| In recent years,under the seismic action of the collapse and slide slope failure often caused incalculable loss to the country and people,the earthquake induced the collapse,secondary disasters is far greater than the harm done by the quake itself.According to the earthquake from haiyuan wenchuan and lushan,the statistical analysis of the characteristics of landslide,found that there are gentle slope failure phenomena,especially the haiyuan haiyuan earthquake triggered large-scale,high-speed landslide,low angle,and the original slope angle is 15°?20°more,generally from the earthquake force caused by soil liquefaction explain this phenomenon,and the wenchuan earthquake and the forth is focused on the earthquake induced landslides between 25°?50°,including slope angle in the wenchuan earthquake in 30°?40°more intense,and 25°?35° slope angle for the gentle slope near the buckling failure mechanism is still no satisfactory explanation,most think with strong earthquake occurred under the action of soil liquefaction and its geological structure and properties of slope and so on.In this paper,the failure mechanism of gentle slope instability is explored from the perspectives of seismology and engineering mechanics.In order to reveal the mechanism of formation of the instability and failure of gentle slope under seismic action,considering the seismic wave propagation in slope body and freedom of slope caused by the wave field separation problem,adopt the method of earthquake synthesis,the dynamic stress formula of slope surface point is derived theoretically,a new method for calculating dynamic safety coefficient is derived by using the idea of pseudo-static method.Considering the two cases of vertical incidence and non-vertical incidence of seismic wave,the displacement,dynamic stress and safety coefficient of slope are calculated by this method,and the change rules of them with different incidence angles and slope angles are analyzed.Finally,the reliability of theoretical calculation results is verified by the numerical simulation software Geo-slope/W.The research results show that:(1)When the seismic P wave is incident vertically on the slope,the peak displacement and dynamic stress of the slope occur near the slope angle of 65°?70°,and with the increase of the slope angle,the dynamic safety factor of the slope gradually decreases,and the stability of the slope becomes worse.(2)When the SV wave is incident vertically on the slope,the peak displacement and dynamic stress of the slope point occur in the slope angle of 30°?35°,and with the increase of the slope angle,the dynamic safety factor of the slope decreases rapidly at first.Obviously,the slope angle that causes the slope surface to reach the peak displacement and dynamic stress under the action of SV wave is much smaller than that under the action of seismic P wave,so the seismic SV wave is the main factor that causes the instability failure of gentle slope.(3)The critical angle of SV wave is closely related to the main mechanism of SV wave induced gentle slope instability.When the incident angle of SV wave reaches a certain angle,the reflected P wave propagates parallel to the ground,and the total reflection of SV wave occurs,and the corresponding incident angle is the critical angle.In this case,the displacement and dynamic stress of slope reach the maximum.For example,the critical angle of the soil slope with a poisson's ratio of 0.35 is close to 30°,which is the most unfavorable slope angle under the action of seismic dynamics.(4)Another reason for the instability failure of gentle slope is related to the non-normal incidence of seismic waves.Seismic wave incidence at large angle will have great influence on slope stability.For example,when slope angle is 30° and P wave incidence degree reaches 80°,the dynamic safety factor of slope reaches the minimum value.In addition to the critical angle,when the incident angle of SV wave reaches about 60°,the dynamic safety factor of slope reaches the minimum value. |
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