After nearly four years of hard-working construction by railway builders, on February 15, a good news came from the Yuxi-Mohan section of China-Laos Railway that the holing-through was completed at Lixin Tunnel, a Level 1 high risk tunnel on the railway.
Lixin Tunnel is located at the junction of Yuanjiang County and Xinping County in Yunnan Province, with a total length of 5.3 km and a maximum burial depth of 247 m. The tunnel passes through 5 fault fracture zones in complicated geological conditions. There are risks such as unsymmetrical loading, large deformation, gushing, collapse and slip hidden in the construction, and the tunnel also needs to underpass Kunming-Mohan Expressway, which makes the construction extremely difficult.
Liu Gang, manager of the third division of Yuxi-Mohan Railway Project Department of China Railway Tunnel Group, said: "during the construction, we encountered 88 times of large and small gushing and topsoil slips. The gushing often rushed out of the tunnel directly, bringing great potential hazards to the construction."
According to the management idea of "controlling pace, seeking progress in stability and achieving excellence at one time", the Diannan Railway Construction Commanding Department of China Railway Kunming Group Co., Ltd. has joined hands with the designer, construction contractor, supervisor and other participating units to lead the construction with technological innovation, and innovated the three-bench invert construction method with core soil reserved and non-explosive excavation technology, and independently developed the "sharp tools" for tunnel construction such as mobile trestle and combined variable cross-section secondary lining trolley.
Since the outbreak of the novel coronavirus pneumonia epidemic, the construction participants of China-Laos Railway have been focusing on both the epidemic prevention and control and the construction of the railway. Up to now, the works completed on Yuxi to Mohan has totaled up to an investment amount of RMB 36.9 billion, more than 66 million m3 of earthwork and stonework for subgrade have been completed, and more than 80% of the construction of extra-large bridges and tunnels have been completed.