Cut and Fill Stoping

Cut and fill stoping is a method of underground mining used in vertical stopes and in mining high-grade irregular ore bodies. The rock mass surrounding the ore deposit is also usually weak unable to support loads over an extended stoping height. As the name of the method implies, successive cutting of the ore into horizontal slices is carried out starting from the bottom of the stope and progressing upwards towards the surface. This horizontal slicing leaves a void that is backfilled with material to provide support until all the ore is extracted from the mine.


Process

In a cut-and-fill stoping operation, ramps or inclined tunnels are excavated to connect the surface to the underground ore body. Drifts are excavated to access the ore; chute raises are excavated to provide the easy removal of ore from the mine.


Drilling is the first stage in removing slices or ore using a mounted pneumatic or rotary percussion jumbo drill. A secondary stage involves blasting the ore to further break it up. Blasting is typically carried out using one or a combination of ammonium nitrate and fuel oil (ANFO), slurries, and emulsions. Bulk blasting methods may also be used. In some circumstances, a mechanism for secondary breakage of the ore is necessary and the drill-and-blast method, mudcapping, or impact hammers are used to accomplish this. It is common to remove horizontal slices of ore that span the entire width and length of the stope.


Mucking of ore is accomplished with a wheel loader, front end loader, or motor scraper that pushes the mucked ore to a mill hole and chute connected to a haulage passage underneath.The ore is then hauled away in dump trucks, load haul dump trucks (LHDs), and scoop trams to a lower elevation within the mine and then transported up to the surface via a ramp by a scoop tram or a load haul dump.
Once a slice of ore has been completely mined from the stope, the empty space left behind is backfilled hydraulically. Sometimes ore waste is mixed with other materials such as sand, cement, waste rock, or dewatered mill tailings—a low-grade ore that has been rejected for processing—to make the backfill. Backfill provides a working floor for miners and equipment as the mining progresses and also supports the stope walls.


Infrastructure Requirements

Cut and fill mining requires a number of unique infrastructural requirements mostly pertaining to bakcfill preparation and delivery. These requirements are dependent on which back fill method is chosen. For paste or hydraulic backfill, the mine site must include a backfill plant and the underground network used to deliver the backfill to the working stopes. The underground network will include piping down to each level, and moveable pipes on each level to reach the individual stopes. Many mines use gravity to drive the delivery system, however sometimes it is necessary to introduce pumps into the system. The nature of the backfill means that wear will occur on the pipes, and their condition must be monitored in order to ensure that the system does not encounter down time when it is most needed. An example of the backfill infrastructure required for paste or hydraulic backfill is displayed below. The infrastructure required for rock fill is somewhat different, typically requiring mechanical dumping access so that LHDs or trucks can transport and deliver crushed rock fill.

Advantages

  • High selectivity and low dilution achieved.
  • Minimal development is required, low capital cost.
  • Versatile for mining method, can follow irregular orebodies.
  • Flexible, mining method can be easily modified.
  • Low equipment investment relative to other methods.
  • Minimizes ground Movement.

Disadvantages

  • Cyclical ore production.
  • Labour and skill intensive.
  • Dangerous working conditions, work conducted a top freshly blasted rock.
  • High degree of ground required.
  • Expensive and costly Ventilation system.
  • Need for backfill infrastructure (piping and paste plant)
  • Not suitable for low grade ore due to high mining cost.


Video explaining the Cut and Fill Stoping:





No comments:

Post a Comment