12 intended for the air intake and the personnel access, on the one hand, and the ore removal and the air return, on the other hand .

These slabs jointly support a mass 13 consisting of caving scree; between these slabs and the caving scree is interposed a flexible metallic trellis 14 which is fixed to the neighboring grounds 15 (called wall) by anchor bolts 16.

We denote by Dp-1, Dp, Dp + 1 ... any successive tiles of the plurality of tiles D1 ...

Figures 3 and 4 schematically illustrate an intermediate stage of operation in which a central cutout 1, between two pillars P, has already been extracted over the entire length of the site (variant not shown, this cutout 1 is extracted so discontinuous, slab by slab, alternating with side cuts 2).

The lateral removals, under the P pillars, are extracted, slab by slab, each slab being lowered from the step of removal, as and when, with controlled and localized caving.

In FIG. 4, the lateral cuts 2 which have been extracted under the pillars of the slabs up to Dp-1, are being extracted under the pillars of the slab Dp. A support device (not shown), preferably hydraulic, maintains the slab Dp during this extraction. The device then ensures the descent of the slab Dp and of the pillars P which are integral with it at the level of the preceding slabs.

For reasons of convenience of extraction under the pillars, these are advantageously translatable laterally as it appears in FIGS. 5A to 5D.

In FIG. 5A, the pillars Pʹ are brought as close together as possible; we first extract the side cuts 1 over the entire length of the site.

We then spread the pillars to the top of the extracted lateral cuts and then lower the slabs; the pillars P'bordent a central cutout 2 which is then extracted (Figure 5B).

To carry out the next extraction phase, the pillars can be brought back to close configuration beforehand and repeat the above operations.

Preferably, the process is carried out in reverse, starting by extracting the central removal 1ʹ (FIG. 5C) then, after bringing the pillars together and lowering the slab, extracting the lateral removals 2ʹ (FIG. 5D).

The extraction cycles thus alternate, in accordance with FIGS. 5A and 5B, or in FIGS. 5C and 5D.

FIGS. 6A and 6B illustrate an operating variant in which a central cutout is extracted first as before. Each slab is here equipped with support and lowering devices 17. In FIGS. 6A and 6B, the extraction of the lateral removals (for reasons of clarity, the "front" pillars of the slabs have been removed) is underway under the pillars of slab D4 which, like the previous slab D3 is supported on its supports 17. Before starting to extract the ore under the pillars of slab D5, (Figure 6C), while this slab on its support and lowering means 17, the slab D3 is lowered by causing a caving above it (FIG. 6D). There is thus a gap of a slab between the last lowered slab and the slab under which ore is extracted. This can facilitate extraction maneuvers by increasing the space available.

As a variant, there is a reduced number of sets of hydraulic cylinders 17 mounted on a movable chassis 18 (see panel D1). These jacks preferably act on the slabs via a distribution plate 19.

Figure 7 shows side by side three rows of tiles Dp, 1, Dp, 2, Dp, 3 surmounted by the same protective trellis.

FIG. 8 presents, seen from above, four rows of tiles Dp, 1 to Dp, 4, defining a succession of rows of 4 tiles.

The progress of the removals can be done row of tiles by row of tiles, or rows of tiles by row of tiles. To facilitate the circulation of operating equipment from one line to another, a row of special tiles D0.1, to D0.4, whose pillars Pʹ are divided, is placed from place to place.

Figures 9 to 16 show alternative embodiments in which the slabs Dp rest on walls or pillars M constituted by the ore itself to be exploited. The removals are in this case located at different levels (see Figure 9).

The central cutout 1 between the pillars M is extracted first. Then the tiles are successively supported on their supports 17 and ore is extracted at the top of the pillars M (see Figures 10 and 11, in the case of a narrow site).

If the walls of the vein are not vertical, the same principle applies, the descent of the slabs having to be accompanied by a horizontal translation (see Figure 12). As a variant, the tiles Dp are inclined so as to be substantially perpendicular to the walls of the vein (FIG. 13).

Figures 14 and 15 show a similar site of greater width, with several parallel rows of tiles Dp, 1 to Dp, 4.

The same indications as for Figures 7 and 8 apply here. It can be noted that the slabs of Figures 14 and 15 are supported by their ends on common ore walls, which are interrupted under slabs D0.1 to D0.4 to allow the crossing of operating equipment.

