To avoid frequent outbursts of shallow natural gas in
the reverse fault area, a case study of the Chengdu metro line 30 is conducted,
and CH4 shortterm and longterm monitoring tests, CH4 recharge test,
and gas chromatography test are employed to explore the characteristics of gas
outburst, recharge, occurrence, and accumulation capacity of shallow gas in
reverse fault areas. The results reveal the following: (1) The shortterm accumulation of shallow natural gas in the active reverse fault
area is strong, outburst volume is large, and recharge speed is high, but the
sustainability of the replenishment is poor. (2) In the broken zone of the
static reverse fault, the shortterm accumulation of
shallow natural gas is strong, outburst volume is large, recharge efficiency
and sustainability are good, and longterm ventilation
measures can effectively reduce the shortterm
accumulation ability and shallow natural gas outbursts in this area. However,
in the fractured zone, shallow natural gas has weak accumulation ability, small
outburst volume, poor recharge efficiency and sustainability, and most of the
shallow natural gas around the borehole can be discharged by longterm ventilation. (3) In the static reverse fault, shallow natural
gas is continuously distributed in the broken zone and unevenly distributed in
the form of air bags within the fracture zone. (4) Shallow natural gas mainly
accumulates within 1~2 km around the reverse fault. With the increase in depth,
the concentration of gas increases, whereas the ratio of methane to other
hydrocarbon gases (C1/C2+)
decreases.
SU Peidong
,
HE Kunchen
,
LI Yougui
,
LE Jian
,
JI Youjun
,
LI Yuan
,
QIU Peng
. Occurrence and Migration Characteristics of Shallow
Natural Gas in Reverse Fault Area: a Case Study of Chengdu
Metro Line 30[J]. Tunnel Construction, 2022
, 42(7)
: 1156
-1166
.
DOI: 10.3973/j.issn.2096-4498.2022.07.004
