The extraction of gas at the bottom of coal seams with
low-angle high-pressure gas outbursts is
difficult, which reduces the extraction efficiency. To address this issue, a
case study is conducted on the Taoziya tunnel on the Zheng′an-Xishui expressway in Guizhou, China.
Based on the variation in the spatial position relationship between the excavation
section and coal seam during tunnel excavation, a step-by-step and zoned coal seam gas extraction plan is proposed. The
similarity between heat conduction theory and gas flow theory is leveraged by
the thermodynamic finite difference calculation software to simulate and
analyze gas outburst prevention and extraction as well as the effect of
constructing a tunnel in the small-angle coal seam.
Results are as follows: (1) The step-by-step and zoned coal seam gas extraction scheme prevents the drilling
of super-long discharge boreholes in the bottom coal
seam, thereby reducing the total drilling length by 31% compared to the overall
one-time extraction scheme; it is also proving more
efficient and reliable. (2) Gas extraction simulation results show that when
the extraction boreholes are evenly distributed on the coal seam section, the
middle drilling and extraction areas reach the gas outburst elimination target
earlier and the edge area lags behind. Therefore, adopting a dense edge and
sparse middle extraction and extraction borehole layout method is reasonable.
(3) A comparison of simulation results of drainage boreholes drilled along the
coal seam dip and those drilled obliquely through the coal seam shows that the
former improves drainage efficiency by ~1/3, with more uniform gas pressure
dissipation. (4) The gas extraction period can be estimated via simulation
based on the extraction plan, which is roughly between the time when the
average gas pressure in the extraction area reduces to the critical pressure of
the outburst and the time when the maximum gas pressure decreases to the
critical pressure of the outburst.
YANG Hong
,
ZENG Zhongyi
,
WU Mingfang
,
TIAN Jiao
.
Gas Extraction Technology for Highway Tunnels Passing Through
Low-Angle High-Pressure Gas Outburst Coal Seams
[J]. Tunnel Construction, 2025
, 45(5)
: 982
-991
.
DOI: 10.3973/j.issn.2096-4498.2025.05.013
