TRIGGERING FACTORS AND FORMING MECHANISM OF LOESS LANDSLIDES

In recent years,the frequency of loess landslide occurrences has the trend of increasing.It is a basis of reducing the landslide hazard risk to investigate the triggering factors and forming mechanism of loess landslides.Field investigation for geological hazards on the Loess Plateau suggests that the induced factors of the loess landslides mainly include earthquakes,precipitations,frozen-thawing,river erosion and human engineering activities.Among them,precipitations and human activities are the most active agents to induce landslides.For the loess landslides triggered by earthquake,mass ejection,dust effect and loess liquefaction caused by seismic acceleration are the main reasons.For the landslides induced by river evolution,the triggering mechanism and failure mode are distinct in different river evolution stages,such as in the lateral and vertical river erosion stages.Whereas,the loess landslide mechanism types include water level raise due to frozen effect and loess strength decrease result from melting effect.The factors of precipitations can be classified as rainstorm and drizzle and of the ground water can be classified as locally concentrated groundwater with priory conducts,water level rising and density increasing.Those of human activities are slope cutting,irrigation,reservoir,and over-burdening.Based on the field investigation for various of loess landslides,the geological characters and triggering mechanism of the landslide triggering by different factors are discussed further in the paper.