Mine Rescue and Safety §

ROCK BURSTRock burst can be defined as “the sudden failure of rocks caused by the stresses (it resembles fragmentation by explosives). It occurs with sharp loud noise, with shaking of the surroundings with an ejection of coal (in case of coal mining) or rock along large quantity of dust. Rock burst can also be felt even at the surface to some distance”.

The rock bursts are dangerous to mine workers and workings (support are sometimes seriously damage or destroyed completely) can disturb work of mine.

Factors affecting the Rock BurstBasically it all boils down to these factors that affect rock burst occurrence:

Mining method Sequencing of developing the underground mine workings Pillar layout and geometry Blasting, as it affects the pillars Presence of very strong rock in the roof and floor. Rockfill and backfill used to fill mined out areas. The danger of rock burst increases with the increase of depth of working exceeds.

Causes of Rock BurstThere are three major causes of Rock Burst,

1. Surface instabilities of the rock mass at the face of the excavation.2. Propagations of shear fractures in the rock mass ahead of working face and,3. Slip along existing discontinuities such as faults, bedding surfaces and interfaces between units.

Rock Burst is the Most Dangerous Hazard in Underground Mines:The violent rock burst (or rock failure) has been considered as one of the major hazard when mining of hard rock is at great depth. When underground excavations are made, significant changes in the potential and strain energies of the rock is potentially occurred.

The potential energies of shattered rock mass from the excavation process and hoisting to the surface is increased by an amount equal to the product of its rock mass. The gravitational acceleration and the depth from where the rock is hoisted, conversely the potential energy of the intake rock around the excavation is decreased by the angle of product of the origin traction that existed across the surface of the excavation. If all the stresses remained constant, the rock behaves elastically. The displacement of the excavated surfaces is produced insufficiently closer to the excavations.

One half of the decrease in the potential energy of the rock around the excavation is stored as concentration of elastic strain as an average of the rock around the excavation.

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Mine Rescue and Safety §

Preventive measuresRock burst prevention therefore remains a key criterion in the general objective of improved mine safety

The following criteria play a key role in rock burst prevention:1. Mine layout planning (e.g. working relief seams)2. Preventive measures3. Situation-oriented monitoring methods4. The use of appropriate stress relief techniques5. Training of technical staff6. Appropriate roof and pillar supporting

The success of this operation is reflected in the fact that rockbursts are less frequent and more importantly, deaths and injury from this source are now a rarity.

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