## 2 Accurate Identification Method of Fractured Rock Structure
### Safety Criteria for the Strength of the Underground Cavern Enclosure of Broken Rock Body  
In identifying the strength criterion of an underground cavern chamber, it is necessary to fully consider the cavern chamber surrounding rock conditions, i.e., groundwater conditions and the location of surrounding rock distribution to propose the safety criterion of surrounding rock strength. Define the safety coefficient of the surrounding rock evaluation unit as the ratio of the maximum principal stress that the unit can withstand to the current maximum principal stress of the unit, where the maximum principal stress that the unit can withstand is calculated according to the strength criterion, and the safety coefficient of the surrounding rock strength criterion of the underground cavern chamber of the fractured rock body is shown in Table 8 below. Study on Inversion of Mechanical Parameters and Deformation and Damage Characteristics of Fractured Rock Masses  
In this paper, taking the underground cavern group of the Liyang pumped storage power station as an example, the mechanical parameters of different fractured rock bodies are solved by using displacement inverse analysis method through real-time monitoring information of stress and deformation monitoring sections in different fractured rock body distribution areas. The model area starts at 443 m in x-direction and ends at 609 m, i.e., 166 m long; starts at 83 m in y-direction and ends at 333 m, i.e., 250 m wide; starts at 116 m in z-direction and ends at 242 m, i.e., 126 m high, and the top arch of the model is about 240 m from the ground. Next, 80\({}^{\circ}\), F54: yield 35\({}^{\circ}\)-55\({}^{\circ}\)/NW/255\({}^{\circ}\)-60\({}^{\circ}\), F57: yield 310\({}^{\circ}\)/NE/270\({}^{\circ}\), F88: yield 275\({}^{\circ}\)-290\({}^{\circ}\)/SW/280\({}^{\circ}\)-85\({}^{\circ}\). The 3D geometry model and the exported model to 3 DEC are shown in Figures 8 and 9. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Surrounding** \\ **Rock Location** \\ \end{tabular} } & \multicolumn{3}{c}{**Factor of Safety for the Strength of the Surrounding**} & \multicolumn{3}{c}{**Factor of Safety for the Strength of the Surrounding**} \\  & \multicolumn{3}{c}{**Surrounding Rock for General Conditions**} & \multicolumn{3}{c}{**Rock Severely Affected by Groundwater**} \\ \cline{2-7}  & **Stable** & **Less Stable** & **Instability** & **Stable** & **Less Stable** & **Instability** \\ \hline Top arch & \textgreater{}1.30 & 1.00\(\sim\)1.30 & \textless{}1.00 & \textgreater{}1.25 & 1.00–1.25 & \textless{}1.00 \\ \hline Sidewalls & \textgreater{}1.25 & 1.00\(\sim\)1.25 & \textless{}1.00 & \textgreater{}1.20 & 1.00–1.20 & \textless{}1.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Safety coefficients for safety criteria for the strength of the surrounding rock in underground caverns of fractured rock bodies. In this paper, the parameter inversion simulation calculation uses three types of rock enclosures with different degrees of fragmentation (III-2 Relative fractured rock, IV-1 Fractured rock, IV-2 Extremely fractured rock). According to the geological conditions revealed by the excavation of the underground cavern group of the Liyang Pumped Storage Power Station, the type of enclosing rock is first determined, and the parameter inversion is carried out according to the monitoring information before and after the corresponding support. In this simulation calculation, the support phase adopts the deployment system anchor support, and a set of anchor rods is deployed every 6 m along the longitudinal direction of the cavern. The specific anchor arrangement is shown in Figure 10 below. The anchor rod selection parameters are shown in Table 9 below. Figure 8: Rhino3D model diagram of fault and plant location distribution. Figure 10: Pictured: 3 DEC anchor model 3D view (**left**) and main view (**right**). Figure 9: Rhino3D plant model drawing and section.