On June 3, with a blast, the right tube of the Sansheng Tunnel—the longest tunnel on the entire Hechang Expressway—broke through, marking the full breakthrough of the tunnel and the completion of all main works of the Hechang Expressway, which will open to traffic this year.

The Hechang Expressway (Hechuan to Changshou) starts at the Shaxi junction interchange of the Tonghe project on the Third Ring Expressway, connects with the Yuwu Expressway, and ends near the Jiantuowan interchange of the Yuchang Expressway. The project is about 76.06 km long, built to a two-way four-lane standard with a design speed of 80 km/h, and includes two service areas.

The Sansheng Tunnel, constructed by the Third Company of CCCC First Highway Engineering Co., Ltd., is a key control project of the Hechang Expressway. It is 7,632 meters long in total, with the left tube 3,802 meters and the right tube 3,830 meters.

The surrounding rock of the Sansheng Tunnel is generally poor, with Grade IV and V surrounding rock accounting for 92.3%, mainly sandstone, and a maximum burial depth of 430 meters, with unfavorable high in-situ stress geology. He recalled that when the Sansheng Tunnel had been driven to about 900 meters, rockburst occurred inside the tunnel, with rock falling off over an area of up to about 30 square meters. The contractor strengthened monitoring and used various means such as advanced geological prospecting to ensure safe construction, and the tunnel finally passed safely through the high in-situ stress section.

As the last tunnel on the Hechang Expressway to break through, the Sansheng Tunnel was clearly not easy to build. The tunnel also passes through coal mine goaf areas and crosses over the Xiangguosi gas storage, with unfavorable geology such as harmful gas and karst, a complex construction environment, and relatively high safety risks.

The contractor installed a toxic and harmful gas monitoring system inside the tunnel and set up blasting vibration monitoring inside and outside the tunnel. At the same time, it optimized the construction technology and adopted weak blasting to reduce disturbance to the surroundings and ensure construction safety.

The full breakthrough of the Sansheng Tunnel also marks the completion of all main works of the Hechang Expressway. Next, the Sansheng Tunnel will enter the construction of ancillary facilities.

It is understood that the Hechang Expressway is the last section of the Chongqing Third Ring Expressway still under construction. It will be completed and open to traffic within this year, which also means the Chongqing Third Ring Expressway will be fully completed, of great significance for further promoting interconnectivity in the Chongqing metropolitan area.