Abstract: A case study is conducted on the K295 debris flow disaster regulation project of the ChengduKunming railway to minimize the risk arising from mountainous railway debris flow and ensure longterm operational safety of the railway. In addition, the situation, scale, zoning, causes, damage extent, and development trend of debris flow disaster are analyzed. Further, a comprehensive debris flow disaster treatment method involving base grouting reinforcement + diversion aqueduct opencut tunnel + tunnel bottom discharge culvert + diversion channel + chute is proposed based on the idea of "focusing on drainage and giving consideration to protection". A technical scheme of prefabrication and assembly of the opencut tunnel arch ring on the existing operating railway is innovatively proposed to ensure normal railway operation during the castinplace construction of the opencut tunnel. Factors such as the onsite terrain, structural safety, and construction period are comprehensively considered. The proposed scheme minimizes the interference between the construction operation and railway transportation and greatly shortens the construction period.

Key words: existing railway, debris flow, diversion channel; prefabrication and assembly, opencut tunnel