## 3 Materials and Methods
### Real-Time Update of Process Simulation Models for Mechanized Tunneling
#### 3.2.1 Selection of Input Parameters for Updating  
First of all, input parameters that might deviate from their predicted value and should therefore be updated must be selected. According to the Pareto principle, selected parameters with the greatest influence on the performance prediction are considered for updating, as updating all parameters would require a disproportionately high data collection and evaluation effort without providing significant added value. As delineated in Table 1, a selection of input parameters is suggested for an update based on an engineering assessment. Depending on the project-specific boundary conditions and objective of the simulation study, further parameters should be considered for an update, such as the conditioning parameters for EPB-tunneling or parameters of the slurry circuit for slurry shield tunneling. A prior project-specific expert assessment is therefore highly recommended. Supporting the selection of parameters for updating, an exemplary sensitivity analysis was conducted by varying the input parameters within a plausible range starting from an initial value. The results are shown in Figure 7. In the conducted sensitivity analysis, the  
Figure 5: (**a**) Raw data of ringbuild duration and (**b**) moving average (q = 10) of ringbuild duration with identified learning curve. Figure 6: Concept for the adjustment process of input data for real-time simulation studies [35]. parameters were varied separately, and uncertainties were discarded in order to achieve comparable results. In this simplified sensitivity analysis, the most frequently expected values should be chosen as initial values, as the analysis only reflects one scenario. In the presented scenario, the following parameters have the highest impact on the project duration: the frequency of disposal trucks, advance, and ringbuild. The influence of the single parameters is highly dependent on the process interactions, available buffers, and performance limits of the system. Surpassing a certain limit, the increase in the performance of the advance and ringbuild production processes no longer shortens the project duration, as a faster advance creates new bottlenecks, and the logistics chain reaches its performance limit. In order to consider uncertainties and the combination of parameter variations in several parameters at the same time, further sensitivity analyses should be carried out in combination with Monte Carlo simulations (MCSs), as demonstrated by [PERSON] [45]. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Abbreviation** & **Process Name** & **Unit** \\ \hline \multicolumn{3}{l}{Core processes} \\ \hline v & Advance speed & [mm/min] \\ \(t_{\text{rb}}\) & Ringbuild duration & [min/ring] \\ \hline \multicolumn{3}{l}{Support processes} \\ \hline \(t_{\text{ext}}\) & Extension pipes and cables & [min] \\ \(t_{\text{main,cw}}\) & Maintenance duration of cutting tools & [min] \\  & \(\bullet\) Number of replaced tools \(n_{\text{discs}}\), Nscrapers, Phbuckets & [pcs/stop] \\  & \(\bullet\) Maintenance intervals \(L_{\text{main}}\) & [m] \\  & \(\bullet\) Penetration p & [mm/rev] \\  & \(\bullet\) Rotational speed U & [rev/min] \\  & \(\bullet\) Working pressure \(\text{p}_{\text{b}}\) & [bar] \\  & \(\bullet\) Geotechnical parameters, if recorded & \\ \(t_{\text{main,tbm}}\) & Maintenance TBM & [min] \\ gr & Annular gap grouting & [m\({}^{3}\)/ring] \\  & \(\bullet\) Amount of injected grout \(\text{m}_{\text{gr}}\) & [m\({}^{3}\)/ring] \\ \hline \multicolumn{3}{l}{Supply and Disposal} \\ \hline fs & Frequency of material supply trucks & [trucks/h] \\ fd & Frequency of muck disposal trucks & [trucks/h] \\ v\({}_{\text{train}}\) & (Mean) Velocity of tunnel transport (train/MSV) & [km/h] \\ \hline \multicolumn{3}{l}{Downtimes} \\ \hline tbf & Time between failure (by cause) & [min] \\ ttr & Time to repair (by cause) & [min] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Selected input parameters for the model update [34].