基于振动台试验的地震作用下岩质边坡位移演化特征

Displacement evolution of rock slope under earthquake based on shaking table test

汶川地震受灾区域岩质边坡失稳频发,灾区滑坡危害问题严重,岩质边坡位移演化特征的研究对灾后边坡监测及预警具有重要意义。本文针对金沙江特大桥桥址边坡开展了包含陡倾结构面及顺向贯通性结构面的复杂岩质边坡振动台模型试验研究。根据相似理论,试验采用水泥、砂、铁粉、黏土与混合剂的配合材料模拟玄武岩,采用PVC板模拟凝灰岩结构面。利用光学测量系统采集了边坡表面实时位移数据,分析了位移响应波形、PGD(测点最大位移值,Peak Ground Displacement)分布以及PGD演化规律。结果表明,水平输入和垂直输入的PGD演化规律基本一致,振动台地震输入烈度在Ⅷ度前,PGD呈线性增大趋势;Ⅷ度时,边坡模型在陡倾结构面处相对位移达到约1.5 cm;大于Ⅷ度时,PGD呈加速放大趋势,可以认为此时边坡呈不稳定状态;Ⅸ度时,边坡呈整体滑动破坏模式,滑动面由陡倾结构面处剪入,在坡脚附近剪出。

Rock slope failure frequently occurs in Wenchuan earthquake area.The research on the characteristics of displacement response to rock slope will be significant to the slope monitoring and early warning in this area.In view of the abutment slope of Jinsha River bridge,the shaking table model test considering steeply dipping-structured surface and connective structural surface is carried out.The basalt is simulated by using mixture of cement,sand,clay and iron powder,and the tuff is simulated by PVC material.The real-time displacement data of the slope surface are collected by the optical measurement system,and the distribution and evolution of PGD(Peak Ground Displacement)are analyzed.The results show that the evolution of PGD both in horizontal and vertical cases are basically the same.PGD showed the tendency of linear increase before the intensity of earthquake up toⅧdegree.Relative displacement of slope model was 1.5 cm on steeply dipping-structured surface when the intensity hitⅧdegree.When the intensity of earthquake was greater thanⅧdegree,PGD is accelerated amplified,and then the slope was in unstable state.When the intensity reached toⅨdegree,the slope showed overall sliding failure mode,shearing from steeply dipping-structured surface to the slope toe.