# Analysis of Slope Stability in Ion-Adsorption Rare Earth Mine Under In Situ Leaching Condition
## 3 Results and Discussion  
### Analysis of Seepage in Rare Earth Mine Slopes  
According to the previously described model and relevant initial conditions, pore water pressure distributions in the rare earth mine slope during each injection period from 0 to 77 days were simulated using SEEP/W. The results illustrate the pore pressure distribution in the rare earth mine slope for each period, as shown in Figures 4 and 5. It should be noted that these figures only present the change trend of different paremeters, not present the real situation on site. Figure 4a illustrates the distribution of pore water pressure under the initial conditions (0 d), indicating that before the commencement of injection, pore water pressure gradually decreases from bottom to top along the groundwater level. Pore pressure is zero at the groundwater level, with the maximum negative pore pressure at the crest and the maximum positive pore pressure at the base of the slope. Figure 4b-h shows the distribution of pore water pressure at different times during leaching. It could be found that as the injection period progresses, the leaching solution infiltrates further into the slope. The negative pore water pressure (matric suction) within the slope gradually diminishes, and negative pore water pressure across the entire weathered layer begins to rise. The area around the injection wells is the first to be influenced by the infiltration of the leaching solution, leading to a steady rise in pore water pressure. As a result, the contour lines become denser, and a high-pressure zone develops parallel to the slope surface. By injection of 30 days, this high-pressure zone has expanded to encompass most of the weathered mineral layers. Figure 5 shows the distribution of pore water pressure at different times during the push-water operation of in situ leaching. It can be observed from Figure 5 that the negative pore pressure in the fully weathered layer continues to increase, with the seepage line rising most rapidly at the bottom of the slope due to leaching solution deposition. As the injection period extends, the injection and recovery rates stabilize, entering a steady seepage phase where the seepage line remains largely unchanged except for small fluctuations in moisture content around the injection wells. Post-injection, the range of increased negative pore pressure on the slope widens, resulting in a higher likelihood and extent of instability. At this point, the seepage line rises to 32 m and intersects with the slope surface, with the downhill side of the intersection experiencing positive pore pressure. An increase in water level reduces effective stress. According to [PERSON]'s effective stress principle, effective stress mainly refers to the pressure between soil particles. When this pressure decreases, the friction between soil particles diminishes, reducing the soil's shear strength and causing deformation (compression) and reduced soil strength. Furthermore, on the one hand, the leaching solution infiltration causes the migration of soil particles, on the other hand, the leaching solution replaces the rare earth ions in clay minerals. This physical-chemical coupling effect of the leaching solution leads to the decline of soil shear strength. This greatly reduces the soil's resistance to shear deformation and failure, significantly increasing the probability of slope instability [38]. Additionally, the increased moisture content in the slope soil heightens its self-weight stress, thereby increasing the downward sliding force. In the process of in situ leaching, the seepage line must be elevated to align with or even exceed the upper surface of the ore layer to enhance resource recovery. As a result, the injection intensity needs to be continuously increased; however, this may lead to greater deformation of the slope and potential landslides.