FIG. 16 represents a variant of FIG. 14 in which the slabs of the same row rest on separate walls or pillars, freeing up corridors under and between each slab (the number of corridors C1 to C7 greater than that of FIG. 14, for a lower number of rows of tiles).

The choice between one or other of the configurations will depend on the resistance of the pillars and the width of the site.

As is known per se in the art of mining, the protection of the empty spaces between the slabs is generally ensured by a flexible and continuous metallic mesh unwound over the slabs at the start of the construction site.

It is possible, if necessary, to provide a seal between the slabs, by any known means.

This protection is alternatively obtained by means of shields 20 supported by deformable triangles 21 shown in FIG. 17.

• un côté AC constitué par la dalle (dans l'intervalle concerné) descendant en premier,
• un côté AB de longueur constante articulé en A sur la dalle et articulé en B sur le côté BC. Ce côté AB supporte le bouclier de protection,
• un côté BC de longueur variable, articulé en B sur le côté AB et coulissant en C à travers un étrier, fixé sur la dalle. Ce coulissement peut être freiné au moyen d'une clavette.

Each triangle includes:

• an AC side consisting of the slab (in the interval concerned) descending first,
• one side AB of constant length articulated at A on the slab and articulated at B on the side BC. This AB side supports the protective shield,
• a side BC of variable length, articulated at B on the side AB and sliding at C through a stirrup, fixed on the slab. This sliding can be braked by means of a key.

The slab Dp, descending in second, comprises at 22 a step causing the descent of the vertex B of the articulated triangle and thus ensuring the sealing of the device.

A device (not shown) is advantageously provided for protecting the empty spaces between slabs and walls of the exploited cavity and for supporting the roof.

The role of this device is twofold. It avoids the eruption of scree in the site and allows the method to be adapted to changes in width of the site. The pressure of the scree in contact with the wall of the site is generally low due to the presence of the slabs which support the entire load.

This device, not shown, provides protection by simply advancing extensions through pins fixed in the slab, these extensions being loaded with a wooden or iron mattress. These easily advance or retractable extensions make it possible to adapt to variations in width of the site. A classic support by props can help during a strong extension of these extensions.

This device can be manually controlled (displacement of the extensions by the force of the wrist) or hydraulically controlled.

The arrangement of the tiles in rows and rows allows to obtain on the site a division into rooms and pillars with overlaps. It is therefore possible to use for the mining of the ore the materials known in these methods of chambers and pillars (shearers for example).

In addition, the existence of slabs, by the ease that they offer to foresee or place there all the necessary suspension means, makes it possible to have in this type of site all the necessary means of lifting and transport. by suspended monorail.

For example, for the exploitation of an ore vein 17 meters wide, slabs (or beams) 16 meters long, 2 meters wide and 1.5 m high are used. The corresponding pillars are cubic with a side of 2 meters, and are spaced 7 meters apart. Such a reinforced concrete slab can be designed to support 200,000 kg / m2, which conventionally corresponds to around 80 m of scree.

The cylinders constituting the support and lowering means 17 have for example a stroke of 1.6 m, a sliding load of 200 tonnes and a lifting effort of 170 t. The complete device can include 6 to 8 cylinders.

• ler cas : Les piliers d'appui des dalles sont en minerai et non en béton. Dans ce cas un châssis amovible comportant les 6 ou 8 vérins prévus sera amené sous la dalle à supporter. La dalle sera prise en charge par le dispositif qui assurera son supportage pendant l'enlevure des piliers puis sa descente. Il sera ensuite déplacé à la dalle suivante. Si les dalles ont des surfaces telles que la stabilité ne soit pas assurée par un seul châssis, on doublera les dispositifs de descente des dalles qui seront placés de manière à assurer cette stabilité.
• 2ème cas : Les piliers d'appui des dalles sont en béton.

   1ère variante : ils sont solidaires des dalles. Dans ce cas, on peut utiliser un châssis comme dans le cas précédent, ou les vérins peuvent être fixés contre les piliers au moyen de ferrures prévues lors de la coulée des piliers.Two cases should be distinguished for the design of these support and lowering means:

• 1st case: The pillars supporting the slabs are made of ore and not concrete. In this case a removable chassis comprising the 6 or 8 cylinders provided will be brought under the slab to be supported. The slab will be supported by the device which will ensure its support during the removal of the pillars and then its descent. It will then be moved to the next tile. If the slabs have surfaces such that stability is not ensured by a single chassis, the lowering devices of the slabs will be doubled, which will be placed so as to ensure this stability.
• 2nd case: The pillars supporting the slabs are made of concrete.

