At the end of the year, the construction site of Wuhan Rail Transit Line 12, the second longest subway loop in the world and the longest in Asia, was busy. Recently, the reporter of Science and Technology Daily walked into many sites and saw that the trenching machine, excavator, crane, pump truck and other equipment were "well coordinated", and the foundation pit excavation and concrete pouring were orderly; Under the surging river, the shield machine army "gnaws" hard rock day and night, driving more than 100 meters a day on average... An Hongbin, general manager of the General Contracting Department of China Railway Construction Investment Group, introduced that at present, several nodes of Wuhan Metro Line 12 project have made breakthrough progress. Zhongyi Road Station is the largest and most difficult underground station of Wuhan Metro Line 12. How big is it? The station is more than 500 meters long, nearly 50 meters wide and about 28 meters deep, which is equivalent to the height of 9 floors. How hard is it? The station is located in the first terrace of the Yangtze River, and the underground pipelines are complex. A slight carelessness in construction will cause water leakage in the foundation pit joints, resulting in settlement of surrounding roads and buildings. How to solve problems? Before construction, the Project Department shall arrange a large number of monitoring points on the construction site for real-time monitoring; During the construction, the section steel joints of the diaphragm wall shall be subject to ultrasonic inspection to monitor their status; After construction, the integrity of the diaphragm wall shall be inspected, and the wall bottom shall be fully grouted and the joints shall be fully reinforced. "The width of the station is about 50 meters, which is very easy to cause deformation of the foundation pit during construction." Yao Haitao, the project leader, said that the foundation pit construction adopted two innovative techniques, namely, "reverse cover excavation method" and "manual two-point positioning method", to effectively solve the problem of uncontrollable deformation during the excavation of large-span foundation pit. Through monitoring, the foundation pit is perfectly formed and the surrounding structures have "zero settlement". The cutter head rotates slowly, the segment erector skillfully picks up, shifts, rotates and splices, and then supports the shoes to complete the assembly. The whole process is as smooth as flowing clouds... This is the construction scene of the large shield machine in Danke section of Line 12. The Danke section is 4 kilometers long, with the tunnel excavation diameter of more than 12 meters. It crosses the Yangtze River from 570 meters downstream of the Erqi Yangtze River Bridge in Wuhan, about 2 kilometers across the river. "Crossing the Yangtze River is the biggest difficulty in the project construction." Ren Ruhua, the person in charge of on-site construction, said that the shield machine crossing Hankou floodplain section and Yangtze River water area section is mostly uneven stratum with "soft upper and hard lower" or "hard upper and soft lower". On the one hand, it is difficult to control the forward posture of the shield machine; on the other hand, the breccia soil layer has great wear on the shield machine tools, which makes it difficult to "change tools" at the bottom of the river and poses great safety risks. In order to ensure the safe and smooth progress of the shield machine, the Project Department conducts detailed research on geological exploration, tool selection and tunneling parameters. Ren Ruhua introduced that, according to the construction characteristics of the project, the project department, relying on "An Hongbin Innovation Studio" during the construction process, carried out research on two innovative topics: "mechanical response and safety control for the construction of foundation pit of strong permeable ultra deep air shaft near the river" and "key technologies for large diameter shield tunnel of super long river crossing subway". According to the research results, it has applied for several patents such as "A Kind of Prefabricated Box Culvert Reinforcement Cage Processing Sample Frame" and "Inorganic All Silicon Fiber Grating Substrate Inclination Sensor", enabling efficient construction with technological innovation. (Liu Xinshe)