库水与地震力共同作用下金沙江特大桥桥址边坡动力响应研究

针对复杂地质构造的岩质边坡稳定性问题,进行含有不连续节理岩质边坡的大型振动台模型试验,研究库水与地震力共同作用下岩质边坡的动力响应规律及其破坏机制。通过向模型箱中注水和抽水来实现库水位升降的模拟,运用消波装置削弱箱壁引起的库水波浪反射波。研究发现,随着地震波的输入,库水面以下的边坡裂缝扩展较快;在相同地震波输入条件下,由于库水压力的存在,高水位工况边坡的加速度放大效应比低水位工况小。模型在库水与地震力共同作用下的破裂观测结果表明:库水入渗加剧了边坡裂缝扩展,库水骤降使边坡表层的加速度放大效应更加明显,不利于边坡稳定。边坡的破坏模式为:地震诱发上层坡体出现沿节理的裂缝,地震力增加及库水入渗加剧裂缝扩展,出现沿节理的贯通性裂缝;在地震力、库水入渗及库水骤降共同作用下,坡体沿上层结构面发生倾覆滑动破坏。

Dynamic response of the slope by the site of Jinsha River Bridge under the action of reservoir water and seismic force

A large-scale model of shaking table test on the rocky slope with discontinuous rock joints is carried out to investigate the stability of rocky slope with complex geological structures. The dynamic response and failure mechanism of the rocky slope with discontinuous joints under the combined effects of reservoir water and seismic force were studied. The experiment simulates the rise and fall of the reservoir water by injecting water into and pumping water out the model box. The wave reflection created by the box wall is reduced by the wave absorbing device. The result shows that with the input of seismic wave，the cracks in slope under the reservoir water level expenses quickly. Under the same seismic wave input，the acceleration amplification effect of the slope for the high water level case is less obvious compared to the low water level case due to the presence of the water pressure. The infiltration of reservoir water aggravates the development of the slope cracks. The sudden drop of reservoir water level brings a greater amplification effect to the acceleration of slope surface，which is not positive to the stability of slope. The earthquake induces the cracks along the joints on the upper layer of the slope. The increase of the seismic force and the infiltration of reservoir water aggravate the development of the cracks and finally result in the appearance of the penetrating cracks. The interaction of the seismic force，infiltration of reservoir water and its sudden drop together lead to the overturn and sliding failure of the slope along its upper discontinuity.