| Loess is widely distributed in China,mainly concentrated in the central and western regions.As a special kind of sediment,the undercompaction and water sensitivity of loess are the main reasons for the frequent occurrence of geological disasters in loess region.In the history,landslides and other geological disasters caused by earthquakes have brought serious disasters to seismic areas.Therefore,it is of profound significance to carry out research on the dynamic characteristics of loess and slope stability analysis under earthquake action.In recent years,the research on the dynamic characteristics of loess has been deepening,but due to its special engineering properties and the limitation of test technology,the research results are not satisfactory.In order to find out the dynamic characteristics of loess in western Henan Province.On the basis of summarizing the existing research results at home and abroad,the dynamic characteristics of loess in western Henan are studied by using GCTS vibration triaxial method.The effects of sample type,initial dry density,water content,confining pressure and vibration frequency on dynamic constitutive relationship,dynamic strength parameters,dynamic modulus,damping ratio and other dynamic characteristics were investigated.On the basis of dynamic triaxial test,the stability analysis of typical deep cut loess slope under seismic load is carried out by using MIDAS/GTS-NX software.The displacement and deformation law of the slope and the distribution characteristics of the internal shear force during the earthquake are analyzed and the stability of the slope under the earthquake load is evaluated.Through the experimental study,the relationship curve between the water content and the empirical constant of dynamic shear modulus of loess in western Henan is established,which provides the basis for obtaining the empirical constant of dynamic shear modulus of loess in western Henan more accurately in the future.Combined with Hartin and Chen Guoxing’s empirical formula of damping ratio,an improved calculation model of damping ratio is established,and the fitting results are good.Combined with the dynamic triaxial test and the finite element analysis of slope stability under seismic load,the experimental data obtained from the test are extracted and used in numerical analysis and calculation.It can be used as a reference for subsequent studies on slope stability under seismic load.The main conclusions of this paper are as follows:(1)Under the hierarchical vibration load,the dynamic shear stress of the loess in western Henan presents hyperbolic growth with the increase of dynamic shear strain.In the cyclic vibration of fixed amplitude,the residual deformation of loess samples will be generated.The back and forth action of dynamic stress will make the specimen fluctuate on the basis of the residual deformation,and the residual deformation will gradually increase with the increase of the duration of dynamic load.(2)The dynamic strength of undisturbed loess is relatively high during the vibration process.The dynamic strength of remolded compacted loess increases with the increase of confining pressure and initial dry density.(3)The dynamic shear modulus of loess samples decreases non-linearly with the increase of dynamic shear strain.With the increase of confining pressure,initial dry density and vibration frequency,the dynamic shear modulus generated by the same dynamic shear strain gradually increases,while the experimental results are contrary with the increase of water content.(4)The damping ratio of loess samples increases with the increase of dynamic shear strain,while the damping ratio of loess samples under the same conditions decreases with the increase of consolidation confining pressure.When the moisture content is high or the sample is saturated,the damping ratio will decrease rapidly with the continuous increase of dynamic shear strain after reaching the peak value.(5)The deep excavation of cutting loess slope in the basic seismic intensity of Ⅶ degrees under the action of earthquake force,internal stress changing,gradually formed near the potential slip surface stress.During the earthquake,the safety factor of the slope fluctuates with the change of seismic force,but the minimum safety factor Fs is still greater than 1.During the earthquake,the overall displacement tended to be stable after 10 s,and a permanent deformation of nearly 1 m occurred at the slope Angle under the seismic force of 24.96 s.In this paper,the influence of water content on dynamic characteristics of loess was studied by actively controlling the moisture content of samples in the process of loess dynamic characteristics test.In subsequent tests,the test device can be improved by adding suction control device to explore the dynamic characteristics of samples under different suction forces.In addition,the effect of pore water is not considered in slope stability analysis under earthquake action,which needs further study.Furthermore,model tests can be carried out in combination with a shaking table to explore the characteristics of slope displacement and deformation under vibration load. |
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