1st variant: they are integral with the tiles. In this case, a frame can be used as in the previous case, or the jacks can be fixed against the pillars by means of fittings provided during the casting of the pillars.

2nd variant: they are translatable. In this case, the use of chassis is imperative.

In both variants, if the tiles have surfaces such that stability is not ensured by a single chassis, the devices will be doubled.

Figures 18 to 20 show a slab articulated in four successive elements 31, 32, 33 and 34 articulated to each other, step by step. This is a variant of slabs (in concrete concrete) for the case of sloping veins with a thickness of 2.8 - 3 m. up to 8 m. for an orientation close to the vertical, or even more for veins of inclination less than 45 ° relative to the vertical.

The extreme elements 31 and 34 are in practice substantially parallel. The element 31 is arranged along the roof 35 of the vein 36 of ore while the element 34 is disposed along the wall 37 of this vein. These elements, called "roof element" and "wall element" are adapted to come to bear on the ore by their lower ends 31A and 34A.

The intermediate elements 32 and 33 jointly form a vault whose opening angle or is all the greater as the width or power of the ore vein is important, as appears from the comparison of Figures 19 and 20 This variable opening of the vault makes it possible to follow the variations in width of the vein.

In the extreme configuration, shown in FIG. 23, this angle is 180 ° and the arch is completely flattened.

The mass of caving scree 38 which hangs over the vault tends to open the angle of the vault, by flattening it, causing a lateral push from the lower edges 32A and 33A of the vault elements towards the roof and the wall, respectively, aimed at ensuring a transverse anchoring, or bracing, of the slab on the roof and the wall (silo effect); the extreme elements result in an energetic plating against the roof and the wall which may suffice, if necessary, to allow the retention of the slab even if the ore is felled under the feet 31A and 34A of these extreme slabs. A spacer cylinder 40 (only shown diagrammatically by its line of action in FIGS. 19 and 20), can however be added to reinforce this transverse cladding.

It will be appreciated that the lateral plating of the end slabs 31 and 34 against the wall, that is to say the rocks constituting the roof and the wall, is all the more important the greater the opening angle of the vault. (provided that it remains below 180 °): there are parallel variations between the weight of the caving scree to be supported and the resulting transverse plating force making it possible to resist all or part of this weight.

The structure of the elements 31, 32, 33 and 34 is clear from FIGS. 18 and 19 (or 20), in particular as regards their mode of articulation.

In the example shown, any articulation of two constituent elements is formed of two side knuckles (hinge elements) integral with one of the elements, framing a central knuckle integral with the other of these two elements. In a variant not shown, the joints are obtained by nesting an odd number of knuckles, on the one hand, and an even number of knuckles, on the other hand, to satisfy an overall symmetry of the elements with respect to a vertical plane perpendicular to the axes of articulations. There may also be knuckles of equal number on each element.

The knuckles of a joint are held coaxial by round bars 41, of steel for example, materializing the axes of articulation.

In the example shown, each of the extreme elements comprises a central knuckle 31B or 34B, pierced with a bore 42 for the passage of the articulation bars 41 while the arch elements 32 and 33 each comprising a pair of lateral knuckles 44 adapted to frame the central knuckles 31B and 34B, and pierced with bores 43 for the passage of the bars 41. In the example shown, these lateral knuckles form the lower bearing edges 32A and 33A of the arch elements.

The element 32 further comprises, opposite its end 32A, a pair of knuckles 45, with bores 46, adapted to frame a central knuckle 47 pierced with a bore 48, formed on the element 33 to l opposite of its end 33A.

To allow the relative angle between the arch elements to take acute values, a central recess 49, of triangular shape, is provided in the element 32 between the roots of knuckles 45 while similar recesses 50 are provided on the element 33 on either side of the root of the central knuckle 47. These recesses allow nesting of the roots of the knuckles: this nesting is almost maximal in FIG. 19, the roots of the knuckles occupying almost the entire volume recesses. Preferably, the diameter of the knuckles is greater than the thickness of the elements 31 and 34, which in particular facilitates these rotations, and reduces the necessary recesses.

As can be seen more precisely from FIGS. 19 and 20, the extreme elements 31 and 34 have, near the knuckles 31B and 34B, zones 31C and 34C thicker than their lower ends, adapted to resist the mechanical stresses appearing near these knuckles in service.

