# Full Life Cycle Evaluation of Stability Pile in High Slope with Multi-Layer Weak Interlayers
## 6 Discussion
### Discussion of the Pile Position (\(L_{y}\))  
In the initial state, the curves of the \(F\)s of the two models showed a similar variation trend of increasing first and then decreasing as the pile position increased from the toe to the top of the slope (Figure 3). This indicated that the curves were both unimodal. The maximum \(F\) of 1.43 in model 1 occurred in the middle of the slope, while that of 1.42 in model 2 occurred in the lower middle of the slope. The results of [PERSON] and [PERSON] [18], [PERSON] and [PERSON] [30], [PERSON] and [PERSON] [48], and [PERSON] et al. [49] illustrate similar conclusions, while different conclusions also can be found [14; 15; 16; 50; 17]. These differences may be a result of the use of different methods and differences in rock and soil masses.  
Figure 12: 10 m below the pile top of Model 1, the correlation between the displacement of the Y direction and \(S_{\mathrm{p}}/D\). **(a–h)**\(S_{\mathrm{p}}/D=\) 1.875, 2, 3,4, 5, 6, 7, and 8, respectively.  
Figure 13: The plastic zone distribution of the middle of two piles of Model 1 with a variety of \(S_{\mathrm{p}}/D\). **(a–d)**\(S_{\mathrm{p}}/D=\) 1.875, 3, 5, and 8, respectively.  
In the 1.35 state, the locations of high compressive stress and high shear stress areas were associated with the depths of weak layers and those of the junctions between the weak layers and other layers. The weak layers controlled the local stress state and may have increased the risk of failure of the pile and slope.  
It is worth noting that the maximum compressive stresses ranged from 13.91 to 16.21 MPa, with an average of 15.12 MPa (Figure 14), and the maximum shear stresses ranged from 6.86 to 8.19 MPa, with an average of 7.48 MPa in Model 1 (Figure 15). In Model 2, the maximum compressive stresses ranged from 10.06 MPa to 29.81 MPa (Figure 14), and the maximum compressive stresses ranged from 4.88 to 17.46 MPa (Figure 15). The distribution of geological materials yielded similar values of stress in Model 1 and large fluctuations of stress in Model 2. Large thicknesses of gravel soil 1, sandy dolomite, and fragmented dolomite 1 have poor mechanical parameters (Table 1), and combining the influence of weak interlayers led to the occurrence of high stress. In other words, the magnitude of stress was strongly controlled by the distribution of the various geological materials.  
Under the limit equilibrium state, the distribution of the plastic zone illustrates that the lower middle to the middle part of the slope may be the optimal position for the stability piles, which is consistent with the result of the initial state. For high slopes with multi-layer  
Figure 14: The correlation between the maximum compressive stress of piles under 1.35 state and pile position. The curve of Model 1 is flat, while that of Model 2 shows considerable fluctuations.  
Figure 15: The correlation between the maximum shear stress of piles under 1.35 state and pile position. The curve of Model 1 is flat, while that in Model 2 shows considerable fluctuations.  
weak interlayers, new potential slip surfaces may occur if the pile is at the toe or the top of the slopes. Piles located in the lower-middle part can effectively support the rock and soil mass behind the pile, reduce the load acting on the mass in front of the pile, and decrease the possibility of multi-stage sliding, which enhances slope stability.  
After the full life cycle evaluation, it can be concluded that piles in the lower middle to the middle part of the slope actively enhance slope stability, resulting in higher or the highest \(F\)s, cutting the continuity of the plastic zone and further improving the safety margin.