At 9 a.m. on July 10, a 500-ton crawler crane and a 320-ton crawler crane worked together to steadily lift a 77-ton reinforcement cage, and with the cooperation of more than a dozen workers, slowly lowered the cage into the trench. It is reported that this is the first diaphragm wall constructed along the entire Taizhou Municipal Railway S2 Line (hereinafter referred to as the "S2 Line"), marking that the project has begun to enter the underground phase.

"This diaphragm wall reinforcement cage is 55 meters deep, 5 meters wide and 1.2 meters thick, and is the deepest reinforcement cage on the entire line. It takes more than an hour to successfully lower the reinforcement cage into the trench, after which the workers will pour concrete into it," said Hong Chao, deputy project manager of the civil construction Section 4 of the S2 Line. He noted that the construction site is located at the S1-S2 connecting line working shaft between Taizhou Station and Taizhou University Station, and the diaphragm wall construction marks that the working shaft has fully entered the stage of enclosure structure construction.

The S1-S2 connecting line working shaft is a key node for the full connectivity of the Taizhou Municipal Railway S2 Line project. The diaphragm wall serves as the enclosure structure of the shield working shaft, totaling 70 panels, and the connecting line working shaft is scheduled to take about one year. In rail transit construction, diaphragm walls are used as the main enclosure structure of deep foundation pits, undertaking the important tasks of retaining water and earth and enhancing the stability of the foundation pit.

The S1-S2 connecting line working shaft is located in Jinyang Wetland Park, in a marine sedimentary plain area with flat and open terrain and a crisscrossing surface water system with many meandering rivers. The surface is mainly composed of marine sedimentary clay, and the lower part is widely distributed mucky soil, so construction is relatively difficult.

"In the early stage, we contacted the command headquarters many times to relocate the valuable greenery in the wetland park, then cleared the muck from the site and hardened the construction access roads to ensure the smooth entry of equipment," Hong Chao said. The construction of all 70 diaphragm wall panels is expected to take two and a half months to complete the lifting and installation.

After the S1-S2 connecting line working shaft is completed, the shield machine will start excavation from there, connecting the S2 Line with the S1 Line. Once completed, the S2 Line will join the municipal railway S1 Line to form the backbone network of Taizhou's urban rail transit in the central urban area featuring "eastward advancement and westward expansion, southward connection and northward crossing," which is of great significance for promoting the integration of "three districts and two cities," improving the comprehensive urban transportation system and improving residents' travel conditions.

It is understood that since the full start of construction of the S2 Line project, 34 work faces, including elevated bridges, elevated stations, mountain tunnels, depot works and shield working shafts, have been fully opened up. From January to June 2024, an investment of 2.085 billion yuan was completed, and the entire line has cumulatively completed 4,856 pile foundations, 299 pile caps, 223 pier columns and 17 spans of girders.