Engineering disasters caused by harmful gases in
tunnels across China are frequent, primarily involving poisoning and
asphyxiation, combustion, and chemical corrosion. While a relatively
comprehensive survey and evaluation system has been established presently for
coal seam gas, it is not well suited for noncoal strata. This inadequacy
substantially hinders the high-quality development of noncoal gas
tunnel construction. To address this issue, field detection, in-situ testing, theoretical analysis, and onsite measurement and
calculation methods are employed to develop a gas risk level evaluation system
for harmful gases in noncoal tunnels during survey and construction phases. The
main findings are as follows: (1) During the survey phase, the conventional
method of midway detection + final hole detection + hole sealing detection can
be used to determine the gas grade in general noncoal gas sections through
boreholes. In high gas concentration zones, gas accumulation and escape testing
enable the determination of gas grade and type based on the gas accumulation
rate (νg) and the
escape curve. (2) During the construction phase, the absolute gas emission (Qabsolute) from
the excavation face can be accurately measured using recorded air duct pressure
ventilation data and an optimized layout of gas detection points. (3) The Qabsolute of the gas pocket in front of the excavation face can be evaluated
using an innovative method of tunnel seismic prediction + advance drilling +
detection test, integrated with forward geological prediction work. (4) This
gas grade evaluation method for noncoal stratum tunnels has been successfully
applied in projects such as the Chengdu-Chongqing high-speed railway and the Chengdu-Meishan urban
(suburban) railway line.
CHEN Minghao
,
ZHOU Hang
,
QIU Peng
,
XU Zhengxuan
,
LI Dong
,
SU Peidong
,
ZHOU Xiaohan
. Gas Grade Evaluation Method for Noncoal Stratum
Tunnels[J]. Tunnel Construction, 2025
, 45(5)
: 895
-905
.
DOI: 10.3973/j.issn.2096-4498.2025.05.004
