Recently, the "Chenggong" shield machine of Xiamen Rail Transit Line 4 broke through the ground, and the right line of the shield-driven section from the shared shield shaft to the Airport West Station on Line 4 was successfully completed. This is the first fully connected subway tunnel in the Xiang'an Airport section of Xiamen Rail Transit Lines 3 and 4, marking key progress for the project.

As a rare island-type airport globally, Xiamen Xiang'an International Airport is an important international airport in China, a regional hub airport, and a gateway airport for exchanges across the Taiwan Strait. Xiamen Rail Transit Line 4 has a total length of 71.23 km, starting at Songyu Wharf, passing through Xiamen North Station, and ending at Xiang'an Airport Station. Once fully completed, the line will rapidly connect the three major transportation hubs of "sea, land, and air," promoting Xiamen's high-quality development.

The right line of the section from the shared shield shaft to the Airport West Station on Xiamen Rail Transit Line 4 has a total length of 3,576.5 meters, a minimum curve radius of 800 meters, and a maximum design gradient of 22 degrees. A dual-mode shield machine with a diameter of 6,980 mm, operating in earth pressure/slurry (standby) modes, was launched from the shared shield shaft with Line 3. The section passes through an intermediate ventilation shaft and involves cross-construction with multiple ongoing projects, including the Airport Avenue, the Airport Expressway, and the integrated utility tunnel. The shield machine advanced safely and precisely like "threading a needle," and after 18 months it was received at the Airport West Station, 7 days ahead of the planned milestone.

There are 12 adjacent and cross-construction projects around this section. The project department did not wait or rely on others but took the initiative. During shield tunneling, it actively coordinated with cross-construction units, the airport command center, and other entities, held special meetings, arranged and organized construction in a coordinated manner, and refined construction plans to ensure smooth passage through existing structures. At the same time, a ground protection inspection system was established, with daily inspections carried out to prevent other projects from adversely affecting the completed tunnel during construction. During shield tunneling, the project department optimized shield tunneling parameters, strictly controlled shield attitude, thrust pressure, advance speed, muck discharge volume, grouting volume, and grouting pressure, and implemented an information-based feedback mechanism. During construction, it monitored and fed back information in real time and adjusted the next tunneling parameters based on monitoring data results, among other measures, to ensure that the shield tunneling direction always remained within a controllable range. This section is located in a reclamation area, where the soil is in an under-consolidated, water-rich state, making tunnel settlement control and surface settlement control difficult. At the same time, the tunnel alignment contains multiple sections of composite strata with soft upper layers and hard lower layers, as well as local medium-coarse sand strata in the upper part. The geology is complex and variable, and tunneling construction is highly difficult. To overcome the construction challenges, the project department adhered to a "short, quick, and efficient" management approach, carefully coordinated deployment, implemented 24-hour construction and a leadership shift supervision system, and held daily handover meetings to keep abreast of on-site dynamics.