SUBLEVEL STOPING: FEATURES, ADVANTAGES AND DISADVANTAGES - SCIENCE - 2025

The sublevel stoping method 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 when the geological plane of the exploitation area intersects with a perfectly horizontal plane.

For its part, the dip is the angle of inclination of the geological plane with reference to the horizontal plane. In both locations, columns can be placed to condition the exploitation area without filling or sinking the surface; that is, without using artificial or natural fortifications.

The sublevel stoping 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.

characteristics

The sublevel stoping 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 mansion, 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 great precision and accuracy as regards 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 deposits. However, the ideal morphology for sublevel stoping is vertical reservoirs.

- Likewise, it is feasible to apply 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.

- For sublevel stoping to be conducive, the rock containing the mineral and the surrounding rock must be extremely stable. This implies that both structures are self-supporting.

- In sublevel stoping, the drilling of the reservoir and the 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 recovery percentages of the mine 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 for diluting 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 the RMR (rock mass rating) classification are those with an RMR index greater than 50. This means that the sublevel stoping method is recommended in regular, good and very good rock massifs, with an angle of internal friction between 35 ° and 45 °.

Construction of parts within the mine

The exploitation process involves the construction of the following parts within the mine:

Production level

Construction of a transport gallery and some structures for cargo transport, to enable mining extraction points.

Ore collecting ditches

Also known as funnels, they are fractions located at the base of the mansion, in which the mineral extracted from the mine accumulates.

Galleries

It refers to the drilling sublevels, which are distributed at different heights, according to the geometry of the reservoir.

Fireplace

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 a slot, through which the initial cut of the entire process is forged.

Advantage

Given the characteristics mentioned above, the sublevel stoping extraction method 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 recorded in one production shift.

- Under good management, sublevel stoping brings with it excellent monthly production rates.

- The sublevel stoping 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 available immediately.

- Mines recover quickly after being subjected to this method.

Disadvantages

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 tilt angles are not steep.

References

1. Castillo, B. (2015). Underground mining methods: Sublevel stoping. Recovered from: es.slideshare.net
2. Gutiérrez, D. (2014). "Application of the method of exploitation sub level stoping in copper mantle". National University of Engineering. Lima Peru. Recovered from: cybertesis.uni.edu.pe
3. Exploitation Methods: Sublevel stoping (sf). Recovered from: u-cursos.cl
4. Rivera, E. (2015). "Subblevel stoping mining method in Corporación Minera Castrovirreyna SA". National University of Engineering. Lima Peru. Recovered from: cybertesis.uni.edu.pe