Study On Slope Instability Mechanism Of Ionic Rare Earth Mine

The pool leaching and heap leaching techniques used in the early mining of rare earth minerals have caused serious damage to the local ecological environment,caused geological disasters such as soil erosion,landslides and collapses,and posed a serious threat to the safety of local people’s lives and property.In order to reduce the deterioration of the ecological environment caused by backward mining technology effectively and reduce the occurrence of geological disasters,the in-situ leaching process is currently being implemented for the development and utilization of rare earth minerals.Compared with the previous two generations,the in-situ leaching process can reduce the damage to local vegetation significantly and increase the mining rate of rare earths,but directly injecting leaching solution into the rare earth orebody can reduce the structural strength of the orebody significantly.Landslides induced by leaching occur from time to time,which damage the life and property safety of mine production personnel seriously.Taking the ionic rare earth mine soil as the research object,the particle size distribution and fractal dimension of ionic rare earth ore samples are obtained by particle size test,which proves that the particle size distribution characteristics of rare earth ore samples can be obtained by washing sieving method.The matrix suction of rare earth ore samples is measured by tensiometer,and the test data points are fitted by Van Genuchten model,Fredlund & Xing 4 parameter model and Gardner model respectively,and the optimal model of soil-water characteristic curve suitable for low suction section of ionic rare earth orebody is obtained.The particle size distribution and fractal dimension of soil samples at different layers were obtained by soil column test,and the vertical variation mechanism of leaching on soil particle size distribution and fractal dimension was analyzed.The changes of stress-strain and shear strength of rare earth ore samples under different moisture content were tested by direct shear test,and the factors affecting the strength of rare earth ore samples were analyzed.The indoor model box test is used to test the changes of physical and mechanical properties in the process of in-situ leaching.Finally,combined with the physical and mechanical tests of rare earth ore samples,the main mechanism of mine slope instability induced by in-situ leaching process is analyzed.The main conclusions are as follows:(1)The classical soil-water characteristic curve model was used to fit the test data,and it was found that the Fredlund & Xing 4 parameter model is a soil-water characteristic curve model describing the low suction section of the ionic rare earth ore body.(2)The effect of leaching on the particle size distribution and fractal dimension of the orebody was studied through the soil column test,and the results showed that the mechanical migration of particles was the main reason for the change of the particle size distribution of the orebody.(3)The deformation and failure characteristics of ionic rare earth ores samples under different moisture contents were obtained by direct shear test.Taking the sample with fine particle content of 55% as an example,when the normal stress of the ore sample does not exceed 100 k Pa and the moisture content is between 7% and 13%,the ore sample is prone to brittle failure under the action of external force,and a more obvious shear failure surface is produced at the shear surface,and the stress-strain curve shows a “softening” type;When the normal stress of the ore sample exceeds 100 k Pa and the moisture content reaches between 13% and 22%,the ore sample is easy to produce plastic failure under the action of external force,and the stress-strain curve shows a “hardening” type.(4)Ore leaching leads to a significant decrease in the strength of ionic rare earth orebodies.Near the plastic limit moisture content of soil samples,the decay rate of cohesion exceeds 90%,and the shear strength of orebodies is provided by the internal friction angle mainly.The three-dimensional surface mathematical model of moisture content,normal stress and shear strength of orebody is established by polynomial fitting;There is an obvious linear relationship between orebody cohesion and moisture content,but the relationship between internal friction angle and moisture content is not significant.The square method was used to fit the relationship between cohesion and moisture content,and the total stress shear strength formula of ionic rare earth orebody was established.(5)The in-situ leaching process has changed the physical and mechanical properties of the orebody significantly.Under the condition of long-term liquid injection,the leaching solution brings fine particles from the orebody into the pores in the depth of the orebody to produce particle rearrangement,resulting in pore blockage and reducing the permeability of the orebody significantly,which increases the local pore water pressure of the orebody and reduces the shear strength rapidly.Under the action of gravity,once the limit equilibrium condition of maintaining slope stability is broken,the landslide will be induced produce.