Jointly developed by China Railway Tunnel Group and China Railway Engineering Equipment Group, the “Caiyun” (Rosy Cloud) TBM is a new type of open TBM for hard rocks. With a cutter head of 9.03 meters in diameter, it is China’s largest homegrown TBM of its type, making the country a world leader in hard rock tunneling. The machine is built to work under difficult geological conditions and has been used in the construction of Gaoligong Mountain Rail Tunnel, Asia’s longest tunnel, along the Dali–Ruili railway.

　　An online advanced geological forecast system, ventilation and cooling system, and other key technologies were applied to the TBM to overcome a series of engineering challenges such as squeezing ground, fault zones and rock burst, water and slurry inflow, and high temperature.