# Analysis of Slope Stability in Ion-Adsorption Rare Earth Mine Under In Situ Leaching Condition
## 1 Introduction  
Rare earth element (REE) is a general term for 15 elements in the lanthanide series in the periodic table of elements. Ion-adsorption rare earths are rich in the world's scarce medium and heavy REEs. REEs are not rare in the Earth's crust, but they occur in low concentrations, making them difficult to mine economically [1]. As the global economy develops and technology advances, society's demand for REEs, especially medium and heavy REEs, has surged. Their importance also extends to strategic considerations [2, 3]. Technology's reliance on rare earths means they play a key role in shaping the modern technological landscape and global sustainable development effort [4, 5]. China is a country with abundant rare earth resources in the world. It has rich reserves and advantages such as complete mineral species and REEs, high rare earth grades, and reasonable distribution of mines. Medium and heavy rare earths are mainly distributed in southern regions such as Jiangxi, Guangdong, and Fujian provinces, where there are considerable ion-adsorption medium and heavy rare earth ores. More than 70% of medium and heavy REEs come from ion-adsorption rare earth ores. Due to their low abundanceand limited reserves, medium and heavy REEs possess significant economic and strategic value. Consequently, they have been designated by the Chinese government as a mineral resource for protected extraction [6]. Ionic rare earth is typically found in the weathered crusts of granites and other igneous rocks. The ore body is distributed in layers within quasi-hilly regions formed by weathering, erosion, and scouring. From the surface to greater depths, the mountain where it is located is generally composed of a topsoil layer, a fully weathered layer, a semi-weathered layer, a slightly weathered layer, and bedrock. Rare earth ions are chiefly located in the fully weathered and semi-weathered layers. Due to their highly stable nature, ion-adsorption rare earths cannot be extracted by traditional physical beneficiation methods such as magnetic separation or flotation. However, rare earth ions can be replaced by cations in electrolytes through exchange reactions. Currently, the in situ leaching techniques are the primary method for ionic rare earth mining [7; 8; 9; 10]. (NH4)2 SO4 and MgSO4 leaching solutions are commonly used for in situ leaching. Compared with (NH4)2 SO4 solution, the use of MgSO4 leaching solution can reduce the environmental pollution caused by NH4+. Therefore, the MgSO4 solution is used as a leaching solution in the ion-adsorption rare earth mining area studied. The leaching reaction can be expressed by the following chemical Equation (1):  
\[2[\mathrm{Al}_{2}\mathrm{SiO}_{5}(\mathrm{OH})_{4}]\cdot\mathrm{nRE}_{(8)}^{3+ }+3\mathrm{nMg}_{(\mathrm{aq})}^{2+}=2[\mathrm{Al}_{2}\mathrm{SiO}_{5}( \mathrm{OH})_{4}]_{\mathrm{m}}\cdot\frac{3\mathrm{n}}{2}\mathrm{Mg}_{(8)}^{2+} +2\mathrm{nRE}_{(\mathrm{aq})}^{3+} \tag{1}\]  
As shown in Figure 1, the leachate is injected into the ore deposit through boreholes and injection wells, percolates, and migrates into the ore layer. Finally, the leachate saturated with rare earth ions is collected at the bottom of the ore body. The in situ leaching process of ion-adsorption rare earth mainly involves convection, diffusion, dispersion, ion exchange reaction, and adsorption and desorption of solutes. In the in situ leaching of ion-adsorption rare earth, the landslides represent one of the most deadly potential safety hazards [11; 12; 13; 14]. In recent years, research on the stability and deformation mechanisms of rare earth mine slopes has found that many factors affect the stability of slopes, such as the effect of water on soil mass, slope topography, and the properties of soil mass [15; 16; 17; 18]. Particularly, the leaching solution significantly impacts slope instability and failure in rare earth mines [19; 20; 21]. [PERSON] et al.