Recently, the Sunyangping Tunnel on the Jinsha-Renhuai-Tongzi Expressway, the longest expressway tunnel under construction in Guizhou Province, built by China Railway 17th Bureau Group, achieved double-line breakthrough, laying a solid foundation for the full opening of the expressway.

The Jinsha-Renhuai-Tongzi Expressway, with a total length of 105 kilometers, is a key transportation infrastructure project in Guizhou Province to strengthen road network connectivity. Once completed and opened to traffic, it will effectively shorten the travel time and distance between Bijie, Liupanshui, Anshun and other cities in western Guizhou and Chongqing Municipality, and build an important economic corridor for the coordinated development of the Central Guizhou Economic Zone and the Chengdu-Chongqing Economic Zone.

The Sunyangping Tunnel on the Jinsha-Renhuai-Tongzi Expressway undertaken by the company is the longest and most difficult tunnel under construction in Guizhou Province. With a total length of 7.2 kilometers, the tunnel is located in a mountainous area with typical karst landforms, with a maximum burial depth of about 525 meters. It passes through unfavorable geological zones such as karst caves, karst cavities and carbonaceous mudstone, where risks such as mud and water inrush and gas overflow are concentrated. After excavation, the surrounding rock has extremely poor self-stabilization capacity, making construction difficult and risky. It is an important controlling project of the entire line.

In response to the unfavorable geological challenges in the construction section, the project team repeatedly joined forces with expert teams from domestic universities and institutions, and together with the owner, design, supervision and other units formed an expert group to conduct on-site surveys. On the basis of scientific demonstration and full reference to similar advanced experience, they formulated special construction plans, adopted the bench excavation method combined with advanced support, and took multiple measures to improve the stability of the surrounding rock and reduce the risks brought by construction in complex geology.

By applying technologies such as TSP advanced geological forecasting, geological radar and geological drilling rigs, the project established a domestically advanced comprehensive advanced geological forecasting system for tunnels, conducting advanced detection and real-time early warning of the surrounding rock ahead of the tunnel face, truly anticipating problems and taking preventive measures to keep safety in construction under tight control. By introducing mechanized tunnel construction equipment such as three-boom rock drilling jumbos, self-propelled mobile 36-meter full-width inverted arch formwork hydraulic trestles and intelligent secondary lining trolleys, the project improved the standardization and intelligence of construction, achieving a maximum monthly excavation of 203 meters under complex geological conditions.

To address the poor self-stabilization capacity of the surrounding rock, the project used a three-dimensional laser profile scanner during excavation to monitor tunnel settlement and convergence deformation in real time, and dynamically adjusted the excavation method and strengthened support parameters based on the data, ensuring the overall structural stability of the tunnel and guaranteeing smooth and orderly construction.

Construction in the gas tunnel section is like crossing a "minefield," posing challenges to the lives and safety of the builders. To ensure construction safety, the project implemented the "one blast, three inspections" system to strengthen monitoring of gas and toxic and harmful gases. Inside the tunnel, 1.5-meter-diameter ventilation hoses with low air leakage rates and small friction coefficients were installed, along with low-noise, energy-saving variable-stage tunnel-specific ventilation fans, providing all-round protection for construction safety.

Technology safeguards quality, and intelligence empowers safety. With the construction of an information-based construction management center as a key initiative, the project installed high-definition cameras, dedicated monitoring base stations and other terminals at key positions such as the tunnel face and lining trolleys, achieving 24-hour remote visual management and carefully safeguarding more than 900 construction days and nights with "zero accidents."