Photo: The "Tongxin" (Concentric) shield tunneling machine. Photo courtesy of CCCC Tianhe Company.

　　Recently, the "Tongxin" shield tunneling machine, independently developed by CCCC Tianhe Company (hereinafter referred to as CCCC Tianhe), a joint venture of the Tianjin-based central enterprise CCCC Tianjin Dredging Co., Ltd., successfully crossed beneath the Beijing-Tianjin-Tanggu Expressway in a "zero-disturbance" mode during the tunneling construction of Tunnel No. 1 — the "throat project" of the Beijing-Binhai Intercity Railway — helping to advance regional transportation integration at a high level. The shield machine has a total length of about 140 meters, an excavation diameter of 13.8 meters, and a total weight of about 3,000 tons, with a domestic content rate exceeding 98%. It is the largest-diameter shield machine applied in the Tianjin area to date.

　　The Beijing-Binhai Intercity Railway is an intercity railway connecting Beijing with the Binhai New Area of Tianjin. Once completed, it will link up with the Beijing-Tangshan and Beijing-Tianjin intercity railways and the Tianjin-Qinhuangdao and Tianjin-Baoding high-speed railways. Travel from Tongzhou District in Beijing directly to the Binhai New Area in Tianjin will take less than one hour, further optimizing transportation options in the Beijing-Tianjin-Hebei region and advancing the building of a "Beijing-Tianjin-Hebei on rails." Tunnel No. 1 of the Beijing-Binhai Intercity Railway has a total length of about 3,000 meters. During tunneling, it must pass through silty clay strata, silty sand layers, and confined aquifers, and cross beneath major risk sources such as the Beijing-Tianjin-Tanggu Expressway, the Beitan Sewage River, and planned roads within the airport. With frequently changing strata and large slope fluctuations, the project imposes high requirements on the shield machine's control of tunneling settlement, attitude, directional error, and segment assembly precision. CCCC Tianhe carried out adaptive design of the shield machine, enabling the "Tongxin" to achieve a segment assembly time of less than 30 minutes per ring, a tunneling directional error controlled within 3 millimeters, and segment assembly precision controlled within 3 millimeters, with no cutter replacement throughout the entire tunneling process. To date, Tunnel No. 1 has been excavated more than 400 meters in total and is expected to be completed by the end of this year.

　　In recent years, CCCC Tianhe has deeply integrated itself into the major strategy of serving the coordinated development of the Beijing-Tianjin-Hebei region, giving full play to its technical advantages in its professional field and demonstrating China's strong capabilities in developing super-large-diameter shield machines. To date, CCCC Tianhe has provided more than 100 shield machines for key projects such as Tianjin Metro Line 11 and the Beijing-Binhai Intercity Railway.