Characteristic Study Of Microstructural Mechanics Of Leached Rare Earth Under Wetting-drying Cyccles

An typical ion-absorbed rare earth ore was chosen as the research object.The sample was sampled in the same location by different time.And the basic physical and mechanical testing was carried out.For the samples before leaching,with the technology of metallurgical microscopy,scanning electron microscopy and XRD techniques,the mechanism of strength change of ion-absorbed rare earth ore was described by means of indoor simulated leaching.For the leached ion-absorbed rare earth sample,utilizing conventional triaxial test,Mechanical strength parameters of leached ion-absorbed rare earth sample under different cycles of dry and wet cycles was measured.With the NMR,the reasons why the shear strength vary under different cycles of dry and wet cycles was explained from the microscopic point of view.Finally,the stability of leached ion-absorbed rare earth slope was analyzed by ABAQUS nonlinear finite element method based on strength reduction analysis.The main research results and conclusions of this paper are as follows.?1?During the leaching process of?NH₄?₂SO₄ solution,the primary mineral feldspar hydrolyzed in an acidic environment will form secondary mineral kaolinite with reduced intermolecular attractive force and weakened interparticle connection.At the same time,the resulting"pin-rod-shaped"kaolinite adsorbs on the surface of feldspar minerals,"wrapping"feldspar minerals.Due to the presence of kaolinite combined with water film,the contact area of feldspar particles becomes smaller and the particles are more prone to dislocation.So it reduce the shear strength.?2?The dilatancy of the sample is determined by the confining pressure and the number of wet-dry cycles.Comparing the change in strength after each wet-dry cycle,it can be found that the strength parameters of the sample decreases as the wet-dry cycle increases.?3?Comparing the strength changes after each wet-dry cycle,it can be found that the strength of the sample decreases with the increase of the wet-dry cycle.After the first wet-dry cycle,the decrease of the sample is the largest;similarly,the shear resistance parameter c and?is also the most significant change after the first wet-dry cycle,with a decrease of 27.6%and 8.4%,respectively.?4?Using the NMR test,we can find that the T2 spectrum of the sample increases with the number of wet and dry cycles,and shifts to the right.It shows that with the increase of the number of wet and dry cycles,the internal fractures continue to accumulate and expand,so the porosity increases.The crack propagation is greatest after the first wet-dry cycle.?5?The safety factor of leached ion-absorbed rare earth slope decreases with the increase of the number of wet-dry cycles,and finally will tend to a certain value.After the first wet-dry cycle,the safety factor decays the most up by 14%.It also shows that the effect of wetting and drying cycle has a great influence on the safe operation of leached ion-absorbed rare earth slope.