On March 25, in the drizzling spring rain, at the right-line tunnel portal of the launch shaft in the Hongxin section of Phase II of the Qingdao Metro Line 6 project, as the cutterhead of the "Hongxing" shield machine slowly rotated, it marked the smooth launch of the first shield machine in the Phase II project. This is the first application of a micro-slurry + earth pressure dual-mode shield machine in Qingdao Metro construction, and also the first case in the country.
The right line of the shield-driven section from Xintun Station to Hongshulin Station is about 1.3 kilometers long, with a total of 2 cross passages. The tunnel depth is about 6.5 m to 22.2 m, the minimum curve radius is 800 m, and the maximum longitudinal slope is 25‰. The shield machine adopts split launching and successively passes beneath two rivers and alongside a major urban arterial road. The complex geological environment has brought enormous challenges to shield construction.
To ensure the smooth launch of the shield machine, Qingdao Metro West Coast Construction Branch took the lead in organizing the Qingdao Metro Line 6 project management department of China Railway Shangtou, the Urban Construction Branch of China Railway Shanghai Engineering Bureau, and other relevant units to systematically review the construction risks and key difficulties of the project, select elite personnel to establish a special task force, and hold multiple special equipment meetings. They conducted detailed analysis and demonstration of the entire process safety plan for shield selection, design, assembly, commissioning, and tunneling, organized scientifically, planned meticulously, and reasonably applied the concept of "seizing every opportunity and making the most of every opening," ultimately determining the use of the country's first micro-slurry + earth pressure dual-mode shield machine.
During this period, the Qingdao Municipal Public Utility Engineering Quality and Safety Supervision Station organized a "send technology to the front line" activity to "diagnose and prescribe remedies" for tunneling in adverse geological conditions in this section. In light of the actual complex geological conditions on site, they coordinated repeatedly with the equipment manufacturer and, on the basis of the existing shield machine functions, added designs such as a high-pressure water flushing device in the cutterhead chamber to prevent mud cake formation and a cavity detection device at the top of the shield. The micro-slurry + earth pressure dual-mode shield machine can quickly achieve conversion between two modes: earth pressure tunneling and slurry film pressure-maintenance tunneling. The use of new technologies and new processes continuously injects "innovative momentum" into metro construction.
The "Hongxing" micro-slurry + earth pressure dual-mode shield machine has an excavation diameter of 6,500 mm. The shield machine and its supporting trolleys are about 95 meters long in total. The shield machine adopts a passive articulation form and innovatively adds a soil chamber visualization system, an automatic slag discharge metering device, and a shield tail clearance measurement system, greatly improving the efficiency and safety factor of shield tunneling and greatly enhancing the shield machine's adaptability under complex conditions.
Next, Qingdao Metro West Coast Construction Branch will closely focus on the goal system of "building a world-class metro" of Qingdao Metro Group, take team building as the cornerstone and the dual prevention mechanism as the starting point, overcome adverse factors in the construction process, and leverage the cutting-edge technology of the "micro-slurry composite earth pressure balance shield machine" to strive to create a model shield tunnel project for Qingdao Metro and make greater contributions to Qingdao Metro construction.
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