## 2 Research Methods
### Numerical Simulation  
Field test data from the underground roadways of the Panlong Lead-Zinc Mine in Guangxi show that water pressure can significantly affect the strata where the roadway is located, with roadway construction occurring in a high hydraulic pressure environment. Therefore, considering fluid-solid coupling more accurately reflects the deformation patterns of the surrounding rock during actual underground roadway excavation. This paper uses the finite difference method software FLAC3D 6.00, which is based on the fast Lagrangian method, to establish a fluid-solid coupling model of the underground roadway. The seepage boundary conditions are determined by referring to the relevant literature [18; 19; 20] and considering the characteristics of high pore water pressure in deep roadways. The model's seepage boundary conditions are as follows: we assume that the surrounding rock of the roadway before excavation is a saturated layer with the pore water pressure as hydrostatic, proportional to the depth of the roadway burial; the seepage boundary conditions are set with a fixed water head at the top, and impermeable boundaries on the left, right, and bottom sides, with the excavation boundary of the roadway being a free seepage boundary, allowing water to freely infiltrate into the interior of the roadway. The model's dimensions utilizing symmetry and the distribution of displacement monitoring points on the surface of the roadway surrounding rock are shown in Figure 1. Due to the symmetry of the model, monitoring is only needed on one side; 14 monitoring points are uniformly arranged from top to bottom on the right side of the roadway as shown in the figure. Displacements at monitoring points 1-14 are denoted as \(h_{1},h_{2},\ldots,h_{14}\). The total displacement \(D\) in the roadway is defined as:  
\[D=2\sum_{i=1}^{14}h_{i}-h_{1}-h_{14} \tag{1}\]  
In simulating the actual construction process of a roadway, the accuracy of the surrounding rock's mechanical parameters is an important factor affecting the results of numerical calculations. To improve the accuracy of numerical simulation results, three types of typical rock samples were selected from the Panlong Lead-Zinc Mine in Guangxi, based on the geological conditions of the ore body, characteristics of the surrounding rocks of the roof and floor, and other engineering geological conditions, for conducting physical and mechanical property tests of typical mine rocks. The three types of typical mine rocks identified are (1) Dolomite (mainly the surrounding rocks of the roof and floor); (2) fresh lead-zinc ore body (ore body group 1); (3) lead-zinc ore stored in the mining area for about 1-2 years, with slight weathering on the ore body surface (ore body group 2). Detailed sampling information for the three typical mine rock samples is provided in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Levels** & **SRC** & **B (m)** & **P (MPa)** & **H (m)** & **W (m)** \\ \hline
1 & III & 400 & 0 & 3 & 3 \\
2 & IV & 500 & 1.5 & 4 & 4 \\
3 & V & 600 & 2.5 & 5 & 5 \\
4 & / & 700 & 3.5 & 6 & 6 \\
5 & / & / & 5 & / & / \\
6 & / & / & 7.5 & / & / \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Level values for each factor. The selected typical rock samples were processed and polished into standard specimens, and conventional triaxial tests were conducted using an INSTRON 1346 type (INSTRON Corporation, Wycombe, UK) electro-hydraulic servo-controlled rigid material testing machine to determine mechanical parameters.