Dynamic Response Characteristics Of Loess Earthquake Slopes In Different Geomorphological Units

The 8.5 magnitude earthquake that occurred in Haiyuan at the end of 1920 was one of the largest and most serious earthquakes of the last century.The earthquake site is located in the loess region of northwest China,where several moderate to strong earthquakes have occurred in recent times,and the earthquakes were accompanied by a large number of landslides,causing great hazards.In order to study the influence of regional topographic features on the seismic loess landslides,to obtain the occurrence pattern of landslides in the loess layer under the action of earthquakes and to make a reasonable analysis of the causes of the formation of seismic loess landslides.Relying on the National Key Research and Development Program of China(2018YFC1504703)and the National Natural Science Foundation of China(41772285),this paper takes the Haiyuan Great Earthquake as the research object,and explores the disaster geomorphic characteristics of different geomorphic units of earthquakes at the time of earthquakes,through field investigation,unmanned aircraft photogrammetry,remote sensing data extraction,and indoor tests and model analysis.The main conclusions are as follows.The main conclusions were obtained as follows.(1)The intensity of the earthquake loess landslide is concentrated between ? and ?degrees,the elevation is between 1600?2000m,the slope is mainly less than 25°,and the main sliding direction is between 70°?110° and 270°?300°.Low elevation and high elevation areas have flat terrain and result in a small number of landslides but a large area.(2)Loess landslides are the most developed in the hilly landscape,while the number of loess landslides is relatively small in the high mountain landscape and the number of landslides is the least in the plain landscape;the number of landslides roughly increases locally and then decreases in the direction from the southwestern border of the hilly area through the high mountain area to the plain area;the number of landslides in the direction of parallel fracture zones in the region varies less with distance,while the number of landslides in the vertical direction varies more with The number of landslides in the direction of parallel fracture zones in the region varies less with distance,while the number of landslides in the vertical direction varies more with distance.(3)The differences in the physical and mechanical properties of the loess in the study area are relatively small and basically belong to the same period of deposition.(4)The seismic acceleration and slope gradient are positively correlated with the strain and total displacement,and negatively correlated with the safety coefficient.The increase of seismic acceleration and slope is equivalent to the reduction of the angle between the combined force and the direction of inertial force field,which leads to the decrease of slope stability.And the relationship between stratum thickness and landslide development should be determined by combining various conditions.