OA20820A - Operating process for an open-pit mining site. - Google Patents

Abstract

An operating process for a mining site comprising a layer (3) of a material to be mined, the process comprising the following operations: - digging a gallery (5) having an end opening to the outside; - arranging a transport conveyor (19) in the gallery, the conveyor extending at least to the end; - digging a shaft (21), opening into the gallery, through the layer (3) the layer (3) of material comprising a majority of superimposed sublayers (23), each step of extracting a sublayer (23) comprising the following operations - fragmentation of the material of the sub-layer (23); - transporting the material to the at least one shaft (21) and dumping it into the at least one shaft (21) - transporting the material by means of the transport conveyor (19) along the gallery (5) at least to the end ( 7).

Description

Operating process for an open-pit mining site

The invention relates in general to the operation of an open-pit mining site, such as 5 an open-pit mine or an open-pit quarry.

Such a site comprises a layer of a material to be mined.

The layer is typically extracted sub-layer by sub-layer, the sub-layers being extracted one after the other starting from the top.

The operation of the site thus results in the création of a pit or the leveling of a 10 mountain progressively, as the sub-layers are removed.

This pit can reach a great depth, since the layer of material to be extracted can be more than 150 m thick.

The material is typically hauled out of the pit by a fleet of dump trucks. These dump trucks, once loaded, weigh several dozen tons. The trucks carry the material from the 15 bottom of the pit to a material storage and/or disposai station. At this station, the material is temporarily stored and then transferred to another means of transport: train, conveyor belt, etc...

Such an operating process requires the use of a large number of trucks, and results in the consumption of a large amount of fuel. Indeed, the trucks are very heavy, and must 20 lift the material to a significant height, the consumption of fossil fuel being therefore high.

In this context, the invention aims at proposing an operating process which consumes less fossil fuel while allowing an efficient operation of the extraction site.

To this end, the invention relates to a process for operating an open-pit mining site such as an open-pit mine or an open-pit quarry, the site comprising a layer of a material to 25 be mined, the process comprising a phase of developing of the mining site, followed by a phase of operating of the mining site, the phase of developing comprising the following operations:

- digging a gallery under said layer, the gallery having an end opening to the outside;

- arranging a transport conveyor in the gallery, the transport conveyor extending at 30 least to the end;

- digging at least one shaft through the layer, the shafts opening into the gallery; the layer of material to be extracted comprising a pluralîty of sub-layers superimposed one on top of the other, the phase of operating comprising successive steps of extractmg one of the sub-layers, the sub-layers being extracted one after the other starting from the top, 35 each step of extracting a sub-layer comprising the following operations :

- breaking of the material of the sub-layer;

- haulage the material to the at least one shaft and dumping it into the at least one shaft;

- transporting the material by means of the transport conveyor along the gallery at least to the end.

Thus, the material is transported to the discharge station by a transport conveyor, running in a gallery under the layer of material to be mined. It is therefore no longer necessary to use a fleet of trucks to bring the material up out of the pit that is created as a resuit of the extraction site.

Trucks are at most used for the transporting operation of the material, from the front of the mine face to the at least one shaft. The at least one shaft passes through ail the sublayers. In order to get from the mine face to the shaft, the différence in height to be covered by the trucks is considerably reduced.

Because of the short distance and the reduced height, the travel time from the mine face to the at least one shaft is short, so that the number of trucks required to transport the material is much less than in a conventional mining method.

Ail in ail, the consumption of fossil fuel for the transfer of the material to the storage and/or disposai station is to a very large extent reduced.

By using a conveyor belt, the material can be transported to the disposai station at a high pace. This makes the operating process extremely efficient.

The operating process can furthermore present one or more of the following features, considered individually or in any technically possible combination.

- a crusher is arranged above the at least one shaft, whereby the material is crushed before dumping into the at least one shaft;

- a plurality of shafts are dug through the layer during the digging operation, each shaft opening into the gallery, the shafts being distributed along the gallery;

- the crusher is mobile, and is moved successively over several shafts during the step of extracting a sublayer;

- during the step of extracting a given sub-layer, the crusher is moved along a trench in the sub-layer immediately below;

- during the step of extracting a given sub-layer the crusher remains at the same level, the crusher being lowered to a lower level at the end of the step of extracting said given sub-layer;

- the haulage operation is carried out by trucks, the trucks remaining substantially at the same level during the step of extracting a given sub-layer;

- a transfer conveyor is arranged under a lower end of the or each shaft, the transfer conveyor being arranged to transfer the material onto the transport conveyor

- a hopper is arranged between the lower end of the shaft and the transfer conveyor, and

- the transport conveyor is a belt conveyor.

