The Characteristics Of Seismic Loess Landslides And Its Dynamic Response Mechanism In Tianshui Maiji Area,Gansu Province

Tianshui Maiji district is located in the hinterland of the Loess Plateau,belongs to intersection part of Qinling orogenic seismic zone north edge and Central Tianshui-Lanzhou seismic zone.Earthquakes happened many times in history.A large amount of loess landslides were induced by these earthquakes,and caused heavy casualties and property losses of local people.By means of field investigation,laboratory test and theoretical analysis,this article analyzed the hazard inducing environment of seismic loess landslides,summarized the characteristics of seismic loess landslides,distribution and influence factors.Provide a basis identifying for historical earthquake loess landslide of the northwest loess region.Calculated stress-strain characteristics of loess landslides under different conditions by means of simulation software Flac3 d.Preliminary calculations of the stability of the landslide,study the formation mechanism and dynamic response mechanisms typical landslide.The following are the results of this paper:(1)A large number of loess landslides in Maiji area induced by the characteristics of fragile of geological environment,strong fault activity,earthquake-prone in history.Western Qinling faulting and earthquake-prone during the recent are the major background of seismic loess landslides development.(2)Maiji seismic loess landslides have the characteristics of large scale and the sliding surface cutting deep,low angle,sliding distance away,high fell,sliding into groups with the advantages of orientation and in groups to band profile.Especially low angle,and other characteristics can be used as important symbol of identify historical earthquakes loess landslides.(3)Influenced by historical earthquakes,seismic loess landslides have the features of back-slope and fault diastrophism direction effects.The development of seismic loess landslide controlled by active faults.(4)In Tianshui district,the loess in the high content of clay minerals,mainly make up by illite smectite mixed layer clay(I/S)and illite.Clay minerals have the characteristics of easy expansion,poor engineering properties,easy to form a soft surface,which control for main slide surface of seismic loess landslides.(5)Shuiwan landslide is a typical loess landslide which induced by earthquake,The loess-mudstone dual structure is the premise of landslide development,seismic force is the direct causative factor of landslide,and rainfall promoted the formation and development of landslide.Flac3 d numerical simulations show that the slope in a stable state under the natural state.when loading seismic,slope deformation and failure,instability decline.