Experimental study on the dynamic response of accumulation slopes under earthquake action in Three-rivers Basin,southeast Tibetan Plateau:a case study of the Xiaguiwa landslide in Batang,Sichuan Province
The three-river basin of the southeast Qinghai—Tibet Plateau has widespread accumu-lation slopes,which can easily evolve into landslide disasters.In this study,the dynamic response characteristics and failure modes of earthquake-induced accumulation landslides in the Xiaguiwa slope in Batang,Sichuan Province,were investigated with shaking table model tests.Results show that the natural frequency of the slope increases because of the compaction of pores in the early stage of earthquake action.Under the excitation of a Maoxian wave,the slope shoulder re-sponds strongly.Under the excitation of a high-amplitude Maoxian wave,the amplification effect weakens because of the decrease in the overall stiffness of the slope.The Hibert spectrum de-scribes the propagation characteristics of the seismic wave in the slope.When propagating to the slope top,the high-frequency energy of the seismic wave is considerably enhanced.The amplifica-tion effect weakens after the seismic wave passes through the accumulation layer.Under the ac-tion of strong earthquakes,the response of the slope surface at a certain depth shows a consistent and violent phenomenon.The upper part of the slope will form a"detachment body",which will show upward and downward jerky motion under earthquake action.The strongest dynamic re-sponse appears at the slope surface approaching a slip.The characteristics of the failure mode of the slope are as follows:in the early stage of the earthquake,soil peeling occurs on the slope sur-face under the coupled action of gravity and earthquake;as the earthquake amplitude increases,relative displacement occurs between the slope shoulder and the accumulation layer,and cracks appear on the surface of the accumulation layer;finally,obvious relative displacement occurs at the slope toe,and the accumulation layer deviates from the bedrock and accelerates to collapse.The sliding process of the slope accumulation layer can be divided into three stages according to the characteristics of seismic signals:(1)stable stage,(2)impending slip stage,and(3)slip stage.
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