On June 9, 2023, the super large diameter (15.53m) slurry balance TBM “Mawan” jointly developed by China Railway Engineering Equipment Group Co., Ltd. (CREG) under CRHIC and China Railway Tunnel Group broke through into the reception shaft on the Right Bore of Guangdong Shenzhen Mawan Cross-Sea Passage, marking the completion of the Right Bore of the Passage as the largest diameter undersea TBM tunnel under construction in China.

The Right Bore TBM section of Mawan Cross-Sea Passage Project is 2,063 meters long, including a sub-sea section of 1,100m, which is crucial for the entire project. “Mawan” TBM, especially designed by CREG for the project, has a diameter of 15.53m and a height of more than 5 floors, with the main component being 140m long. During the boring process of “Mawan” TBM, four major construction challenges have been solved. The first challenge is that the Mawan Cross-Sea Passage has a complex geological structural stratum, of which, 50% is uneven soft and hard rock stratum and 34.15% full-section hard rock stratum, which means a long distance of boring through high-strength rock stratum. The second challenge is the great possibility of TBM floation and deviation from the designed route due to the complex terrain in the sub-sea section, combined with the risk of severe cutter wear and the subsequent need for cutter changes, making construction more difficult. The third challenge lies in the location of the tunnel, which is at a depth of over 40m under the sea, with the maximum water pressure of 5bar and the maximum rock strength of 193MPa. The fourth challenge is that the tunnel cross-section is large and the segment outer diameter exceeds 15m, and the undersea TBM adopted, which is the largest of its kind in China, is demanding on equipment performance and construction technology.