## 4 Design and Stability Analysis of Surrounding Rock-Supporting Structure of Shaft
### Numerical Calculation Model and Model Parameters  
According to the actual situation in the field, the magnitude of the horizontal anisotropic geostress in the shaft is almost equal and the sections are circular. The convergence  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Well Circle** & \multicolumn{3}{c}{**Resin Anchor Rod (End Anchor)**} & **Concrete** \\  & **Shed Distance d\({}_{1}\)** & **Diameter \(\Phi\)** & **Length L** & **Row Spacing d\({}_{2}\times\) d\({}_{3}\)** & **Thickness t** \\  & **(m)** & **(mm)** & **(m)** & **(m)** & **(mm)** \\ \hline Original plan one & 1.5 & 22.0 & 2.5 & 1.0 \(\times\) 1.2 & 600 (C30) \\ Original plan two & 1.2 & 22.0 & 2.5 & 1.0 \(\times\) 1.2 & 700 (C30) \\ \hline \end{tabular}
\end{table}
Table 6: Initial support design.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & & \(\mathbf{P_{\max}}\) & **K/** & \(\mathbf{u_{\max}}\)/ & **E/** \\  & & **(MPa)** & **(MPa\(\cdot\)m\({}^{-1}\))** & **(mm)** & **(GPa)** \\ \hline \multicolumn{5}{c}{Well ring (No.28 A-shaped I-beam)} & 0.29 & 230 & 31 & 210 \\ \multicolumn{5}{c}{Anchor rod} & 0.31 & 12 & 150 & 180 \\ \multicolumn{5}{c}{High-strength anchor} & 0.46 & 25 & 220 & 220 \\ \multicolumn{5}{c}{t = 600 mm} & 2.48 & 1023 & 28 & 30 \\ \multicolumn{5}{c}{C30} & t = 700 mm & 2.88 & 1214 & 29 & 30 \\ \multicolumn{5}{c}{C35} & t = 700 mm & 3.36 & 1275 & 26 & 31.5 \\ \hline \end{tabular}
\end{table}
Table 7: Characteristic curve parameters of the supporting structure.  
Figure 9: Vertical shaft excavation and supporting process: (**a**) design of well circle support; (**b**) design of support for well circle and anchor rod; (**c**) design of well circle, anchor rod, and concrete support.  
constraint method is, therefore, applied in this paper to calculate the rock support structure stability and FLAC\({}^{\text{3D}}\) software is used to numerically solve the strain-softening model for equivalently jointed plutons. The structure dimensions for building the vertical well computational model are shown in Figure 10a and the model boundary conditions are shown in Figure 10b,c, where \(P_{\text{v}}\) is the vertical principal stress, \(P_{\text{H}}\) is the maximum horizontal principal stress, and \(P_{\text{h}}\) is the minimum horizontal principal stress. During the excavation process, the section height was 2 m and a total of 30 excavations were cycled. The surrounding rock GRC was calculated using an equivalent two-dimensional model [39], as shown in Figure 10c. Suppose the virtual support pressure \(P_{\text{i}}\) is gradually released, each release is 2% of the original rock stress, and the release cycle is repeated 50 times. The relationship curve between the surrounding rock pressure and rock displacement is obtained, and the model calculation parameters are listed in Table 3.  
The reliability of the strain-softening model for deep weak rock masses is tested using numerical simulation methods to calculate and analyze the stability of the support design system in combination with the actual damage of the on-site supporting structure and on  
Figure 10: The numerical model; (**a**) Model size picture; (**b**) Model longitudinal section boundary conditions; (**c**) Model transverse section boundary conditions.  
site observations. The ideal elastoplastic model and equivalent jointed rock strain-softening model are used to calculate the stability of the surrounding rock support structure based on the Mohr-Coulomb criterion.