China News Service, Chengdu, April 21 (Reporter Wang Peng and Liu Zhongjun) The reporter learned from China Railway Chengdu Bureau Group Co., Ltd. on the 21st that the Dechang Tunnel of the Chengdu-Kunming Railway Expansion Project undertaken by China Railway 11th Bureau Group was successfully completed that day. It marks the completion of all 25 tunnels of the Mianning-Miyi section of the Chengdu-Kunming Railway Expansion Project (Cheng-Kun Railway Double Line).
The Chengdu-Kunming Railway Expansion Project is a key construction project of the country’s western development, with a total length of 623.339 kilometers and the Cheng-E section of 128.698 kilometers. It will be opened at the end of December 2017; the Mipan section will be 108.307 kilometers and will be opened at the end of May 2020.
At present, there are only 156 kilometers of Mianmi section and 230 kilometers of Mian'e section. These two sections are the most difficult to construct and the longest in mileage.
There are 95 bridges and 25 tunnels in the Mianmi section alone, with a bridge-to-tunnel ratio of 63%.
The picture shows the construction site of Dechang Tunnel.
Photo courtesy of China Railway Chengdu Bureau Group Co., Ltd.
The Dechang Tunnel that was penetrated this time is located in Dechang County, Liangshan Prefecture, Sichuan Province. It has a total length of 14,365 meters and a maximum buried depth of about 1,000 meters. It is a double-lane tunnel. It is a difficult and high-risk project on the whole line. There is high pressure and rich water in the tunnel. Poor geology such as areas, fault fracture zones, high ground stress, high geothermal, etc., pose great challenges to construction technology.
Zou Yongmu, the commander of the Xichang Headquarters of the Chengdu-Kunming Railway Company, told the reporter that during the construction of the Dechang Tunnel, soft rock deformation and landslides at the entrance of the tunnel and mud-rock flow occurred successively, and the soft rock in the "Xigeda" formation in the tunnel deformed. It has the characteristics of turning powder into wind and turning into mud when it meets water. During the most difficult period, the single working face advances only 22 meters per month, which is called “tunneling in the'tofu'”.
For this reason, the Chengdu-Kunming Railway Company has organized the China Railway Second Hospital and domestic geological experts to conduct more than 20 special consultations, and finally adopted the pre-reinforcement of the surrounding rock of the tunnel body, the inverted arch with bolts, and the face of the tunnel with medium-sized pipes. Measures such as building sheds, optimizing the drainage system in the tunnel, and adding arches in the second lining arch have broken through the extremely difficult "Xigeda" geological layer.
The picture shows the construction site of Dechang Tunnel.
Photo courtesy of China Railway Chengdu Bureau Group Co., Ltd.
In addition to the bad geology of "Xigeda", large regional fractures, rock bursts, high ground temperature and other bad geology also brought a lot of trouble to the tunnel construction.
According to Qiao Hongyan, executive deputy manager of the Emi Project Department of China Railway 11th Bureau, since May 2019, the highest temperature of the Dechang Tunnel construction work surface has reached 43 degrees Celsius, with an average of 38 degrees Celsius, and as many as 30 ice cubes are sent to the face of the tunnel every day. More than tons, the builders not only have to often "shower" in the "curtain hole", but also "steam the sauna" in the "steam room".
At 8:18 on the 21st, with the successful completion of the last blasting of the Dechang Tunnel site, the construction workers at both ends of the tunnel achieved a successful meeting in the tunnel, marking the complete completion of the Dechang Tunnel. At present, all 25 tunnels of the Mianmi section of the Chengdu-Kunming Railway Expansion Project have been completed. The roadbed and bridge projects have been basically completed, and the construction has entered the final sprint stage. There are 10 tunnels left in the Mian'e section. (Finish)