Outburst mechanism of tunnelling through coal seams and the safety strategy by using “strong-weak” coupling circle-layers
•Outburst mechanism of tunnelling through coal seams is theoretically and numerically studied.•Outburst hazard is high at the moment of roadway uncovering coal seam from rock.•The higher original stress perpendicular to roadway will increase the hazard significantly.•A typical outburst is triggered...
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Veröffentlicht in: | Tunnelling and underground space technology 2018-04, Vol.74, p.107-118 |
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Sprache: | eng |
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Zusammenfassung: | •Outburst mechanism of tunnelling through coal seams is theoretically and numerically studied.•Outburst hazard is high at the moment of roadway uncovering coal seam from rock.•The higher original stress perpendicular to roadway will increase the hazard significantly.•A typical outburst is triggered by the nearby energy and developed by the distant energy.•Strong-weak coupling structure can efficiently control outburst and is proved by field data.
The gas outburst potential is typically high when roadways uncover the gassy coal seams associated with outburst hazards. This paper describes the complex stress and displacement evolution that occurs in roadway tunnelling through coal seams under different original stress conditions, which is helpful for better understanding how the stress leads to an outburst accident, and proposing some relevant control measures.
The stress concentration is primarily resulted from the strength difference between coal and rock, and the abutment stress increases gradually as the forward residual rock thickness decreases when the roadway excavation enters a coal seam from rock stratum. When the abutment stress is sufficiently high, the forward residual rock will suddenly be broken after the next cycle, and the stress will decrease rapidly to release elastic energy and generate new fractures. Meanwhile, the coal and rock in front of the heading face will move rapidly towards the free space. Therefore, an outburst accident may occur immediately when the gas pressure in front of the heading face is high enough. Once the outburst accident is triggered, the gas expansion energy and elastic energy distant from the heading face will contribute to developing the accident. The stress perpendicular to the roadway is the primary factor causing such outbursts. The abutment stress concentration will be higher when the maximum original stress is perpendicular to the roadway, which will increase the outburst potential. Therefore, it is suggested that arranging roadways parallel to the maximum original stress, if possible, can also reduce the outburst threat.
Outbursts are triggered by the elastic energy near the heading face and developed by the gas expansion energy and elastic energy distant from the heading face. In this study, the method of “strong-weak” coupling circle-layers was proposed to reduce the outburst hazard when roadways excavated through gassy coal seams. This method was proven to be valid by the comparative experiment. The weak |
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ISSN: | 0886-7798 1878-4364 |
DOI: | 10.1016/j.tust.2018.01.013 |