Abstract:

The Sichuan-Tibet Railway (STR) is one of the most important main railway lines under construction of China. However, the STR is located in the east of the Tibetan Plateau, which is characterized by complex topography and geology. The complex geological backgrounds and fragile geological environments make geohazards highly develop along the STR and its adjacent area, which in turn threat the construction and operation of the STR. This paper firstly developed an improved frequency ratio method for geohazard susceptibility assessment, which overcomes the discontinuity of frequency ratio values faced by the traditional frequency ratio method, and increases the capability of distinguishing geohazard sensitivity of influencing factors, and also reduces the subjectivity during the classification of influencing factors. The merit of the improved method compared with the traditional method was verified by quantitative analysis on geohazard susceptibility models using ROC curve and spatial entropy. According to the developing and spatial distribution characteristics of geohazards, this paper chose topographic elevation, topographic slope, topographic aspect, topographic curvature, topographic relief, engineering geological strata, peak ground acceleration, density of faults, distance to rivers, distance to roads, precipitation and vegetation index as the fundamental influencing factors of geohazards. The geohazard susceptibility assessment and zonation along the STR and its adjacent area were implemented based on the improved frequency ratio method and historical geohazard data. The results showed that, the spatial distribution of the geohazard susceptibility along the STR and its adjacent area is mainly constrained by the spatial distribution of those linear features such as faults, waters and roads as well as the spatial distribution of topographic factors such as topographic slope and topographic relief, while density of faults and topographic relief are two factors with the highest capabilities of distinguishing geohazard sensitivity. The extreme high and high geohazard susceptibility zones are mainly located along the major rivers and roads in the research area. Since the railway lines are mainly distributed along rivers and existed roads, those zones should be paid particular attention during the construction and operation stages of the railway regarding the monitoring and prevention of geohazards.

Key words: Sichuan-Tibet Railway, Tibetan Plateau, geohazard, susceptibility assessment, improved frequency ratio