## 3 Analysis of Slurry Diffusion Test Results
### Analysis of the Influence Degree of Independent Variables
#### 3.2.3 Variable Sensitivity Analysis  
The predominant failure mode observed in the test specimens is the sliding failure at the interface between the anchorage body and the soil. Consequently, an in-depth investigation into the mechanical parameters of this interface is crucial for enhancing the anchoring performance of self-drilling anchors and for establishing design specifications for their application. Based on the results of the comprehensive comparative tests, a sensitivity analysis was conducted to evaluate the influence of each factor on the peak pull-out force, guided by the findings of the range analysis. This analysis provides a more intuitive understanding of the trends in how each factor affects the peak pull-out force, as illustrated in Figure 7. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Factor** & \begin{tabular}{c} **Sum of Squares** \\ **of Deviations** \\ \end{tabular} & \
\begin{tabular}{c} **Degree of** \\ **Freedom** \\ \end{tabular} & **Mean Square** & **F** &
\begin{tabular}{c} **Significance** \\ **Level** \\ \end{tabular} \\ \hline Proportion of fine particles & 11,990.89 & 2 & 5995.44 & 73.02 & **—** \\ Injection pressure & 262.89 & 2 & 131.44 & 1.60 & **—** \\ Water cement ratio & 830.89 & 2 & 415.44 & 5.06 & **—** \\ Error & 164.22 & 2 & 82.11 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Anchor pullout peak variance analysis. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Factor** & \begin{tabular}{c} **Sum of Squares** \\ **of Deviations** \\ \end{tabular} & \
\begin{tabular}{c} **Degree of** \\ **Freedom** \\ \end{tabular} & **Mean Square** & **F** &
\begin{tabular}{c} **Significance** \\ **Level** \\ \end{tabular} \\ \hline Proportion of fine particles & 9.10 & 2 & 4.55 & 4.90 & * \\ Injection pressure & 2.53 & 2 & 1.27 & 1.36 & — \\ Water cement ratio & 1.54 & 2 & 0.77 & 0.83 & — \\ Error & 1.86 & 2 & 0.93 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Analysis of variance of ultimate displacement of bolt. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Factor** & \begin{tabular}{c} **Sum of Squares** \\ **of Deviations** \\ \end{tabular} & \
\begin{tabular}{c} **Degree of** \\ **Freedom** \\ \end{tabular} & **Mean Square** & **F** &
\begin{tabular}{c} **Significance** \\ **Level** \\ \end{tabular} \\ \hline Proportion of fine particles & 439.26 & 2 & 219.63 & 71.08 & **—** \\ Injection pressure & 19.34 & 2 & 9.67 & 3.1 & * \\ Water cement ratio & 9.92 & 2 & 4.96 & 1.61 & * \\ Error & 6.18 & 2 & 3.09 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Anchor body diameter variance analysis. As illustrated in Figure 7, the proportion of fine particles, grouting pressure, and water-cement ratio all influence the peak pull-out force. The peak pull-out force decreases as the proportion of fine particles increases. With increasing grouting pressure, it initially decreases and then rises. The water-cement ratio exhibits a critical value, similar to the anchorage length observed in field tests. Within this critical range, the peak pull-out force increases with a higher water-cement ratio; however, beyond this threshold, it decreases as the water-cement ratio continues to rise. Among these factors, the proportion of fine particles exerts the most significant influence on the peak pull-out force. When the proportion of fine particles is relatively low, the soil exhibits higher porosity, allowing for more uniform and extensive slurry diffusion during grouting. This results in a larger contact area between the anchorage body and the soil, thereby increasing the pull-out resistance of the bolt. Conversely, as the proportion of fine particles increases, the soil porosity decreases, and the distribution of large and small pebbles in the sandy pebble stratum becomes more irregular. This irregularity hinders effective slurry circulation during diffusion, leading to inconsistent diffusion ranges within the same horizontal plane. Consequently, the bonding force at the interface between the anchorage body and the soil becomes uneven.