地震和降雨耦合作用下黄土边坡动力响应的振动台试验研究

2013年岷漳Ms6.6级地震诱发的永光村泥流状滑坡表明,单一因素下稳定的黄土边坡在地震和降雨耦合作用下会诱发严重的岩土灾害。因此,基于防御与减轻地震灾害的现实需求,开展了地震和降雨耦合作用下黄土边坡振动台模型试验,通过加载卓越频率差异较大的原始波和压缩波,研究了地震和降雨耦合作用下黄土边坡的动力响应特征。试验结果表明:边坡动力作用过程,土体微结构不断损伤演化,土体动力参数——共振频率与阻尼比随动载强度增大不断调整变化,从而引起边坡不同部位加速度响应特征(频谱、幅度)的变化。PGA放大效应取决于边坡自振频率与荷载主频接近程度,当二者愈接近,放大效应越明显,反之放大效应越弱甚至响应衰减(放大系数小于1)。根据边坡模型宏观变形以及相关物理量的变化特征,地震和降雨耦合作用下的边坡失稳破坏过程可划分为:弹性动变形阶段、残余变形快速增加阶段、液化滑移阶段,不同阶段边坡动力响应各具特点。

Shaking table tests on dynamic response of loess slopes under coupling effects of earthquakes and rainfalls

The muddy loess landslide in Yongguang village induced by the Minxian-Zhangxian Ms 6.6 earthquake shows that the loess slope being stable under the action of single factor will induce severe disaster under the coupling effects of earthquakes and rainfalls. Therefore, based on the realistic demand of defense and mitigation of earthquake disasters, the shake table model tests on loess slopes under the coupling effects of earthquakes and rainfalls are carried out to study their dynamic response characteristics. The test results show that the dynamic process of slopes is the process of continuous damage of loess microstructure, and the natural frequency and the damping ratio of soil mass continuously change with the increase of load intensity so as to cause the changes of the acceleration response characteristics (spectrum and amplitude) of different parts of the slopes. The PGA amplification effect of loess slopes depends on the close extent of natural frequency of slopes and load frequency. When the two are closer, the amplification effect is more obvious. On the contrary, the amplification effect is weakened and even is reduced (The amplification factor is less than 1). According to the macroscopic deformation and related physical changes, the instability failure process of slopes under the coupling effects of earthquakes and rainfalls can be divided into the following stages: elastic dynamic deformation stage, rapidly increasing residual deformation stage and liquefaction sliding stage, and the dynamic response of slopes at different stages has its own characteristics.