Shallow destruction and movement characteristics of the inner dumping site under rainfall

Under a rainfall condition，the inner dump of a surface mine is prone to erosion and shallow landslide.Re⁃ vealing the initiation and movement characteristics of shallow landslide is the basis for studying the mechanism of shal⁃ low landslide in the inner dump of a surface mine. Taking the inner dump of Yuanbaoshan opencast coal mine in Inner Mongolia as an example，various physical simulation tests based on similarity theory were conducted to investi⁃ gate the shallow failure characteristics of the inner dump. After considering actual unsaturated infiltration layer，the im⁃ proved Green⁃Ampt rainfall infiltration model and the stability analysis equation of the inner dump were derived， and the sensitivity stages of the slope stability coefficient to the rainfall infiltration depth were divided. With the aid of the discrete element method (MatDEM)，a rainfall infiltration and shallow landslide model was constructed，which simulated the whole process of rainfall infiltration and shallow landslide in the inner dump，and explored the fail⁃ ure characteristics of shallow landslide from the perspective of dynamics. The results show that under the rainfall infil⁃ tration conditions， the slope erosion of the inner dump changed from splash erosion groove to runoff or surface flow. With the further infiltration of rainfall，the soil above the infiltration peak began to lose stability as a whole and showed some shallow failure characteristics. The more saturated cohesionless soil tended to exhibit particle flow and slide earlier，thus manifesting themselves as erosion. According to the rainwater infiltration depth，the change of the slope stability coefficient could be divided into three stages:high sensitivity，weakened sensitivity and low sensitivity. The early rainwater was mainly infiltration，but as the depth of rainwater infiltration gradually deepened，the wa⁃ ter transport path gradually lengthened，and the infiltration rate of the later rainwater gradually decreases. At the stage of shallow landslide， all layers of soil in the inner dump showed the rule that the movement speed increased rapidly，maintained short⁃term rapid movement，then gradually decreased，and finally tended to be stable. The movement speed of the landslide surface and front edge soil was always higher than that of the bottom and trailing edge，and most of the kinetic energy converted from potential energy during sliding was dissipated by friction near the sliding zone. Continued rainfall produced new saturated and infiltrated layers，and then shallow landslide would contin⁃ ue to occur. Chemical materials could be added to the slope topsoil to increase the topsoil viscosity，thereby reduc⁃ ing the scale of slope erosion in shallow landslide. The inner dump slope should be stacked at a gentle gradient，which would effectively reduce the kinetic energy accumulation of landslides and increase the friction loss between land⁃ slides during shallow landslide. The obtained stability analysis method and shallow landslide movement characteristics of the inner dump could provide reference for the development of the inner dump disaster prevention and reduction.