On August 29, the left tube of Xianghe No. 2 Tunnel, constructed by China Railway 15th Bureau Group Co., Ltd., and the left tube of Yaoshuixia No. 4 Tunnel, constructed by the Sixth Engineering Co., Ltd. of CCCC First Highway Engineering Co., Ltd., were successfully holed through, marking the full breakthrough of all tunnels along the Zhaduo Highway.
Xianghe No. 2 Tunnel is located in the Xianghe Village section within Huangyuan County. Construction began in June 2016. It is a curved separated two-way four-lane tunnel with a design speed of 100 km/h, a tunnel construction clearance net width of 10.75 meters, a net height of 5 meters, and an excavation width of 12.7 meters. The left tube has a total length of 1,803 meters, and the surrounding rock is classified as Grades III, IV, V, and VI. Yaoshuixia No. 4 Tunnel is located in the Dongxia gorge section of Huangyuan Gorge. Construction began in June 2016. It is a curved separated two-way six-lane tunnel with a design speed of 80 km/h, a tunnel construction clearance net width of 14 meters, a net height of 5 meters, and an excavation width of 16.29 meters. The left tube has a total length of 2,059 meters, and the surrounding rock is classified as Grades III, IV, and V.
Since the start of construction, in response to the actual conditions of poor surrounding rock and high construction difficulty, the Provincial Transportation Investment Company has made scientific and reasonable arrangements, organized experts to conduct on-site surveys multiple times, and urged the construction units to scientifically assess and formulate special construction plans and continuously optimize them. The construction units strictly followed the principles of “advance pipe roofing, strict grouting, short advance, weak blasting, strong support, timely sealing, and frequent measurement,” carefully organized implementation, innovatively applied new techniques and methods, and successfully overcame many construction difficulties, including poor geological surrounding rock grades, developed fissures, fractured rock masses, large-section excavation, and high risks in crossing fault fracture zones, ensuring the smooth progress of tunnel construction. The successful breakthrough of these two tunnels has laid a solid foundation for completing the Zhaduo Highway construction task on schedule.