Influence of Post-Earthquake Rainfall on the Stability of Clay Slopes (IPL-192)

Abstract

Open image in new window Rainfall and earthquakes are considered two of the major causes of landslides worldwide. These landslides cause billions of dollars in property damage and revenue losses, as well as the deaths of thousands of people each year. While researchers have been examining the effect of either rainfall or earthquakes on the deformation and stability of slopes, the combined effect of rainfall and earthquakes on deformation and slope stability has not been evaluated systematically. In this study, a series of model slopes were constructed in a Plexiglas container placed on top of a shake table. The model slopes were prepared to have different initial void ratios of 0.89, 1.0 and 1.2 and various slope inclinations of 30°, 40°, and 45°. These slopes were instrumented with accelerometers, tensiometers and inclinometers and subjected to a number of sinusoidal seismic motions with different seismic accelerations from 0.1 to 0.3 g, with several frequencies ranging from 1 to 3 Hz for various durations ranging from 10 cycles to 50 cycles of loading. Following the earthquake event, a rain simulator system was used to induce rainfall at intensities of either 18, 30 or 60 mm/h. The seepage velocity, spatial variation of suction and the deformation of the slopes were determined. The results obtained were compared to those obtained from similar slopes subjected to rainfall without an earthquake event. The study showed that the seismic shaking resulted in a reduction in the seepage velocity in the slope, which led to an increase in the factor of safety of the slope with time.