## 6 Conclusions  
This study focuses on the No. 1 Tunnel project of the Jakarta-Bandung High-Speed Railway, examining the variation patterns and correlations of the tunneling parameters  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Algorithms** & **MSE** & **RMSE** & **MAE** & \(\mathbf{R^{2}}\) \\ \hline ANN & 46.960 & 6.853 & 4.964 & 0.691 \\ DNN & 41.756 & 6.461 & 4.711 & 0.725 \\ BPNN & 50.035 & 7.611 & 5.581 & 0.611 \\ SVM & 84.456 & 9.190 & 6.764 & 0.444 \\ MNR & 64.174 & 8.011 & 6.085 & 0.577 \\ RF & 25.955 & 5.094 & 3.468 & 0.829 \\ \hline \hline \end{tabular}
\end{table}
Table 12: Comparison of the evaluation indexes of the models.  
Figure 15: Comparison of the models’ error values.  
during shield tunneling through volcanic ash strata. The prediction performance of six algorithms in terms of the excavation speed is compared and analyzed.  
(1) In the volcanic ash strata, there is a positive correlation between the slurry pressure and the tunnel depth. The recommended grouting pressure is approximately 0.22 MPa higher than the slurry pressure. The total thrust shows a strong negative correlation with the mud pressure, reaching \(-0.77\) in the \"volcanic ash debris + round gravel\" composite strata. The cutter speed exhibits weak or extremely weak correlations with the total thrust, and the tunneling excavation speed is extremely weakly negatively correlated with the cutter speed.  
The data are derived from the correlation analysis of the shield tunneling parameters in Section 4, as shown in Figure 13.  
(2) In contrast to other strata, the volcanic ash strata exhibits high cementation, compressibility, and heterogeneity. During shield tunneling, the grouting pressure experiences considerable fluctuations. The shield tunneling excavation speed is deliberately slower in volcanic ash strata to minimize strata disturbance. Under the same propulsion speed, the volcanic ash strata demands a higher total thrust for the shield, resulting in significantly larger cutter head torque and a lower cutter speed.  
(3) In the context of predicting the shield excavation speed, the RF model outperforms the others, exhibiting the lowest MSE, RMSE, and MAE. The R\({}^{2}\) reaches 0.829, indicating superior predictive accuracy. Conversely, the SVM and MNR models demonstrate poor performance, suggesting limited suitability for excavation speed prediction.  
Conceptualization, Z.T. and J.Z.; methodology, X.F.; software, X.F.; validation, X.F., J.Z. and B.Z.; formal analysis, X.F.; investigation, X.F., Y.C. and Y.J.; data curation, B.Z.; writing--original draft preparation, X.F.; writing--review and editing, X.F., J.Z. and B.Z.; visualization, Z.T. and X.F.; project administration, Y.C. and Y.J. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available in article.  
Authors [PERSON] and [PERSON] were employed by the company Power China Railway Construction Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.