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Recent Advances in Key Technologies of Shield Tunnel Engineering in China
QIAN Qihu, HU Xiaoqiang, LI Shuchen, CHEN Jian, ZHU Weibin
The authors provide an overview of the latest progress
in five key technologies of shield tunnel engineering in China, including
accident analysis of the main bearing during large-diameter
shield tunneling and independent R&D of domestic main bearings, muck
adaptability improvement technology and supporting materials for efficient
tunneling in shield tunnel engineering, safety technology and materials for
shield tail seal, new segment connection technology for shield tunnel
engineering, and key technologies of
three-mode boring machine in urban tunnel
engineering. The overview covers research background and methodology,
mechanisms/principles, materials/equipment, technical verification,
experimental research, and engineering applications. It is concluded that: (1)
In terms of the purity of large rings and rollers, fatigue performance of the
large ring, hardness uniformity of the large roller, hardenability and depth of
hardening layer of the ring material, as well as the fatigue life and tensile
breaking force of the retainer welds, the independently developed main bearings
with a diameter of 8.01 m for super large shield are superior to the imported
counterparts. The design method of large roller with real logarithmic curve is
established, achieving a breakthrough in high-precision
large roller processing technology and reaching an internationally advanced
level. The high-precision assembly ensures that the
dimensional accuracy and geometrical tolerance of parts meet the design
requirements. Through product acceptance, installation application
demonstrations, and engineering applications, it has been demonstrated that the
use of this large-diameter main bearing does not lead
to insufficient contact fatigue strength or fretting fatigue wear. Therefore,
this kind of main bearing can be used in the super-large-diameter shield tunnel engineering. (2) In order to improve the rock-soil environment, focusing on complex strata such as cohesive
strata, sandy strata, and hard rock strata, a series of environmentally-friendly muck conditioners has been developed including polymer foam
agents with high arrangement density, polymer antiadhesion
agents, gushing prevention agents, and wear-resistant
dust suppressant. In addition, the active prevention and control technology for
insitu improvement of the shield mud cake, gushing,
and wear has been developed, and the technical system for dynamic improvement
of adaptability of all-strata muck in shield tunnel
engineering has been established, thus ensuring safe and efficient tunneling of
the shield machine. (3) In response to the challenging issue of shield tail
seal failure during shield tunneling, a new type of shield tail sealing grease
with "adhesive-viscous-fluid"
properties has been developed. It exhibits low temperature sensitivity
(viscosity-temperature coefficient: 0.4) and strong
water pressure resistance (maximum water pressure resistance: 3.5 MPa). The overall performance is
improved by 1.3 times, providing strong assurance for shield tail safety.
Addressing the difficulties of slurry bleeding and segregation of synchronous
grouting as well as stratum settlement during shield tunneling, a filling agent
for synchronous grouting has been developed. By optimizing the mix ratio of the
inert filling slurry, zero bleeding
within 30 minutes as well as inert filling behind the wall were achieved,
ensuring the quality of grouting behind the segment wall (i.e., grouting of
cavity between excavation face and segment) and the refined control over the
stratum settlement. (4) A connection form of circumferential seam insertion +
longitudinal seam sliding is adopted for the new segment connection technology,
enabling high-standard control of joint opening and
dislocation of the tunnel. With high precision in segment fabrication and
assembly, it can reduce the waterproofing difficulty of joints, enhance the
quality of formed tunnels, eliminate the need for handhole setting and manual
fastening operations, as well as achieve high levels of automation and
construction efficiency. This approach can save construction costs and improve
the assembly environment inside the tunnel. (5) The developed "EPB +
slurry + TBM" three-mode boring machine is able to
meet the tunneling construction requirements of almost all types of strata,
including complex and varied strata, as well as uneven soft/hard composite
strata. It can achieve rapid switching of tunneling modes without the need to
stop or dismantle equipment. Under the TBM tunneling mode, the screw conveyor
and slurry pipeline work together to discharge the muck, effectively solving
the problem of difficult muck removal during tunneling in water-rich hard rock strata. The machine features a high level of
mechanization and intelligence, guaranteeing construction safety and
reliability while also improving construction efficiency. It enhances working
conditions for workers, ultimately saving time and costs. China has achieved
significant progress in shield tunnel construction, which has driven the
development of shield tunnel technology not only in China but also worldwide.
However, shield accidents still occur, necessitating further research and
breakthroughs in equipment, materials, technologies, and management. In the
foreseeable future, shield tunnels in China, especially for large-diameter shield tunnels, will continue to experience rapid
development. Construction conditions will become increasingly complex, and the
technical challenges will also grow. To achieve fast, safe, and healthy shield
tunnel construction, it is crucial to address key issues in shield tunnel
technology and make breakthroughs in critical core technologies in this field.
The above key technologies still need to be continuously improved, promoted and
applied, so as to promote the development of China′s
shield tunnel construction towards high adaptability, high intelligence, high
reliability, high benifit, high quality, high safety, and low energy
consumption, forming new shield tunnel technologies suitable for the
"soil" of China.
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