On January 16, the only extremely high-risk tunnel in China's severe cold region—the highest risk level—the Aimin Tunnel on the Harbin-Mudanjiang Passenger Dedicated Railway, defined by domestic tunnel experts as the "biggest challenge in China's severe cold regions," was successfully completed. The tunnel overcame numerous challenges, and its innovative practices are worth referencing for tunnel construction in China's severe cold regions.
According to reports, the 292.995-kilometer Harbin-Mudanjiang Passenger Dedicated Railway is the northernmost "horizontal" line in China's "Eight Vertical and Eight Horizontal" high-speed rail network and an important component of the rapid passenger transport network in Northeast China. At the same time, the Harbin-Mudanjiang Passenger Dedicated Railway forms a major transport corridor from Suifenhe, a port in eastern Heilongjiang Province, to Manzhouli, a port in the Inner Mongolia Autonomous Region, and is very important for building the Eurasian Continental Bridge. When Harbin-Mudanjiang high-speed trains enter the Mudanjiang urban area, they will enter the 2,940-meter-long Aimin Tunnel in the suburbs, then ascend to the surface near Mudanjiang Station, forming an overall "V" shape to reduce the impact of the high-speed rail on the urban environment and people's lives. This also creates a height difference of 41.8 meters in the tunnel, with slopes of 14.8‰ and 18‰ on both sides, while the slope of high-speed rail lines is generally 5‰.
According to reports, the Aimin Tunnel is located in China's cold region, with an extreme minimum temperature of minus 35 degrees Celsius, and faces technical challenges such as frost heave prevention, snow damage prevention, and winter construction. The entire line passes through multiple "loose sedimentary layers," "Tertiary mudstone and sandstone" and other strata, with Grade V and Grade VI surrounding rock accounting for 95% of the length, earning it the name "Geological Museum of Severe Cold Regions." In particular, between the tunnel entrance and No. 1 inclined shaft, and between No. 1 and No. 2 inclined shafts, the interbedded sandstone and mudstone sections of more than 470 meters are geologically weak, with even mountain creep, causing severe settlement and convergence of the tunnel arch frames and continuous collapses, forcing construction to stop several times. The construction unit established a technical research team, adopting "anti-slide pile protection + surface grouting" for the creeping geology at the tunnel entrance section, and implementing full-curtain grouting for the interbedded sandstone and mudstone sections between No. 1 and No. 2 inclined shafts, thereby improving soil stability and ensuring safe excavation.
After conducting on-site surveys, tunnel design master Shi Yuxin believes that the proportion of soft rock in the Aimin Tunnel is rare in China, especially with large deformations and many control points. The technical research team and relevant experts together overcame challenges such as severe cold, shallow cover, asymmetric pressure, water-rich conditions, and large spans. Their innovative practices are worth referencing for tunnel construction in China's severe cold regions.