On August 14, the left-line TBM tunnel of the Qingyi Dongyuan Station to Shilaoren Bathing Beach Station section (Qingshi section) of Qingdao Metro Bid 5-2-8, undertaken by China Railway No. 2 Engineering Group, was successfully holed through, marking that the project's **TBM section achieved the goal of double-line holing through 15 days ahead of the owner's schedule.

Since the start of construction on the Qingshi section, under the supervision and guidance of the Qingdao Municipal Public Utility Engineering Quality and Safety Supervision Station and the Third Construction Branch of Qingdao Metro Group, the project management team, guided by Qingdao Metro's "1+6 goal system for building a world-class metro," has systematically advanced construction management and work-team building, adopting a variety of innovative and efficient measures to drive the smooth achievement of early launch milestones for the left and right line TBMs in the Qingshi section, creating the preconditions for early double-line holing through.

▲TBM successfully received▲

The left line of the Qingshi section is 700.57 m long, with a tunnel depth of 23.06–29.46 m, and the tunnel body runs largely through slightly weathered granite strata. During TBM tunneling, the project department implemented a quality improvement management campaign:

First, taking Qingdao Metro's work-team building as the starting point, the "mini-legislation" focused on assessing key processes such as waterproofing material application, segment assembly, bolt re-tightening, and backfill grouting, strengthening the quality awareness of all work-team members;

Second, emphasis was placed on full-process segment management, implementing supervision and manufacturing management across the entire process of segment production, curing, finished-product protection, factory acceptance, transportation, and storage; segments failing acceptance were strictly prohibited from entering the site, and a dedicated segment storage yard was set up where segments were placed on custom-made steel supports to prevent damage;

Third, multiple measures were taken to control tunneling, mainly including parameter control, attitude control, survey control, and segment selection, effectively reducing segment misalignment and damage, achieving the tunnel's "no seepage, no leakage" goal, and earning high praise from the owner and all parties during quality observation activities.

▲Tunneling data monitoring▲

It is understood that after double-line holing through of the Qingshi section, the two double-shield TBMs will successively be pushed through Qingyi Dongyuan Station without excavation, in preparation for the launch of the Guoxin Gymnasium to Qingyi Dongyuan Station section (Guoqing section).

Next, the project department will continue to focus on Qingdao Metro's goal of "building a world-class metro," deeply grasp the essence of quality improvement, fully carry forward the striving-for-perfection "craftsmanship spirit," systematically enhance engineering construction quality, and strive to build a premium project that satisfies the client and gives the public confidence.