Characteristics of failure area and failure mechanism of a bedding rockslide in Libo County, Guizhou, China

Owing to the continuous rainfall, a bedding rockslide occurred at a construction site on the San-Li highway (Sandu County to Libo County) at 18:05 (UTC+8) on September 23, 2017, in Libo County, Guizhou Province, China. This bedding rockslide caused three deaths, six injuries, and an accumulation zone of approximately 1.8 × 105 m3 of medium weathered limestone that blocked the main line of the M ramp. To explore the triggering factors of this rockslide, the engineering geological condition, hydrogeological condition, slope excavation scheme, and statistics of rainfall data were investigated based on field investigations and geophysical drilling. The blasting failure of the upper unstable and dangerous rock masses after the bedding rockslide was analyzed. Three instability behaviors characteristics are distinguished: (1) the bedding characteristics of the rock formation and weak interlayer, (2) the steep slope (the largest dip angle being 46°), and (3) the appearance of the free face induced by the slope excavation. The results indicate that the above conditions are objective factors, and continuous rainfall triggers the bedding rockslide. The landslide follows the step-path failure mode.