层状岩质斜坡竖向动力响应特性的振动台试验研究

Shaking table test for vertical dynamic resonse behavior of layered rock slopes

以‘5·12’汶川地震灾区典型斜坡岩体组合结构为模拟特征,采用水平层状上硬下软和上软下硬两种岩性组合概念模型,设计、完成了大型振动台试验。基于有限元计算的模态分析及仪器记录结果表明,模型箱具有一定刚度,既不会与模型产生共振,也不会产生放大效应。基于斜坡灾害中竖直向地震作用日益突出,相关试验研究少,通过绘制不同振动强度下斜坡模型竖直向峰值加速度及放大系数沿高程变化规律曲线,揭示了正弦波尤其汶川地震波作用下模型的竖直向加速度动力响应特性。主要有:①在两种波作用下,竖直向峰值加速度表现出高程放大效应,模型下段放大速度稍快,最大放大值出现在中上部;②在汶川地震波作用下,随着振动强度增加,斜坡模型上段的峰值放大系数逐渐降低至趋于变化稳定,下段基本不变,表明斜坡模型的高程放大效应逐渐减弱;③合成向地震波作用强度大于单向地震波作用,加载方向对竖直向加速度响应规律性影响不明显;④上软下硬斜坡模型的竖直向加速度响应程度高于上硬下软斜坡模型。对斜坡竖直向加速度响应特性的研究有助理解地震作用下一些由竖向地震力引起的变形破坏现象,也能为斜坡动力稳定性计算中竖直向地震力取值提供参考。

A large scale shaking table test was conducted for two 1：100 scaled slopes, they had the lithological combinations of hardness-upwara or softness-upward formed broadly in 2008＇5.12＇ Wenchuan Earthquake areas,Sichuan Province, China. Ruled by Buckingham π＇ s similitude theorem, waves of different inputted at the base of models. Modal test results based on FEM and instrumental kinds, directions and amplitudes were records showed that the model box has enough rigidity, no resonance with model slopes and no amplification effect during shaking. With the more and more importance of vertical ground motion and lack of its test study, here, based on the recorded data, the peak vertical accelerations and their amplification factors along different elevations were mapped under incremental excitation levels, when subjected to sine waves and especially real waves scaled from Wenchuan earthquake waves. Results showed that ① the amplification effect occurs in vertical components with increase in elevations upper part is basically smaller than middle and upper part; ② when decrease gradually to a final stable that in the lower part of model slopes, though excited by Wenchuan earthquake waves, the , however, the amplifying speed in the the maximum amplification occurs in the amplification factors in the upper part state but those in the lower part have little change with increase in excitation intensity,so the amplification effect gradually weakens; ③ the responses under earthquake waves in combined directions are than those in vertical direction only, but the difference in excitation directions has little effect on the change vertical accelerations; ④ the responses of the softness-upward model slope model slope. Results provided a good understanding of the damage caused stronger laws of are stronger than those of the hardness-upward by vertical component of earthquake, and also a guide to select the more reasonable vertical seismic coefficient during slope dynamic stability calculation.