| Due to the dynamic vulnerability of the Loess and the multiple earthquakes in the Loess Plateau and its surrounding area,the slope instability and failure have occurred many times in the region,such as landslide and collapse.As a result,the risk of potential earthquake in the cities and major projects is very high,and earthquake safety issues are becoming increasingly prominent.Therefore,the dynamic stability analysis of loess slope considering the characteristics of micro-structure under the action of earthquake has an important practical and scientific significance for the construction and operation of major projects and earthquake disaster evaluation in the Loess Plateau.In this paper,based on the microstructural characteristics,the dynamic characteristics of the loess are discussed;and the dynamic response characteristics of the loess slope are analyzed,and the influence of the microstructure parameters on the dynamic response of the loess slope is revealed by using following methods which including field sampling,indoor dynamic and static triaxial tests and SEM tests,combined with numerical simulation and large shaking table tests.The main conclusions are summarized as follows:(1)The dynamic triaxial tests with different water contents and different stress states were carried out.Combined with the microstructure images,the effects of water,confining pressure,and the microstructure of the soil on the dynamic characteristics of the loess were systematically studied.The experimental results are summarized as follows: With the increase of water content,the dynamic shear modulus decreases and the damping ratio increases.With the increases of consolidation confining pressure,the dynamic shear modulus increases and the damping ratio decreases.And then,the micro-characteristics of the soil have important influences on the dynamic characteristics.The presence of overhead voids,the distribution of uneven particle size distribution,the large particle spacing of particle,and the poor compaction can lead to a decrease of the dynamic shear modulus and an increase of the damping ratio.(2)The shaking table model test was carried out,and the general dynamic response characteristics and variation rules of loess slope under earthquake action are studied with the analysis of soil sample structure.The experimental results are summarized as follows: Compared with the loess in the Xiji region,the porosity of the loess of model is smaller,the pores are mostly medium and small,and the particle shape is more "round",and the particles in the soil are evenly distributed in all directions.The acceleration peaks at each point of bi-directional loading are slightly larger than the acceleration peaks at each point of unidirectional loading under corresponding operating conditions.This characteristic is more obvious when the amplitude of input seismic waves is larger than before.With the increase of input seismic load amplitude,PGA does not always increase with the amplitude of seismic load.The peak time and amplitude of input seismic wave affect the process of instability and failure of the slope model.(3)Based on the shaking table test model,a numerical calculation model with a ratio of 1:1 was established.The numerical model is in good accord with the shaking table test model.By changing the material parameters of the model,the influence of the microstructure parameters on the dynamic response of the loess slope are studied.The results show that under the action of earthquake,the acceleration response peak value of the soil with higher porosity,higher probability entropy and higher fractal dimension is smaller,and the response stress difference of soil pressure is larger.The Loess in the Xiji area has the characteristics of high porosity,large average area and high shape coefficient,and the pore type is dominated by the pores of the scaffold pores.The Loess Slope in this region is easily damaged and forms a large mass of loess landslides under the action of earthquake. |
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