Study On Morphological Evolution Mechanism Of Loess Landslide In Heifangtai

This paper makes study on Loess landslide caused by irrigation in Heifangtai.The morphological characteristic of different time phase landslide are obtained through the field investigation on area's landslide development distribution characteristic,the low altitude UAV Photogrammetry and the scene survey.the progressive failure process of the landslide is also analyzed,combined with the historical satellite image of the landslide,the evolution process of landslide group is analyzed,the development model of landslide is summarized,and the morphological evolution mechanism of loess landslide is discussed,the main conclusions are as follows:(1)The main investigation sections are Dangchuan,Jiaojia and Moshigou,and the total landslides are 30.Results show that the Loess Landslides account for the majority and can be divided into 7 types;the annual frequency of the historical landslide shows a certain unstable yielding phenomenon;landslides are most concentrated in in March,followed by July,at the fewest in December.(2)The evolution process of two typical landslides in Dangchuan section are analyzed by using low altitude photogrammetry and on-site investigation.In horizontal direction,the evolution of landslide has traceability backward and lateral expansion and clustering characteristics;in the longitudinal direction,the sliding surface of the landslide gradually evolves from the straight state of the original slope into a circular groove,and the back wall of the landslide continues to retreat,which shows the trend of progressive destruction.(3)According to the historical image analysis,the landslide occurred continuously,and the scale and quantity increase with the passage of time in the key landslide section of Heifangtai;the landslide forms an arc trailing edge on the tableland early,and later shows an inherited regression in the sliding direction,and there is an obvious "shrinkage" feature;the spatial position of landslide group is located in the concave edge of the Heitai plateau,so that the concave area of the tableland develops towards a more concave trend.The trend of the regional evolution of the landslide gradually develops from Eastern Jiaojia to the Moshigou and Dangchuan.(4)The morphological evolution model of the Loess landslide in Heifangtai is summarized,and the evolution mechanism of the loess landslide in the Heifangtai is discussed:?Dthe underground water level line at the edge of the Heitai is higher than the water level line on the edge of the convex part,so the slope in the edge of the platform is prone to landslide;the terrain in Heitai is high in the west and low in the east,so with the rise of groundwater level,the landslide is developing from east to west;?Local irrigation will make the local groundwater level increased,and the saturation area near the edge of the platform is large,which makes these concentrated irrigated more prone to landslides;the concentrated irrigation will produce the collapsible fissure,when the irrigation continues to occur,the crack continues to develop,gradually forms the advantageous infiltration channel,accelerates the water infiltration,destroys the loess structure stability;? The freezing stagnation effect accelerates the development of landslide and makes the characteristic of"shrinkage" more obvious.