On January 9, with the completion of the final truckload of concrete pouring, the main structure construction of the turnaround-line section from the starting point to Renmin Huitang Station on Qingdao Metro Line 4 was fully completed, marking the successful completion of the largest cross-section mined section on Line 4.

The Qiren section has a total length of 302.95 meters, with a standard cross-section 21 meters wide and 14 meters high, a cross-sectional area of 260 square meters, and a single-tube four-track composite lining structure, making it the largest cross-section mined section on Qingdao Line 4. The tunnel passes through an area densely packed with old buildings, and the surrounding environment is extremely complex. In addition, the clearance of the civil air defense cross-section at the portal of the inclined shaft is relatively small, so concrete transport vehicles cannot directly enter the tunnel, creating great difficulties for structural concrete pouring.

Facing various difficulties, the Project Department of Section 01 of Qingdao Metro Line 4 of China Railway 12th Bureau Group Co., Ltd. earnestly followed the construction requirements of Qingdao Metro Line 4 Company and the CRCC headquarters, made meticulous arrangements, and optimized the plans. By using the TBM launching shaft at the large-mileage end of the station as a concrete feeding opening and carrying out construction simultaneously with the main structure of Renmin Huitang Station, they overcame many difficulties such as numerous work faces, frequent cross-operations, discontinuous concrete supply, and difficult material turnover, and ultimately completed the main structure construction task of the section with both quality and quantity guaranteed. In 2019 and 2020, this section was consecutively awarded the honorary title of "Engineering Quality Entity Model Site" by Qingdao Metro Group.