On the evening of September 7, at the construction site near Tianjin Binhai International Airport, as the first diaphragm wall reinforcement cage, standing 64.95 meters tall, was hoisted safely and smoothly into the trench in three sections, it marked the smooth commencement of the No. 3 receiving shaft of Tianjin Airport Station on the Tianjin Airport No. 2 Tunnel of the Beijing-Binhai Railway Section V project, laying a solid foundation for the smooth breakthrough of the tunnel's 4-3 section.

Hoisting of the first diaphragm wall

The Beijing-Binhai Railway Section V project is located in Dongli District, Tianjin. It connects to the Tianjin Airport underground station to the north and, after passing beneath the Jishan Expressway elevated section, emerges at ground level to the south, with a total length of 9,596 meters. The main construction content includes the 8,663-meter Tianjin Airport No. 2 Tunnel and 933 meters of subgrade. The shield-driven section is 7,720 meters long and is configured as a single-tube, double-track tunnel, constructed using two shield machines, "Jingbin Xietong" and "Jingbin Chuangxin," working on the 4-3 and 6-5 sections respectively.

The No. 3 receiving shaft of Tianjin Airport Station is used to receive the "Jingbin Xietong" shield machine. The shaft foundation pit is 23 meters long and 21 meters wide, with a maximum excavation depth of approximately 35.53 meters. It contains a total of 19 diaphragm wall panels, with a total concrete volume of approximately 9,233.5 cubic meters. The first diaphragm wall panel is 6 meters wide and 1.5 meters thick, weighs approximately 127 tons, and uses H-shaped steel plate joints. That evening, with the coordinated operation of one 200-ton and one 450-ton large crawler crane, the reinforcement cage of the first diaphragm wall was lifted in parallel section by section, rotated in the air to a vertical position, and hoisted to the predetermined trench location to complete the insertion task.

Alignment map of Tianjin Airport No. 2 Tunnel

The No. 3 receiving shaft lies on the critical route of the Beijing-Binhai Intercity Railway and is key to whether the "Jingbin Xietong" shield machine can proceed smoothly. Given the tight schedule and heavy tasks, China Railway 14th Bureau Group established a dedicated work promotion team to supervise the construction task of Shaft No. 3. Since entering the site on August 26, as of September 7, they had completed 640 meters of access roads and the diaphragm wall guide wall construction, while efficiently completing on-site temporary facilities.

Because the No. 3 receiving shaft is located within the airport control zone with a height limit of 45 meters, construction must ensure the normal operation of the airport, and construction requirements are extremely strict. Therefore, the diaphragm wall construction adopted the method of integral fabrication, sectional (three-section) hoisting, and trench-mouth connection. Compared with normal hoisting construction, each panel takes about ten extra hours to hoist. The diaphragm wall construction task is expected to be completed in 23 days.

To overcome construction challenges, the project construction team strictly controlled the trench excavation progress according to changes in geological conditions. To ensure trench verticality, the frequency of ultrasonic testing was increased during construction, and timely correction was made to the verticality of problematic trench sections. At the same time, relevant experts were invited to review the construction plan and provide technical guidance on diaphragm wall construction technology, reinforcement cage hoisting safety, and concrete mix proportions, promptly and effectively solving on-site problems.

Completed tunnel of the 4-3 section