Recently, the TBM for the left line of the Laoshan Science and Technology City Station–Zhangcun Station section of Qingdao Metro Line 4, undertaken by China Railway Construction Bridge Engineering Bureau Group, was successfully launched. The TBM-driven left line of the Laoshan–Zhangcun section is 1,675.6 m long. The tunnel body in this section consists partly of medium-coarse sand, moderately weathered granite and slightly weathered granite. The tunnel crown lies 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.

Qingdao Metro Line 4 is 30.7 km long, and 16 stations have so far completed main structure construction.