World’s Largest Diameter Hard Rock TBM Breakthrough

On April 23, 2024, the world’s largest diameter hard rock TBM “Caucasus” broke through in Georgia, completing its construction assignment 30 days in advance.

With an excavation diameter of 15.08 m (49.5 ft) and a total length of 182 m, the TBM weighs 3900t and has a maximum thrust of 22,600t and a total power of 9900kW, which is so far the largest diameter single shield hard rock TBM in the world.

With a maximum overburden of 1,121m, the main tunnel of the Kvesheti-Kobi highway tunnel project is around 9km long among which the TBM completed 8,860m of boring with no intermediate access. The geology is mainly tuff and marl, with a maximum rock strength of 130MPa. To deal with the complicated geological conditions and the construction challenges brought by long-distance and deep-overburden tunneling, CREG has customized the hard rock TBM with some targeted designs for the first time, including active articulation system, bi-directional rotation cutterhead, and dual-speed input reducer, which enables not only the precise adjustment of main machine attitude and the rapid breakout in adverse ground, but also the efficient tunneling in good surrounding rock. During the tunneling, the TBM reached the maximum daily advance rate of 20m and the maximum monthly advance rate of 426m.

The North–South Corridor (Kvesheti–Kobi) Road Project is an important passage that connects Russia, Georgia, Armenia, Azerbaijan and other countries. Because of the snowy winter in Gudauri area, the traffic interruptions often occur. Upon completion, the traffic on the Gudauri section will proceed without interruptions in the winter, which can effectively guarantee the transportation of local production goods and daily necessities.

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