Seismic behaviors of moraine-soil slope under inadequate freezing and earthquakes

Inadequate freezing is an inevitable intermediate state in freeze-thaw cycles and an important factor affecting the seismic behavior of moraine-soil slopes along Sichuan-Tibet railway. A self-made incubator was employed to complete the inadequate freezing process of the moraine-soil slope, and serial shaking table tests on moraine-soil slopes were conducted using existing shaking table devices. A speckle analysis system and accelerometers were adopted to track the slope displacement and acceleration response, and the slope seismic behavior was revealed through the evolution characteristics of acceleration, displacement and frequency spectrum. These results show that: (1) Under inadequate freezing and earthquakes, the main change of slope dynamic characteristics is a decrease in natural frequency and an increase in damping ratio. (2) Dynamic failure process of the moraine-soil slope after inadequate freezing could be summarized into four stages: elastic deformation stage with peak acceleration less than 0.4g, brittle failure stage with peak acceleration from 0.4g to 0.8g, plastic failure stage with peak acceleration from 0.8g to 1.1g, and failure slip stage with peak acceleration greater than 1.1g. (3) Seismic behaviors of the moraine-soil slope after inadequate freezing exhibit significant frequency effects, amplitude effects, slope-surface effects and elevation effects. (4) Low temperature freezing amplifies the slope dynamic response, and the larger the freezing coefficient, the stronger the dynamic response. (5) Under inadequate freezing and earthquakes, the failure pattern of a moraine-soil slope is an overall landslide along the slip surface formed by connecting cracks, which is similar to that of a rock slope with weak slip surfaces. These results have important reference value for further researches of slope seismic behaviors along Sichuan-Tibet railway.