On December 3, the entrance excavation of the Malizhai Tunnel on the Yuxi-Mohan Railway, undertaken by the Yumo Railway Project Department of China Railway 21st Bureau Group Co., Ltd., reached 1,004 meters, achieving an important phased breakthrough.
The Malizhai Tunnel has a total length of 4,264 meters and is divided into two work areas: the entrance and the exit. The entrance section is constructed by the No. 1 Sub-department of the project department, which began tunneling in August 2016. The tunnel is characterized by complex geology. The designed unfavorable geological conditions include karst, landslides, bedding-parallel strata, and possible high in-situ stress and radioactivity. The strata are mainly mudstone, which softens easily when exposed to water. The entrance section contains the Manlingshan syncline.
To complete the tunnel construction to high standards and with high quality, the No. 1 Sub-department deployed a strong construction team and well-equipped machinery, with a deputy manager in charge. During the process, measures such as pre-job training, technical briefings, red-line control, and construction method implementation were strictly enforced. The construction principles of “advance pipe forepoling, weak blasting, short advance, strong support, rapid sealing, and frequent measurement” were adhered to. Each procedure and technique was carefully studied, and monitoring and measurement, advance forecasting, advance drilling, systematic rock bolts, lining quality, ventilation, and harmful gas detection were effectively strengthened. Difficulties such as the steep portal location and access road, large variations in surrounding rock, high temperatures inside the tunnel, and numerous material supply challenges during the rainy season were overcome. While steadily advancing construction, single-month records were continuously broken. In June this year, excavation first reached 107.2 meters, and in November a new record of 110.7 meters was set. The team also won top honors for consecutive months in the labor competition organized by the project department, completed the annual plan 32 days ahead of schedule, and became the portal with the fastest main tunnel excavation and the highest single-month advance rate in the contract section.
At present, they have entered the final month of the year for the year-end sprint. They remain neither arrogant nor impatient and vow to achieve even better results to bring 2017 to a successful conclusion.