#blockcaving #metalmining #stoping
In this video i've discussed about the block caving method of underground metal mining. below you'll get the written note of this topic.
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Block caving:
It is an underground mining technique used to mine large massive ore body.
Development:
- Access to the ore body with incline and shaft (drives by jumbos and rock bolts for safety)
- After gaining access a series of parallel extraction drive are developed from one side of the ore body to the other
- Between the extraction drive drawbells are developed.
- Undercut level is developed at same time as the extraction drives, rings of drill holes are charged and fired from one side of the ore body to the other.
- The drawbells are drilled and blast to become a series of funnels that will feed the broken ore to a draw-point.
- This process breaks the layer of rock across the bottom of the block ore and leaves a large unsupported area which starts fracturing and caving under its own weight.
- The ore body is starts to cave once the undercut is complete and ore is remove from the drawbells creating a void.
Once the development is complete and the ore body has been undercut the mining process is relatively simple with continuous fracturing and breaking of the rocks to smaller rocks for the extraction without any further blasting
Low profile LHD collect ore from draw point and dump it in the ore pass or underground crusher.

Applicability:
-Large ore body
-Low grade ore body
-Steep gradient more than 45 deg.
-Weak ore body (cave under its own weight)
-Weak wall rock
-Surface should be allowed to subside

Development carried out for:
- Extraction level development:
o Drilling done by Jumbo drill
o ANFO charging
o Blasting
o Scoop-tram Mucking and dump to ore pass
o Support : fiber rich feed shotcrete spray and wire-mesh anchor

- Undercut development:
o Making connection to apex level and ore block from undercut level
o Drilling long hole by long-hole drill from undercut connecting apex level , block to undercut level
o Charging
o Blasting perform to enable connection between the level and ore body

- Drawbell development:
o Connecting undercut & extraction level
o Connection made between two extraction level.
o Support :
 Cable bolt, steel set sprayed with fiber reinforced shotcrete.
 Wire mesh of walls and sprayed with fiber reinforced shotcrete
 Drawpoint intersection bolts at junction of extraction level and drawpoint.
o Drilling of 30” slot raise by In-The-Hole drill(ITH drill) up-to undercut level.
o Long hole drill for drilling long-holes drawbells.
o Charging on long holes
o Blasting
o Scoop-tram mucking from both side of drawbell
- Further undercut and drawbells are developed under the ore body
- Ore is dumped down ore pass to haulage level and transported to underground crusher then to surface.

Advantages:
- The accident rate is fairly low
- After the caving starts a high rate of production is possible
- Control of ventilation is less compare to others methods of mining
- Mining cost is low

Disadvantages:
- Preparation of stope is complicated and time consuming
- The ore is diluted with waste and there is some loss of ore.
- Caving is difficult to control
- No scope of selective mining of high and low grade ore
- Excessive dilution if caving is uncontrolled
- Capital expense is large
- There must be careful supervision of ore drawing
- Mechanization is possible only to a limited extent
- Secondary blasting is required on a large scale.



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