## 4 Calculation of working conditions  
Combined with the design of the tunnel excavation in the cross section, four working conditions are selected for the mechanical characterization of the excavation methods in the influence area, and the numerical calculation conditions are as follows: upper and lower step blasting method excavation (UPBM), upper and lower step static method excavation (UPSM), CD blasting method excavation (CDBM), and CD static method excavation \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Area of** & **Excavation** & & & & & \\
**Influence** & **Method** & **Rock Type** & \(\gamma\) & **_E_/**GPa** & \(c^{\prime}\)**/MPa** & \(\varphi^{\prime}\)/\(f^{\circ}\) & \(\upsilon\) \\ \hline \multirow{4}{*}{New tunnels} & Blasting & Malmstone & 23.13 & 2.98 & 0.80 & 27.90 & 0.27 \\  & excavation & Mudstone & 23.89 & 1.10 & 0.33 & 13.77 & 0.38 \\  & Static & Malmstone & 23.13 & 3.98 & 0.97 & 32.23 & 0.23 \\  & excavation & Mudstone & 23.89 & 1.47 & 0.44 & 17.53 & 0.35 \\ \multirow{4}{*}{Existing tunnels} & \(\bullet\) — & Malmstone & 23.13 & 3.58 & 0.86 & 31.48 & 0.24 \\  & & Mudstone & 23.89 & 1.32 & 0.38 & 16.72 & 0.36 \\ \multirow{4}{*}{Overlap zone} & Blasting & Malmstone & 23.13 & 2.59 & 0.69 & 25.60 & 0.28 \\  & excavation & Mudstone & 23.89 & 0.96 & 0.27 & 11.91 & 0.40 \\ \multirow{4}{*}{Metric} & Static & Malmstone & 23.13 & 3.58 & 0.89 & 31.03 & 0.24 \\  & excavation & Mudstone & 23.89 & 1.32 & 0.39 & 16.39 & 0.36 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Table of mechanical parameters for rock modeling in different regions of influence. Figure 10: Grid model for mechanical characterization of tunnel excavation under double-line highway tunnel passing through existing railway. (CDSM), as shown in Figures 11 and 12. The blasting and static method excavation is determined based on the mechanical parameters of the rock body computed by the different perturbation coefficients, D, in the Hoek-Brown criterion. Figure 11: Upper and lower step method excavation process grid model diagrams: I—new tunnel blasting excavation influence area, II—anchor reinforcement area, III—secondary lining support, and IV—initial support; 1—pre-excavation cross-section, 2—upper step excavation, 3—upper step initial support, 4—upper step anchor reinforcement area imposition, 5—upper step peripheral rock influence area imposition, 6—lower step excavation, 7—lower step initial support, 8—lower step anchor reinforcement area imposition, 9—lower step peripheral rock influence area imposition, and 10—secondary lining support. Figure 12: Grid model diagram of excavation process using the CD method: I—blasting excavation influence area of new tunnel, II—anchor reinforcement area, III—secondary lining support, IV—initial support, e1—left upper guide pit area, e2—left lower guide pit area, e3—right upper guide pit area, and e4—right lower guide pit area; 1—pre-excavation cross-section view, 2—left upper guide pit excavation, 3—left upper guide pit initial support, 4—left upper guide pit anchor reinforcement zone applied, 5—left upper guide pit perimeter rock influence zone applied, 6—left lower guide pit excavation, 7—left lower guide pit initial support, 8—left lower guide pit anchor reinforcement zone applied, 9—left lower guide pit perimeter rock influence zone applied, 10—right upper guide pit excavation, 11—right upper guide pit initial support, 12—right upper guide pit anchor reinforcement zone imposed, 13—right-side upper guide pit perimeter rock influence zone imposed, 14—right-side lower guide pit excavation, 15—right-side lower guide pit initial support, 16—right-side lower guide pit anchor reinforcement zone imposed, 17—right-side lower guide pit perimeter rock influence zone imposed, and 18—secondary lining support. The left line tunnel is set as the first excavation tunnel, which is excavated from the inlet (left) to the outlet (right).