Rock burst

A rock burst is a spontaneous, violent fracture of rock that can occur in deep mines. The opening of a mine shaft relieves neighboring rocks of tremendous pressure, which can literally cause the rock to explode as it attempts to re-establish equilibrium. Rock bursts are a serious hazard; in South Africa, they kill roughly 20 miners each year. Rock bursts basically depend on the size and depth of the excavation.

Rock bursts result from brittle fracturing of rock, causing it to collapse rapidly with violent spalling of rock that is approximately 100 to 200 tonnes, or more. This release of energy reduces the potential energy of the rock around the excavation. Another explanation is that the changes brought about by the mine's redistribution of stress trigger latent seismic events, deriving from the strain energy produced by its geological aspects.

The likelihood of rock bursts occurring increases as the depth of the mine increases. Rock bursts are also affected by the size of the excavation (the larger the more risky), becoming more likely if the excavation size is around 180 m and above. Induced seismicity such as faulty methods of mining can trigger rock bursts. Other causes of rock bursts are the presence of faults, dykes, or joints.

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