On August 12, the arch of Huashan Yilu Station was successfully broken through. With this, the arches of all six mined stations in Qingdao Metro Line 6 Phase I have been fully connected, and the milestone target has been achieved, pressing the "fast-forward" button for the next stage of construction.

　　Since the planning and construction of Line 6 began, Metro Line 6 Company has adhered to innovation-driven development, established a top-level planning and design philosophy, and set the construction goals of "safety, quality, innovation, green, intelligence, and harmony." It has made comprehensive efforts in the following four aspects to build a demonstration benchmark for mined-tunnel engineering on Qingdao Metro.

　　Making safe production the "number one task"

　　Preventing collapse is the number one task in metro mined-tunnel engineering. To reduce geological risks, the Line 6 Phase I project, after two years of research and demonstration, adopted a "deep-burial scheme" suited to Qingdao's geology of soft upper strata and hard lower strata. On the basis of the preliminary design, the burial depth was increased so that all stations are located in moderately and slightly weathered strata, saving substantial grouting costs. Thirty Level I risk sources were avoided and 25 Level II risk sources reduced, and the construction schedule has also been effectively guaranteed.

　　First-of-its-kind support technology saves investment and accelerates progress

　　Metro Line 6 Company invited top national experts, including Academician Qian Qihu, to review and validate the scheme, and also engaged Shi Yuxin, a national master of survey and design, as an expert consultant. Together with universities and research institutes, it formed a team of scientific research experts to conduct the first in-depth study and successful application of active support technology for mined stations in China's metro construction sector.

　　The active support technology for mined stations is characterized by being new, fast, and effective. Under this technology, each station has no fewer than three excavation faces, and arch excavation construction changed from the "double-side drift or CD method" to the bench method. It took only five months to achieve arch breakthrough, nearly two months shorter than similar mined stations. While improving efficiency, the six stations saved more than 20 million yuan in investment in total. Automated monitoring technology and controlled blasting technology were used throughout, with little impact on the external environment and no housing damage compensation claims.

　　Various innovations save investment

　　During construction, Metro Line 6 Company fully promoted mechanized construction techniques for mined stations and applied mechanized equipment such as rock drilling jumbos, mucking machines, concrete spraying manipulators, and anchor drilling rigs. The use of new techniques greatly reduced labor input, ensured worker safety, improved the construction quality and efficiency of mined stations, and effectively shortened the time for closing excavation support. Up to now, through various innovations, the Line 6 Phase I project has saved a cumulative investment of about 350 million yuan compared with the preliminary design.

　　Party building leadership opens up the "last kilometer of management"

　　During the construction of Line 6, guided by the working approach of "Party members into work teams, management into work teams," the company carried out labor competition activities such as "implementing the plan, going to the grassroots, and celebrating the Party's founding" to extend Party building and business management to frontline work teams, continuously strengthen red-line awareness, uphold bottom-line thinking, and open up the last kilometer of project management. This has effectively improved on-site safety and quality management and laid a solid foundation for building a demonstration line.

　　Up to now, in addition to the full breakthrough of the arches of the six mined stations on Qingdao Metro Line 6, one of the 14 open-cut stations has been successfully capped, and 13 stations have entered the main structure construction stage. One of eight shield machines and one TBM have completed launching, and the remaining TBMs/shield machines are expected to all meet the conditions for launching and tunneling by the end of the year.