The construction of structures underpassing and
overpassing an existing metro shield tunnel disturbs the existing structure
repetitively, resulting in large deformation and crack leakage. Therefore, to
address these issues and design a rational deformation control scheme, a case
study is conducted on the Gangxiabei comprehensive transportation hub project
in Shenzhe, China. Prereinforcement, auxiliary engineering
measures, and key technologies of excavation and support are adopted for the
mined cable tunnel at the lower level, and the numerical simulation of
different precipitation depths, longitudinal segment sequence length, and
basement reinforcement schemes are adopted for the parallel upper span of the
underground commercial space at the upper level. Through informatized
monitoring, the influence patterns of engineering construction on the
deformation of adjacent existing metro shield tunnel is explored and validated.
The results reveal the following: (1) The mined cable tunnel is considerably
affected by the disturbance within 20 m, and the pipe roof prereinforcement measures with a length over 20 m can be used to
control the deformation. (2) The effective measures to reduce the deformation
of the existing metro tunnel are to improve the stiffness of the arch frame of
the cable tunnel and increase the number of footlocking
anchors. (3) The prereinforcement grouting pressure
should be controlled at 0.5 MPa, and the floating of the existing shield tunnel
should be controlled within +2 mm. (4) The underground commercial space at the
upper level is excavated in parallel to the existing metro shield, and the
largearea unloading will cause a sudden change of
floating deformation under the timespace effect. The
length of the structural segment and the exposure time should be shortened. (5)
The dewatering construction should be implemented step by step to reach the
depth of the bottom of the existing metro shield tunnel, which can reasonably
balance the consolidation settlement of soil caused by dewatering and the
floating of tunnel caused by earthwork excavation. (6) The actual deformation
of the existing metro shield tunnel caused by the parallel construction of the
underground commercial space is more significant than that of the numerical
simulation within the range of 30 m under the influence of the disturbance, and
the influence on the deformation of the existing structure decreases with an
increasing disturbance distance.
SHU Zhihua, WANG Dingjun, ZHANG Lei, WANG Xianbao
. Deformation Control of MultiStructure
Underpassing and Overpassing an Existing Metro Shield
Tunnel: A Case Study of Gangxiabei Comprehensive Transportation
Hub Project in Shenzhen, China[J]. Tunnel Construction, 2023
, 43(S2)
: 504
-512
.
DOI: 10.3973/j.issn.2096-4498.2023.S2.055
