On July 18, the Shiyuan Tunnel, the longest tunnel on the entire Linxia-Dahejia Expressway, achieved breakthrough. Three boom-type roadheaders from China Railway Equipment successively entered the site and drove toward each other, helping the project set a "Lin-Da speed" in Gansu Province's expressway construction history: a 3.2-kilometer tunnel completed in 12 months of construction.

The Shiyuan Tunnel is designed as a separated dual-direction four-lane structure, with the left tube 3,181 meters long and the right tube 3,202 meters long, and a maximum burial depth of 294.5 meters. The geology in the tunnel area consists mainly of strongly weathered and completely weathered sandy mudstone, with poor geological stability and considerable construction difficulty, making it the longest tunnel project on the entire line.

Two CTR300R boom-type roadheaders from China Railway Equipment successively entered the right-line entrance and exit of the Shiyuan Tunnel on July 19 and August 15, 2020, driving toward each other. They operated for 324 days and 328 days respectively, with cumulative cutting time of nearly 5,000 hours and excavation volume exceeding 250,000 cubic meters, averaging more than 70 cubic meters per hour. They set a tunneling record of 133.14 cubic meters excavated in a single cutting hour, helping the tunnel achieve safe breakthrough 12 months ahead of schedule.

After completing its scheduled tunneling task for the Liugou No. 1 Tunnel on the Lin-Da Expressway, the third boom-type roadheader from China Railway Equipment was relocated on May 1, 2021, to excavate the left tube of the Shiyuan Tunnel, driving toward another roadheader that had completed the right-tube tunneling task, accelerating the construction progress of the left tube and ensuring the safe early breakthrough of the entire tunnel.

It is understood that the Shiyuan Tunnel on the Lin-Da Expressway took the lead in the large-scale promotion and application of boom-type roadheaders, effectively improving construction efficiency and ensuring safety during construction, playing a positive leading and demonstrative role in tunnel construction along the entire line and even across Gansu Province. The breakthrough of the tunnel is of milestone significance for the smooth progress of the entire line's construction tasks and has laid a solid foundation for achieving the goal of smooth completion and opening of the Lin-Da Expressway.