## 3 Case Study  
### Project Description  
In this study, the tunnel construction project between Qilin Town Station and Dongjiao Town Station of Nanjing Rail Transit S6 Line in Nanjing, China was investigated. The underground section of the tunnel is 1342 m long, the maximum buried depth is about 19.97 m. The cover depth of tunnel varies from 10 to 28 m; The shallowest buried depth is located at the long deep highway near the open excavation section, which is only about 2.5 m. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Unit** & **Strategy A** & **Strategy B** & **Strategy C** & **Strategy D** & **Strategy E** \\ \hline Lower saturated uniaxial compressive strength (\(\delta_{d}\)) & MPa & \(x12\) & \(x12\) & & \\ \hline composite ratio (\(p\)) & / & & \(x13\) & & \\ \hline Comprehensive volume weight (\(\omega_{1}\)) & KN/m\({}^{3}\) & & & \(x7\) & \\ \hline Comprehensive coefficient of lateral earth pressure (\(\omega_{2}\)) & / & & & \(x8\) & \\ \hline Comprehensive saturated uniaxial compressive strength (\(\omega_{3}\)) & MPa & & & \(x9\) & \\ \hline Comprehensive volume weight (\(\alpha_{1}\)) & KN/m\({}^{3}\) & & & \(x7\) & \\ \hline Comprehensive coefficient of lateral earth pressure (\(\alpha_{2}\)) & / & & & \(x8\) & \\ \hline Comprehensive saturated uniaxial compressive strength (\(\alpha_{3}\)) & MPa & & & \(x9\) & \\ \hline Maximum volume weight (\(\psi_{1}\)) & KN/m\({}^{3}\) & & & & \(x7\) \\ \hline Maximum coefficient of lateral earth pressure (\(\psi_{2}\)) & / & & & & \(x8\) \\ \hline Maximum saturated uniaxial compressive strength (\(\psi_{3}\)) & MPa & & & & \(x9\) \\ \hline Advance rate (AR) & mm/min & \(y\) & \(y\) & \(y\) & \(y\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 4: Input parameters of each strategy. During the excavation process, the EPB shield tunneling will encounter very complex and variable strata. The geological conditions of the longitudinal section of the tunnel can be divided into the following three categories according to the rock strength: 1 Full-section soft rock/soil (accounting for 47%), 2 full-section hard rock formations (29%), and 3 upper-soft lower-hard composite formations (24%). The ever-changing geological conditions will have a great impact on EPB shield tunneling, leading to great difficulties in the prediction of EPB shield tunneling parameters. Therefore, a high-precision shield tunneling parameter prediction model is urgently needed. The geological profile of the longitudinal section of the tunnel is shown in Figure 5, which clearly shows the various strata that will be encountered during the excavation process. The upper part is mostly clay, silty clay, residual soil, etc. While the lower part is mostly granite or ash with different degrees of weathering. Meanwhile, due to the special geological conditions in Nanjing, there are still individual karst caves in this area. In order to ensure the safety of shield construction, those karst caves were fulfilled with water glass grouting before. The physical and mechanical parameters of each soil layer are presented in Table 2, these parameters play a key role in the operating parameters of the shield tunneling. The geological profile of the shield tunnel approach is shown in Figure 6, and various geological conditions that will be encountered during the excavation process are clearly exhibited.