Risk Analysis Of Seismic Loess Landslides In Beishan,Tianshui City

Tianshui City is located on the Loess Plateau in the north of the West Qinling Mountains.It is the northwest traffic fortress.It is located at the intersection of the north-south seismic belt and the Qinling earthquake belt.The historical earthquakes are frequent.Since the record,there are 55 or more earthquakes of magnitude 6.0 and above,The area is a potential strong earthquake or strong earthquake disturbance zone.Earthquakes triggered a large number of landslides,debris flow and other geological disasters,the region caused great life and property damage.Based on the investigation of the loess landslide in the eastern part of Tianshui City,Qinzhou District and the southern part of Qingshui County,the earthquake loess landslide of Beishan is selected as the object of study.Through field investigation and indoor comprehensive analysis,combined with previous research results and existing data This paper summarizes the background of the quake of the loess landslide and analyzes the development characteristics of the faulted loess landslides.Taking the Huangqi Mountain earthquake loess landslide as a typical case,the formation mechanism and evolution process of the earthquake landslide are simulated and analyzed.The improved Newmark cumulative displacement model on the ArcGis platform is used to analyze the risk of the earthquake loess landslide of the Beishan in Tianshui City.Metro construction and construction projects to provide disaster prevention and technical support and geological support.Tianshui City is mainly for the loess gully ditch gully,terrain height difference,the geological environment is fragile,fault activity is strong,frequent historical earthquakes,induced a large number of earthquake loess landslides.The west of the West Qinling fault belt is active and strong earthquakes in the surrounding are the main disaster backgrounds of the earthquake-prone loess landslide in the study area.Beishan earthquake loess landslide with a large amount of sliding body,sliding surface cutting deep,low slope of the slope,slope distance,the back wall close to the top of the beam,sliding direction has the advantages of directional angle,multi-stage activity,and other characteristics.The results show that the slope position of the loess slope has a magnification effect on the seismic wave under the action of dynamic load.The shear stress of the slope of the slope slope,slope shoulder and slope foot is increased abruptly.Sliding surface through,and finally lead to slope instability.The evolution of the performance processThe safety factor of slope with thick soil,slope,close to the slope of the top of the loess beam is low in Beishan,such as the red flag mountain-Xiushan-Sun Jiaping area,Yejiaguuo around-Shuizhaizhai around and West Lake Village-Chenjiashan area.In the earthquake or rainfall under the prone to instability.In the PGA=0.3g earthquake conditions,the probability of slope instability is about 19.2%in the area of Sun Jiaping,Xiaojiazhuang,Shuijiazhuang,and Jinzhuang village in Chenjiazhuang area and Chengji New Town,which belongs to high-high risk area,area Which is about 4.5%of the total area of Beishan.When the slope encounters both earthquakes and rainfall,the risk of landslide in Beishan is greatly increased and the proportion of high-high risk area is increased to 10.1%.The introduction of the dominant slope angle factor in the improved Newmark model can effectively improve the accuracy of seismic landslide hazard assessment.The method of "vector-grid-point-density analysis" is used for the vulnerability layer,which is worthy of further study and popularization compared with the interpolation method.