Study On Seismic Dynamic Response Characteristics Of Slopes With Weak Interbeds

The widespread existence of weak interbeds and frequent earthquakes in southwest mountainous areas provide the material basis and external force conditions for the instability and failure of slopes with weak interbeds,which makes southwest mountainous areas extremely vulnerable to earthquake landslides.With the implementation of the Western Development Strategy and the “One Belt and One Road” initiative,more major infrastructure will be built in the region.The dynamic stability of slope has become the key problem of the engineering construction in this area.As the basic of the dynamic stability of slope rock mass,dynamic response also presents new challenges to the scientific and engineering circles.Ground motion characteristics and the characteristics of the interbed itself will have a great influence on the dynamic response of the slope.Therefore,this paper takes numerical simulation as the technical means to preliminarily explore the dynamic response law of slope with weak interbed.The effects of the amplitude,frequency and waveform of ground motion,the thickness and inclination of the weak interbeds and the ratio of wave impedance on the dynamic response of the slope are studied,and the similarities and differences of the effects of the inclined,horizontal and anti-inclined interbeds on the dynamic response of the slope are compared.Finally,the dynamic stability and response distribution law of slope reinforcement are studied through a case study of slope reinforcement in practical engineering.The main findings are as follows:(1)The slope response amplification factor is not sensitive to the amplitude of input ground motion.However,it is sensitive to the frequency of ground motion.If the frequency of input ground motion is higher than the natural frequency of the slope,the interbed will produce isolation effect.If the frequency of input ground motion is lower than the natural frequency of the slope,selection amplification effect will occur in the interbed.When the Fourier spectrum of the input ground motion is higher in the frequency band near the natural frequency of the slope,the response of the slope is stronger,and the frequency band near the natural frequency of the slope is mainly amplified above the interbed.On the contrary,the slope mainly amplifies the frequency band near the main frequency of ground motion.(2)The weak interbed has a magnifying effect on the dynamic response of the slope.With the increase of the thickness and inclination of the interbed,the slope amplification coefficient tends to increase.The response of the down-dip interbed slope is mainly affected by the thickness of the interbed and the wave impedance ratio,while that of the anti-dip interbed is mainly affected by the thickness of the interbed and the dip Angle.Small wave impedance ratio or large thickness is not conducive to the transmission of seismic waves,and isolation effect is easy to occur in horizontal and anti-dip sandwich slopes.(3)The existence of weak interbed makes the slope selectively amplify the input spectrum.Selective amplification of inclined interbed slope occurs above the interbed and tends to amplify the frequency band close to the natural vibration frequency of slope.However,the anti-dip interbed slope selectivity amplification occurs in the region below the interbed and tends to amplify the frequency band close to the natural vibration frequency of the slope.Both upper and lower levels of the horizontal interbed tend to amplify the frequency band close to the natural vibration frequency of the slope.With the increase of the thickness and dip Angle of the interbed,the selection amplification effect becomes stronger.With the increase of the wave impedance ratio,the selective amplification effect tends to decrease.(4)By modeling and calculating the actual engineering slope,it is found that the vertical seismic action has little influence on the slope stability,and the vertical seismic action can be ignored in the engineering seismic design and only the horizontal earthquake effect can be considered.The failure mode of the slope is "extrusion" failure along the lower part of the weak interbed.The dominant frequency of the slope Fourier spectrum is the dominant frequency of the input ground motion.Affected by the weak interbed,the slope surface will select the frequency band near its natural frequency for amplification.Under the action of designed ground motion,the reinforcement measures of chair pile and anchor cable antislide pile can limit the deformation of slope and play a good effect of shock absorption.