Study On Slope Stability And Leaching Efficiency Of A Novel Growable Pile For Heap Leaching Of Rare Earth

Rare earths are important strategic resources in China,heap leaching is a major leaching process in the process of rare earth mining,it is usually used for ion adsorption rare earth mining in Gan Nan area.However,the traditional rare earth heap leaching process of "leaching first,restoration later" separates rare earth leaching and vegetation restoration,which delays the time of vegetation restoration of rare earth slopes and causes problems such as water and fertilizer loss,low land restoration rate and difficult restoration treatment.Therefore,the development of rare earth heap leaching slope structure and leaching agent injection scheme adapted to vegetation restoration is of great significance to achieve green and efficient mining of rare earth resources.In this paper,a new type of growable rare earth heap leaching structure and leaching agent injection scheme are proposed to address the problem that the traditional rare earth heap leaching structure is not adapted to vegetation restoration.Next,a combination of theoretical analysis,numerical simulation and indoor test is used to study the stability and leaching efficiency of the slope of the new type of growable rare earth heap leaching structure.According to the results,the structural form of the new type of growable heap leaching slope is determined and a engineering measures is proposed to propose the efficiency of leaching.The main conclusion are as follows:(1)A new type of growable rare earth heap leaching structure and leaching agent injection scheme adapted to vegetation restoration is proposed.The heap structure arranges a pipe network at the end of the heap leaching site for lateral liquid injection,divides the rare earth heap into multiple stages for growable heap leaching,and controls the slope height and slope angle of each stage.To improve the leaching efficiency,a weakly permeable layer is arranged in the middle of each stage of the slope,and the heap of the next stage begins after the leaching of each stage.When the lateral injection and stage heap leaching is implemented,the vegetation restoration can be achieved on the top of the slope which reduces the damage and impact of rare earth heap leaching on the environment.(2)A model tank test is implemented to compare the seepage characteristics and destabilization damage modes of the slope between the traditional rare earth heap leach structure and the new growable rare earth heap leach structure.The conclusion shows that the seepage characteristics of the two structures differ greatly depending on the liquid injection method,with the new growable structure slope leach spreading outward from the end injection pipe network in the direction of liquid injection,and the traditional structure slope leach spreading from top to bottom at the top.The destabilization damage of the traditional structural slope is a sudden and rapid damage with a large slip surface,while the damage of the new growable structural slope is a local shallow damage.The test results show that the saturated water content of the new growable structure slope at the slope surface is smaller than that of the traditional structure slope,which makes the new growable structure slope have a later time of damage and better stability.(3)The theoretical analysis and COMSOL numerical simulation are used to study the safety coefficients and damage modes of the slope of the new growable structure under different slope heights,slope angles and lateral stacking lengths.On the same time,the geometric form of the new growable heap structure was optimized based on stability analysis.The study shows that the slope height and slope angle are the main factors affecting the stability of the slope body of the new growable heap leach structure,and the lateral heap length has little effect on the stability of the slope.Based on the stability analysis of the slope,the recommended slope height for the new growable rare earth heap leach structure is 10-15 m and the corresponding slope angle is 57°-45°.(4)COMSOL and model tank tests were used to study the slope of the new growable heap leach structure,and the evolution of the seepage field and influencing factors are determined.Analyzing the leaching efficiency of the slope of the new growable structure,and propose engineering measures to enhance the leaching efficiency of the new growable heap structure.The study shows that the slope angle is the main factor affecting the leaching rate of leaching agent,and the larger the slope angle,the shorter the leaching time required.Considering the leaching agent seepage path,the lateral heap length is the main factor affecting the leaching range of leaching agent in the new growable heap leaching structure.The new growable structure has a shorter leaching time and a larger leaching agent leaching range when the slope angle is greater than 51° and the lateral stacking length is less than 10 m.To improve the leaching range of leaching agent,a seepage field regulation measure of arranging a weakly permeable layer in the middle of the slope is proposed.Numerical calculations and experimental results show that the arrangement of a single weakly permeable layer can increase the leaching range of the new growable slope by 5%-6%.