Recently, as the "Pengcheng" shield machine broke through the soil and arrived precisely at the Dachen Bay receiving shaft, the left-line shield tunnel of the Mawan Cross-Sea Passage Project was officially completed. With this, Shenzhen's first undersea tunnel has achieved bidirectional breakthrough, laying a solid foundation for the completion and opening of the entire line.

Starting at the intersection of Mawan Avenue and Yueliangwan Avenue in the Qianhai Mawan Port Area, and ending at the Dachen Bay Toll Station of the Yanjiang Expressway and the intersection of Jinwan Avenue and Xixiang Avenue in the Bao'an Dachen Bay Area, the route has a total length of 8.05 kilometers. According to reports, the key part of the project consists of two super-large-diameter cross-sea shield tunnels. The right-line shield tunnel, with a total length of 2,063 meters, was officially completed on June 9, 2023. The left-line shield tunnel, with a total length of 2,060 meters, was excavated by the "Pengcheng" shield machine. The shield machine was jointly developed by Herrenknecht and Shanghai Tunnel Engineering Co., Ltd. With a total length of 104 meters and a diameter of more than 15 meters, it is currently the largest-diameter slurry shield in China, standing taller than a five-story building.

The undersea tunnel of the Mawan Cross-Sea Passage has a large excavation cross-section and great burial depth, and the geological conditions of the areas it passes through are complex, of which 37.4% is full-face hard rock, 48.1% is upper-soft lower-hard strata, and 14.5% is soft soil; fault zones exist in local sections of the tunnel. In response to the special geological conditions in the project area, the "Pengcheng" adopted a number of innovative technologies such as a atmospheric pressure cutterhead and a telescopic main drive to address engineering risks under complex working conditions.