The method sublevel stoping It is a method of exploitation with natural support, in which pillars are used in the course or dip of the area of interest. The bearing is the imaginary line that is drawn by intersecting the geological plane of the exploitation area and a perfectly horizontal plane..
For its part, the dip is the angle of inclination of the geological plane with reference to the horizontal plane. Columns can be placed in both locations to condition the exploitation area without filling or sinking the surface; that is, without using artificial or natural fortifications.
The sublevel stoping it is used only when the deposit has favorable characteristics for it; otherwise it is an extremely dangerous mechanism.
As the tension of the columns and their measurements increase, the exploitation technique must evolve towards transitional methods.
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The sublevel stoping It is an excavation method that consists of dividing the deposit into several vertical sections, to empty the basic unit of mining exploitation, called mansion.
The mineral that is collected in the mine is accumulated in trenches placed at the foot of the house, and from there the extraction begins applying different techniques, according to the convenience of the case..
The technique is called sublevel to refer to the sublevels or galleries of the deposit, in which mining is carried out. The main characteristics of this method of mining are the following:
- The sublevel stoping requires a lot of precision and accuracy when it comes to the design of the perforation meshes.
- This method is applicable in tabular reservoirs with a width greater than 10 meters. For the method to be successful, it is recommended that the body of the mineralized structure be regular.
- It is recommended for long and sloping reservoirs. However, the ideal morphology for the sublevel stoping are the vertical reservoirs.
- Likewise, it is feasible to apply the sublevel stoping in mantle-type reservoirs (horizontal mantle or inclined mantle). In this case, the massif is divided into sections separated by pilasters, until the entire area is divided.
- So that the sublevel stoping However favorable, the rock containing the mineral and the surrounding rock must be extremely stable. This implies that both structures are self-supporting.
- In the sublevel stoping reservoir drilling and blasting - that is, the separation and fragmentation of the rock massif - can be carried out as independent processes.
- This method is massive and highly productive. The productivity indices show average values between 15 and 40 tons of extraction per man in each production shift.
- Each mansion is capable of producing more than 25,000 tons per month, depending on the nature of the mine..
- It is a fairly inexpensive underground mining method compared to other mining extraction strategies. The cost of mining ranges between 7 and 14 US dollars per ton extracted.
- The mine recovery percentages are between 60% and 80%. The variation depends on the quality and nature of the excavation slabs..
- It is a safe method, in which the possibility of rockfall is controlled.
- Depending on the exploitation method used, the dilution - that is, the percentage of sterile material that is mixed with the extracted mineral - is between 3% and 10%. The material to dilute the pure mineral is generally located on the ceiling and hanging walls.
- The drills used have lengths of up to 30 meters. The diameter of the drill bit can vary between 50 and 200 millimeters, depending on each case..
- Applicable reservoirs according to RMR classification (for its acronym in English: rock mass rating) are those with an RMR index greater than 50. This means that the method of sublevel stoping it is recommended in regular, good and very good rocky massifs, with an internal friction angle between 35 ° and 45 °.
The exploitation process involves the construction of the following parts within the mine:
Construction of a transport gallery and some structures for cargo transport, to enable mining extraction points.
Also known as funnels, they are fractions located at the base of the mansion, in which the mineral extracted from the mine accumulates..
It refers to the drilling sublevels, which are distributed at different heights, according to the geometry of the reservoir..
It is a ramp that facilitates access to the drilling galleries. This fireplace is located at the back of the house.
In this the excavation of the compensation chamber is carried out, also known as slot, through which the initial cut of the entire process is forged.
Given the characteristics mentioned above, the extraction method sublevel stoping It offers multiple advantages when it comes to the mining industry. Some of these are detailed below:
- It is a highly efficient method. Production caps of up to 110 tons per man have been registered, in one production shift.
- Under good management, the sublevel stoping brings with it excellent monthly production rates.
- The sublevel stoping it is an extremely safe method, since the personnel are exposed to the area for much less time, compared to other extraction alternatives.
- Low dilution implies a higher state of purity of the extracted mineral.
- Once the production blasting begins, the mineral is immediately available.
- Mines recover quickly after being subjected to this method.
Some of the disadvantages of sublevel stoping are as follows:
- It is a non-selective method. This means that, necessarily, the mineral body must have a regular silhouette; in other cases the method is not feasible.
- The method is inefficient when the lean angles are not steep.
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