Baoji-Tianshui railway was built before sept. 1949. lot of diseases and hidden dangers were left at that time. After that time a large-scale of controls were carried out. The state investiment has broken through two millions per kilometer. It is full enough to construct another Baoji-Tian-shui railway. Direct loss and influnce caused by landslides are even more immeasurable.The policy that is taken in tackling these geological hazards by railway department is to rely mainly on putting prevention first while making treatment subsidiary

and to combine treatment with prevetion. However

for prevention we should have a pretty clear idea of how things stand. And it is necessary for treatment in order of importance and urgency. Just for this goal we carried out landslide investigation and research on Baoji-Tianshui railway.The investigation and research are divided into two stages: general survey of landslide distribution and dynamic analysis and comparison of landslides. The former was completed through interpretation of panchromatic black and white aerial photographs

imaged on August 20th

1985

on the scale of 1:10000. To accomplish the latter were used panchromatic black and white

infrared color airphotos of difference time phases and on several scales. For inspecting physiographic environment and geological background were analysed MSS images of Landsat also.In process of general survey of landslides for inspecting natural distribution laws of landslides

our remote sensing image analysis v/as carried out over a more wide range that involves two sides of each kilometer of railway. In interpretation of airphotos 398 landslides and 206 collapses were found out. Landslides directly related to the railroad is 61 while collapses-94. The former is concentrated on the sections Hudian-Fenggeling and Jianhe-Boyang. The latter is concentrated on section Yanjiahe-fenggeling. They are concentrated in the middle part. They reach the peak from Pingtou

and then stretch right to the west of Boyang.Generally speaking

such conditions reflect the following factors: topography

geology

hydrology and human activity. Looking from the topography

the middle part of Baoji-Tianshui railway winds through the gorge of Weihe river. Qinling mountain and Lupan Mountain hold it under duress from left and right. The railway was situated at the foot of the Mountain and beside the river. The high filling and deep cutting were compelled to take. Undoubtedly

this is closely related with the design idea and engineering measures at that time. Therefore it also reflected the influnces of man-made factors. Intense lateral erosion of Weihe river is the main hy-drologic factor while the influence of ground water is also important. As for geologic factors

here they mean frequent magmatic intrusion

violent tectonic movement

crushing and weathering of meta morphic rocks as well as peculier nature of loess. The generation of landslides and collapses is closely associated with lithology. According to the preliminary statistics the landslides generated in loess are the most. They are totalled up to 271 and make up 71.7 percent of the sum total. The landslides generated in crushed metamo-rphic complex and weathered granite series are the second. The two are respectively 51 and 54

that make up 13.5 and 14.3 percent of the sum total. The landslides generated in sandstone-conglomerate series only make up 0.5 percent of the sum total.Collapses generated in granite series are the most. They are totalled up to 102 and make up 49.5 percent of the sum total. The collapses generated in metamorphic complex are second. The total of them is 74 and make up 35.9 percent of the sum total. Collapses generated in loess are far less

only 28 and make up 13.6 percent of the sum total. As for collapses generated in sandstone-conglomerate series

they are seldom seen. They amount only to 2 and make up 1.0 percent of the sum total.Looking from the general lithological distribution of landslides and collapses

the advantage is also laid with loess-61.2 percent. The granite series a