## 4 Establishment of a Prediction Model for Dual-Mode Shield Tunneling Parameters  
### Filter Input Feature Parameters  
The predictive model in this study comprehensively considers the influence of various factors, including geological parameters, shield machine excavation parameters, and shield tunneling modes. Therefore, detailed explanations for the parameters mentioned above are provided in the following sections. 1. Composite Geological Characteristics Parameters  
When considering the geological conditions within the Liubai section's left tunnel range, this study employs rock mass rating and the soft-hard compound ratio as in  
Figure 1: Five-fold time series cross-validation diagram. Figure 2: Flow chart of multi-algorithm optimization model. put parameters for composite geological features. According to the national standard 'Code for geotechnical engineering investigation of urban rail transit' (GB50307-2012) Appendix F [25], the geotechnical construction engineering classification of each rock and soil layer revealed by this investigation is carried out. Grade III rock mass predominates along the left tunnel route, accounting for 46.78% of the tunnel length. Grade IV rock mass represents 12.7% of the tunnel length, Grade V rock mass accounts for 38.56%, and Grade VI rock mass covers 1.95%. To better reflect the conditions of alternating soft and hard layers in the composite geological formation, the thickness of the weak soil layer at the excavation face to the total excavation face thickness is defined as the soft-hard compound ratio, representing the composite geological formation. The definition of the soft-hard compound ratio is given by Formula (5):  
\[\mu=\frac{H_{i}}{H_{i}+H_{j}}, \tag{5}\]  
The equation \(\mu\) represents the soft-hard compound ratio, within the range of 0 to 1; \(H_{i}\) is the thickness of the weak soil layer, and \(H_{j}\) is the thickness of the hard rock layer. Operating parameters of shield machine  
The original data in the research phase comprises 220-dimensional parameter indicators. Based on the mechanisms affecting shield tunneling speed, this study primarily considers several excavation parameters as input variables for predicting tunneling speed:  
1. Total Thrust: A more significant total thrust reduces resistance encountered by the shield machine during excavation, enabling faster advancement. As the shield machine progresses, the total thrust must overcome the resistance and friction in the geological layers to propel the machine forward. Therefore, the magnitude of the total thrust directly influences the shield tunneling speed. 2. Thrust Pressure: It represents the force exerted by the shield machine during the excavation process, directly affecting the machine's forward speed in the geological layers. The thrust pressure of the shield machine should be controlled within a specific range to ensure the stability and safety of shield tunneling. 3. Cutterhead Torque: It represents the force exerted by the shield machine during the excavation process, directly affecting the machine's forward speed in the geological layers. The thrust pressure of the shield machine should be controlled within a specific range to ensure the stability and safety of shield tunneling. 4. Cutterhead Speed: The higher the rotation speed of the cutterhead on the shield machine, the stronger its cutting ability, resulting in faster advancement of the shield machine in the geological layers. 3. Shield tunneling mode parameters  
To consider variations in the tunneling state of the dual-mode shield machine, it is necessary to select different excavation modes based on distinct geological conditions and excavation performance. They need to be labeled accordingly to differentiate between the EPB and TBM excavation modes. After multiple test runs, the EPB mode is ultimately labeled 1, and the TBM mode is labeled 3.