Abstract: In order to solve the technical difficulties commonly encountered in the design and construction process
of super large span highway tunnels, such as the selection of construction methods and the determination of
support parameters, based on the construction example of double-hole eight-lane super span highway tunnel in
Shenshanxi Expressway extension project in Guangdong province, Through research, engineering analogies,
simulation calculations, and other methods, the construction method, supporting parameters, "one hole nine-line"
large-scale mechanized tooling configuration and related optimization design of super span highway tunnel are
studied. Finally, the design scheme is verified by monitoring and measuring. The results show that: 1) the design
methods of two-and three-lane tunnels in the current specifications are still basically applicable to four-lane tunnels.
2) The CD method is suitable for deep buried strong regolith, and the thickness of the strong regolith in the arch is
not less than 1 times the excavation width of the hole; the three-step method is suitable for deep buried regolith,
and the thickness of the regolith in the arch is not less than 1 times the excavation width of the hole. 3) It is
feasible to carry out mechanized construction in Class IV surrounding rock with Φ51mm advanced middle pipe
shelter, glass fiber anchor, expanded shell prestressed anchor and C30 early high-strength shotcrete. 4) Under the
premise of advanced pre reinforcement and support optimization mentioned above, When the distance between the
invert and the palm face is optimized to 106m (CD method) and 118m (three-step method), and the distance
between the secondary lining and the palm face is optimized to 160m (CD method) and 190m (three-step method),
the mechanized construction can reach the expectations of safety and efficiency.