地震作用下顺层岩质边坡动力响应和破坏模式大型振动台试验研究

5?12汶川大地震触发了大量的顺层岩质滑坡，对其进行研究很有必要。根据动力模型试验的相似关系，设计制作了1个坡角大于岩层倾角的尺寸(高×长×宽)为1.6 m×1.75 m×0.8 m的顺层模型边坡，并完成了大型振动台试验。试验结果表明，在坡体表面和内部竖直方向上，加速度放大系数随着坡体高程增加而增大，并且随着高程增加，加速度放大系数增大的速度加快；在坡体内同一高程上，坡面处的加速度放大系数大于一定水平深度坡体内部的加速度放大系数，表现出趋表效应；地震波输入频率对坡体动力响应有明显影响，随着频率的增加，越接近坡体的自振频率，加速度放大效应越显著；加速度放大系数随着输入波振幅的增加，总体上表现为递减趋势；通过和均质边坡振动台试验加速度监测数据对比，发现坡体结构对坡体加速度放大系数也有一定的影响，结构面对地震波的反射和折射作用加大了坡体加速度的放大效应。,对试验过程中坡体破坏特征的描述和分析发现，边坡的破坏模式为地震诱发－坡肩拉裂张开－坡面中部出现裂缝－裂缝贯通－发生高位滑坡－转化为碎屑流－堆积坡脚。研究成果对地震灾区滑坡形成机制的认识和减灾防灾有一定的价值。

The large-scale shaking table test study of dynamic response and failure mode of bedding rock slope under earthquake

It is necessary to study bedding rock landslides induced by “5?12” Wenchuan earthquake. According to the similar relationship of dynamic model test, a bedding model slope is built with a height of 1.6 m, length of 1.75 m, width of 0.8 m and a slope angle larger than the dip angle of the rock stratum. A large-scale shaking table test of the model slope is performed. The results show that amplification coefficients of the acceleration along slope surface and in vertical direction increase with the elevation increasing. And its increment speeds also increase with the elevation increasing. At the same elevation, the amplification coefficients of the acceleration on slope surface are larger than that in slope body. The input frequency of seismic waves has obvious effects on dynamic responses of slope. The amplification effect of acceleration enhances evidently with the frequency increasing and approach to the natural frequency of the model slope. The amplification coefficients of the acceleration decrease with the earthquake amplitudes increasing. Comparing with the acceleration monitoring data obtained by the shaking table test of the homogeneous slope, it is found that structural surface of the slope also has effects on the amplification coefficients of the acceleration. Because of reflection and refraction of structural surface, the amplification effect of acceleration enhances evidently. Based on analysis of failure features of the slope, the failure process is described as earthquake induction-loosening of rock mass and tensile failure of the crest of the slope-propagation and coalescence of cracks in the middle part of slope surface-occurrence of high locality landslide-formation of debris flow-accumulation at the slope toe. The study results are helpful to reveal the formation mechanism of landslide under earthquake and provide valuable references for disaster prevention and reduction.