Located in Nanchong City, Sichuan Province, the Huangjiashan Tunnel is a single-tube double-track tunnel designed for a speed of 350 km/h, with a total length of 3,106 meters and a maximum burial depth of 125 meters. The construction environment is complex, requiring the overcoming of challenges such as karst formations, coal seam gas and harmful gases, making it quite difficult. Currently, 91.6% of the tunnel construction has been completed. The Chengdu-Dazhou-Wanzhou High Speed Railway is a vital part of China's "Eight Vertical and Eight Horizontal" high-speed rail network along the Yangtze River. The line starts from Chengdu in Sichuan, passes through Dazhou, and connects to the existing Zhengzhou-Chongqing High Speed Railway in Chongqing, with plans to be completed and operational by 2027. Once operational, the travel time from Chengdu to Wanzhou will be reduced from nearly three hours to about one and a half hours.
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