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