Landslide mechanism of waste rock dump on a soft gently dipping foundation: a case study in China

In Miyi County of Sichuan Province of China, landslides are the most common type of waste dump failure, resulting from poorly compacted waste rock dump on weak soil. A waste dump failure on a soft, gently dipping foundation is examined in terms of the geological conditions, failure characteristics, movement processes and deposit forms, including the long run-out feature of the landslide. The waste dump failure and the subsequent deformation to the foundation are caused by an increase in pore water pressure and developed through the soft foundation underlying the heavy waste. The landslide run-out distance is influenced by the liquefiable silty clay layer. In this study, the landslide was triggered by the heavy load of waste rocks on top of a soft foundation of low-bearing capacity. The increased pore pressure in the foundation could not be released, which caused deformation of the foundation and triggered a landslide. The stability evolution is also researched in this study. In this study area: (1) the landslide mass is accelerated by the liquefaction of the saturated and water-rich silty clay layer, and the plastic deformation of the foundation caused by the collapsed waste dump; (2) the shear strength is strongly influenced by the water content; (3) when a waste dump is constructed on top of a water-sensitive gently dipping ground, it is important to provide drainage to dissipate pore water pressure; and (4) considering low factors of safety during heavy rains, secondary landslide is possible in the event of heavy rain and earthquake, indicating that heavy rainfall is the leading cause of the waste dump failure.