Abstract
Coal and gas outbursts compromise two-phase gas–solid mixtures as they propagate as shock waves and flows from their sources. Propagation is influenced by the form of the outburst, proximity to source, the structure and form of the transmitting roadways and the influence of obstacles. The following characterizes the propagation of coal and gas outbursts as two-phase gas–solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior. The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models. The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small corner roadways leading to significant attenuation of outburst shock waves. The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways. The most significant attenuation appears in small angle corners and bifurcations in roadways with the largest attenuation occurring in blocked roadways. These results provide basic parameters for simplifying transport in complex roadway networks in the far-field, and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.
Highlights
Coal and gas outbursts in underground coal mines are capable of rapidly and energetically ejecting significant masses of coal and gas into the roadways and stopes (Yu 1992; Zhao et al 2020)
The following characterizes the propagation of coal and gas outbursts as two-phase gas–solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior
The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small corner roadways leading to significant attenuation of outburst shock waves
Summary
Coal and gas outbursts in underground coal mines are capable of rapidly and energetically ejecting significant masses of coal and gas into the roadways and stopes (Yu 1992; Zhao et al 2020). In 1977 recorded a static pressure head of gas and pulverized coal flow in the initial stage of the outburst at 0.3 – 0.6 MPa (Wang and Yu 2005)—confirming that the outburst shock waves entrain significant destructive energy. Attenuation mechanisms of shock waves have been deduced (Cheng and Chen 2000; Cheng et al 2004) including the use of physical and numerical models (Otuonye and Sheng 1994) These have defined the principal characteristics of shock wave propagation in roadways (Miao et al 2013) including the influence of the gas phase (Wang et al 2012, 2011; Zhou and Wang 2017). We applied appropriate initial and boundary conditions to this twophase gas–solid flow model of pulverized coal and gas to explore propagation characteristics of the outburst shock waves and their interaction with different roadway structures and obstacles to define the spectrum of destructive impacts. The coal particles have a tendency to settle due to gravity, but the drag force added by the high horizontal velocity of the gas is dominant and resists this with inertia
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