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Wednesday, 25 July 2018 01:00

Block caving: A new mining method arises

Block caving-A new mining method arises Block caving-A new mining method arises.

Block caving is a new alternative method of developing new mines or extending the operation of open pits.

Block caving is an underground hard rock mining method that involves undermining an ore body, allowing it to progressively collapse under its own weight. It is the underground version of open pit mining. In block caving, a large section of rock is undercut, creating an artificial cavern that fills with its own rubble as it collapses. This broken ore falls into a pre-constructed series of funnels and access tunnels underneath the broken ore mass. These mineworks are sheltered from the collapsing ore inside bunker-like mass of rock, and miners extract it continuously from here. The collapse progresses upward through the ore body, eventually causing large areas of the surface to subside into sinkholes.

The cost of block cave mining is about 1/10 of the correspondent cost of conventional methods. The production rates can reach 30,000 to 100,000 tons per day. Moreover, drilling and blasting costs are far less, and there are no backfilling costs. Another benefit of block caving is the large reduction in surface waste disposal needs. As open pits get deeper, their ratios of waste rock to ore often get higher and the waste must be placed in surface storage areas. The amount of waste rock generated from underground methods like block caving is a fraction of this, reducing surficial land impacts.

The key factors for selecting block caving method are:

  1. A region with a massive deposit that has sufficient height and footprint area to initiate and propagate the natural caving of the rock mass.
  2. Beneficial geomechanical characteristics such as in-situ rock fractures to encourage fragmentation during the caving process, sufficient rock mass strength to support long life drawpoints and excavation tunnels, and manageable ground stresses.
  3. Ore value that is not only able to cover operating costs, but also the relatively high initial capital costs, and extended pre-production periods, as compared to most other methods. As a minimum, the ore value should be two to three times the site operating costs (mining, processing, and general and administration costs).
  4. The acceptance of surface disturbance above the cave. This zone of disturbance must be accounted for when considering existing or planned infrastructure and environmental considerations.

As large open pit mines come to the end of their lives, many companies are examining the feasibility of transitioning to low-cost, large-scale underground operations. Block cave mining is the only underground method that can offer comparable open pit production rates and operating costs. For new developments, block cave mining offers the further advantage of a smaller surface footprint with significantly less waste disposal requirements.

Source: Golder.com/insightsGeologyforinvestors.com

Read 340 times Last modified on Wednesday, 25 July 2018 15:16

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Block Caving Mining Method

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