Landslide dam deformation analysis under aftershocks using large-scale shaking table tests measured by videogrammetric technique

The Ms 8.0 Wenchuan earthquake triggered at least 257 landslide dams. More than 849 aftershocks with magnitudes higher than Ms 4.0 occurred after the Wenchuan earthquake by 12 March, 2012 (Shen et al., 2013), which might largely influence the structure and soil properties of these dams. This paper aims to study the dynamic deformation of landslide dams under aftershocks through larger scale shaking table tests. Videogrammetric technique was applied to measure the dynamic deformation of the model dams. Two groups of shaking table tests were conducted with two types of landslide dam materials: one with quartz sands containing 10% kaolin (Dam I) and the other with only quartz sands (Dam II). The dam deformation and its influencing factors were analyzed with the results measured by videogrammetric technique. The deformations were generally higher on the surface of the dams, either on the crest or on the both upstream and downstream slopes. Higher peak ground acceleration (PGA) resulted in larger dam deformations due to higher seismic force. The deformations under the combination of X- and Z-directional shakings were larger than those under X-directional shaking for sufficient vibratory compaction. Water rising led to the increase of dam deformations because that the water seepage reduced the effective soil stress, especially reduced the matric suction. The settlements of the dam composed of more fine particles were larger than that composed of large particle size because that the soil pores in the former were filled more sufficiently with fine particles. The aftershocks may not directly trigger the failures of landslide dams, but accelerate the overtopping failures by lowering the dam crest with settlement and cracking.