It is generally desirable for the plane containing the articulations of the end elements 31 and 34 to the arch elements 32 and 33 to be generally perpendicular to the roof 35 and to the wall 37. It is possible to provide for this purpose extreme elements of different lengths, adapted to bear, by their advantageously bevelled lower ends, on an approximately horizontal ground: the extraction of the ore in this ground can thus be done by horizontal layers in spite of the slope of the vein 36.

Preferably pins 51 are provided on the side knuckles of the arch elements, for the attachment of temporary jacks, represented by their axes 52, for assisting in the descent of the slabs.

Networks of transverse bores 53 are advantageously provided in the end elements 31 and 34, to allow, in the case if necessary, bolting of these elements in the roof and the wall. Figures 18, 19 and 20 show square arrays of bores 53 of slightly different designs.

For example, for a slightly inclined vein (for example 30 ° relative to the vertical), 8 meters thick, the elements have for example the same width of 1.5 m. with 0.5 m knuckles. thick. Elements 32 and 33 have a length of 4.9 m. (including knuckles), and elements 31 and 34 have respective lengths of 6.2 and 4 meters. The width of the tiles may even be less (0.8 to 1 m, for example).

In service, a plurality of articulated slabs are placed side by side, and ore is extracted step by step under each of them. This extraction can be done under the ends 31A and 34A of the extreme slabs, as long as the lateral anchoring of the slab on the wall walls (roof and wall) is sufficient. The jack 40 is provided to consolidate this anchoring by applying a separation force between the roof and the wall, perpendicular to them (hence the advantage that the joints 31-32 and 33-34 are in a plane perpendicular to those -this); however, it can sometimes be suppressed, or even neutralized (at least in the absence of extraction) when the caving scree is correctly distributed on the vault 32-33. If necessary additional jacks (not shown) can be mounted on the slab, in practice under the jack 40, to further strengthen the support of the extreme elements on the wall and the roof.

After a layer of ore has been removed under a slab, the latter is lowered by any appropriate means: the lateral bearing force is reduced and the descent of the slab is controlled along the wall and the roof.

To reduce the lateral support force, one of course begins by reducing the spacing thrust applied by the jack 40, and the complementary jacks, between the elements 31 and 34. It is also possible, thanks to the jack 52, to cause a bringing together of the lower ends 32A and 33A of the arch elements.

• des moyens hydrauliques (vérins) de prise en charge de la dalle;
• une ossature métallique propre à guider la dalle;
• un moyen de traction complémentaire lorsque cela s'avère nécessaire.

In a very general version, this guidance is provided by a support and lowering device comprising:

• hydraulic means (jacks) for taking charge of the slab;
• a metal frame suitable for guiding the slab;
• additional traction when necessary.

This device is mobile, and preferably self-propelled and equipped with tires.

In the case where there is no need for a traction element, the descent of the slab can be controlled by means of jacks removably attached to the arch elements of the slab, by fittings provided in the slab when of his confection.

Figures 21 and 22 illustrate, by way of example and partially, a mobile device 55 without traction arrangement. This device comprises a movable frame 56, vertical cylinders 57 supporting sleepers 58 on which end plates come to bear by means of recesses 59 provided for this purpose; horizontal cylinders 60 are also provided for the lateral anchoring of the device on the slabs framing those during descent. The frame 56 is completed with a similar frame next to it, for the descent of the other extreme element of the slab.

FIG. 23 illustrates in section a variant of an articulated slab made definitively flat, for the case for example where the width of the vein becomes too large. The main difference between this slab 61 and that of FIGS. 18 to 20 (apart from minor differences in profile) lies in the presence of transverse irons 63 formed in the arch elements during their preparation. Reinforcement bars 63 are hung on these transverse bars, on each side of the axis 41 of articulation of the arch, the latter having been laid flat. Maintaining the vault in a horizontal configuration can be ensured by coming into abutment with possible confrontation surfaces provided on the vault elements and / or by pressing the articulation zone of the vault on the reinforcement bars. We then proceed to formwork these irons 63 to stiffen the slab. The extreme elements can then be removed, so as to have only one horizontal slab. Such a monobloc slab can be laid in support on appropriate support means (ore wall or concrete pillars).

In the event of an increase in the power of the vein rendering slabs of a given type unusable, these can be left permanently by bolting the end elements to the wall with the help of the bores 53; new slabs of a more appropriate type are installed below the first to continue operation.