Further features and advantages of the invention will be apparent from the detailed description given below, by way of indication and not in any way limiting, with reference to the appended figures, of which:

[Fig. 1] Figure 1 is a top view of an open-pit mining site;

₁ θ [_Fig 2] Figure 2 is a longitudinal sectional view of the mining site of Figure 1, showing the gallery dug underneath the layer to be mined and the various shafts opening into the gallery;

[Fig. 3] Figure 3 is a magnified view of a shaft, showing a crusher positioned above the shaft;

[Fig. 4] Figure 4 is a magnified view of the crusher; and

[Fig. 51 Figure 5 is an enlarged view of the transfer conveyor positioned below the shaft in Figure 3, allowing the crushed material to be transferred to the transport conveyor running through the gallery.

The process that will now be described is a process for operating an open-pit mining 20 site of the type shown schematically in Figure 1.

This mining site 1 is an open-pit mine or an open-pit quarry.

The site comprises a layer of a material to be mined 3. This layer 3 typically has a significant length, width and depth.

For example, the layer 3 présents a longitudinal length of several kilometers, a 25 transverse width of several kilometers, and présents a depth of several tens or even several hundred meters.

The longitudinal direction corresponds to the direction in which the layer 3 présents its largest dimension. The transverse direction is the direction perpendicular to the longitudinal direction.

3θ For example, layer 3 présents a length of 8 km, a width of 2 km and a depth of 170

m.

The mass of material to be extracted is several million tons, for example 90 million tons.

The material to be extracted is of any type: ore containing a métal such as iron, 35 aluminum or nickel, coal, etc...

The process comprises first of ail a phase of developing the mining site 1, followed by an phase of operating the mining site 1.

The phase of developing comprises an operation to dig a gallery 5 underneath the layer 3.

The gallery 5 is an underground gallery.

Advantageously, the gallery 5 is arranged in such a way as to traverse the layer 3 over its greatest length, in other words, longitudinally.

it extends along the entire longitudinal length ofthe layer 3.

The gallery 5 has an end 7 opening outwards at a distance from the layer 3.

The end 7 opens on the surface.

It is typically located in the vicinity of a material storage and/or disposai station 9, as illustrated in Figure 2.

Thus, the gallery 5 comprises a main section 11 located in line with the layer 3, in other words, vertically underneath the layer 3.

This main section is typically substantially horizontal. It is located at a shallow depth underneath the layer 3.

The gallery 5 also comprises an inclined section 13 connecting the main section 11 to the end 7. The inclined section 13 ascends from the level of the main section 11 to the ground level, at which the end Ί is located.

At the end opposite to the end 7, the gallery 11 is closed, or as shown in Figure 2, has another end 15 opening to the outside. The other end 15 opens at ground level, longitudinally on the other side of the layer 3 from the end 7. The other end 15 is connected to the main section 11 by another inclined section 17.

Station 9 is provided for temporary storage and/or disposai of the material.

At station 9, the material is for example stored in a heap, or in a mass, as illustrated in Figure 2. At station 9, the material is loaded into a means of transport (not shown) for removal of the material from the site to an end use location.

This means of transport is of any suitable type: train, conveyor belt, truck, etc...

Alternatively, the station 9 comprises means to transform the material 9, for example to extract a component of interest from the evacuated material.

The phase of developing further comprises an operation of arranging a transport conveyor 19 in the gallery 5.

The conveyor is visible in Figures 3 and 5.

The transport conveyor 19 extends at ieast to the end 7 of the gallery 5.

Typically, it extends to the material storage and/or discharge station 9.

It extends over at least part of the length of the gallery 5.

Typically, it extends along the entire length of the gallery 5.

The transport conveyor 19 is of any suitable type. Typically, it is a beit conveyor.

The phase of developing further comprises the digging of at least one shaft 21 through the layer 3. The at least one shaft 21 opens into the gallery 5.

The at least one shaft 21 extends through the entire thickness of the layer 3, from the upper surface 8 of the layer 3 to the gallery 5.

