Tests On Dynamic Response And Failure Mode Of Different Soil Slopes Under Earthquakes

The landslide caused by earthquake is one of the most common geological disasters in the mountainous areas of Western China. With the implementation of the strategy of developing the west of China, Many large-scale key projects will be built in strong earthquake areas or through strong seismic areas. How to ensure the safety construction and operation of the project, the stability of the slope under earthquake puts forward higher requirements. Due to the seismic failure mechanism of the slope is complex, a correct understanding of the dynamic response laws and failure mode of slope could provide technical supports for the seismic protection of actual slope engineering, which has important theoretical and practical significance.Based on the similarity theory, a large scale shaking table model test of three kinds of soil slopes, sand, gravel and clay, with a geometric scale of 1:20. is designed and completed. The influences of seismic wave type, dynamic strength and frequency on the dynamic response of the slope are mainly discussed,Based on a large number of experimental data and abundant experimental data, the failure process and failure mode of soil slope are analyzed. Mainly achieved the following results:(1) When the input amplitude is 0.2g,sand, gravel and clay slope model under different seismic waves, the slope horizontal acceleration response that present nonlinearly increasing trend along the elevation overall, but gravel soil slope in WenChuan waves was increased linearly.When the same dynamic amplitude seismic wave excitation, under the action of WenChuan wave, the PGA amplification coefficient of the same measuring point is the biggest, the 3Hz sine wave is the smallest, and the EL-Centro wave is between them.Under the action of 3Hz sine wave,related to the size of the incentive slope dynamic response, mainly for microquake from the damping effect, strong earthquake has the function of amplifying.(2) Under the action of WenChuan wave, the amplification effect of the sand slope is the strongest at the top of the slope. When the input amplitude less than 0.6g, PGA of slope measured with the dynamic strength increases in a linear increasing trend, and the amplification coefficient of PGA showed a decrease trend.The amplification of high frequency wave is weakened, and the energy of low frequency wave is strengthened. When input 3 Hz sine wave, with the increase of the dynamic strength, the slope and the slope of the PGA and its amplification factor are enlarged.(3) When the WenChuan wave acting on gravel soil slop, input amplitude less than 0.2g, slope point measured PGA and amplification coefficient increases with the input dynamic strength increases.When the input amplitude more than 0.3g, the PGA continues to increase, while the amplification coefficient of PGA decreases rapidly, and then decreases gradually.Slope of the high frequency wave performance of the filter, the low frequency wave amplification.When the input 3Hz sine wave excitation, with the increase of the dynamic intensity, the slope of the vertical measurement point PGA and its amplification coefficient is basically linear increasing trend.(4) With the increase of the dynamic strength of the clay slope in the WenChuan wave, the height of the vertical elevation measurement point PGA increases, the amplification coefficient decreases, and the soil enters the nonlinear stage. Under the action of strong earthquake, the amplification effect of the clay slope on the seismic wave attenuation along the height of the seismic wave. When the 3Hz sine wave acts on the clay slope, with the increase of the vibration intensity, the PGA and its amplification coefficient of Slope interior and surface showed varying degrees of increasing trend. When the role of microseism, clay slope plays the role of shock absorption, when the effect of strong earthquakes, the slope along the elevation amplification effect increases gradually.(5) In a certain frequency range, with the increase of the dynamic frequency, the PGA amplification coefficient of same measuring point show an increasing trend. The gravel soil and the clay slope is first decreased and then increased along the elevation overall. When the frequency is greater than 5Hz, gravel and clay model of slope PGA amplification coefficient is larger than the middle toe. When the frequency is greater than 5Hz, the PGA amplification coefficient at the middle of slope surface is larger than the toe.(6) Under the conditions of this test, the failure mode of soil slope is retrogressive landslide, the failure mode of the gravel soil and the clay slope is the thrust-type landslide. Gravel and clay slope in landslide occurs, the stages are similar, but before the failure of the different deformation characteristics, clay slope crest and slope with large deformation while deformation of gravel soil is not obvious. The failure mode of soil slope is different from gravel soil and clay, but the characteristics of soil slope are similar to those of clay slope. It is different that local slope failure of sand slope happens before overall instability.It is similar that both slop crest and shoulder have large deformation before instability.Gravel soil and clay model of slope sliding surface is deep in the shape of a circular arc, the sand model of slope sliding surface is flat and shallow circular arc shape and near the slope shoulder.