A case study is conducted on the Dongmachang No. 1
tunnel of the Huali expressway crossing the ChenghaiBinchuan
active fault to address the issues of support deformation, cracking, and
destruction during tunnel construction in areas with active fractures. A high
amount and rate of uneven destruction with a long duration and difficulty in
achieving convergence are observed for the deformation of the primary support
of the tunnel during the construction. Because of the influence of the Chenghai
fault, the geological tectonic stress level(considering the horizontal tectonic
stress as the main stress) in the tunnel site is high, and the section affected
by the fault exceeds 2 km in length. Using the analytical results of the monitored
data and test results, a comprehensive support system using a combination of
long and short supports, active control, layered supports, timely ring close,
and reserved inner space is proposed based on the deformation, cracks, and
destruction conditions of the tunnel support in the excavated section. The
analytical results of the monitoring data show the following: (1) The average
cumulative settlement and average cumulative convergence after implementing the
optimized plan are, respectively, 12.46% and 26.57% higher than the values
before plan optimization; this result is attributed to the long operation time
before optimization. (2) After the implementation of the optimized plan, the
surrounding rock deformation is mainly concentrated in the first primary
support layer stage, where the generated deformation accounts for approximately
70% of the total deformation; After the implementation of the second primary
support layer and the inverted arch, the deformation rate decreases drastically
and is within 0.8~1 mm/d before the secondary lining pouring.
WANG Shaofei
,
CHEN Shuwang
,
ZENG Zerun
,
YU Jia
,
ZHAO Qian
,
WANG Shanshan
. Large Deformation Characteristics and Support Systems
of HighGeostress SoftRock
Tunnels in Active Fracture Areas[J]. Tunnel Construction, 2023
, 43(1)
: 141
-150
.
DOI: 10.3973/j.issn.2096-4498.2023.01.015