Typically, the at least one shaft 21 is vertical.

Its upper end is open at the level of the upper surface 8 of the soil. Its lower end communicates with the gallery 5.

Preferably, a pluralîty of shafts 21 are excavated through the layer 3 during the excavation operation, each shaft 21 opening into the gallery 5.

The shafts 21 are distributed along the gallery 5. Preferably, the shafts 21 are evenly distributed along the gallery 5. In Figure 2, some shafts are not shown.

The transport conveyor 19 is preferably arranged so as to pass each shaft 21.

The layer 3 of material to be extracted comprises several sub-layers 23, one on top of the other.

The phase of operating comprises successive steps of extraction of one of the sublayers 23, the sub-layers 23 being extracted one after the other starting from the top.

In other words, the site is mined layer by layer, the material of one layer being mined before starting the mining of the next layer.

Each sub-layer 23 présents a height typically of between 5 and 15 meters. It may also be referred to as a “step”.

The sub-layers 23 are not physically distinct from each other. Each sub-layer simply corresponds to the thickness of material removed during a step of site operation.

Typically, during an extraction step, only one area of the sub-layer 23 is extracted. in the next extraction step, the area of the lower sub-layer located exactly below the area of the upper layer already extracted is extracted. In other words, the site is mined area by area, which makes it possible to reach the depths where products of interest are found more quickly.

Alternatively, the entire sub-layer 23 is removed before the lower sub-layer is started.

Each step of extracting a sub-layer 23 comprises the following operations:

- breaking of the material of the sub-layer 23;

- haulage of the fragmented material to the at least one shaft 21 and dumping it into the at least one shaft 21 ;

- transporté the material by means of the transport conveyor 19 along the gallery 5 to the outside, typically to the material storage and/or disposai station.

The breaking operation is carried out by any suitable means: explosives, mechanical shovels 25, scrapers, etc. (Figure 3).

The breaking of the sub-layer is carried out, for example, from one longitudinal end of the area to be extracted, progressé longitudinally towards the other end.

The mine face 26 thus moves substantially longitudinally from one end of the sublayer to the other.

Haulage of the material is performed by large capacity dump trucks 27, as shown in Figure 3.

The trucks 27 are used to transport the material from the face 26 to the at least one shaft 21. At the face 26, they are loaded by, for example, mechanical shovels 25 or loaders not shown.

They transport the material to the shaft 21 closest to the mine face 26.

Advantageously, and as illustrated in Figures 3 and 4, a crusher 29 is arranged above the shaft 21, the material being crushed before discharge into the shaft.

The crusher 29 is of any suitable type. For example, the crusher 29 is a primary gyratory crusher.

The crusher 29 crushes the material transported by the trucks 27 into blocks of suitable size for transport on the transport conveyor 19.

As seen in Figures 3 and 5, a transfer conveyor 31 is arranged under a lower end of the or each shaft 21.

The transfer conveyor 31 is arranged to transfer the material onto the transport conveyor 19.

The transfer conveyor 31 is for example a plate conveyor.

The plates 33 are metallic and are hinged to each other to form a continuous track. This track is in a closed loop and is mounted around two turning drums 35, located at the two ends of the transfer conveyor.

The track thus comprises an upperstrand 37 receiving the material arriving from the shaft 21, supported by a large number of support rollers 39. It also includes a lower return strand, running under the upper run.

A hopper 41 is arrangée! between the lower end of the shaft 21 and the transfer conveyor 31. The hopper 41 directs the material exiting the shaft 21 onto the transfer conveyor31.

A downstream end of the transfer conveyor 31 is located immediately above the transport conveyor 19. Another hopper 43 is located below said downstream end. It is arranged so as to receive material from the transfer conveyor 31, and to guide it to fait onto the transport conveyor 19.

It should be noted that métal plating 45 is placed around the top strand 37 and around the downstream end of the transfer conveyor. This plating 45 extends up to the lower opening of the hopper 41. The plating 45 keeps the material coming through the hopper 41 on the upper strand 37 of the transfer conveyor, and at the downstream end of the transfer conveyor, guides the material to the hopper 43.

The transfer conveyor 31 is mounted on a rigid frame 47, capable of supporting a considérable weight.

Similarly, the transfer conveyor 31 is also capable of supporting a large mass of material.

