China News Service, Dazhou, October 20 (Reporter Liu Zhongjun) On October 20, after 1,320 days of construction, Xiangyang No. 2 Tunnel, one of the control projects of the Kangyu Section of the Xi'an to Chongqing High-Speed Railway (hereinafter referred to as the "Xi-Chongqing High-speed Railway"), was connected, laying the foundation for the entire line to be completed and opened to traffic on schedule.
The completion ceremony of Xiangyang No. 2 Tunnel. Photo by reporter Liu Zhongjun
It is understood that the Xiangyang No. 2 Tunnel is located in Xuanhan County, Dazhou City, Sichuan Province, in the hinterland of Daba Mountain. It has a total length of 12,673 meters and a design speed of 350 kilometers per hour. It is a single-hole, double-line tunnel with a maximum burial depth of approximately 1,150 meters. The tunnel has a high proportion of Grade IV and Grade V surrounding rocks, and passes through unfavorable geology such as strong karst, high gas, broken rock zones, and large deformation of soft rock. The geological "three highs" and "four more" are superimposed, that is, high water head, high gas, high steep and dangerous rocks, many fault folds, many coal-bearing strata, many underground river pipelines, and many landslide rock piles. It is a Grade II high-risk tunnel, which is a key and difficult point in the entire construction.
"The geological conditions of the tunnel are complex, and risks such as water inrush, mud surge, and high gas are intertwined." Li Chengzhi, manager of the Xiyu High-speed Railway Project of the China Railway 20th Bureau, said that during the construction, the project department relied on the high-precision advanced geological forecasting system to identify and deal with risks such as karst, fracture zones, and gas in advance; for High-pressure water inflow in karst areas adopts a complete set of processes such as water drainage, curtain grouting, and dangerous rock reinforcement, forming a mature solution for water inflow control in complex karst areas; gas monitoring combines automated monitoring with manual detection to continuously, fixed-point, and long-distance monitor toxic and harmful gases, and is equipped with sound and light alarms.
An excavator is clearing debris inside the Xiangyang No. 2 Tunnel. Photo by reporter Liu Zhongjun
In order to speed up the progress, the tunnel was divided into 4 work areas and 6 working faces were constructed in parallel. Large-scale intelligent equipment such as C7 multi-function drilling rig, three-arm rock drilling rig, and arch integrated rig were used. It was also equipped with an intelligent steel structure factory. The production efficiency was significantly improved compared with traditional methods. The application of 3D scanning, electronic sand table, BIM and other systems has enabled on-site safety, quality and progress to be simultaneously advanced. This has provided an additional experience for reference in the construction of similar long tunnels with complex geology in China. “The Kangyu section of the West-Chongqing High-speed Railway has run through 68 tunnels, and the project has entered the critical stage of remaining projects such as ballastless track construction, station building construction, and installation of four electrical engineering projects.” said Yao Yunxiao, Party branch secretary of the Dazhou headquarters of the Beijing-Kunming High-speed Railway Xikun Co., Ltd.
Engineering and technical personnel are carrying out measurement operations in Xiangyang No. 2 Tunnel. Photo by reporter Liu Zhongjun
The Xi'an-Chongqing High-speed Railway is an important part of the Beijing-Kunming Channel and the Baotou (Yin)-Sea Channel in the national "Eight Vertical and Eight Horizontal" high-speed railway network. The main line is about 739 kilometers long and is divided into two sections from Xi'an to Ankang and Ankang to Chongqing (Kangyu Section). The approximately 90-kilometer Fankuai to Wanzhou connection line via Kaizhou is also being constructed simultaneously. At present, the section from Xi'an to Ankang has been opened for operation on September 28.
