地震作用下均质土坡动力特性的振动台试验研究

设计并完成比例尺1∶100的边坡振动台模型试验,讨论模型的相似关系、传感器的布置及模型的建造,并编制相应的动荷载加载方案。通过输入不同类型、不同幅值、频率的动荷载,分析模型边坡在地震作用下的动力响应规律以及地震动参数对边坡动力特性和动力响应的影响。试验结果表明,在坡体的表面和坡内的竖直方向上,加速度放大系数均随着高程增加而明显增大。当输入不同压缩比的地震波时,压缩比越大坡体的动力响应越明显,即随着输入动荷载的频率增加,越接近土体的自振频率加速度放大效应越明显;在坡体的同一高程处,坡面的加速度放大系数略大于坡体内的加速度放大系数,表现出一定的趋表效应,同时随着输入地震波振幅的增加,加速度放大系数整体出现递减的趋势。实验结果分析有助于揭示土质边坡在地震作用下的失稳破坏机制,为今后边坡工程的抗震设计提供积极的参考。

Shaking Table Tests on Dynamic Characteristics of Homogeneous Soil Slopes during Earthquake

In this paper, we design and complete a shaking table model test with respect to slope with a scale of 1:100, and discuss the similarity relation of the model, sensor layout, and process of model construction, as well as the seismic wave loading system. We built the model slope in soil with a height of 50 cm, length of 100 cm, and thickness of 45 cm, and performed a series of tests with inputs of different seismic wave types, amplitudes, and frequencies. We discuss the dynamic characteristics and responses of the slope in an earthquake and the influence of the ground motion parameters. The results show that the acceleration responses at the same slope position have obvious differences under different seismic loading inputs. The amplification coefficients of acceleration along the slope surface and in the vertical direction increase smoothly with increasing elevation, and otherwise increases dramatically in the slope body. At the same time, the input frequency of seismic waves has obvious effects on the dynamic slope responses. As it approaches the natural frequency of the model slope, the amplification effect of acceleration is clearly enhanced with increasing frequency. The amplification coefficients of acceleration on the slope surface are larger than those in the slope body at the same elevation. The amplification coefficients of acceleration decrease with increasing earthquake amplitudes. With an increase in vibration number, the damping ratios increase, and the amplification coefficients of peak acceleration in the slope decrease with increases in the seismic amplitudes. Based on the shaking table test results, we present the influence of the ground motion parameters on the dynamic slope characteristics. The acceleration amplification coefficients increase nonlinearly as the elevation increases, and the distribution of acceleration in slope changes as the input seismic wave frequency changes. Acceleration amplification coefficients increase with increments of seismic wave amplitude, but amplitude does not change the distribution of acceleration in the slope body. The duration time of the input seismic wave has little influence on the distribution and amplitude of acceleration in the slope. These results help reveal the mechanism of slope instability during earthquakes, and can provide valuable references for aseismic slope engineering design.