As explained below, in operation, the shaft 21 is filled almost to its full height with the crushed material from the crusher 29. At least a fraction of the weight of the column of material filling the shaft 21 is supported by the transfer conveyor 31, and this weight is taken up by the frame 47. The frame 47 and the transfer conveyor 31 are sized to support this weight.

As seen in partîcular in Figure 4, the crusher 29 is mobile, and is moved successively above each shaft 21 of the area to be extracted during the operating phase of extracting a sub-layer.

The crusher 29 is mounted on tracks 48, so that it can be moved from one shaft 21 to another.

As seen in Figures 3 and 4, during the step of extracting a sub-layer, the crusher 29 moves along a trench 49 that is provided in the immediately lower sub-layer 23.

The trench 49 is substantially parallel to the gallery 5.

It passes through ail the shafts 21 in the area to be mined. It extends over a fraction of the length of the gallery 5 and is located vertically in line with it.

The trench 49 is partially covered by a floor 51, supported by piles of blocks 53, typically made of concrète. An opening 55 is made in the floor 51, in line with the hopper 57 for feeding the crusher 29.

The dump trucks 27 dump their load through the opening 55, to feed the crusher 29.

Thus, during the operating phase, each sub-layer 23 is successively excavated, starting with the upper sub-layer.

Typically, for a given sublayer, the mine face 26 moves longitudinally from one end of the area to be extracted from the sublayer 23 toward the other end. Once the mine face . 26 has passed the first shaft 21, located closest to the starting end, a first section of the trench 49 is created in the lower sublayer 23, and the crusher 29 is positioned above the first shaft 21.

The material extracted from the mine face 26 is loaded into the trucks 27, which transport it to the first shaft 21. in orderto do this, the trucks drive over the upper surface of the lower sub-layer.

They dump the material into the opening 55.

The hopper 57 guides the dumped material into the crusher 29.

The material is crushed in the crusher 29 and reduced to blocks that fall into the shaft 21.

The shaft 21, as shown in Figure 3, is constantly filled with a column of crushed material. Thus, the fall height of the crushed material is relatively limited, so that the shock to the transfer conveyor 31 at the bottom of the shaft 21 is very small.

At the bottom of the shaft 21, the crushed material exiting the shaft is dîrected through the hopper 41 onto the transfer conveyor 31. The upper strand 37 moves the crushed material to the downstream end of the transfer conveyor.

During its movement, the crushed material is guided by the plating 45.

At the downstream end, it falls into the hopper 43, which guides the crushed material so that this falls onto the transport conveyor 19.

The transport conveyor 19 carries the material along the gallery 5, to the outside of the gallery, typically to the storage and/or disposai station 9.

The flow rate of material supplied by the trucks 27 is substantially equal to the flow rate of the crusher 29.

Similarly, the flow rate of the transfer conveyor 31 is set to be equal to the flow rate of the crusher 29. The transport conveyor 19 is set so as to discharge the material at a rate equal to that from the transfer conveyor 31.

This prevents material from accumulating at the crusher 29, in the shaft 21, at the transfer conveyor 31 or at the transport conveyor 19.

Once the mine face 26 has passed the second shaft 21, the trench 49 is extended, and the crusher 29 is moved to the second shaft 21.

The trucks 27 then transport the material from the mine face 26 to the second shaft, so as to limit the amplitude of the material transport.

The mine face 26 moves progressively to the other end of the area, ail the shafts 21 located in the area being used in turn to evacuate the material to the gallery 5.

The trench 49 is extended from shaft to shaft as the mine face 26 advances.

Thus, the shafts 21 distributed along the gallery 5 are put into service successively during the extraction stage of the sub-layer 23 as the mine face 26 advances.

Once the mining of a given sub-layer 23 is completed, or substantially completed, the mining of the sub-layer 23 immediately below begins. The crusher 29 is then moved to the lower level.

Thus, during the step of mining a given sublayer 23, the crusher 29 is moved exclusively within a single level, which in the example shown corresponds to the level of the next lower sub-layer 23. The crusher 29 is lowered to the lower level at the end of the extraction step of said given sub-layer.

Similariy, during the extraction step of a given sublayer, the transport operation is performed by the trucks 27, these trucks remain at substantially the same level throughout the extraction step of the sub-layer 23.

The method described above has multiple advantages.

