## 2 Literature Review
### Prediction of Slope Stability  
Predicting slope stability has been the subject of numerous studies over the last few decades. These research methodologies can be broadly categorized into three groups: the finite element technique (FEM), limit equilibrium method (LEM), and limit analysis method (LAM) [14]. Due to its ease of use, the LEM is one of the most popular approaches among them [15]. However, several idealized assumptions about the LEM lead to its imprecise response. Because it puts strict restrictions on limit state solutions [16] and offers a straightforward calculation procedure, the LAM is commonly used in slope stability [17]. However, it can be difficult to create theoretical formulations of upper or lower bounds when dealing with complicated slope structures and variable soil deposition [14]. Compared to the LEM and LAM, the FEM appears to be a more reliable and adaptable processing technique for slope performance modeling and evaluation [14; 18; 19; 20]. [PERSON] et al. [21] constructed a finite element model to simulate the Bianjiazhai landslide near the Suofengying reservoir at the Wu River in Guizhou Province, China. Their results showed that sudden reservoir level fluctuations had a critical effect on the stability of the slope. In addition, a strength reduction analysis confirmed that the deformation behavior of the slope was mainly a shear-slip phenomenon, and the associated shear zones were identified. In order to accurately and efficiently simulate in situ stress prior to seismic loading, [PERSON] et al. [22] used pseudo-static finite element analysis. They also investigated how sensitive the analysis findings were to the finite element mesh level. The main metric used to assess slope stability is the safety factor [23], which is the ratio of the available shear strength to the equilibrium shear stress along a specific failure surface [4]. Assumptions on the form and location of the failure surface are not required when utilizing the FEM for a slope stability analysis. According to the FEM, failure occurswhen the soil's shear strength is not strong enough to support the sliding force of the slope, and it is feasible to model how displacement and slope failure develop. The FEM often employs the soil shear strength reduction technique to calculate the slope's safety factor [24]. During the slope failure process, soil cohesion \(c\) and internal friction angle \(\varphi\) continue to decrease. According to the literature, no matter how the slope is formed, when it reaches the failure state, the reduced cohesion tends to have the same value. Accordingly, [PERSON] et al. [25] reduced the strength parameters (\(c\), tan\(\varphi\)) of a slope step-by-step through a reduction factor of \(1/N\), and the reductions for the two parameters were equal. When reduced to the failure state, the \(N\) value at this time can be defined as the safety factor of the slope. [PERSON] and [PERSON] [26] calculated the slope's overall safety factor by examining the link between the node displacement and the change in soil strength characteristics (cohesion and friction angle) using the region close to the top of the neighboring slope toe as the chosen node. [PERSON] [27] determined the system's overall safety factor iteratively by adopting a minimal system safety factor value for the material's strength (\(c\) and \(\varphi\)). To determine whether the system was unstable, they then performed finite element analysis using the converted material strength. [PERSON] and [PERSON] [28] used their developed PLAXIS finite element formula to calculate the slope's safety factor and the corresponding sliding surface failure position in addition to the shear strength reduction technique. The idea of shear strength reduction was used by [PERSON] and [PERSON] [29] to assess slope safety factors and the emergence of possible slip surface failure. Additionally, the shear strain in the failure process that extends from the slope's base to its summit (i.e., total shear failure) was classified as slope failure.