Abstract
Coal and gas outbursts are small-scale geological disasters controlled by tectonic movement, and tectonic coal is widespread in outburst zones. In this study, we compare tectonic and intact coal specimens to examine the basic properties of tectonic coal. We estimate the different energies and limits of the crushing work ratio of coal from five typical outburst cases using on-site outburst data, and discuss the relationship between outbursts and tectonic coal. The results show that tectonic coal is a product of tectonic movement and its original primary structure is destroyed during the tectonic process. Compared with intact coal, tectonic coal shows low strength properties and a crushing work ratio of 22.11 J/m2. The specific surface area and total pore volume of the minipores, mesopores, and macropores of the coal strongly increase under conditions of intense tectonism, which indicates that tectonic coal has a very high capacity for rapid initial gas desorption. An adequate supply of gas is required to transport outburst coal, such that the existence of coal particles smaller than the critical diameter is important. Our calculations indicate that the crushing work ratio of coal from the five outburst case ranges from 22.19 to 78.67 J/m2. Only the crushing work ratio of tectonic coal satisfies the requirement for these cases. Therefore, the properties of the tectonic coal and crushing work ratio for the five cases indicate that the widespread occurrence of tectonic coal plays a crucial role in outbursts.
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Abbreviations
- \(f\) :
-
Protodyakonov coefficient
- \(a\) :
-
Gas adsorption constant
- \(b\) :
-
Gas adsorption constant
- M ad :
-
Moisture content
- A d :
-
Ash content
- V daf :
-
Volatile content
- \(W\) :
-
Total crushing work
- \(m\) :
-
Mass of the hammer
- \(h\) :
-
Drop height
- \(g\) :
-
Gravitational acceleration
- \(n\) :
-
Impact times
- \(\varGamma\) :
-
Crushing work ratio
- \(\Delta S\) :
-
Newly added surface area
- \(w_{ij}\) :
-
Crushing work of each test
- \(F\) :
-
Applied force
- x :
-
Displacement
- \(S_{i}\) :
-
Surface area of the coal particles
- \(G\) :
-
Coal mass
- \(\gamma_{i}\) :
-
Mass proportion
- \(d\) :
-
Coal particle size
- \(\rho\) :
-
Density of coal
- \(S_{0}\) :
-
Surface area of initial coal particles
- \(d_{\text{m}}\) :
-
Average particle size of the initial coal particles
- \(W_{\text{e}}\) :
-
Stress energy
- \(W_{\text{g}}\) :
-
Gas energy
- \(W_{\text{f}}\) :
-
Additional energy causing by mining activities
- \(W_{1}\) :
-
Crushing work
- \(W_{2}\) :
-
Transport work
- \(W_{3}\) :
-
Remaining energy
- \(E_{\text{e}}\) :
-
Stress energy per unit volume
- \(\sigma_{i}\) :
-
Triaxial stresses
- \(E\) :
-
Elastic modulus
- \(\mu\) :
-
Poisson’s ratio
- \(P\) :
-
Gas pressure
- \(V\) :
-
Gas volume
- \(\kappa\) :
-
Adiabatic coefficient
- \(V^{\text{f}}\) :
-
Free gas volume
- \(\phi\) :
-
Coal porosity
- \(V_{\text{m}}\) :
-
Coal volume
- \(D\) :
-
Diffusion coefficient
- \(t\) :
-
Diffusion time
- \(Q_{\text{t}}\) :
-
Gas desorption volume at time \(t\)
- \(Q_{\infty }\) :
-
Final gas desorption volume
- \(P_{\text{a}}\) :
-
Atmospheric pressure
- \(V^{\text{a}}\) :
-
Adsorbed gas volume
- \(Q_{it}\) :
-
Gas desorption volume in the \(i\) particle-size range
- \(W_{2i}\) :
-
Transport work of the \(i\) segment
- \(m_{i}\) :
-
Outburst coal mass of the \(i\) segment
- \(l_{i}\) :
-
Distance from the outburst point
- \(f_{\text{m}}\) :
-
Friction coefficient
- \(\theta\) :
-
Coal seam angle
- \(v\) :
-
Initial gas desorption rate of coal particles
- \(\zeta\) :
-
Correction factor
- \(\eta\) :
-
The ratio of the average horizontal principal stress to the vertical stress
- \(H\) :
-
Cover depth
- \(\sigma_{\text{H}}\) :
-
Maximum horizontal principal stress
- \(\sigma_{\text{h}}\) :
-
Minimum horizontal principal stress
- \(\sigma_{\text{V}}\) :
-
Vertical stress
- \(\bar{\gamma }\) :
-
Average density of the overlying strata
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Acknowledgements
The authors are grateful for the supported by Outstanding Innovation Scholarship for Doctoral Candidate of “Double First Rate” Construction Disciplines of CUMT. Yueqiang Xing is gratefully acknowledged for his assistance with the language revision. Comments by all of the anonymous reviewers are highly appreciated.
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Tu, Q., Cheng, Y., Ren, T. et al. Role of Tectonic Coal in Coal and Gas Outburst Behavior During Coal Mining. Rock Mech Rock Eng 52, 4619–4635 (2019). https://doi.org/10.1007/s00603-019-01846-0
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DOI: https://doi.org/10.1007/s00603-019-01846-0