Hard rock bursts

The factors of coal and rock structure for rock-burst risk are included hard roof (main roof), hard coal, hard floor and key strata et al. Different combinations represent distinct dangerous levels. For example, Huafeng Coal Mine, which the characteristics of coal and rock structure are hard main... 

Make an analysis on the distribution of critical rock stratum that induces burst hazard and its relationship with the location of coal seam About 20 m above the main roof of coal seam, there is fine sand strata with a thickness of 9.76 21.65 m. The presence of this hard roof will aggravate the stress concentration of working face, crossheading and area near the pillar. It is a crucial stratum for inducing rock burst. 

There is extremely thick and hard stratum of red medium-sand, 132.2 186.3 m away from the roof of coal seam No.3. The key stratum may induce mine earthquake if disturbed. Since the stratum is far from the earth s surface (about 340 m), there won t be direct impact on the earth s surface during a mine earthquake. This stratum is also critical for inducing rock burst. 

Most of Uquid explosives, in practice, can be successfully detonated in mining operations, whatever in hard rocks or water holes, with a favorable detonation property. In comparison with condensed explosives, liquid explosives have distinct advantages to be used in the bursting of extremely hard rocks and multi-waterholes. 

Mechanism of brittle fracture and rock burst Rock burst, which is a kind of brittle fracture of hard rock, has become a difficult problem and disaster in underground construction for decades. 

White, B.G., J.K. Whyatt, and D.F. Scott. 1995. Geologic factors in rock bursts in the Coeur d Alene mining district. In Proceedings Mechanics and Mitigation of Violent Failure in Coal and Hard Rock Mines. USBM SP 01-95. 217-230. 

Most of the required science for most mining hazards is now well understood (with one or two notable exceptions, for example, rock bursts in deep hard rock mines). However, even when the science is known and the necessary control measures are fiiUy understood and documented for all to follow, the real control and the everyday rehability of risk management, hes in the hands of the people at the mine. If methane monitoring standards are not maintained, if effective dust control measures are not introduced, if PPE is not worn, if mles and procedures are not used, etc. then all the hard won knowledge which, theoretically, allows us to control risk will have been wasted. 

The function has its maximum (1.0) at the optimum depth of burst, i.e., where the crater volume reaches its maximum. In case of hard and moderately strong rock, this maximum occurs at a scaled cover depth of around 0.5 to 0.6 (m/kg ). 

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