Recently, the Guangyuan-Mianyang expansion project of the G5 Beijing-Kunming Expressway (hereinafter referred to as the Guang-Mian Expansion Project), which is led and invested in by Sichuan Expressway Company of Shudao Group, designed by Sichuan Provincial Highway Design Institute, and constructed by Sichuan Road & Bridge Transportation Construction Group, achieved the smooth double-tube breakthrough of the Songjiashan Tunnel, the longest tunnel and a major and difficult control project on the entire line, marking a breakthrough progress in the construction of the Guang-Mian Expansion Project and laying a solid foundation for the completion and opening of the entire line.

Songjiashan Tunnel

is located in Liugou Town, Jiange County, Guangyuan City, with a left tube length of 3,730 meters and a right tube length of 3,680 meters. It is a double-tube, two-way separated extra-long tunnel. The tunnel is a small-clearance tunnel with high clearance and large span. The area where it is located has fault fracture zones, developed fissures, horizontally layered rock masses, and poor integrity. The overall geological conditions are unfavorable, making blasting work extremely difficult.

During construction, the participating units overcame unfavorable factors such as high temperatures and flood seasons, continuously optimized construction plans, introduced advanced construction equipment, and steadily advanced the construction progress.

01 In terms of safety management

Safety management systems such as the tunnel access control system, video monitoring system, personnel positioning system, and blasting warning system were applied to carry out all-round real-time monitoring and early warning of the tunnel, achieving zero accidents and zero casualties throughout the entire production process.

02 In terms of innovation leadership

The "three-spray, three-scrape" process was adopted to strictly control the flatness of the initial support and focus on improving the appearance quality of the tunnel secondary lining. The advanced anchor bolt construction method was adopted to enhance the stability of the tunnel structure. At the same time, the ring-shaped LED strip lighting system was introduced into the under-construction expressway project, significantly enhancing visibility inside the tunnel and effectively preventing operational accidents. The longitudinal micro-mist system was adopted to effectively control dust concentration and significantly improve the tunnel construction environment, marking the first application in an under-construction expressway in Sichuan.

03 In terms of environmental protection management

Environmental protection laws and regulations were strictly observed, construction areas were rationally planned, and ecologically sensitive and fragile areas were avoided as much as possible, maximizing the protection of the ecological environment of two provincial-level nature reserves: the Xihe Wetland and the ancient cypresses of Cuiyun Corridor.

04 In terms of complex geology

The eighteen-character policy of "advance pipe forepoling, strict grouting, short excavation, strong support, early closure, and frequent measurement" was adhered to. Advanced technologies such as geophysical prospecting for advanced geological prediction and smooth weak blasting were used, and well-known experts were invited to the site for guidance many times, ensuring the tunnel was opened on schedule under the premise of construction safety.

As of now, the Guang-Mian Expansion Project has completed a cumulative investment of 15.488 billion yuan, accounting for 53.06% of the estimated total investment of 29.191 billion yuan.

After the Guang-Mian Expansion Project is completed, the expressway from Chengdu to Guangyuan and on to Shaanxi, a northbound route out of Sichuan, will be substantially expanded, and the existing traffic pressure will be greatly alleviated. It will further provide safe, comfortable, efficient, and sustainable transportation services for people's travel and promote the integrated social, cultural, and tourism development of the areas along the project.

The Guang-Mian Expansion Project is an important part of the capital radial line G5 Beijing-Kunming Expressway in the longitudinal line 8 expressway network of the national "ten vertical and ten horizontal" comprehensive transportation corridors. The project starts at Zhoujiahe in Guangyuan City (south of the Heishuitang hub interchange of the Lanzhou-Haikou National Expressway), connects to the under-construction Hanzhong-Guangyuan expansion project of the G5 Beijing-Kunming Expressway, and ends at the southeast side of Weicheng Town in Mianyang City. It has a total length of 123.984 kilometers, a bridge-tunnel ratio of 54.6%, a total of 21 tunnels and 74 bridges, including 9 extra-large bridges, and 12 interchanges. It is designed to a two-way six-lane standard with a design speed of 120 kilometers per hour.

Since the commencement of construction, the Guang-Mian Expansion Project has successively built smart beam yards, smart engineering management centers, and intelligent mixing stations; vigorously applied digital intelligent lining trolleys and actively introduced digital intelligent manufacturing platforms and equipment such as the tunnel intelligent safety management system and the intelligent CNC form traveler system, strengthening efforts in digital and intelligent construction. At the same time, measures such as "optimized design, permanent-temporary combination, green construction, and energy conservation and emission reduction" were adopted to promote the harmonious unity of highway construction and ecological environmental protection, accumulating experience in green development of expressway construction and improving quality and efficiency in ecological and environmental protection.