On April 23 Georgia time, “Caucasus”, the world’s largest diameter full face hard rock TBM jointly developed by CREG and CRTG, successfully broke through, marking the completion of the tunneling phase for the Kvesheti-Kobi Highway as part of the North-South Road Corridor in Georgia, achieving a 30-day advancement over the overall construction schedule.

With a boring diameter of 15.08 meters, a total length of 182 meters, a total weight of 3,900 tons, a maximum full thrust of 22,600 tons and a total power of 9,900 kilowatts, the 'Caucasus' is currently the world's largest single-shield rock tunnel boring machine, designed by China on China’s standard and manufactured all by China.

The main tunnel section of the Kvesheti-Kobi Highway totals 9,068m in length, adopting “Caucasus” TBM for blind heading. In view of the construction problems caused by the long distance and large depth of burial, the CREG design team employs synchronous tunneling and assembly technique for the first time, using active articulation system, bi-directional rotating cutter and two-speed reducer system to realize precise adjustment of the host attitude and have the ability of quick relieving from adverse geological conditions, enabling the equipment to have efficient boring capacity under good surrounding rock conditions. The maximum daily and monthly drilling footage are 20 meters and 426 meters respectively.