秦岭甘湫池花岗岩质崩塌振动台试验研究

LARGE SCALE SHAKING TABLE TEST OF GANQIUCHI GRANITE ROCK AVALANCHE IN QINLIN MOUNTAINS

地震诱发山体崩塌常形成巨大的灾害,特定地形地质条件下山体地震动力响应特性及破坏机制研究是工程地质的重要难题。本文以秦岭地区具代表性的翠华山甘湫池花岗岩崩塌为研究对象,制作有效反映花岗岩工程地质结构的试验模型,开展大型振动台试验,研究山体地震动力响应规律和崩塌变形破坏机制。试验发现,边坡内部加速度放大系数随激振强度的增加呈现出显著的三阶段变化趋势;水平加速度响应呈现出随高程的增加而单调增大的特征,而竖直加速度响应随着高程的增加出现先增加后减小再增加的波动变化特征;边坡的固有频率变化曲线可以分为3个阶段,整体呈现下降的趋势,表明边坡动力特性发生变化;破坏后的边坡可以分为2个区域:后缘启动区和崩塌堆积区。边坡在地震激振作用下的破坏过程为地震波激振输入→坡体后缘形成拉张裂缝→裂缝向下扩展贯通→不稳定坡体滑动→堆积坡脚。反演了山体破坏的4个阶段:振动致裂阶段、高速启动阶段、撞击减速阶段和堆积阶段,结果与现场工程地质调查分析十分一致。研究翠华山甘湫池花岗岩崩塌的发育特征、成因机理和演化过程,研究成果对揭示秦岭北缘乃至秦岭地区崩塌形成机制、发育规律和灾害有效防控、地质遗迹开发和保护具有重要意义。

Huge hazards,which are often caused by earthquake-induced mountain avalanches,are a serious secondary,and the study of dynamic response characteristics and failure mechanism of the avalanches in certain geological condition is an important issue in engineering geology and geotechnical engineering.In this paper,a large-scale shaking table test was carried out to study the Ganqiuchi granite avalanche relic in Cuihua Mountain,which is typical in Qinling District.The testing results show that the amplification coefficient of the acceleration peak value inside of the model slope presents a significant three-stage trend with the increase of the excitation intensity.The horizontal acceleration response increases monotonously with the increase of elevation,while the vertical acceleration response first increases,then decreases and finally increases with the increase of elevation.The natural frequency curve of the model slope can be divided into three stages,showing a downward trend,indicating that the dynamic characteristics of the model have changed.The damaged model can be divided into two regions:the source area and the accumulation area.The failure sliding characteristics and evolution process of the model slope under seismic excitation are as follows:seismic wave excitation input→tension cracks formed on the trailing edge of the slope→the fracture extends downward and penetrates→unstable slope sliding→accumulating at the foot of the slope.Four stages of mountain failure are inversed:vibration-induced fracturing stage,high-speed start-up stage,impact and deceleration stage and accumulating stage.The experimental results are quite consist with field observation and can help to explain the failure mechanism of granite slope,and provide the basic data and scientific support for disaster reduction and the development and protection of Qinling Mountain landscapes and geological heritages.