Experimental study on the dynamic characteristics of low-angle loess slope under the influence of long- and short-term effects of rainfall before earthquake

Landslides on low-angle slopes can be caused under the coupled effect of rainfall and earthquake. In order to investigate the influence of duration of time between rainfall and earthquake on the scale and failure mode of landslides, a low-angle loess slope at Lanzhou New Area was adopted as a prototype, and a large-scale shaking table test was performed. By using self-designed artificial rainfall equipment, 30 mm of rainfall 12 h before shaking and 20 mm rainfall immediately before shaking were exerted on the slope model to investigate the responses and determine the differences in the failure mode of the low-angle slope under different rainfall cases. To measure the dynamic response of the test model at each working condition, 18 acceleration sensors, 7 soil-pressure sensors, 10 pore water-pressure sensors, and optical measurement techniques were used. The results show that the acceleration amplification effect increased with increasing intensity and the soil pressure increased with decreasing elevation under the long-term effects of rainfall before earthquake, but the value on the slope surface decreased under the short-term effects of rainfall before earthquake. The dynamic pore pressure value varied considerably between positive and negative and the maximum displacements at slope surface increased about 69.7% under the short-term effects of rainfall before earthquake. Large displacements and deep cracks occurred on the surface of the slope, mainly caused by the loess losing its strength and the large inertial force on the surface owing to the long-term effect of rainfall before the earthquake. The damage to the low-angle slope was mainly caused by liquefaction and the loss of loess strength under the influence of short-term rainfall before the earthquake. The failure of the slope was soil flow, which was similar to the sliding process of the Yongguang village landslides. Finally, we note that the effect of coupled effect on the low-angle slope should be evaluated in future work from two aspects: the intensity of rainfall and earthquake and the time when rainfall occurred before the earthquake.