• les éléments extrêmes présentent des zones de moindre largeur (grâce par exemple aux décrochements 59 précités) permettant d'engager des calages en bois entre ces éléments et les épontes en cas d'irrégularité de celles-ci;
• les vérins d'écartement 40 et les vérins de rapprochement neuvent être remplacés par des vérins d'écartement et de rapprochement à double effet;
• les éléments de dalle présentent, en regard de la tranche des charnons des éléments qui leur sont articulés, des tôles arrondies (épousant avec jeu ces tranches) qui peuvent faire partie du coffrage de ces éléments lors de leur fabrication.

According to preferred arrangements not shown:

• the extreme elements have zones of narrower width (thanks for example to the abovements 59 mentioned above) making it possible to engage wooden wedges between these elements and the walls in the event of their irregularity;
• the spacing cylinders 40 and the new reconciliation cylinders be replaced by double-acting spacing and reconciliation cylinders;
• the slab elements have, opposite the edge of the knuckles of the elements which are articulated to them, rounded sheets (matching these slices with play) which can be part of the formwork of these elements during their manufacture.

The lateral anchoring of the slabs on the wall can also be done by means of piston rods which come directly to anchor in the wall, as is shown in FIGS. 24 to 26 which represent monobloc slabs 71 having cavities 72 of where laterally run channels 73.

In FIG. 24, a slab 71 is supported by low walls 74 and 75 of ore and is supported on the left against a hanging wall 76. In the cavity 72 are cylinders 77 whose cylinders 77A are supported against the left wall of the cavity and whose pistons 77B are extended by pins 78 intended to pass through the channels 73 and to come into abutment against the wall 79. These jacks are supplied with fluid by flexible pipes, not shown.

As is apparent from FIGS. 25 and 26, three jacks 77 can be provided at each end of each slab put into operation, the time to cut down the ore located at the top of the walls 74 and 75.

A carriage 80 fitted with wheels comprises a support structure 82, movable in height under the action of jacks 81 adapted to come to rest on the ground for reasons of stability, carrying cradles 83 for groups of transverse jacks 77 and rails 84 adapted to come to bear under the slabs to allow support and guidance downhill.

The tiles, for example, are 7 m long. a width of 7.5 m. and a 0.5 m cavity. Depth.

As the operating front advances (from left to right in Figure 26), the bottom of the gallery is first cut down, then the top of the gallery. Before cutting down the ore at the top of the walls supporting a slab (here two slabs), the latter is placed in lateral support by the installation of jacks 77; the top of the minerals is cut down (most often the cart 80 is removed for reasons of space), then the cart 80 is brought back and the slab is supported by the rails 84 while the pressure in the jacks 77 is released; the descent of the slabs is controlled by the cylinders 81. The operation is then repeated for the slab (s) immediately to the right.

In FIGS. 24 to 26, the jacks 77 all act in the same direction by pressing the slab towards one hanging wall and pins towards the other hanging wall. In a variant not shown, recommended when the wall surface is irregular, the jacks are arranged head to tail, with pins, protruding through channels 73 formed on either side of the central cavity, each side of the slab whose walls of the central cavity take up the spacing forces.

It goes without saying that the foregoing description has been offered for information only and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention.

Thus, for example, the cylinders 40 for plating the end elements against the wall can be replaced by a plurality cylinders individually pressing one end element against a wall, by pressing directly on the other wall, through the opposite end element. Such jacks can, for example, act on the flared part of an end element (near thick areas 31C or 34C) and pass through the end element opposite by means of a recess 29 (see FIG. 22). Such individual plating means make it possible, for example, to lower the opposite end elements alternately, one end element remaining fixed while the other descends, and vice versa. The extraction on the ground is then done alternately, sometimes along one wall, sometimes along the other wall.

Claims (26)

