On June 9, at the right-line receiving shaft of the Mawan Cross-Sea Passage in Qianhai, Shenzhen, the 15.53-meter-diameter "Mawan" slurry balance shield machine broke through the rock, marking the breakthrough of the right line of the Shenzhen Mawan Cross-Sea Passage—the largest-diameter subsea shield tunnel currently under construction in China—jointly built by the Shenzhen Transportation Public Facilities Construction Center, China Railway Southern Investment Group, and China Railway Tunnel Group.

The Shenzhen Mawan Cross-Sea Passage is a key demonstration project for interconnected transportation construction in the Guangdong-Hong Kong-Macao Greater Bay Area and Shenzhen's first cross-sea passage. The project starts at the intersection of Mawan Avenue and Yueliangwan Avenue in the Mawan Port Area of Qianhai and ends at the Dachan Bay Toll Station of the Yanjiang Expressway and the intersection of Jinwan Avenue and Xixiang Avenue in the Dachan Bay area of Bao'an. The route has a total length of 8.05 kilometers and is divided into above-ground and underground road sections. The underground road is planned as an urban expressway with six lanes in both directions and a design speed of 80 km/h; the above-ground road is planned as an urban arterial road with six lanes in both directions and a design speed of 40 km/h.

The Shenzhen Mawan Cross-Sea Passage project is divided into right and left lines. China Railway Tunnel Group is responsible for constructing the right-line section—Section 2 of the Shenzhen Mawan Cross-Sea Passage. The shield section of the project is 2,063 meters long and is the controlling engineering component of the entire route. During construction, world-class subsea tunnel challenges were overcome, including tunneling through soft strata in the reclamation area, crossing long-distance soft-hard uneven strata and full-face hard rock strata under high subsea water pressure.

To overcome one subsea tunnel construction challenge after another, builders from China Railway Southern and China Railway Tunnel Group carried out a number of targeted designs tailored to the "Mawan" super-large-diameter slurry balance shield machine, innovatively applying multiple cutting-edge technologies such as atmospheric cutter replacement technology, a real-time cutter monitoring system, a large-flow slurry circulation system, and a telescopic oscillating main drive system. Through sound construction management, these targeted designs greatly improved shield tunneling efficiency. During the process, the project achieved a national record for daily tunneling of a large subsea shield, with a maximum daily advance of 10 meters.

Technological innovation was used to enhance the quality of intelligent subsea tunnel construction. During construction, builders vigorously promoted the application of intelligent construction technologies. Relying on the "Smart Shield Big Data Platform" of China Railway Tunnel Group, they used the big data system to comprehensively analyze construction data for the entire process, achieving real-time intelligent monitoring and automatic early warning of tunneling parameters. This ensured efficient, continuous, and safe underwater tunneling by the super-large-diameter shield and made important explorations for the intelligent construction of subsea tunnels in China.

In terms of green and environmentally friendly construction, the builders practiced the concept of green development, built a high-standard slurry treatment center, and scientifically optimized the slurry pipeline design, achieving 100% collection of slurry within the pipes and meeting the control standards of zero slurry leakage and zero pollution, balancing the project's economic and environmental benefits.

Once completed, the Shenzhen Mawan Cross-Sea Passage will further improve Shenzhen's road network structure, connect port-related freight traffic in the Nanshan Port Area, and also accommodate passenger traffic linking areas such as Mawan, Chiwan, and Dachan Bay. It will separate passenger and freight traffic and transit traffic in the Qianhai area, further expand urban development space, facilitate transportation for Shenzhen residents, provide strong support for building Shenzhen into a transportation powerhouse, and help advance the construction of the Guangdong-Hong Kong-Macao Greater Bay Area and Shenzhen's demonstration area of socialism with Chinese characteristics.