On January 24, 2021, as the final reinforcement cage was slowly lowered into the trench, the main retaining structure of JCXSG-11 of the Shanghai Rail Transit City Line Airport Link Line was successfully completed. In 50 days, 86 diaphragm walls were built, and the project team set a construction record for the entire line, with an average speed of nearly 2 walls per day and a maximum speed of 3 walls per day.

The retaining structure of the Lingkong Road transfer shaft of JCXSG-11 of the Shanghai Rail Transit City Line Airport Link Line consists of 1200mm-thick diaphragm walls with a depth of 50/55m and concrete strength grade C35. There are 86 diaphragm walls in total. The standard panel width is 6m, and trenching is carried out with a trench cutter. The maximum weight of a full reinforcement cage for a diaphragm wall is 98.2t (including all embedded ironwork), of which the upper 38m-long cage weighs 77.8t and the lower 17m-long cage weighs 20.4t. 400t, 200t, and 100t crawler cranes are used in coordination for sectional hoisting construction.

On October 28, the owner's construction kickoff meeting was officially held, announcing the official start of construction on the entire line. Faced with cumbersome greening relocation procedures and a large volume of greening relocation, the project actively joined forces with the owner's preliminary work department to fully communicate with local environmental protection bureaus, forestry stations, urban management and other units, proactively investing manpower and material resources to accelerate greening relocation and pipeline relocation. At the same time, the block construction method was adopted, three-axis reinforcement was constructed in sections, and guide wall construction followed closely. On December 6, the first diaphragm wall concrete pour was successfully achieved, creating a favorable situation of simultaneous construction of trench wall reinforcement + guide wall + diaphragm wall. During construction, a project schedule management system was formulated, and coordination meetings were held every day to sort out tasks, monitor objectives, and maintain stable and high output. After enduring the test of the "extreme cold" rarely seen in Shanghai in decades, when the whole city was forced to suspend work for 3 days, all 86 diaphragm walls were completed on January 24, 2021.

The project department is well aware that the construction quality of diaphragm walls is key to the success of the foundation pit and affects whether earthwork excavation and shield launching can proceed on schedule. Therefore, while optimizing personnel and equipment input and accelerating progress, it strictly controlled quality, exercising strict control from drawings and plans to trenching, reinforcement cage processing, and slurry control at every stage. Through the "seven strict" quality control measures, it ensured controllable diaphragm wall construction quality: first, strictly control incoming materials; second, strictly control trenching quality; third, strictly control slurry mixing quality; fourth, strictly control reinforcement cage processing quality; fifth, strictly control measurement review; sixth, strictly control trench inspection before lowering; seventh, strictly control concrete pouring.

Ultimately, the ultrasonic testing report on diaphragm wall trench verticality issued by a third-party testing unit showed that the trench verticality of all 86 diaphragm walls constructed by our project met the design requirements, with verticality within 1/400.