Study On The Stability And Hydraulic Characteristics Of Ionic Rare Earth Tailings Aggregates Under The Action Of Vegetation Roots

As a special geological body with anisotropy,disordered structure,weak cementation or no cementation,ionic rare earth tailings often cause problems such as low survival rate of Ecological Restoration Vegetation,serious shallow water and soil loss and frequent small-scale landslides due to low aggregate stability and weak water retention and storage capacity in the process of ecological restoration,Taking the ionic rare earth tailings under the action of Typical Ecological Restoration Vegetation roots in southern Jiangxi as the research object,through field investigation,indoor geotechnical test,field infiltration test,tailings matrix suction test,theoretical analysis and other methods,this paper systematically studies the characteristic parameters of Ecological Restoration Vegetation roots and the basic physical properties,mechanical stability,particle size distribution and stability index of ionic rare earth tailings under the action of roots The particle size distribution and stability index,permeability characteristics and matrix suction of water stable aggregates,and the interaction relationship were compared and analyzed to explore the stability and hydraulic characteristics of ionic rare earth tailings aggregates under vegetation roots.The main conclusions are as follows:(1)The roots of vegetation were dense at the top and sparse at the bottom,and were mainly concentrated in 0-30cm depth(about 97.8%-99.5%).The root characteristic parameters RL(root length density),RD(root density)and RV(root volume)decreased exponentially with the depth downward.The basic physical properties of rootless tailings do not show a certain law with depth,and the bulk density,water content and porosity of rooted tailings increase with depth.(2)Compared with rootless tailings,vegetation roots effectively reduced the bulk density of tailings,increased the water content and porosity,and changed the basic physical properties of tailings from disorder to order.The partial correlation coefficient method was used to analyze that the bulk density of tailings was significantly correlated with the root characteristic parameters RL,the water content of tailings was significantly correlated with RD and RV,and the porosity of tailings was significantly correlated with RL,RD and RV.(3)The effect of vegetation roots on the mechanical and water stability of tailings aggregates with>5mm size and<0.25mm size is obvious,which shows that the large aggregates decrease and the micro aggregates increase with the depth downward.Under the same depth of each rooted(no)containing tailings aggregate distribution differences,different root system under the action of tailings aggregate presents the regularity,suggests that the vegetation root system effects are not confined to small aggregate cohesive,but the root according to their own growth needs,decide tailings aggregate distribution changes of direction,the passive influence of aggregate structure and stability.(4)By analyzing the rooted(no)containing tailings aggregate stability index,no root tailings aggregate stability index chaotic,not with depth to present certain regularity,including the root mechanical stability of tailings aggregate stability with depth is reduced,the water stability of aggregate with depth change rule is consistent with the mechanical stability of aggregate,Vegetation roots can effectively improve the stability of tailings aggregates and their ability to resist external forces or environmental changes,hydraulic dispersion or external hydrological changes while maintaining their original shape.PLS regression analysis showed that root characteristic parameter RL was the most important factor affecting the stability of rooted tailings aggregates.The larger RL was,the higher the stability of rooted tailings aggregates was.The effects of various types of vegetation roots on the stability of mechanical and water stabilized aggregates were different.(5)Vegetation roots improved the hydraulic conductivity and water storage functions of tailings,and delayed the emergence time of stable permeability rate.The initial permeability rate,stable permeability rate,average permeability rate and total permeability of rooted tailings were higher than those of rootless tailings.Permeability characteristic parameters of rooted tailings are significantly linearly correlated with bulk density and porosity.Based on the correlation between RL and bulk density and porosity above,it can be seen that root length density RL is significantly linearly correlated with permeability characteristic parameters.(6)Vegetative roots can improve the matric suction of tailings.Vegetative roots can not only improve the matric suction of rooted tailings,but also improve the matric suction of rootless tailings at a certain depth(the maximum depth can reach 3 times the root depth)below the root distribution area.The linear fitting of root surface area index(RAI)and match-suction increment △s of rooted(rootless)tailings after drying for five days showed that the influence of vegetation roots on match-suction of tailings was positively correlated with the slope of fitting line.According to the soil water characteristic curve of rooted(rootless)tailings,vegetation roots can effectively improve the matric suction of tailings in saturated and unsaturated states,but the matric suction of rooted(rootless)tailings in high water content(30%or more)shows a certain weakness.