According to China Railway Tunnel Group on the 24th, on the afternoon of April 23, Georgia time, the Gudauri Tunnel on the KK Highway of the Georgia North-South Corridor, constructed by China Railway Tunnel Group, was successfully holed through, 30 days ahead of schedule.

The Gudauri Tunnel was constructed using a 15.08-meter-diameter full-face hard rock tunnel boring machine (hereinafter referred to as TBM) named "Caucasus." The early holing-through of the tunnel has laid a solid foundation for the future opening of the KK Highway of the Georgia North-South Corridor.

The KK Highway of the Georgia North-South Corridor has a total length of 22.7 kilometers. The LOT1 project constructed by China Railway Tunnel Group has a total length of 10 kilometers, of which the Gudauri Tunnel is 8,860 meters long and designed as a two-lane bidirectional road. Nearly half of the Gudauri Tunnel has an overburden depth of more than 700 meters, with a maximum depth of 1,121 meters, the greatest along the entire line. The tunnel is mainly composed of tuff and marl, with the highest surrounding rock strength of 130 MPa (megapascals). The geological conditions are complex, with numerous problems such as carbon dioxide outbursts, abundant groundwater, long-distance reverse-slope drainage, and soil layer intrusion. At the same time, the project design and construction adopt European standards, with high requirements for construction process standards and great technical difficulty, making it a key controlling project along the entire line.

During construction, the builders of China Railway Tunnel Group used a TBM "Caucasus," independently designed and manufactured by China, for single-head excavation. The "Caucasus" is 182 meters long, weighs 3,900 tons, and has a total power of 9,900 kilowatts. The TBM is equipped with synchronous excavation and segment assembly technology, enabling simultaneous shield excavation and segment assembly, effectively improving construction efficiency.

To ensure the smooth entry of the TBM, the builders of China Railway Tunnel Group adopted on-site assembly and commissioning technology for the main drive and the entire machine for the first time. To prevent the TBM from getting stuck in unfavorable geological conditions during excavation, the TBM was specifically equipped with a series of new functions such as active articulation, dual-speed reducers for getting out of jams, and bidirectional cutterhead rotation for mucking. At the same time, through measures such as optimizing the ventilation scheme, adding ventilation fans, implementing real-time gas monitoring throughout the tunnel, and carrying out key monitoring at key locations, they overcame problems such as sudden outbursts of harmful gases including carbon dioxide and hydrogen sulfide during excavation, as well as reduced oxygen content in the TBM main machine area, ensuring the operational safety of construction personnel.