# Investigation of Steep Waste Dump Slope Stability of Iron Ore Mine--A Case Study
## 3 Results and Discussion
### Slope Rectification  
The dump profile is mainly characterized by a single-step waste dump with a step height of 78 m, a slope angle of 25\({}^{\circ}\), a soil material cohesion of 4.8 kPa, and an internal friction angle of 25.63\({}^{\circ}\). The current calculation shows that the slope stability does not meet the design specification requirements, and the shape of the slope should be appropriately rectified. Therefore, a rectification scheme for slope morphology is proposed. The cost of reducing the step height or compressing the width of the platform above the slope is very high. Therefore, the present investigation suggests the following plan for the waste dump:  
1. The safety platform is constructed in a top-down manner through controlled material dumping. Initially, level the dumpling line +3948 m within 10 m and clear the  
Figure 11: Particle displacement distribution before rectification: (**a**) top view of the two-dimensional displacement, (**b**) side view of the slope displacement in the \(x\) direction, and (**c**) side view of the slope displacement in the \(y\) direction.  
Figure 10: Waste dump model and particle displacements (m) in the \(x\) and \(y\) directions: (**a**) Slope model before rectification, (**b**) slope displacement in the \(x\) direction, and (**c**) slope displacement in the \(y\) direction.  
slope of any loose stones, large blocks, and other debris to ensure the safety of the excavation work.
2. Construct the safety platform +3938 moving from north to south. The width of the safety platform +3938 is 10 to 12 m. After that, remove unstable loose soil and debris at +3938 m and +3948 m slopes.
3. Gradually lower the safety platform +3938 to create the safety platform +3928 m, while adhering to a 30\({}^{\circ}\) slope angle. This is accomplished with leveling, resulting in a final 10 m wide +3928 m safety platform.
4. Construct the safety platform +3918 from north to south. Clear any unstable loose soil and debris on the slope from +3918 m to +3928 m.
5. Level the safety platform +3918 by lowering it to the safety platform +3908 m along the slope angle of 30\({}^{\circ}\), thereby establishing a safety platform with a width of 10 m +3908 m.
6. Repeat the same procedure to form the +3898 m platform, which is subsequently lowered to form the +3888 m safety platform.
7. During the formation of safety platforms +3908 m and +3888 m, a part of the space may require additional tailings to fill any gaps. The decision on this matter will be made according to the actual conditions during construction on site.  
Figure 12a illustrates the profile of Waste Dump#1 before rectification, with a slope height of 78.0 m and a steep slope angle of 25.43\({}^{\circ}\). The angle of the lower part of the base is 9.14\({}^{\circ}\), and that of the upper part is 22.67\({}^{\circ}\). Figure 12b demonstrates the profile pattern of Waste Dump#1 with a side slope height of 75.3 m and a slope angle of 25.14\({}^{\circ}\). The height of the lower step of the slope is 15.3 m, and the height of the remaining three steps is 20 m. The slope angle of the step is 30\({}^{\circ}\), and the width of the platform is 10 m.  
Figure 12: Profiles of Waste Dump#1 slope before and after rectification: (**a**) before rectification, (**b**) after rectification (note: the domains with dark-green and yellow colors in order represent the quartz schist and discharged material).