1. A mining or underground quarrying method by downward slicing under a roof, characterized in that the roof being substantially horizontal it is divided into a plurality of roof areas supported independently of one another by a plurality of independent roof slabs (D1, ..., Dn, Dp, 32, 33, 71) juxtaposed side by side and supported by supporting means so as to form conjointly a roof protecting against material which caves in and, as the mineral ore is mined below this roof, the said areas are progressively caved in individually to a limited height by successively lowering each of the roof slabs under which the ore has already been mined using, in order to do this, mechanical means for temporary support and for lowering (17, 55, 80) which are fixed to at least one movable frame which is used successively for the different roof slabs.
2. A method according to claim 1, characterized in that the roof slabs bear on pillars (M) of ore and after the ore has been mined from between the pillars the roof slabs (Dp) are supported artificially (17) by the said mechanical means for temporary support and for lowering, the height of the pillars is reduced and the roof slabs are lowered.
3. A method according to claim 1, characterized in that the roof slabs comprise supporting posts (P) and after the ore has been removed from between the posts the roof slabs are supported mechanically, the ore is removed from below the posts and the roof slabs are lowered.
4. A method according to claim 3, characterized in that the supporting posts (P) are movable laterally and after the ore has been removed from between the posts the roof slabs are supported mechanically, the posts are moved laterally, the roof slabs are lowered and the ore is mined from the locations from which the posts were moved.
5. A method according to claim 1, characterized in that the roof slabs are supported by bearing laterally against the walls of the lode in the case of narrow veins.
6. A method according to any one of claims 1 to 5, characterized in that the roof slabs are disposed in lines and rows, and the workings are advanced and the roof slabs are lowered line by line.
7. A method according to any one of claims 1 to 5, characterized in that the roof slabs are disposed in lines and rows, and the workings are advanced and the roof slabs are lowered row by row.
8. A supporting installation for mining and underground quarrying by downward slicing under a roof adapted to implement a method according to any one of claims 1 to 7, characterized in that it comprises a substantially horizontal roof protecting against material which caves in which is formed by a plurality of independent elementary roof slabs (Dp...) juxtaposed side by side and equipped with supporting means (P, M) and variable height mechanical means (17, 55, 80) for supporting and for lowering adapted to lower these roof slabs individually step by step, these means (17, 55, 80) for supporting and for lowering roof slabs being fixed on one or more movable frames which are used successively for the various roof slabs.
9. An installation according to claim 8, characterized in that the means (17, 55, 80) for supporting and for lowering roof slabs comprise hydraulic jacks.
10. An installation according to claim 8 or claim 9, characterized in that the roof slabs (Dp) are made of reinforced concrete.
11. An installation according to any one of claims 8 to 10, characterized in that the supporting means (M) consist of the ore itself.
12. An installation according to any one of claims 8 to 10, characterized in that the supporting means (P) are fixed and attached to the roof slabs.
13. An installation according to any one of claims 8 to 10, characterized in that the supporting means (P') are movable laterally.
14. An installation according to claim 12 or claim 13, characterized in that the supporting means (P, P') are made of reinforced concrete.
15. An installation according to any one of claims 8 to 10, characterized in that when the roof slabs (31, 34, 71) occupy almost all the width between the lode walls the supporting means are means (40, 77) for bearing laterally against the lode walls.
16. An installation according to claim 15, characterized in that the means for bearing laterally are jacks (40, 77).
17. An installation according to any one of claims 8 to 10 and 15, characterized in that the roof slabs comprise two elements (32, 33) of an articulated vault (41) forming a variable angle vault supported flying buttress fashion on the lode walls and complemented by two end elements (31, 34) articulated to the vault elements and adapted to lie along the lode walls.
18. An installation according to claim 17, characterized in that horizontal jacks (40) are provided to press these end elements against the lode walls.
19. An installation according to claim 17 or claim 18, characterized in that at least one jack (52) is provided for reducing the angle between the vault elements.
20. An installation according to claim 15, characterized in that the unitary construction type roof slabs (71) comprise a central cavity bordered by transverse walls and a plurality of transverse channels (73) on at least one side of the said cavity, horizontal jacks (77) being adapted to bear against the walls of the lode through the said channels whilst bearing against one of the walls of the cavity.
21. An installation according to any one of claims 8 to 20, characterized in that a flexible metal mesh (14) is placed between the roof slabs (Dp) and the roof.
22. An installation according to any one of claims 8 to 20, characterized in that in order to protect the open gaps, the roof slabs comprise shields (20) supported by deformable triangles (21).
23. An installation according to claim 22, characterized in that the roof slab (Dp) adjacent to a roof slab (Dp-1) equipped with a shield (20) supported by deformable triangles (21) comprises a cusp (22) adapted to press the shield down when this adjacent roof slab is lowered.
24. An installation according to any one of claims 8 to 23, characterized in that it comprises at least one row of roof slabs the supporting means (P, M) of which are sufficiently far apart to permit mining machines to pass between them.
25. An installation according to any one of claims 8 to 24, characterized in that the roof slabs adjacent to the walls of the working site comprise forepoling irons that can be advanced or retracted to provide protection between the roof slabs and the walls of the cavity being mined.
26. An installation according to claim 25, characterized in that the forepoling irons are also supported by pit props.

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