| Debris flow is a natural disaster usually with sudden occurrence, strong destructive power. With the development of economy in mountain area and extension of railway line, debris flow disaster encountered in railway increases. The study area is located in Songpan county, Sichuan province. The area is shown with poor mountain stability, rock fragmentation, complicated geological structure and frequent earthquake activity. With the effect of monsoon climate, rainfall is uneven distribution on time and space, that is to say, the rainstorm weather occurs frequently. Along with the unreasonable human activities, debris flow disaster is aggravated in this area. The chengdu-lanzhou railway will pass through Zhenjiangguan Town, in which the railway station will be built. The railway will pass through Miaozi gully and Donglong gully which is the accumulation area of debris flow. The debris flow of Miaozi gully and Donglong gully both belong to mountain- gully-type debris flows. The geological history is in the decline and dwell period under natural conditions. In recent 50 years, debris flows in the middle and large scales are not occurred. As the occurrence of M8.0 wenchuan earthquake on May 12, 2008 and the destruction of human activities, massive loose material is formed in the two gullys, in which have already down the conditions of bursting debris flows. Once the debris flow breaks out, it will be a harmful influence on the railway bridge and the railway station. In order to guarantee the chengdu-lanzhou railway safely and smoothly and guarantee the station and bridge safely, it takes the following measures: The properties, characteristics and formation conditions of the two debris flow gullys are investigated. The risk assessment of the debris flow about the two gullys is carried out. The influence of the debris flow to the station is analyzed. The suggestions of engineering measures are proposed. It has important significance to the disaster prevention and reduction in Railway Engineering.The background conditions of forming the two debris flow gullys are introduced firstly in this paper. The development characteristics of the debris flow are elaborated. The watershed features of the two debris flow gullys in the forming region, flowing region and accumulation region are described. According to the characteristics of debris flow gullys and selecting the newest research results of debris flow, the dynamic parameters of the two debris flow gullys such as velocity, peak flux, total quantity, impact force, under different design frequency are figured out. Using the calculation formula of the risk in the single debris flow gully, the risk in the two debris flow gullys is calculated. The farthest runout distance of debris flow is predicted by using the evaluation model about runout distance in meizoseismal area which Doctor Tie Yongbo proposed in 2009. The depositional area under different frequency is calculated by using the prediction model about the depositional area of debris flow accumulation which Matteo Berti proposed in 2007. The probability of river blocking is analyzed on the basis of the evaluation result.Based on terrain features of accumulation area and the distance between main gully and accumulation area, the risk zoning of debris flow is analyzed by using GIS. Combined with the topographic features of gully and the results of calculation analysis, effects of the debris flow on Zhenjiangguan station and bridge are analyzed respectively. Finally, based on development conditions, movement characteristics and the depositional area about the two debris flow gullys, the"combination with interception and drainage"preventive measures and suggestions about the debris flow are put forward.
|
PDF Full Text Request