| Introduction of the author: Duan Yong-Kun,male, was born in June, 1984 whose tutor was Professor Tangchuan graduated from Chengdu University of Technology in Geology engineering major and was granted the Master Degree in June, 2010.The total length of Cheng-Lan railway (Chengdu-Jiuzhaigou section) is 435.2km, located in the transition zone between the western Sichuan plateau and the Sichuan Basin, with special environmental geological conditions, the risk of debris flow is higher.Particularly, the debris flow is becoming intensive in this area after the Wenchuan earthquake. Moreover, 13 new stations, bridges and tunnels which its total length is 80% of the Main Line Rail, mostly across the debris flow gullies, are suffered the threat of debris flows. Therefore, in order to protect the safety of the railway construction and operation in the future, with Survey on debris flows along Cheng-Lan railway ,it is is very necessary that to recognize the basic characteristics of the debris flows so as to analysis on the negative influnce of accumulation characteristics on the railway project.In this paper, we select one section on both sides of the Longmen Shan fault zone which is Jushuihe and Maoxian-Songpan section as the study area so as to analyze and contrast. On the basis of widely collecting up the previous research results and environment geological conditions of debris flow which are obtained by means of investigation and observation and experiment in the study area, it is used that the indoor remote sensing interpretation, field investigation,engineering geological analogy and so on, the basic characteristics of the debris flows are analyzed and summarized.Four existing calculation methods of amount the debris flow run out all over the world are discussed and contrasted, the relationship between amount the debris flow run out and accumulation is evaluated, the calculation formula suited for calculating the amount the debris flow run out in the study area is found out finally, the evidences are provided for the further quantitative evaluation of the accumulation characteristics of debris flow.By means of the remote sensing interpretation and field investigation, the accumulation characteristics of debris flow are qualitatively realized from the nature of the alluvial fan, flat shape, size range, thickness and longitudinal degradation etc. in the study area.On the basis of the study above, according to engineering geological condition of the study area, the reasonable calculation formula and model of predicting accumulation areas likely to be flooded by debris flow are selected,taking typical cases of bridges and stations for example, we calculate the total deposition height during the design working life,then considering the height the huge rock exceed the mud site,the superelevation of the mud site of the debris flow,the scouring height when the debris flow encountering resistance, design safety value and so on, the safety value under the bridge is ascertained, and then the negative influnce of accumulation characteristics on the bridge are quantitatively evaluated; According to field investigation results, the running out distances of a debris flow at different frequencies and accumulation width are calculated, on the basis of microtopography varying,and adequately considering the characteristic which debris fans drift downstream, we calculate accumulation areas at different frequencies finally so as to evaluate the negative influnce of accumulation characteristics on the station.In accordance with line position of location survey of Cheng-Lan railway,considering the location of the railway through the debris flow gully is defferent, connecting with the field of engineering geological conditions and project types, Prevention Countermeasures are proposed ,and giving examplesive examples espectively.
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