The use of a crusher arranged above the shaft allows the material to be reduced into blocks that can be easily transported by the transport conveyor 19. This contributes to the efficiency of transporting the material.

The fact that several shafts are dug along the length of the gallery 5 means that a shaft close to the mine face can always be used for the removal of the material. This reduces the distance that the trucks transporting the material from the face to the shaft hâve to travel and reduces the amount of fuel used.

The use of a mobile crusher is economical, as the same crusher is used at ail stages of the site operation. The investment in equipment is reduced.

Moving the crusher in a trench in the sub-layer immediately below the mined sublayer allows for easy dumping of material into the crusher. This contributes to the efficiency of the operating process.

The fact that the crusher remains at one level throughout the extraction of a given sub-layer reduces the number of moves and the complexity of moving the crusher, which contributes to the efficiency of the operating process.

The fact that the trucks during the extraction step of a given sub-layer remain substantially at the same level contributes to the réduction of fuel consumption by these trucks.

The use of a transfer conveyor arranged under the lower end of each shaft to transfer the material to the transport conveyor makes this transfer efficient and economical.

The use of a belt conveyor allows the material to be transported along the gallery efficiently and economically, with low energy consumption.

The operating process can be varied in many ways.

It is possible to excavate several galleries under the layer. These galleries can be parallel or non-parallel. A transport conveyor is arranged in each gallery. Alternatively, a single transport conveyor is used, which is dismantled and reassembled from one gallery to the next.

The development phase can comprise the digging of a single shaft, or on the contrary, several shafts.

The extraction step of a given sub-îayer may not be complété when the extraction of the next lower sub-layer starts. For example, the extraction step of the next lower sublayer may start when the extraction step of the sub-layer is only 50% complété.

In this case, several shafts are advantageously in operation at the same time, one shaft for the upper sublayer and another for the lower sublayer.

Several crushers are used simultaneously.

The haulage of the material to the shaft can be done by any suitable vehicle or machine, not necessarily by the trucks shown in the figures.

Claims (10)

1. An operating process for an open-pit mining site, the site comprising a layer of a material to be mined, the process comprising a phase of developing the mining site, followed by a phase of operating the mining site, the phase of developing comprising the following operations:

- digging a gallery under said layer, the gallery having an end opening to the outside;

- arranging a transport conveyor in the gallery, the transport conveyor extending at least to the end;

- digging at least one shaft through the layer, the shaft opening into the gallery; the layer of material to be mined comprising a plurality of sub-layers superimposed one on top of the other, the phase of operating comprising successive steps of extracting one of the sub-layers, the sub-layers being extracted one after the other, starting from the top, each step of extracting a sub-layer comprising the following operations :

- breaking of the material of the sub-layer;

- haulage of the material to the at least one shaft and dumping into the at least one shaft;

- transporting the material by means of the transport conveyor along the gallery at least to the end.

2. The operating process according to claim 1, wherein a crusher is arranged above the at least one shaft, the material being crushed before dumping into the at least one shaft.

3. The operating process according to claim 1 or 2, wherein a plurality of shafts are dug through the layer during the digging operation, each shaft opening into the gallery, the shafts being distributed along the gallery, said shafts being brought into operation successively during the step of extracting a sub-layer as a mine face advances.

4. The operating process according to claim 3 and claim 2, wherein the crusher is mobile, and is successively moved over a plurality of shafts during the step of extracting a sub-layer.

5. The operating process according to claim 4, wherein during the step of extracting a given sub-layer, the crusher is moved along a trench provided in the next lower sub-layer.

6. The operating process according to claim 4 or 5, wherein during the step of extracting a given sub-layer the crusher remains at the same level, the crusher being lowered to a lower level at the end of the step of extracting said given sub-layer.

7. The operating process according to any of the claims 1 to 6, wherein the haulage operation is performed by trucks, the trucks remaining substantially at the same level during the step of extracting a given sublayer.

8. The operating process according to any of the claims 1 to 7, wherein a transfer conveyor is arranged under a lower end of the or each shaft, the transfer conveyor being arranged to transfer the material onto the transport conveyor.

9. The operating process according to claim 8, wherein a hopper is arranged between the lower end of the shaft and the transfer conveyor.

10. The operating process according to any one of the claims 1 to 9, wherein the transport conveyor is a belt conveyor.