Study On Rainwater Infiltration Characteristics And Shallow Failure Mode Of Inner Dump Of Open Pit Coal Mine

The number of inner dump of open pit coal mines has increased year by year,and the scale has been increasing year by year.Although the site selection and dumping scale of the inner dump have been carefully designed before dumping,the overall stability during and after dumping was ensured.However,the loose and low-strength characteristics of the soil in the inner dump make it prone to shallow instability and damage under rainfall conditions,which seriously threatens the safety of mine production and the safety of life and property.Therefore,the study on rainwater infiltration characteristics and shallow failure mode of inner dump slope is the basis of early warning and prevention of inner dump instability.In this paper,the inner dump of yuanbaoshan open pit coal mine is taken as the research object,the physical properties of the soil in the study area are analyzed,the indoor test model of rainwater infiltration characteristics is built,and the seepage characteristics of the typical design section of the inner dump are simulated and analyzed by using seep/w in Geostudio software.The main research results are as follows:(1)Through the study of the hydraulic and mechanical properties of the soil in the inner dump,it is shown that the relationship between the saturated permeability coefficient and the void ratio conforms to the form of quadratic parabola and power function.The unsaturated strength parameters of soil materials increase rapidly and then slowly with the increase of dry density,and the turning point is when the dry density is 1.5g/cm~3.(2)The failure mode of rainwater infiltration in the inner dump is summarized in four parts,namely the splash erosion stage,runoff erosion stage,traceability erosion stage,through the erosion and destruction stage.The peak pore water pressure and the volume moisture content stability value decrease with the increase of dry density,and the response time of the sensor is also delayed with the increase of dry density,which indicates that the impermeability of soil increases with the increase of dry density.(3)Compared with the classic Green-Ampt model,the calculation results of the Green-Ampt improved model have a significant improvement in prediction accuracy,especially in the shallow range,an average increase of 81.68%.A method for analyzing the stability of shallow slopes considering the characteristics of rainwater infiltration is proposed,and the discriminant equation of shallow landslides under infiltration is deduced.(4)Using seep/w to simulate and analyze the cumulative infiltration volume,pore water pressure distribution,and zero water pressure line migration of soils with different dry densities in the inner dump under certain rainfall conditions.It is found that with the increase of dry density,the infiltration capacity of soil decreases,the cumulative infiltration is small,the influence depth is shallow,and the zero water pressure line moves slowly downward,It indirectly reflects that the soil has strong impermeability and instability resistance;On the contrary,the result is opposite.