On sudden rock and gas mass outbursts
Some rocks and in particular certain deposits of hard coal form multiphase media made up of a skeleton of a solid body and gas (CO2, CH4) deposited in it. The greater part of the gas is adsorbed on the surface of the coal substance or dissolved in its molecular lattice. From the hyperbolic non-linear system of equations for the conservation of mass, momentum and energy of a rock and gas medium there follows the possibility of the generation of a shock wave in this medium. The “catastrophic gradient” within the area of this wave may cause a phase transition and the destruction of the medium inside which this wave is propagating. Within the region of phase transitions the medium is characterized by the inequality (3), this implying the existence of a rarefaction shock wave. The consequence of such a wave is the situation presented in Fig. 2. The surface of the shock wave is being displaced at a velocity U > 0 . This discontinuity surface separates the undisturbed rock and gas medium from the mass of crushed rock and gas, thrown out at a velocity μ < 0 , This phenomenon is known from the mining practice.
In the latter case, in an adiabatic state, when the medium does not exchange heat with the surroundings the source of heat for the adsorbed thermal energy is the heat drawn from the medium inside which the rarefaction shock wave is propagating. This causes a temperature drop in the medium. Such an effect can be observed as a rule during sudden outbursts of a mass of coal and gas.
KeywordsShock Wave Crushed Rock Hugoniot Curve Undisturbed Rock Sudden Outburst
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