On the morning of February 1, the "Caiyun Hao," China's self-developed largest-diameter hard rock tunnel boring machine (TBM), was successfully launched at the Gaoligongshan Tunnel on the Dali-Ruili Railway—China's longest railway tunnel. This is the first time a domestically produced hard rock TBM has been formally applied to railway construction in the complex geological conditions of southwestern Yunnan, and it will rewrite the history of China's long and large railway tunnel projects being long constrained by foreign technology in mechanized construction, marking that China's hard rock TBM technology has reached the world's leading level.
　　The Dali-Ruili Railway is located in western Yunnan Province, with a total length of about 330 kilometers. It is part of the China-Myanmar international railway corridor of the Trans-Asian Railway (western line). The Gaoligongshan Tunnel, with a total length of about 34.538 kilometers, is a key controlling project of the Dali-Ruili Railway and is China's longest railway tunnel and Asia's longest railway mountain tunnel. The tunnel has a maximum burial depth of 1,155 meters, and the area it passes through features "three highs" and "four actives." Its complex and variable geological conditions are rarely seen nationwide, making it worthy of being called a "geological museum" in the history of railway construction.
　　The "Caiyun Hao" TBM is a new type of open hard rock TBM with China's largest diameter, jointly developed independently by the China Railway Tunnel Group and China Railway Engineering Equipment Group. Its cutterhead excavation diameter reaches 9.03 meters, filling the gap in China's independent development of large-diameter hard rock TBMs of over 9 meters. It is new equipment tailor-made to adapt to complex geological environments. This TBM has made breakthroughs in key technologies such as excavation of weak and large-deformation variable cross-sections, rockburst prevention and control, rapid excavation in broken strata, response to high geothermal environments, and tunnel water inrush prevention and control. It is equipped with an online real-time advanced geological prediction system, ventilation and cooling systems, and others to cope with risks that may be encountered during excavation, such as surrounding rock deformation, fault fracture zones and rockbursts, sudden water and mud inrush, and high geothermal heat.
　　On August 1, 2017, the "Caiyun Hao" officially rolled off the production line in Kunming. After months of careful assembly and debugging, the "Caiyun Hao" TBM was successfully launched on the morning of the 1st. Excavation work at the tunnel exit officially shifted from the drill-and-blast method to TBM construction, replacing long-distance tunnel excavation that cannot be completed manually. After adopting TBM excavation, the average tunnel excavation speed can reach 350 meters per month or even higher, which will provide a reliable guarantee for completing the Gaoligongshan Tunnel and the entire railway connection in western Yunnan.