Abstract: Songjia gully is an active debris flow gully. A large-scale debris flow disaster occurred in history, posing a potential threat to the newly built Shenghang bridge of Sichuan-Tibet Railway. The development characteristics and formation conditions of debris flow in Songjia Gully are analyzed, and the risk of debris flow in Songjia Gully is assessed based on comprehensive approaches inclusive of data collection, remote sensing interpretation, field investigation, indoor analysis and parameter calculation. Prevention and control measures targeted to the impact of debris flow on railway engineering are also proposed. The loose solid materials of debris flow in Songjia gully mainly come from slope surface erosion, collapses, engineering wastes, and the gully. Debris flow in Songjia Gully risk is in developing stage, moderately hazardous, consistent with survey results. The research findings offer reference for disaster prevention and mitigation of similar projects along the Sichuan-Tibet Railway.

Key words: Sichuan-Tibet railway, debris flow, development characteristics, risk assessment, prevention and control measure