| Landslide is a global geological disaster,causing a large number of casualties and incalculable economic losses around the world every year.The deposit slope with bedrock is a kind of slope with loose accumulation in the upper and bedrock in the lower.There are a large amount of deposit slopes in the southwest of China.The development of overburden layer is very common,and the large sliding body often blocks roads or rivers,which not only directly forms disasters,but also adversely affects the rescue work.Compared with homogeneous slope,it is a kind of"soil-rock mixture"binary structure between rock and soil,so the failure characteristics,instability mechanisms and dynamic response are quite different.Based on the geological prototype in Cuiping District,Yibin City,Sichuan Province,the failure characteristics and dynamic responses of layered deposit slope with different layered inclination,soil layer slope angle and different soil layer distribution under earthquake and post-rain earthquake are studied through model test in this paper.The critical condition law of slope instability is summarized by using a series of dimensionless parameters.Combined with relevant theories such as soil stress condition,upper limit analysis method and Optum G2 software,the instability laws and mechanisms are explained.Compared with the existing results,the similarities and differences with other types of slopes are discussed from the aspects of instability characteristics and dynamic responses.The main conclusions of this paper are as follows:（1）When the layered soil slope（no interface）is destroyed under earthquake,the failure characteristics only occurs in the top layer,and it is determined by the properties of the top soil.The clay shows collapse-sliding failure,the sand shows shearing failure,and the gravel soil shows collapse-failure.The acceleration amplification effect of gravel layer is the largest,followed by sand layer,and clay layer is the smallest.The failure range of three kinds of soil layers is clay,sand and gravel soil from large to small.For the critical acceleration of instability of layered slope under earthquake,the clay-gravel-sand group is the largest,the clay-sand-gravel group is the second,and the sand-clay-gravel group is the smallest.（2）The failure characteristics of the‘concave’group are concentrated in the upper clay layer,those of the‘convex’group are concentrated in the lower sand layer,while those of the‘linear’group are concentrated in the upper clay crack and the lower sand shear slip.The acceleration magnification factor of‘concave’group is the smallest.The acceleration amplification effect of the‘linear’group is mainly concentrated on the top,that of the‘concave’group is mainly concentrated on the shoulder,and that of the‘convex’group is mainly concentrated on the back edge.With the increase of the variable slope angle coefficientβ1/β2,the critical acceleration of slope instability a/g increases accordingly.（3）With the increase of layer interface inclination,the failure surface of clay and sand layer tend to expand to the interior of the slope.When the layered interface inclination is small,the tension crack and shear failure first occur in the sand layer.When the layered interface inclination is large,the tension crack and collapse failure first occurs in the clay layer.With the increase of layered interface inclination,the sliding displacement of the slope along the interface increases,the settlements of layered interfaces are more uneven and decrease at first and then increases,and the shear outlet of the sand decreases at first and then increases.With the increase of layered interface inclinationα,the effective impulse coefficient of seiamic force at0/gts decreases.（4）For the clay-sand-gravel group,the failure characteristics are more complex,and each soil layer has typical features.The clay-gravel-sand group finally has only one failure line through three soil layers.The sand-clay-gravel group slope finally has only one failure line in the top sand layer.At the same magnitude,the acceleration amplification factor of clay-sand-gravel group is the largest and the amplification effect is concentrated on the back edge of the top.While those of sand-clay-gravel group and clay-gravel-sand group are relatively close.The acceleration amplification effect of sand-clay-gravel group is concentrated on the shoulder,and that of clay-gravel-sand group is concentrated on the top.For the instability critical acceleration of layered deposit slope with bedrock under earthquake,the clay-sand-gravel group is the largest,the clay-gravel-sand group is the second,and the sand-clay-gravel group is the smallest.（5）For the conditions under post-rain earthquake,the rainfall time required for the infiltration line to cover the sand layer is in the following order:sand-clay-gravel group<clay-sand-gravel group<clay-gravel-sand group.The infiltration rate for rain water at the interface is in the following order:sand-bedrock interface>sand-gravel interface>clay-sand interface.In the process of earthquake,the failure characteristics mainly appear in the sand layer.When the sand layer is located in the middle and bottom,the local tensile cracks appear at the layered interface in the sand layer.When the sand layer is located at the top,the collapse cracking appears.In the process of earthquake,the increase of pore water pressure mainly occurs in sand layered interface.For the effective impulse coefficient of seismic force under post-rain earthquake,the sand-clay-gravel group is the largest,the clay-sand-gravel group is the second,and the clay-gravel-sand group is the smallest.（6）Compared with the homogeneous and weak-interlayer deposit slope with bedrock,the slip occurs along the interface under earthquake,but the failure mode of the layered deposit slope with bedrock is more complex,the deformation is larger,and the failure characteristics develope from the inside to the outside on the layered interface.Under post-rain earthquake,the failure mode of layered deposit slope with bedrock is greatly affected by the layered interface.The distribution of water content during rainfall and pore pressure distribution during earthquake are also affected by the layered interface. |
