The Trial Research On Basic Mechanical Properties Of Ion-absorbed-rare-earth Orebody In Longnan

This paper considers ion-adsorption rare-earth ore of Longnan as the research object,focus on key issues in the process of in-situleaching,we systematically study and discuss the soil water characteristics,the pore distributionthe,the shear strength and the creep characteristics,through a large number of field research,field testing and laboratory testing,main study results as follows:(1)Whether undisturbed ore or remoulded ore,the soil water characteristic curve has the same trend,that water content of the ore body increases with the increase of the matrix suction,and undergoes 3 processes: stable,fast decreasing and slowly decreasing.By fitting the measured datas of soil water characteristic curves,it is concluded that the Fredlund & Xing model is the best models to describe the soil water characteristics of the low suction section of this type of ion-adsorption rare-earth ore.(2)The cumulative total pore volume of undisturbed ore body with 0.92 void ratio is 0.2345 cm3/g,volume of large pores?medium pores and small pores account for 58%?15% and 27% respectively,refiguration remained the same void ratio increased the volume of small pores by 3.0%,it indicated that undisturbed and remoulded ore body have obvious differences in pore size distribution,refiguration remained 0.97 void ratio reduced the volume of small pores by 1.0%,pore size distribution reach the original state.(3)The stress-strain relation of saturated ore are weak strain softening,cohesion of rare earth mineral particles contributed slightly to shear strength,the shear strength is mainly borne by the frictional resistance.The shear strength of unsaturated ore body has a large sensitivity with matric suction,suction strength increases nonlinearly with increase of matric suction,the stress-strain relation changes from hardening type into weak softening type,shear strength of unsaturated ore body increases,internal friction angle of matric suction decreases nonlinearly,it shows that contribution of matric suction to the shear strength of unsaturated ore body is limited.By using power function to fit the relation between matric suction and suction strength,the shear strength formula for ion-adsorption rare-earth unsaturated ore body of Long nan and effective stress formula were proposed.(4)The under deviatoric stress level of no more than 50%,stable creep is mainly appeared,instantaneous elastic deformation accounted for the main part,creep deformation is very small,Samples in a steady state;Deviatoric stress level reaches 70%,unsteady creep occurred,samples damaged in a short period of time with rapid development of deformation,after deceleration creep and equal velocity creep.Confining pressure and moisture content have a great effect on deformation characteristics,the samples reach acceleration creep soon with reduction of confining pressure,destruction time is sooner.Great deformation and softening strength occurred with increase of moisture content.Based on test results,the applicability of the Burgers model?Nishihara Masao model and power function model were discussed,based on Burgers model,nonlinear viscous element was introduced to establish a new visco-elasto-plastic model,which can describe the whole process of creep of ion-adsorption rare-earth ore.