The Chinese project involves a 2,063m TBM drive, including a 1,100m subsea section.
During boring, the TBM, manufactured by China Railway Engineering Group Co (CREG), overcame four major construction challenges. The first was the complex ground conditions, including 50% of mixed ground and 34.15% of full-face hard rock, which meant the TBM had to bore through a long stretch of high-strength rock.
The second was the difficult construction. The complex terrain in the subsea section could have caused the TBM to float and deviate from the designed route, as well as increasing the risk of severe cutter wear.
The third challenge was the large overburden. The tunnel is located at a depth of more than 40m under the seabed, with a maximum water pressure of 5bar and a maximum rock strength of 193MPa.
The fourth issue was the large cross-section, with an outer diameter of the segmental ring of more than 15m.
Mawan set a best monthly advance of 172m in mixed ground and a best daily advance of 10m, setting a new record for daily advance of large-diameter subsea TBMs in China.
Shenzhen Mawan Subsea Tunnel is expected to open in 2024. It will play an important role in expanding the city’s urban development and promoting transport interconnectivity in the Guangdong-Hong Kong-Macao Greater Bay Area.
