Recently, the reporter learned from China Railway 18th Bureau Group that the "Yuecheng Liangshan" TBM, which is undertaking construction of the Daliangshan No. 1 Tunnel on the Lexi Expressway, has set a national record of 32 meters of daily advance in highway tunnel excavation. In just nine months, it achieved a cumulative advance of 3,000 meters, setting the fastest record for single-head tunneling of 3,000 meters in a highway tunnel in China. This marks a major breakthrough for TBM application in highway tunnel construction and once again enhances the group's reputation as the "TBM ace force."

It is understood that the Lexi Expressway is China's first prosperity-promoting corridor and eco-tourism corridor extending deep into the heart of the Greater and Lesser Liangshan Mountains. It crosses the Hengduan Mountains of the Qinghai-Tibet Plateau, climbing from the mountainous terrain of southwestern Sichuan at an elevation of more than 600 meters to alpine meadows at more than 2,000 meters, with a total elevation difference of 1,450 meters and a bridge-to-tunnel ratio as high as 82%. The route passes through nature reserves and areas with highly variable microclimates, with no roads, electricity, or communications. The geological conditions are extremely complex, and the construction technology is exceptionally difficult, which is extremely rare among mountainous expressways in China.

The 15.3-kilometer Daliangshan No. 1 Tunnel, a key controlling project on the entire line in which China Railway 18th Bureau Group is participating, is the longest expressway tunnel in southwestern China. The tunnel passes beneath the Mamize Nature Reserve at an elevation of nearly 4,000 meters. The ecological environment is fragile, and the project faces severe challenges.

To rapidly achieve opening of the Lexi Expressway and further consolidate the achievements of poverty alleviation in the Daliangshan region, according to design requirements, the builders of China Railway 18th Bureau Group adopted TBM boring machine construction in the Lexi Expressway project. This is also the first application of a TBM in expressway construction in China.

The "Yuecheng Liangshan" TBM used in the Daliangshan No. 1 Tunnel of the Lexi Expressway was formerly China's first large-diameter open-type TBM, which had rendered outstanding service in the Jilin Yinsong project. As China's first TBM with independent intellectual property rights, it once achieved a best monthly advance of 1,209.8 meters. China Railway 18th Bureau, together with experts from CRCC Heavy Industry and other organizations, fully analyzed the engineering characteristics and geological conditions of the Daliangshan No. 1 Tunnel, fully combined its own more than 20 years of TBM construction experience and rich experience in dealing with adverse geological conditions, optimized and modified the TBM, and creatively proposed a new design scheme for initial support and advance reinforcement. This restored and improved the TBM's functions and performance, not only laying a solid foundation for stable and high production in the Lexi project, but also representing a breakthrough successful attempt in the reuse of idle TBM equipment.

It is understood that the Lexi Expressway is hailed as "a road awaited for a thousand years" and is the long-held expectation of generations of the 2 million Yi people in the Greater and Lesser Liangshan Mountains. After the Lexi Expressway is completed and opened to traffic in 2025, it will not only completely end the history of no expressway access in Zhaojue, Meigu, and Leibo counties in Liangshan Prefecture, but will also shorten the driving time from Zhaojue, Meigu, and Leibo to Chengdu from more than 10 hours at present to 4 hours. It will play a very important role in consolidating and expanding the achievements of poverty alleviation in Liangshan Prefecture, supporting rural revitalization and cultural exchange with the outside world, and achieving common prosperity for people of all ethnic groups.