Hazard Assessment Of Landslide Geological Disaster In Xuecheng Area Based On GIS

Xuecheng area at Zagunao River is located in medium high mountion canyon landscape, physical landforms are well developed. The characteristics of landslide geological disasters are large-scale and high-frequency. Xuecheng area is the most concentrated areas of landslide hazard in Lixian County. The economic construction and human engineering activities suffer severe obstruction. It threats the safety of frequent passing vehicles and pedestrians. Therefore, carrying out the hazard assessment of landslide geological disaster has important realistic significance to landslide disaster prevention and effectively decreasing the loss caused by landslide disaster in Xuecheng area.Based on the field investigation, we combined with previous research. It analyses the distribution and development regularity, formation controlling factors and mechanism of landslides in Xuecheng area. Based on Arc GIS software, the model of landslide disaster risk prevention is built by respectively using logistic regression and deterministic coefficient. And then using the model to predict and zone the risk of landslide disaster in research area. The research results and conclusion in the following areas:(1)Xuecheng area is located in the northwest of Sichuan Province. The main landform is high mountain and high and middle mountain. The evolution of valley landscape is divided into slow cut gully region and the strong cut canyon period. The slope structure in left bank of mainstream Zagunao River is steep consequent slope, the right bank is steep reverse, and tributary is transverse slope or insequent slope. The main rock group is thin layer of phyllite, secondly is crystalline limestone and metasandstone.(2)There are 39 landslides in the area, include Xindianzi landslide, Heiziping landslide, Zengtougou landslide, Xuechengzhongxuehoushan landslide, Taoping landslide, etc. The vast majority of landslides are large-scale landslide. The total volume is over 160000×104m3.(3)The plane distribution law is the number of landslide in Zagunao River and Mengtun River main stream is more than in the tributary, linear distribution along the main stream.Affected by slope and arcuate structure, the landslides on the right bank of Zagunao River are more than on the left bank.(4)The distribution law of 23 landslides in Zagunao River main stream is the shear opening relative valley elevation in the 0-12 m and 400-450 m elevation. The formation time of landslide is multi-stages, only 4 landslides formed in strath and 19 landslides formed in canyon.The most of the landslides in Zagunao River main stream occurred in canyon stage.(5)According to the volume of landslide, there are 24 huge landslides, 13 large landslide and 2 middle and small landslides. According to the thickness of the main landslide body, there are 7 super-deep level landslides, 13 deep level landslides, 17 medium thickness landsides and 2 shallow landslides. According to the substance and structure, there are 37 rock landslides and 2 soil landslides.(6) The formation of slope is under control by internal and external factors, including: topography and geomorphology, formation lithology, slope structure, water system, rainfall and human engineering. Statistical analysis shows: the landsides in Xuecheng area are highly sensitive to 20°~40° slope and relative valley elevation 0~400m area. Most of landsides form in phyllite formation and reverse slope structure.We summarized the conceptual models of formation mechanism of the landsides in research area. There are 3 geomechanics conceptual models of genetic mechanism of the landslides, they are bending and breaking type,ladder sliding and fracturing type, creep-cracking type.(7)Based on logistic regression model, we predict landslide hazard evaluation.The evaluation result shows: the extreme high risk zone of landslide geological disaster is located in the main stream of Zagunao River and Mengtun River, the risk of right bank is greater than the left bank. High risk area is mainly distributed in the middle and lower reaches of the tributary and the toe of slope. The middle danger zone is mainly distributed in upper and middle reaches of the tributary. The low risk area is mainly distributed in the high altitude and upstream of tributary, the stability of slope is better.