Dynamic characteristics of high-elevation and long-runout landslides in the Emeishan basalt area: a case study of the Shuicheng “7.23”landslide in Guizhou, China

On July 23, 2019, a catastrophic high-elevation and long-runout landslide occurred in Shuicheng County, Guizhou Province, the karst mountainous area of southwestern China, causing the death of 51 people and the destruction and burial of 21 houses. The landslide movement consisted of a three-stage chain disaster that included landslide instability, impact and scraping, and debris flow deposit. A field investigation, unmanned aerial vehicle(UAV) image analysis, and dynamic analysis determined that this landslide had the following main characteristics: (1) initiated at high elevation, the elevation difference between the landslide front and the toe of surface of rupture was 340 m, and the horizontal sliding distance was 1360 m, categorizing this landslide as a high elevation and long runout; (2) induced by heavy rainfall, there was no notable sign of pre-landslide deformation but catastrophic events occurred, suggesting heavy rainfall as the main inducing factor for landslide failure; (3) significant entrainment effect, the volume of the sliding body was 70 × 10 4 m 3 , and the deposit volume reached 200 × 10 4 m 3 , and the impact and scraping characteristics were remarkable, enlarging the scale of the landslide disaster and increasing the difficulty of the rescue effort; and (4) extremely high fluidity, the basalt fragments and quaternary clay were fully and evenly mixed, reflecting the turbulent characteristics and super high mobility of the sliding body during the movement. To date, multiple high-elevation and long-runout landslides of Emeishan basalt have been recorded in the southwestern mountainous area of China, causing enormous casualties. Research establishing early identification and risk zoning methods for high-elevation landslides in the Emeishan basalt mountainous area should take into account the effects of landslide impact, scraping, and the disintegration effect during collision, and further research should be conducted into the post-failure dynamics of high-elevation and long-runout landslides.