Recently, as the various systems of the TBM on the left line of the Laoshan-Zhangcun section began operating, the TBM on the left line of the Laoshan Science and Technology City Station—Zhangcun Station section in the civil engineering Work Zone 10 of Qingdao Metro Line 4, undertaken by China Railway Construction Bridge Engineering Bureau Group, was smoothly launched.

It is reported that the TBM on the left line of the Laoshan-Zhangcun section is 1,675.6 meters long in total. The tunnel body in this section consists partly of medium-coarse sand, moderately weathered granite and slightly weathered granite. The tunnel crown is relatively close to the Quaternary medium-coarse sand layer, and the surrounding rock has poor stability and good water yield, making it prone to collapse and sand inflow; the surrounding rock is classified as Grade VI. After the TBM on the right line of the Laoshan-Zhangcun section was launched on March 25, Work Zone 10 successively completed important milestone objectives such as the reception, maintenance and station pass-through of the left-line TBM, and overcame difficulties such as equipment maintenance and cross-construction during the station pass-through, laying a phased foundation for the scheduled launch of the left-line TBM.

Since the TBM on the right line of the Li-Jiu section was launched on June 1, 2019, Work Zone 10, with the help and guidance of Qingdao Metro Line 4 Co., Ltd., has scientifically arranged construction organization plans and rationally allocated resources, and has smoothly completed the launch of the TBM on the left line of the Li-Jiu section, the dual-line TBM of the Li-Lao section, the shield of the right line of the Zhang-Li section and the TBM of the right line of the Laoshan-Zhangcun section. During the process, through advanced detection and advance planning, and in combination with on-site construction conditions, measures such as surface grouting reinforcement and in-tunnel advance reinforcement were adopted to overcome, one by one, 15 sections of various unfavorable geological zones totaling more than 978 meters, smoothly pass under the unnamed arch bridge, the Zhangcun River and high-voltage power towers, and pass alongside the Tianma Gas Station and other risk sections, eliminating various influencing factors. A large amount of construction experience was summarized during this period, creating favorable conditions for the launch of the TBM on the left line of the Laoshan-Zhangcun section.

Qingdao Metro Line 4 is 30.7 kilometers long in total. After completion, it will be able to interchange with Metro Lines 2, 3 and 11 as well as Lines 1 and 8 under construction, becoming an “east-west major artery” and adding a brilliant touch to Qingdao's rail transit network. At present, 16 stations on Line 4 have completed the construction of their main structures. Line 4 Company will continue to strive ahead, accelerate construction progress, improve the connection between processes, and complete the construction task of Line 4 with guaranteed quality and quantity.