On May 31, 21 meters underground at Changhong Square in Ziyang City, as the cutterhead of the "Tongcheng No. 2" shield machine broke through the soil, the right line of the shield-driven section between Baotai Avenue Station and Changhong Square Station on the Ziyang Rail Transit Line achieved "tunnel breakthrough." This marks the full completion of the Ziyang Rail Transit Line, the first intercity rail transit line in Southwest China, laying a solid foundation for its completion and opening in 2024.

The Ziyang Rail Transit Line is an express rail transit line connecting Chengdu Tianfu International Airport, Tianfu International Airport New City, and Ziyang City. The line has a total length of approximately 39 kilometers and comprises 7 stations, including 3 elevated stations (Futian Station, Lujiazui Station, and Airport Economic Zone Station) and 4 underground stations (Jiaozi Avenue Station, Changhong Square Station, Baotai Avenue Station, and Ziyang North Station). Its completion and opening will facilitate travel for residents along the route, improve the road network of the Chengdu metropolitan area, and further advance the construction of the Chengdu-Chongqing economic circle and the integration of Chengdu, Deyang, Meishan, and Ziyang.

"The section between Baotai Avenue Station and Changhong Square Station, which achieved tunnel breakthrough this time, runs a long distance beneath major risk sources such as the Tuojiang River and the Tuojiang No. 1 Bridge, presenting unprecedented difficulties," said Zou Fuqing, project manager of the Ziyang Line project of China Railway 14th Bureau Group. The underground section of the Ziyang Rail Transit Line is about 10 kilometers long and includes 4 underground stations and 4 shield-driven sections. It requires long-distance tunneling through moderately weathered mudstone, sandstone, and composite strata. Shield tunneling underground is comparable to "threading a needle in the dark," posing enormous challenges to tunneling technology.

To ensure the safe and smooth progress of the project, Chengdu Rail Transit Group, together with the participating construction units, invited renowned domestic experts in the shield tunneling field to conduct on-site surveys and analyses on multiple occasions. In response to the special geological conditions of different sections, earth-pressure and slurry dual-mode shield machines were used for tunneling construction. "Compared with traditional shields, the dual-mode shield machine can flexibly switch between earth-pressure and slurry modes according to actual conditions such as the geological strata being excavated and risk sources," Zou Fuqing said. With the "support" of the dual-mode shield machines, the line successfully crossed the Tuojiang River, with the right line reaching 425 meters, setting a new record in Chengdu rail transit construction.

As a landmark project in the integration of Chengdu, Deyang, Meishan, and Ziyang, the construction progress of the Ziyang Rail Transit Line has attracted much attention. Yang Yong, project commander of the Ziyang Line project of Kunlun Group, introduced that to ensure the project schedule progressed as planned, the Ziyang Rail Transit Line deployed 5 shield machines for simultaneous construction, with more than 800 people working together at peak times each day. The maximum monthly shield tunneling advance reached 460 meters, accomplishing a tunneling task of 16 kilometers in less than 20 months.