地震作用下黄土滑坡加速度深度放大效应及震后变形模式研究

Study on acceleration depth amplification effect and deformation model of loess landslide under earthquakes

基于相似比理论,设计并完成了典型黄土滑坡物理模型试验,采用先进的离心机振动台技术,实现水平+垂直振动,研究黄土滑坡的地震动放大效应及变形模式,并配合有限差分数值模拟方法相互验证。结果表明:沿滑坡体浅表层加速度放大作用具有明显的趋表效应,水平向和垂向加速度放大效应呈非线性增加,且水平向大于垂向;在滑坡体的滑动面附近加速度放大作用呈现出岩性结构效应;随高程增加加速度响应逐渐增大,表现出高程效应,滑坡后壁放大作用明显。随入射地震波强度的增加,滑坡体内部关键部位加速度放大作用基本是先增大后减小的趋势。强震作用下黄土滑坡的破坏形式为:滑坡后壁形成拉裂隙并逐渐扩展,滑坡后壁发生崩塌,滑体略有下挫,形成拉槽,坡体中部鼓胀,坡脚有大量崩积物。研究结果为探讨地震作用下黄土滑坡的加速度放大效应和变形破坏情况,以期为天水地区黄土滑坡的地震稳定性评价和抗震设计提供参考。

Based on the similarity theory, a typical model of loess landslide was established. The acceleration response characteristics of the loess landslide was studied by using the advanced centrifuge shaking table technology with the implementation of combined horizontal and vertical shakes. And the mutual verifications were performed between finite difference numerical simulations and experiments. Results show that： the toward surface effect of acceleration amplification along the shallow surface layer of the landslide is obvious ; the amplification effects of horizontal and vertical accelerations tend to increase nonlinearly, and the horizontal acceleration is generally larger than the vertical one. The acceleration amplification near the slip surface of the landslide exhibits the effect of lithological structure. With the increase of elevation, the acceleration response gradually increases, the elevation effect is presented, and the amplification effect at the rear of the landslide is apparent. With the increase of the intensity of the incident seismic wave, the dynamic response of the landslide increases firstly and then decreases. The deformation and failure process of the loess landslide can be summarized as ： tension cracks occur at the rear of the landslide and then gradually propagate, the rear of the landslide collapses, the sliding mass slightly slides downwards with kerves formed, the middle part of the landslide bulges and a large amount of colluvial deposits stack at the slope toe. The study results provide references for the investigation of the acceleration amplification effect and deformation failure of loess landslides under earthquake, and seismic stability evaluation and seismic design of loess landslides in Tianshui area.