The construction on the Kvesheti-Kobi Highway Tunnel in the North-South Corridor of Georgia has been going well. It is a key transportation construction project of the “Belt and Road Initiative”. With the cooperation of the China Railway Equipment Technical Service Team and the Project Department, the world’s largest diameter hard rock TBM “Caucasus” completed 7 rings (14 metres) on 3 January 2022, setting a record for the highest daily advance since its launch. This record is exceptional due to the environmental conditions of the project site, as the Gudori Mountains of Georgia are more than 2 kilometres above sea level, with constant snowfalls reaching 1 metre heights, and temperatures down to negative 20 degrees Celsius.

The “Caucasus” hard rock TBM has a diameter of 15.08 metres and is currently the world’s largest diameter hard rock TBM. For the first time, the equipment was assembled and delivered on-site at overseas construction sites, which greatly reduced the manufacturing cycle. The TBM excavation length is 8.86 kilometres, and the maximum buried depth of the tunnel is 1.121 kilometres, with the average burial depth being more than 600 metres. The tunnel lithology is mainly tuff and marl. In view of the construction difficulties caused by the long distance and large burial depth of the project, the CREG Design Team adopted a specific design targeting this application to enable the equipment to have efficient excavation capabilities under different geological conditions.