## 4 Results and Discussion
### Illustration of Controversies Regarding Effects of Isolation Piles on Tunnel Deformation  
As shown in Table 1, the current understanding of the working mechanism of isolation piles can explain the patterns observed by the author, but it does not fully account for the  
Figure 24: Relationships between horizontal control efficiency and distance between the foundation pit and isolation piles for varying pile lengths: 10 m (**a**), 15 m (**b**), 20 m (**c**), 25 m (**d**), 30 m (**e**), 35 m (**f**), and 40 m (**g**). differing results reported by other researchers. Therefore, this section aims to clarify these controversial conclusions based on the proposed mechanism. Regarding the influence of pile head depth, current research primarily focuses on two aspects: maintaining a constant pile toe depth or keeping the pile length fixed. Firstly, in the case of keeping the pile length constant, a statistical analysis [28] of Figures 13-15 reveals the variation pattern of the control efficiency of isolation piles with respect to pile head depth, as illustrated in Figure 25a. Figure 25a indicates that the trend in the control efficiency of isolation piles can be categorized into three types: monotonic (either increasing or decreasing), unimodal (first increasing then decreasing or vice versa), and oscillatory (changing N times). Specifically, when the isolation pile is near the foundation pit, the horizontal control efficiency exhibits an oscillatory pattern for pile head depths exceeding 20 m, a unimodal pattern for depths between 15 and 20 m, and a monotonic pattern for depths less than 15 m. For piles located in the middle of the foundation pit tunnel, the transition points for these patterns are at depths of 25 m and 15 m, while for piles near the tunnel, the transition points are at 25 m and 20 m. In the case of a constant pile toe depth, the control efficiency can also be divided into three categories, as illustrated in Figure 25b. For isolation piles near the foundation pit,  
of pile lengths studied, which align well with the findings in Table 5. It is noteworthy that the study by [PERSON] et al. [10] found that the control efficiency of isolation piles initially decreased and then increased with increasing pile length, whereas the analysis in this table reveals a trend of initial decrease, followed by an increase, and finally a slight rise. This discrepancy may be attributed to the fact that [PERSON] et al. 's research [10] was based on theoretical analysis, which could not account for the influence of soil displacement fields and tunnel cross-sectional deformation. However, overall, the findings of [PERSON] et al. [10] are largely consistent with the conclusions of this study. Therefore, in practical engineering applications, by referring to this table, one can easily determine the control efficiency of isolation piles by analyzing the range of pile lengths under investigation. Regarding the influence of pile-to-tunnel distance, the variation trend of the horizontal control efficiency of isolation piles is primarily influenced by the pile length and the pile head depth. Based on Figure 24, the pile lengths can be categorized into four groups, and the burial depths into two groups, resulting in a total of six categories, as summarized in Table 6. The controversial conclusions in Table 4 regarding the pile-to-tunnel distance are mainly due to differences in the studied pile lengths and burial depths, which can be well explained by the data presented in Table 6.  
Comprehensive Analysis of the Influences of Isolation Piles on the Horizontal and Vertical Displacement of Tunnel  
The influence of isolation piles on the horizontal and vertical deformation of the tunnel was comprehensively analyzed from three key aspects: the variation patterns, the relative magnitudes of these two deformations, and whether the isolation piles have a positive effect.