Numerical Simulation Research On Dynamic Response And Stability Of Deposit Slope With Bedrock Under Earthquake

Deposit slopes with bedrock are widely distributed in southwestern China.The safety reserve of this slope is low,and it is susceptible to failure under earthquake.In addition to frequent microseisms in the southwest region,rainfall is also abundant,and the slope is more prone to instability under the action of earthquakes after rain.Therefore,a n accurate understanding of the instability characteristics and mechanism of deposit slope under earthquake is of great significance for slope engineering design,landslide monitoring and prediction.Based on the model test results of research group team,dynamic responses,instability characteristics,instability mechanisms and stability of the deposit slope with bedrock under earthquake are studied through FLAC3 D software.The dynamic response and stability of the slope under post-rain earthquake are also analyzed and compared with that under pure earthquake conditions.The research results are as follows:The ground motion parameters has great influence on the dynamic response characteristics of the slope.When the frequency of earthquake is close to the natural frequency of slope,the effects of PGA with “surface tendency” and “top tendency” are more obvious.When the earthquake frequency is higher,only the response at the foot is strong,and the PGA of the slope surface increases with the growth of horizontal or vertical earthquake amplitude.The interface effect has an obvious influence on the dynamic response characteristics of overburden soil,and the “surface tendency” effect is obvious when the interface is rougher.When the interface is closer to the top or the interface inclination angle is larger,the dynamic responses of overlying soil is stronger.The dynamic response law of the slope under post-rain earthquake is consistent with that under pure earthquake,but the response characteristics are different.The PGA of interior slope is greater than that of the interface under pure earthquake,however,the results under post-rain earthquake are opposite,indicating that rain water has the effect of seismic isolation and the dynamic response at the foot is strong.The instability modes of the deposit slope with bedrock under earthquake are as follow:“overall slip failure”,“local slip failure” and “tension-local slip failure”.The factors such as interface inclination,interface roughness and slope angle have significant influence on the instability characteristics of the slope,while the waveform and vertical earthquake have little influence on the instability characteristics but at the surface of the slope.Under pure earthquake,the top of the slope deforms first,causing a tensile plastic zone.While under postrain earthquake,the slip surface moves downwards,the displacement of the slope increases,the soil at the foot deforms first,and there is no tensile plastic zone at the top.The seismic loads has a tension-compression effect on the soil.When the additional tensile stress is applied by seismic loads,the soil stress is close to the limit equilibrium state and the slope is prone to instability.The instability trend is more obvious when the soil is subjected to bothway seismic loads.The interface plays a controlling role in the instability of the slope,among which the interface roughness and inclination will affect the anti-sliding force.The earthquake reduces the normal stress of the interface soil and increases the sliding force.The mechanisms of slope instability under post-rain earthquake can be divided into two types.One is the ‘trigger effect' mainly caused by the earthquake inertia force and decrease of interface shear strength under the action of Wenchuan wave,Another is the “cumulative effect”mainly caused by the increase of dynamic pore pressure and the decrease of effective stress under the action of Kobe wave.