Seismic Dynamic Amplification And Permanent Displacement Analysis Of Slope

At the time of the earthquake,the local site conditions have an important influence on the amplitude and spectral characteristics of the ground motion.The site effect can amplify or attenuate the acceleration of the earthquake ground motion,among which the existence of irregular topography may greatly aggravate the catastrophic consequences of strong earthquake motion.Slope,especially the slope of water conservancy and hydropower engineering,is one of the most typical site conditions.A seismic dynamic response analysis can improve the seismic performance of slopes when designing,excavating and maintaining slopes.It has very important practical significance.In this paper,the program is designed to study the seismic input of the slope and the amplification effect of the earthquake along the slope.With the help of SLIDE software,the seismic stability of the high slope of a hydropower station in Tibet is analyzed based on the Newmark sliding block method.The main research results are as follows:(1)A slope seismic input model based on the time-domain wave analysis method is constructed,including the viscoelastic boundary considering the radiation damping of the infinite foundation and the seismic wave input method,which can be used for the dynamic amplification response analysis of slope with oblique incidence of seismic waves.The numerical simulation of the oblique incidence of seismic waves is realized by compiling the corresponding calculation program.The example shows that the calculation program has higher precision.(2)When the P wave is incident,the PGA amplification coefficient of the slope surface and the slope vertical plane AB decreases first and then increases with the increase of the incident angle,presenting a nonlinear growth trend along the elevation direction,and the overall PGA amplification coefficient is between 0.9 and 1.4.(3)When the SV wave is incident,the PGA amplification factor of the slope surface and the slope vertical plane AB increases gradually with the increase of the incident angle,and the growth rate is accelerated.The overall PGA amplification coefficient is between 0.75 and 1.6.(4)Near the foot of slope,the change of slope angle has no obvious effect on the dynamic response of rock slope.As the height h of the slope surface point is larger than 0.5H,the PGA amplification coefficient increases with the increase of the slope angle.When the P wave is incident,the PGA amplification factor is roughly concentrated between 0.95 and 1.5;when the SV wave is incident,the PGA amplification factor is roughly concentrated between 0.8 and 1.7.(5)The Newmark sliding block analysis method is used to calculate the dynamic response and permanent displacement of the high slope of a hydropower station in Tibet under the action of different seismic amplitudes.The results show that the slope is stable under the designed ground motion,and the total slip is increasing with the increase of seismic amplitude.For different types of seismic waves,although the peak acceleration of the input is the same,the difference of ground motion parameters will affect the permanent displacement of the slope.The main innovative achievements are as follows:(1)In seismic response analysis of structure,the incidence of plane seismic waves is usually considered as vertical.At present,the obliquely incident seismic input method has not been implemented in the commercial computer program,and the phase characteristics of the input seismic wave cannot be reflected reasonably.In this paper,a slope seismic input model based on time-domain wave analysis method is constructed,and the dynamic amplification response of slope under obliquely incident seismic wave is analyzed.(2)This paper deduces the equivalent load of boundary node when plane P wave and SV wave is obliquely incident,and applies it to viscoelastic boundary to realize the external obliquely input of seismic wave,which can be used to accurately simulate the seismic wave input at any angle.The independent calculation program is carried out to study the influence of obliquely incident seismic wave on the dynamic response of the slope.The model material parameters and seismic wave parameters can be changed according to the actual situation,which is suitable for the finite element dynamic calculation of general plane problems.(3)The amplification effect of seismic along the slope surface under obliquely incident conditions is summarized.That is,when the P wave is obliquely incident,the PGA amplification coefficient of the seismic along the slope surface is between 0.95 and 1.5.When the SV wave is obliquely incident,the PGA amplification coefficient of the seismic along the slope surface is between 0.8 and 1.7.It is found that the results calculated by the analytical method without considering the seismic dynamic amplification effect of the slope are not safe,and the research results can provide some basis for the pseudo-static method to determine the seismic action coefficient.(4)The SLIDE software is used to analyze the permanent displacement of the high slope of a hydropower station in Tibet based on the Newmark sliding block analysis.Two indexes of slope stability evaluation(permanent displacement and safety coefficient)are connected,which can provide reference for similar slope engineering stability analysis.