Seismic Damage and Analysis of the Xiker Earth Dam During the 2020 Jiashi Earthquake, Northwestern China

The 2020 Jiashi Mw 6.0 earthquake occurred at the Kepingtage fold-and-thrust belt in the South Tianshan front, Northwestern China. The ground shaking caused extensive co-seismic deformation of the Xiker dam in the meizoseismal area. We obtained strata distribution characteristics of the dam foundation through drilling. Using laboratory and in situ tests, the particle size distribution, standard penetration, and shear wave velocity of each layer were obtained. Along with peak ground acceleration, we evaluated the potential of sand liquefaction in various layers and proposed a relationship between dam fissures and sand liquefaction. Our results suggest that sand liquefaction occurred in the silty sand layer 0–3 m beneath the dam foundation. Sand liquefaction occurs behind the dam, resulting in uneven settlement of the dam foundation, making the horizontal deformation of the backslope of the dam significantly larger than the foreslope of the dam. Using numerical simulations, we found that sand liquefaction behind the dam can cause different horizontal deformation vectors (maximum deformation is ∼7.45 cm) in the dam foreslope and backslope, which cause the dam to rotate in the downstream direction. Large fissures also formed on the dam crest.