## 4 Digital Twin Modelling Methodology
### TBM Twin Modelling  
The TBM design includes the data from 2D and 3D design charts, design dimensions of electric and mechanical devices, CAD, and sensor-based data of the physical TBM for the validation purpose of the TBM model. A detailed TBM design is shown in Figure 6. The physical model of the TBM is a general hard rock open gripper TBM with a tunnel diameter of 8.5 m selected for the description of the framework. The TBM has hard rock drum-type cutterheads with single- and double-disc cutters. The cutter shield has a design load of 300 \(\mathrm{KN/m^{2}}\) with a boring stroke length of 1800 mm, having four propelling cylinders. Data are the core elements in the digital twin paradigm. The goal is to obtain precise and accurate information to better develop the digital twin-based TBM model and record the data during tunnel construction. The TBM design includes the data from 2D and 3D design charts, design dimensions of electric and mechanical devices, CAD, and sensor-based data of the physical TBM. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Type of Data** & **Properties** & **Name** & **Unit** & **Min Value** & **Max Value** & **Average Value** \\ \hline \multirow{4}{*}{Input} & \multirow{4}{*}{Machine parameters} & Boring energy & (\(\mathrm{N/mm^{2}}\)) & 0.9 & 24.9 & 11.97 \\  & & RPM & (\(\mathrm{Rev/min}\)) & 2.1 & 5.4 & 3.70 \\  & & Torque & (\(\mathrm{KN/m}\)) & 100 & 2700 & 1336.34 \\  & & Thrust force & (\(\mathrm{KN}\)) & 1502 & 8239 & 3871.56 \\  & & Speed & (\(\mathrm{mm/min}\)) & 25 & 58 & 44.98 \\  & & Gripper pressure & (\(\mathrm{bar}\)) & 184 & 249 & 197.65 \\  & & Total revolution & (\(\mathrm{Rev/min}\)) & 61 & 188 & 106.94 \\  & & Rock properties & Q-value & Q-value (theo) & 3 & 4 & 3.75 \\  & & & Q-value (TBM) & 2 & 5 & 3.91 \\ \hline \multirow{2}{*}{Output} & \multirow{2}{*}{Penetration Advance rate} & \(\mathrm{mm/rpm}\) & 8 & 14.8 & 12.19 \\  & & Advance rate & \(\mathrm{m/h}\) & 1.26 & 3.69 & 2.73 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of selected TBM data. Figure 6: Details of TBM 696: (**a**) tunnelling system, components, and their arrangement; (**b**) cutterhead with the arrangement of components; (**c**) TBM 696 photograph. The TBM structure created for the program in a gaming environment and Python consists of several steps. First of all, the required libraries are requested, and then, using the required libraries, all the variables involving the process are declared, such as working time, simulation time, etc. These variables are used in all the processes performed by the person operating the machine. The process methods are defined for every process to obtain the times for the simulation, and the machine environment is created, in which all the states and variables are set to their initial positions: working and not working. Furthermore, the methods in the machine environment are defined for required modification in the machine operation. Finally, the results, such as the rotation speed, and cycle time are shown. The TBM digital twin model is linked with the cloud database and depicts the actual progress in the virtual environment. A brief overview of the visual demonstration is shown in Figure 7.  
The most important part of the TBM is the cutterhead design, which is very sensitive to the performance of the TBM. The cutterhead is equipped with seventeen-inch disk cutters, including fifty single- and four double-disk cutters in the center. The rotation of the cutterhead causes the discs to roll in concentric tracks on the tunnel face. The cutterhead also contains six buckets. The excavated muck is collected by the buckets with the rotation of the cutterhead and deposited on the belt conveyor via the muck ring. The cutterhead is equipped with ten water injection nozzles to reduce the temperature and dust formation at the tunnel face. The main drive consists of the housing, main bearing, ring set, pinions with bearings and shaft, planetary gears, electric motors, safe sets, sealing systems (inner/outer), and brake.