Chunfeng Tunnel is the first bi-directional four-lane highway tunnel in Shenzhen, China, with two decks within one tunnel. The tunnel is 3,603m long; its average radius of curve is R750m and its biggest gradient reaches 49%. The main geological conditions along the tunnel cover granite, fractured rock, metamorphic sandstone and shist. Rock stratum amounts for about 80% of its total length. Meanwhile, the tunnel drives through 11 fault zones with a total length of 431m. And the maximum net head pressure reaches 5.9 bar. The tunnel is being driven by a Φ15.8m Slurry TBM supplied by China Railway Engineering Equipment Group Co., Ltd. (CREG).
There are several challenges during the construction of Chunfeng Tunnel including large excavation section, long driving distance, high water pressure, small radius of curve, many buildings above, fractured stratum, high strength rocks etc. Designed to overcome these challenges, the TBM is equipped with an accessible cutterhead, main drive capable of telescopic movement and swinging, and four-circuit pressure maintaining system. Other innovations include muck treatment with two crushers, online cutter monitoring system, and free grouping of thrust cylinders.