The primary supports of
tunnels crossing asymmetrical-pressurized
faults are prone to asymmetric large deformation during construction. In this
study, a case study is conducted on the Nanlangshan No.1 tunnel of the Menglian-Menghai expressway in Yunnan, China, and large deformation
treatments and control measures are analyzed. Further, the causes for
asymmetric large deformation of the tunnel are determined according field
measuring data and revealed tunnel face conditions, and the double-layer primary support is proposed to control asymmetric large
deformation. Finally, the operation timing of the double-layer primary support is optimized using numerical simulation
method. The results reveal the following: (1) The on-site
monitoring data and the primary support failure situation show that the
original support method cannot withstand the great and uneven surrounding rock
pressure, and the slip of the weak interlayer of surrounding rock causes
asymmetric large deformation to the tunnel. The slip mainly occurs when the
weak interlayer is completely exposed, resulting in local bending failure of
the tunnel′s left shoulder and local shear deformation
failure of the right arch waist. (2) When applying double-layer primary support, properly delaying the timing of the second-layer primary support effectively lowers the tunnel asymmetrical
pressure. However, excessive lag distance of the second-layer primary support will lead to excessive tunnel deformation
convergence and yield failure of the primary support. A 2 m lag distance is
recommended for the second- and the first-layer primary supports. (3) The optimized double-layer primary support effectively controls the shearing slip failure
of surrounding rock, the tunnel arch settlement and horizontal convergence are
controlled within required values, and the deformation difference between the
two sides of the tunnel is significantly reduced, showing that the asymmetrical
pressure of surrounding rock is significantly minimized.
XU Wanmin
,
XU Jiaxin
,
XU Jinfeng
,
LI Shouren
.
Asymmetric Large Deformation Control Technology and Primary Support Optimization of Deep-Buried Asymmetrical-Pressurized
Highway Tunnels: A Case Study of Nanlangshan No.1 Tunnel
[J]. Tunnel Construction, 2024
, 44(S2)
: 435
-444
.
DOI: 10.3973/j.issn.2096-4498.2024.S2.044
