When shallowburied largecrosssection tunnel crossing underneath
operational highway in soft rock stratum, problems such as over settlement,
collapse, and hidden danger to highway easily occur. Hence, a case study is
conducted on the #4 inclined portal of the Tongzi tunnel crossing underneath an
operational highway in soft and waterrich strata in
Guizhou, China. Then, comprehensive reinforcement inside and outside tunnel is
proposed, which include: (1) The temporary steel bridge guarantees the smooth
flow of the highway and scatters concentrated load. (2) In the shallow section
of the tunnel portal, surface grouting is carried out and the surrounding rock
stability is improved by blocking the water paths in the cracks. (3) The pipeshed support, combined with pregrouting
with a doublelayer micropipe, and the application of
bench reservation core soil are used to ensure the surrounding rock stablility
during the excavation with a milling machine. (4) A new type of locking anchor
is proposed to enhance the stability of the anchoring rock. Finally, the
effectiveness of the scheme is confirmed by monitoring and measurement.
Compared with the conventional mountain tunnel portal construction plan, the
methods recommended can effectively control the complex terrain tunnel
settlement and overbreak, ensure the smooth flow of surface traffic, reduce the
consumption of shotcrete, and avoid collapse, roof collapse, landslides, and
other geological disasters.
YANG Hui
,
PEI Junhao
,
ZHU Jibin
,
LIU Ning
,
JIANG Xiaobo
,
LAI Qingzhao
. Construction Safety Technology of ShallowBuried
LargeCrossSection Tunnel Portal Crossing Underneath Operational Highway[J]. Tunnel Construction, 2022
, 42(S2)
: 440
-448
.
DOI: 10.3973/j.issn.2096-4498.2022.S2.055
