Safety And Stability Analysis Of Different Particle Size Composition Of Tailings Dam On Dam Safety Under Heavy Rainfall

Tailings reservoir,as a dangerous source of artificial high debris flow,is vulnerable to external impact during operation.Heavy rainfall has great harm to the tailings dam.Therefore,it is particularly important to study this main external cause,at the same time,the tailings with different particle sizes have different physical and mechanical properties,which affect the safety and stability of the dam.This paper mainly studies the safety situation of tailing dam with different particle gradation under the condition of rainfall.The physical and mechanical parameters of the tailings of the stacked sub dams were tested.The tailings of the top sub dam were selected to build tailings sub dam,and the influence of rainfall intensity on dam break was explored.The actual dam body model was built,and the stability of tailings dam under different rainfall conditions and different tailings dam group conditions were simulated by GTS NX software.The main contents and results are as follows:(1)Each sub dam has different particle size distribution.Particle size distribution analysis was made for tailings of the sub dam,and 6 groups with distinct difference in grain size gradation were selected.The non-uniform coefficient and curvature coefficient of different fabrics were calculated.The TST-70 permeameter was used to measure the permeability coefficient of the tailings of different structures.It is found that when the proportion of tailings at 0.154 mm and below is relatively small,the permeability coefficient is at the 10-3cm/s level.When the particle size distribution is relatively uniform,and there is no lack of fine tail sand.the permeability coefficient is at the 10-4cm/s level.The more uniform the distribution of tailings,the smaller the permeability coefficient.Through the triaxial shear strength test of the tailings,the cohesive force and friction angle of the 6 groups of tailings were obtained.The cohesive force is proportional to the non uniform coefficient of the tailings,and is inversely proportional to the curvature coefficient.(2)Tailings of the top sub dam were used as test material,and self-made test device simulated the process of dam failure of tailings sub dam under heavy rainfall.It is concluded that within the distance from the original dam body about the dam height,the sub dam failure with a rainfall intensity of 60 mm/h is the most dangerous.In the range above the height of the dam from the initial position,the dam with a rainfall intensity of 80 mm/h has the most serious hazard.The rainfall intensity is 20 mm/h and non-rain dams have no impact on dam break.With the increasing of rainfall intensity,the capacity of tailings transport is significantly enhanced,and dry tailings have basically no harm to far away from the downstream.(3)A tailings dam in Hunan was selected as the research object.The model was established by using GTS NX software.The rainfall length was different with the rainfall intensity 30 mm/h,and the tailings dam with 6 different particle sizes were considered to analyse the stability of the tailings dam.The safety factor of the tailings dam is positively related to the cohesion and is not significantly related to the friction angle.The safety factor is roughly proportional to the coefficient of inhomogeneity and inversely proportional to the coefficient of curvature.Different fabrics affect the size and distribution of the maximum shear strain.With the increasing of cohesion,the range and size of the maximum shear strain show an increasing trend,so is the shear stress.The tailings of different structures affect the negative pore water pressure through the distribution of particle size,and the more reasonable the particle size distribution,the greater negative pore water pressure.When the rainfall is longer than 4 h,the distribution of particle size affects the vertical hydraulic gradient.The more reasonable the distribution of particle size,the greater the vertical hydraulic gradient,and the worse the permeability.The more dense the dam,the safer the upper surface of the dam.