Analysis Of Multi-layer Loess Slope’s Dynamic Response

Loess topography is widely distributed in China,especially in the area of loess plateau between Wushaoling and Taihang Mountains.In this area,the accumulation thickness of the loess is very large and the natural landscape is rugged.With the development of the exploitation of loess area,a large number of aritificial loess slopes come into being.Our country is a harder-hit earthquake area,and the loess plateau area is an earthquake-prone one.Since the composition of the loess grains arevery complex and the structure is loose,there were a large number of loess slopes induced by the earthquake in history.Analysis of multi-layer loess slope’s dynamic response is now a very important problem which requires immediately solution.And researches about this are imperfect,so the subject of this paper is of great significance.This paper analyses the Dynamic response of multi-layer loess slope,using the FLAC3D finite difference software.It mainly analyses the composition of the slope’s soil layer’s effects on the transmission of seismic wave and the slope’s free surface’s effects on the amplification of acceleration.It also researches common loess slopes’effects on the response and stability of slope earthquake acceleration and calculates the effects of common loess cave on the stability of the loess slope via the finite difference numerical simulation.(1) Calculations of two-layer model and three-layer model indicate that:Compared to single inhomogeneous slope,it’s plastic zones amplify when the slope is on the bedrock.When the material parameter is small, it will produce a interconnected glide plane.While material parameter is high,the plastic zone only appears at the point of the slope toe and it presents as a semicircular towards the inside of the slope.And the slope’s tension-shear failure zone expands towards the inside of the slope with the reduction of the material parameters.(2) Dynamic response results of different layers of loess slopes show that:the PGA amplification factor comes to the maximum at the top of the slope,it gets to the median at the slope toe,and the minimum appears from1/3to1/2of the height of the slope.Under this circumstance of multi-layer loess slopes,the descending range will decrease during the descending branch of the PGA amplification factor.The smaller caves inside of the slope make the horizontal PGA amplification factor increase.And the PGA amplification factor increases at the lower part of the slope and decreases at the upper part.(3) When caves exist at the lower part of the inside of the Slope, the tensile shear failure zone shifts to the inside of the slope.The damage depth increases.Tensile failure appears in the area form the cave to the slope surface along the diagonal direction.The plastic zone inside of the slope expands towards to the top of the slope along the latent glide plane.When caves exist at the middle part of the inside of the Slope, the plastic zone on the latent glide plane is connected with the slope surface through the caves.It will damage the slope partially and even destroy the stability.And When caves exist at the top of the inside of the Slope,it has little effects on stress distribution of the whole slope and the displacement,it only affects partially.