# Analysis of Mining Waste Dump Site Stability Based on Multiple Remote Sensing Technologies
## 3 Methodology
### Limit Equilibrium Method  
Limit equilibrium (LE) methods have been widely utilized to obtain approximate solutions for stability problems in soil mechanics, due to their simplicity and accuracy [58]. There have been many LE methods developed for slope stability analysis, such as the ordinary method of slices, [PERSON]'s modified method, [PERSON]'s generalized procedure of slices and [PERSON]'s method [59; 60; 61; 62; 63]. These methods are based on the assumption that the failure surface is in simple shapes, e.g., a plane, circular arc or log spiral surface. These assumptions may not be particularly well founded, but often give acceptable results. Overall, [PERSON]'s simplified method is the most popular method since it is simple and yields results close to the rigorous limit equilibrium in many practical problems [64]. Therefore, the [PERSON]'s simplified method was used in the numerical simulation of the dump's stability. The slope of a dump site is more complicated than a natural slope in many ways. First, there are always several platforms along the slope, which makes mechanical analysis difficult. Second, the slope of a dump site is usually a mixture of loose top soil and fragmented rocks, instead of pure rock slope or soil slope. It is usually piled with gravel and the gaps are filled with soil brought by rainfall, which results in a special slope. Due to the complexity of the causal factors, the characteristics of the slope-forming materials are non-uniform and have a variety of severity, cohesion and internal friction angles. Because of the existence of multiple weak aquifer layers, the stability of weak layers in a dump site must also be attended to. In consideration of the variations in the parameters, stability analysis was carried out base on different parameters and a numerical simulation was carried out along three different slope profiles to estimate their LE state. The locations of the three profiles are depicted in Figure 6, where two platforms divide the MM\({}^{\prime}\) and NN\({}^{\prime}\) profiles into three parts and one platform divides the KK\({}^{\prime}\) profile into two parts. In the limit equilibrium analysis, the choice of parameters directly influences the results of the numerical simulation, no matter how the failure surface is assumed. The geometrical and mechanical characteristics of the slope were examined during field investigation. The values of these crucial parameters (e.g., the gravity density \(\gamma\), cohesion and internal friction angle \(\phi\)) were determined by statistical analysis on samples collected during the field investigation. It was generally believed that the internal friction angle of the slope depended on the mutual friction between different rock fragments because their particle grading and lithology were different. Since there is no cohesion between different rock fragments, the natural slope's limit angle, formed when the mining wastes were first dumped, was considered the internal friction angle. After investigating the limit angles of 31 different spots on the dump site, an average internal friction angle (\(\phi\)) of 38 degrees was selected for the simulation. The cohesion of the slope usually depended on the cohesive force of the soil between the gravel. The soil between the gravel is brought by rainfall, precipitated between the gaps and compacted after a very long time. Since the soil was already disturbed and reshaped, it was hard to collect the original samples to detect the cohesion. In addition, the soil was filled by rainfall and its characteristics changed greatly, which was identical to mixed surface filling soil. Therefore, a cohesion value of 12, for mixed filling soil in this area, was used for the simulation. In the numerical simulation of the Xudonggou dump site, two types of failure surfaces were simulated, a plane surface and a circular arc surface.