# Full Life Cycle Evaluation of Stability Pile in High Slope with Multi-Layer Weak Interlayers
## 5 Result
### The Effect of the Pile Position (\(L_{y}\))  
In the initial pile positions from toe to top of the slope, the \(F\)s were 1.33, 1.34, 1.33, 1.35, 1.39, 1.40, 1.42, 1.42, 1.43, 1.43, 1.41, 1.41, 1.40, 1.39, 1.39, and 1.35 in Model 1 (Figure 3). Except for four piles in the lower part and one at the top of the slope, all the \(F\)s > 1.35, satisfying the requirement of GB 50330-2013 [32]. In Model 2, \(F\)s were 1.31, 1.34, 1.35, 1.36, 1.38, 1.42, 1.40, 1.39, 1.38, 1.38, 1.39, 1.39, 1.39, 1.39, and 1.38 from toe to top of slope (Figure 3). The \(F\)s > 1.35 as long as the pile was located between the toe of S2 and the top of the slope. Only the runs with \(F\)s > 1.35 could be further evaluated in the 1.35 state. The results of the 1.35 state show the stress distribution (Figure 4). For the signs in the figures, the compressive stress was negative and the tensile stress was positive. The following features are displayed in the maximum principal stress contour under the 1.35 state. Firstly, the pile fronts exhibited one or two high compressive stress areas, with magnitudes significantly lower than those behind the pile (Figure 4a). Secondly, the compressive stress where the pile touched the weak interlayer was higher than in other areas. The high compressive areas predominantly appeared in fragmented dolomite beneath the bottom-most weak interlayers (Figure 4b,c). The piles at S2 and S3 exhibited two high-compressive areas along the bottom of fragmented dolomite 1 and the bottom-most weak interlayer (Figure 4c). Thirdly, low-magnitude tensile stress occurred at the top of piles; this was to ensure the continuity of deformation, as model disengagement was not allowed (Figure 4a). One or more high shear stress areas appeared at the pile front or back, and the maximum shear stress usually occurred at the junction between fragmented dolomite and the weak interlayer (Figure 5a). Figure 3: Correlation between safety factors and pile position. The horizontal dotted line represents a safety factor (\(F\)) of 1.35. The vertical dotted lines represent the locations of the slopes and the platforms. Similar to the principal stress, the high shear stress areas were mainly distributed in fragmented dolomite under the bottom-most weak interlayer in the two models. In addition, high shear stress areas were also found at the stratigraphic junction in Model 2 (Figure 5b,c). It was assumed that the slopes had slid along the bottommost weak interlayer in Model 1, and several shear bands may have existed in Model 2, leading to multistage sliding. Figure 6 presents the plastic zone distribution of the two models with a variety of pile positions under the limit equilibrium state. There was the continuous presence of plastic zones through the top of the pile, as the pile was at the lower part of the slope (Figure 6a,d). The plastic zones were distributed at the pile fronts and the lower part of the slope if the pile positions were set at the top of the slope (Figure 6c,f). By comparison, the piles located in the middle of the models effectually cut the continuity of the plastic zone, thereby actively improving slope stability and resisting sliding (Figure 6b,e). Figure 4: Maximum principal stress contour of the 1.35 state. (**a**) Maximum principal stress distribution of the piles in Model 1 and Model 2, where \(L_{y}\) = 45.8 m. (**b**) Maximum principal stress distribution of the pile fronts of various pile positions in Model 1. (**c**) Maximum principal stress distribution of the pile fronts of various pile positions in Model 2. Figure 5: Maximum shear stress contour of the 1.35 state. (**a**) Maximum shear stress distribution of the piles in Model 1 and Model 2, where \(L_{y}=45.8\) m. (**b**) Maximum shear stress distribution of the pile backs of various pile positions in Model 1. (**c**) Maximum shear stress distribution of the pile backs of various pile positions in Model 2. Figure 6: Plastic zone distribution of the two models, both with a variety of pile positions under the limit equilibrium state.