Recently, with the successful pouring of the last batch of concrete in Zone 2, the main structure of Huajing Station on Section 4 of the Shanghai Municipal Railway Airport Link Line has been successfully topped out. The project is invested in and constructed by Shanghai Shentie and built by Tunnel Engineering Co., Ltd. (Shanghai Tunnel), marking the station's full entry into the ancillary structure construction phase. This is the deepest-excavated station on the Airport Link Line and one of the deepest excavation projects currently under construction in Shanghai.

▲ Rendering of Huajing Station

Huajing Station is located on the south side of the intersection of Huazhan Road and Pingchi Road in Meilong Town, Minhang District. It is an underground four-level side-platform station with two entrances and is designed to enable transfers with Metro Line 15 and the under-construction Line 19. The station is approximately 563 meters long in total, and the deepest point of the foundation pit excavation is about 44 meters.

The standard section of the Huajing Station foundation pit is excavated to a depth of about 38 meters and is supported by 8 levels of concrete struts; the west end shaft is excavated to a depth of 43 meters and the east end shaft to a depth of 44 meters, both supported by 9 levels of concrete struts. The excavation volume is 720,000 cubic meters.

Among them, the foundation pits in Zones 1 and 3 completed structural topping-out on August 5, 2022 and March 27, 2023, respectively. The foundation pit in Zone 2 is currently undergoing construction of the landscape foundation and waterproofing on the roof slab.

During construction, the project team fabricated the reinforcement cages on ground formwork, and used gas welding at key positions to ensure precision. They applied the **MC128 trench cutter in an alternating "grab-and-cut" combined trenching method, with continuous monitoring throughout, achieving a verticality of 1/1000 and completing a total of 321 diaphragm wall panels with a maximum depth of 107.5 meters.

During the construction of the retaining structure, unlike the previous "diaphragm wall plus internal bracing" system, the team drew on the technical concepts of hydraulic steel bracing in foundation pit engineering and integral slipform construction in building engineering, combining the two technologies to form an integral sliding-and-lowering pre-support system. The system consists of four major modules: a steel frame support module, a jack hydraulic system module, a vertical sliding-and-lowering module, and a monitoring and control module. Through this system, active support can be achieved. During the period from the start of construction of each level of support (reinforced concrete) to the point at which it becomes effective, the deformation of the diaphragm wall is reduced from the conventional 5 to 10 millimeters to 3 to 5 millimeters. This effectively improves construction efficiency and quality while ensuring construction safety and guaranteeing the orderly progress of the project.