# One-Dimensional Convolutional Neural Network for Pipe Jacking EPB TBM Cutter Wear Prediction
## 5 EPB Cutting Tool Wear and Machine Parameters  
The EPB TBM (Figure 2) was dressed in different cutter tools, namely, a block bit, reamer bits, and disc cutters. Block bit tools are used to excavate nonabrasive soft-to-medium strength geological formations. Disc cutters are preferred for very dense, well-cemented soil and gravel boulders. Generally, disc cutters perform well in rock, but when a TBM excavate soft ground, disc cutters are exposed to frequent blockage and stop rotating. Therefore, disc cutters are faced with wear due to geological formation changes [41; 42; 43]. In this project, the total number of cutting tools changed to complete a full cutter head was 157: 52 disc cutters, 32 reamer bits, 68 block bits, and 5 leading bits. The cutter tools are shown in Figures 6-9, respectively. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Borehole** & **Depth (m)** & **Soil** & **Soil** & **Test** & **Elastic** & \multicolumn{2}{c}{**Consolidated**} \\
**Number** & **Depth (m)** & **Lossers** & **Soil** & **Lossers** & **Module** & \multicolumn{2}{c}{**Module**} \\  & & **Layers** & **Layers** & **Layers** & **Layers(MN/m\({}^{2}\))** & **Cohesion** & **Friction** \\ \hline No. 1 & 7.50 & Silty clay & Vcs & 6 & 15.97 & 16.4 & 31.04 \\  & 10 & Sandy silt mixed with gravel & Vcs & 5 & 14.76 & 21.4 & 41.37 \\ \hline No. 2 & 16 & Sandy clay & Vsg & 50 & 83.45 & 92.1 & 31.27 \\  & 19.50 & Silty sand & Vsg & 18 & 45.20 & 60.5 & 23.33 \\ \hline No. 3 & 11 & Silty clay & Vcs & 4 & 4.37 & 19.7 & 27.25 \\  & 14.50 & Silty gravel & Vg & 34 & 62.37 & 2.7 & 40.44 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Description of lithologies. Figure 5: Triangular grain size distribution and characteristics: (**a**) Triangular system, (**b**) triangular coordinates for medium classification, (**c**) subclassification of coarse soil and fine-grained soil. Figure 8: Block bits. Figure 6: Disc cutter tools. Figure 7: Reamer bits. In previous studies [44; 45], cutter life was defined as the amount of excavated material divided by the cutters consumed (m\({}^{3}\)/cutter), the hours of boring time divided by the cutters consumed (hours/cutter), and the excavated length by the total number of cutters (m/cutter). In this research, actual cutter life was obtained on the basis of excavated volume per disc cutter wear extent (m\({}^{3}\)/mm) due to the fine- or coarse-grained size of sandy gravel formation and normal or abnormal wear. [PERSON] et al. [46] provided a prediction formula for the wear amount of disc cutter life to evaluate the normal and abnormal wear of disc cutters. The formula of the wear amount of the disc cutter is given in Equation (1). \[E_{f}=\frac{\pi\cdot D^{2}\cdot L}{4\cdot M} \tag{1}\]  
where \(D\) is the tunnel diameter, \(L\) is the excavated tunnel length, and \(M\) is the total amount of normal and abnormal disc cutter wear. During the construction of the water tunnel project, all machine data were recorded in real time. While excavating the tunnel, 32 operational parameters were monitored and recorded. Among the 32 machine parameters, 18 machine parameters were selected for disc cutter wear as the input parameter of the 1D CNN regression model. A descriptive analysis of the machine parameters is shown in Table 3. The selected machine parameters are related to EPB TBM wear issues. Therefore, the thrust force, torque, cutter rolling speed, screw pressure, propulsion speed, screw rotation speed, four sides of earth pressure in the cutter chamber, two different shield jack strokes, gate opening, mud injection pressure, add mudflow, back in injection rate, digging velocity (left), and digging velocity (right) were determined to anticipate the disc cutter life. According to [PERSON] et al. [41], thrust and torque are critical parameters for cutter life because, if the thrust and torque are higher than the requirement, cutter tools are exposed to brittle failure.