The author learned from the Chengdu-Guiyang Railway Project Department of China Railway 15th Bureau Group of CRCC that, as of October 8, excavation of the high-risk Qishanyan Tunnel undertaken by the unit has passed the 800-meter mark, reaching 800.8 meters. It is understood that during the long holiday, the builders continued to advance the tunnel construction day and night.
　　The Qishanyan Tunnel on the Chengdu-Guiyang Railway has a total length of 2,548 m. The tunnel passes through complex strata with severely twisted rock layers and greatly varying attitudes, and contains unfavorable geological conditions such as karst, goaf areas and groundwater. At the entrance end, 665 meters pass through 7 coal seams with a single seam thickness of 0.2–2.0 m; this is a high-gas section with risks of gas outburst, water inrush and mud inrush. Its initial risk rating is high risk, making it a key tunnel for safety production management along the entire line. 　　As a high-gas tunnel, it not only carries high safety risks, but also has its entrance and exit located on remote mid-slope mountainsides, making the transport of materials and equipment difficult, the working space narrow and construction extremely challenging. To this end, the Chengdu-Guiyang Railway Project Department of China Railway 15th Bureau Group established information-based management systems including an advanced geological prediction system, an automatic gas detection and alarm system, automated surrounding rock monitoring and measurement, an access control system and a personnel positioning system; set up special teams such as a gas detection team, a ventilation management team and a rescue and emergency team; equipped special devices such as explosion-proof secondary lining trolleys, explosion-proof cables, explosion-proof lighting, explosion-proof wet shotcrete machines, explosion-proof total stations and explosion-proof walkie-talkies; and carried out explosion-proof modifications on machinery and equipment such as excavators, loaders, muck trucks and concrete mixer trucks. Construction follows the principles of "short advance, weak blasting, strong support, frequent measurement, and strengthened ventilation and gas monitoring," and adopts multiple new devices and new processes. To respond to emergencies, the project department has also signed a mine rescue agreement with the local mine rescue brigade and regularly conducts safety emergency drills.
　　It is reported that because construction at the tunnel entrance is still in the high-gas section, with high safety requirements and complex construction processes, progress is relatively slow. Once the high-gas section is passed, construction progress will accelerate noticeably.