To optimize the stress of support structure and
control surrounding rock deformation of soft rock tunnel with high insitu
stress, the hole type and supporting time of doublelayer
primary support are examined. First, the supporting effect of single and doublelayer primary support and
surrounding rock deformation law of soft rock tunnels with high insitu stress
are analyzed based on onsite monitoring data. Then,
FLAC3D software is used to compare and analyze the force and deformation of the
tunnel under three kinds of hole types, such as horseshoe (heightspan ratio of 0.80), quasicircular (heightspan ratio of 0.90), and circular (heightspan
ratio of 1.00), and the tunnel force and deformation conditions after applying
second primary support when the deformations of the first primary support reach
300, 350, and 400 mm. The results are as follows: (1) As for the twolane tunnel in grade Ⅲ surrounding rock with
high insitu stress, the doublelayer primary support
can effectively control the surrounding rock deformation better than the singlelayer one, but the phenomena of arch shoulder failure and inverted
arch cracking still occur. (2) Appropriate increase in tunnel depthspan ratio can effectively reduce the deformation of surrounding
rock and supporting structure. The effect reaches the highest when the heightspan ratio is 1.00. (3) Appropriate increase in reserved deformation
space in the first layer of primary support and delay of the second primary
support will cause a great reduction of supporting stress, so it is recommended
to apply the second primary support when the deformation of the first primary
support reaches 400 mm.
XIE Jinchi
,
KOU Hao
,
HE Chuan
,
NIE Jincheng
,
YANG Wenbo
,
XIAO Longge
. Hole Type and Supporting Time of DoubleLayer
Primary Support for Large Deformation Soft Rock Tunnel
with High Insitu Stress[J]. Tunnel Construction, 2022
, 42(9)
: 1578
-1588
.
DOI: 10.3973/j.issn.2096-4498.2022.09.009
