2. Introduction
The one u/g mining method that has the potential to rival
surface mining in output and cost is block caving. Block
caving is the mining method in which masses, panels, or
blocks of ore are undercut to induce caving, permitting the
broken ore to be drawn off below. If the deposit is overlain by
capping or bounded by drawing the ore. This method is unlike
sublevel caving, in that both the ore and the rock are normally
involved in the caving. As in sublevel caving, The caving
proceeds in a columnar fashion to the surface. The result is
massive subsidence, accompanied by the exceptionally high
production rate and great areal extent characteristic of block
caving.
3.
4. The site will be mined using a technique called block caving,
which uses gravity to extract ore
5. Sequence of Development
Development for block caving is typically extensive and
expensive, but generally less so than that for sublevel caving
on a unit cost basis. Mine level development commences from
the shaft station in the usual way, providing for high speed,
high capacity haulage and simple ventilation airflow capacity.
Main haulageways are often paralleled by laterals,
interconnected by crosscuts to ensure good ventilation and to
provide adequate lanes or stub crosscut for loading. One or
more additional sublevels are required for grizzly or slusher
operation, increasing the development costs for these two
methods.
To provide ore drawing facilities, chutes, drawpoint, or
trenches are prepared in the ore body under the block to be
mined
6. Cycle of operations
As in the most other vertical stoping and caving operations for
hard rock mining, the development and exploitation cycles of
operations are separate and distinct.
the cycle of operation consist of the following:
Drilling (undercut): Pneumatic or hydraulic powered
percussion jumbos; hole size 2 to 3 in. (51 to 76mm ).
Blasting (undercut): ANFO, slurries; bulk charging by
pneumatic loader or pump, firing electrically or by detonating
fuse.
7. Secondary blasting (on sublevel or in haulage drift): Impact
hammer, dynamite bomb, drill and blast mudcap.
Loading (through bells and ore passes ): Gravity flow to
chutes; LHD, front end loader, slusher at drawpoints.
Haulage (on main level): LHD, rail, truck, belt conveyor.
8. Applicability condition
1. Ore strength: Weak to moderate or fairly strong, prefer friable,
fractured, or jointed rock, not blocky; should cave freely under
own weight when undercut; free running, not sticky if wet, not
readily oxidized.
2. Rock strength: Weak to moderate, similar to ore in
characteristics.
3. Deposit shape: Massive or thick tabular deposit, fairly regular.
4. Deposit dip: Fairly steep (>60 degree) or vertical; can be fairly
flat if sufficiently thick.
5. Deposit size: Very large areal extent; thickness >100 ft ( 30m ).
6. Ore uniformity: Fairly uniform and homogeneous; sorting not
possible.
9. Advantages
1. Relatively high productivity.
2. Fairly low mining cost, least of the underground mining
method (relative cost about 10%)
3. Highest production rate of the underground stoping
methods; large scale method.
4. High recovery (90 to 125%).
5. Ventilation is generally very satisfactory; good health and
safety factors.
10. Disadvantage
1.Caving and subsidence occur on a large scale.
2.Draw control is critical to success of the method.
3. Slow, extensive, costly development.
4. Dilution may be high (10 to 25%).
5. Maintenance of openings in production areas is substantial
and costly if pillars load excessively.
