At 8:18 on August 18, the left tube of the Dajiangshan Tunnel on Huaguan Road in Guiyang was successfully holed through, taking 139 days, 20 days ahead of the expected schedule. This marks a major milestone victory for Section 4 of the Huaguan Road project and lays a solid and firm foundation for subsequent construction.
　　It is understood that Huaguan Road in Guiyang is a key project of Guizhou Province in 2018, with a tight schedule and heavy tasks. The 1,290-meter-long Section 4, constructed by China Railway Tunnel Group First Engineering Co., Ltd., includes tunnel engineering, bridge engineering, subgrade engineering, pipeline engineering, tunnel decoration engineering, management building engineering, etc., among which the Dajiangshan Tunnel is the key controlling project of the entire line. 　　The entrance section of the tunnel is located in the Economic Development Zone, and the exit section is in Huaxi District. It is designed as a double-tube, two-way, six-lane small-clearance tunnel, with a spacing of about 5 meters between the left and right tubes. The total length of a single tube is 472 meters, including a 357-meter mined section and a 115-meter open-cut section at the exit. The entire tunnel is designed for Grade IV to V surrounding rock, with shallow cover at the entrance and exit, and a burial depth of 5-10 meters. The geology consists of moderately to strongly weathered dolomite intercalated with argillaceous sandstone of the Middle Triassic Guiyang Formation (T2gy), with developed joints and fissures, highly broken rock mass, small karst cavities, and surrounding rock that softens upon contact with water. As a three-lane large-span tunnel, it has high technical requirements and a very tight schedule.
　　Zeng Dong, the project chief engineer, introduced that since the start of construction at the Dajiangshan Tunnel entrance on April 1, all participating employees have upheld the project spirit of "stay true to the original aspiration, keep the mission firmly in mind, be loyal and responsible, and lead the way," and actively carried out labor competitions such as the "China Railway Tunnel Leader Cup" and "Merit-Building First Engineering Cup," as well as Party-building themed activities like "Standards on Party Members, Quality Products from Party Members," fully mobilizing the enthusiasm and initiative of the employees to quickly and effectively launch construction production. During construction, they organized work scientifically, adjusted resources dynamically, strengthened on-site technical services internally, and optimized construction plans; externally, they actively communicated with the owner, local government, community, urban management, and nearby residents, doing a good job in reassuring and explaining to residents, and overcoming various difficulties during construction. Among them, because the exit direction has a burial depth of only 5 meters and is close to a residential area, in order not to disturb residents and to ensure house safety, after discussion, a cantilever roadheader was used for non-blasting excavation. 　　"There are three tunnels under construction on Huaguan Road: Yangzhong Tunnel, Guida Tunnel, and Dajiangshan Tunnel. Among them, the Dajiangshan Tunnel has the longest excavation length and the greatest construction difficulty. The project department has successively overcome various technical challenges such as shallow cover, small spacing, large span, poor surrounding rock, and sliding layers, achieving an excellent record of over 70 meters of average monthly excavation and support in Grade IV and V surrounding rock. The left tube was successfully holed through 20 days ahead of schedule. As of now, about 20 meters remain in the right tube, which will also be holed through soon," said Zeng Dong. As the leading enterprise in the national tunnel and underground engineering field, China Railway Tunnel Group will carry forward the fighting spirit of "especially able to endure hardship and especially able to fight," keep the mission firmly in mind, strictly control safety and quality, and with high morale, overcome difficulties to lay a solid foundation for the full breakthrough of Huaguan Road in the next step.