## 3 Results and Discussion
### Weathering Transition Zone Stability Monitoring Criterion
After using the function fitting, it is found that the Logistic function can better characterize the gradient variation characteristics of the axial force of the bolt in the hydraulic fluctuation stage, and the fitting curve parameters of the remaining monitoring points are summarized in Table 6.  
The slope stability criterion is shown in Figure 12. The logistic function can simultaneously characterize the relationship between bolt axial force and pore water pressure in the rainfall infiltration stage and hydraulic fluctuation stage. The parameters \(C_{1}\) and \(C_{2}\) have different physical meanings in different loading stages. Figure 12a shows that \(C_{1}\) represents the preload force of the initial state bolt in the rainfall infiltration stage. The continuous erosion of the slope causes the preload force to decrease. As the erosion failure rate decreases, the axial force tends toward \(C_{2}\). Figure 12b shows that the pore water pressure is large at the initial stage of hydraulic fluctuation, and the anchor bolt axial force corresponds to \(C_{2}\). The increase of seepage cracks during rock sliding leads to a decrease in pore water pressure, and the lateral displacement of the slope increases the axial force of the bolt. When the position of the rock is stable, the axial force of the bolt tends to stabilize at \(C_{1}\). Due to limitations in experimental conditions, the gravity acceleration similarity ratio \(C_{g}\) in this study was set to 1, and this was used as the basic dimension to calculate the derived dimensions. The influence of 1-g condition on the model test is as follows:  
1. In this study, artificial porous media materials were used to simulate the real geological body. However, it is impossible to realize that all physical parameters satisfy the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Variable**} & \multicolumn{4}{c}{**Constant**} & \multirow{2}{*}{\(\mathbf{R^{2}}\)} \\ \hline
**A Data Set from** & **P Data Set from** & \(\mathbf{C_{1}}\) & \(\mathbf{C_{2}}\) & \(\mathbf{P_{0}}\) & \(\mathbf{n}\) \\ \hline ITS-2 & P-3 & 15.74 & 14.33 & 1.87 & 92.35 & 0.73 \\ ITS-3 & P-3 & 17.51 & 12.18 & 1.87 & 115.41 & 0.89 \\ ITS-5 & P-3 & 2.74 & 1.59 & 1.86 & 115.94 & 0.76 \\ ITS-6 & P-3 & 11.09 & 9.43 & 1.87 & 148.25 & 0.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Fitting parameter during hydraulic fluctuation period. Figure 12: The physical meaning of the fitting model: (**a**) Rainfall infiltration stage; (**b**) Hydraulic fluctuation stage. similarity laws in the material research, which results in differences between the deformation characteristics of the model slope and the prototype. 2. The similarity ratio of rainfall time was not considered, and the hydraulic effect caused by rainfall infiltration and groundwater fluctuation may not reflect the real situation [37]. In addition, the distribution of the effective stress field is different from that of the prototype slope, so the failure process of the real slope cannot be fully simulated. 3. A large number of studies have shown that the effective stress level is an important factor affecting the slope failure mode [38; 39]. Since the distribution of the effective stress field in the model test is different from that of the real situation, the failure mode of the prototype slope cannot be accurately simulated. 4. The slope stability monitoring criterion obtained in the model test essentially uses the slope deformation to feedback on the hydraulic failure of the weathering transition zone. Considering the defects of the 1-g model, the monitoring criterion obtained from the physical model test cannot characterize the evolution laws between all monitoring points. The centrifuge model test is an important method for studying the mechanisms of slope disaster under rainfall conditions [40; 41]. Centrifuge test technology can simulate contractive and dilative behaviors in prototype slopes.