On April 23, 2024, the world’s largest diameter hard rock TBM “Caucasus” broke through in Georgia, completing its construction assignment 30 days early. With an excavation diameter of 15.08m and a total length of 182m, the TBM “Caucasus” weighs 3900t and has a maximum thrust of 22,600t and a total power of 9900kW, and is, according to CREG, the largest diameter single shield hard rock TBM in the world to date.
With a maximum overburden of 1121m, the main tunnel on the Kvesheti-Kobi highway tunnel project is some 9km long, of which “Caucasus” completed 8860m of boring without any intermediate access points.
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 induced by long-distance, deep-overburden tunnelling, CREG customized the hard rock TBM including implementing an active articulation system, a bi-directional rotation cutterhead, a dual speed input reducer. During tunnelling, the TBM reached a maximum daily advance rate of 20m and a maximum monthly advance rate of 426m.
The North–South Corridor (Kvesheti–Kobi) Road Project is a vital route that connects Russia, Georgia, Armenia, Azerbaijan among other countries. Due to adverse snowy winter conditions in the Gudauri area, traffic disruption frequently occurs. Upon completion, the tunnel will effectively guarantee the transportation of local people and goods without delay.
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