Research On The Evolution Of Loess Slope On North Bank Of Jinghe River In Pingliang City

In the Loess Plateau region,due to the large distribution range of loess,the thickness of the sediments and the loose soil structure,the loess tableland had been eroding,the tableland slope and the slope on both sides of gully had been gradually forming under the internal and external geological function.In the course of the evolution of loess slopes,with a large number of loess landslides,collapse,mudslides,loess cracks and other geological disasters,all of these seriously restrict the socio-economic development.Therefore,in this paper,based on the concept of slope structure of loess slope and the distribution characteristics of geological disasters,the loess slope of the north shore of Jinghe River in Pingliang City is selected as the research object.Comparing the numerical simulation results,the evolution rule of loess slope is investigated,so as to provide reference for geological disaster prevention and management in loess area.The main results of this paper are as follows:(1)According to the lithological combination,the type of slope structure in the study area is divided into two types: pure loess slope and loess-bedrock slope.Furthermore,the pure loess slope is divided into four sub-categories according to the intercrossing relationship between the contact surface and the airport condition,and the pure loess slope is mainly distributed in the upper part of the plateau and the middle-upper part of the plateau slope;the loess-bedrock slopes are divided into four subclasses according to the characteristics of lithological assemblage in the lower part of the bedrock and features of contact surface,which are mainly distributed in the slope of the slope side of the slope and the front of the two sides of the slope.(2)The landslide in the study area mainly includes loess-bedrock contact landslide and landslide in the loess layer.The collapse includes loess cave collapse and natural slope collapse,the latter includes dumping collapse,cantilever collapse and falling collapse according to collapse features.The landslide in the loess layer is mainly distributed in the middle-upper part and the top of the slope.The loess-bedrock contact landslide is mainly distributed in the slope of the north bank of the Jinghe River.The loess collapses are mainly distributed at the top of the slopes and the slopes of the gully and the ditch.(3)Based on the formation process of the loess slopes,the evolution rule of loess slopes in the study area can be divided into two types: the evolution rule of the valley-type loess slope,the evolution rule of the gully-type loess slopes.The both types has similar symmetry,similarity,and the disaster simultaneity.In the process of evolution,the loess slope is gradually eroded into internal of loess tableland in the forms of landslide and collapse,resulting in the gradual decrease of the loess slope height,the gradient slackens of the slope and the formation of the saddle topography at the local ridge.The results are the same as those of the numerical simulation.