## 4 The Process of Changing Mining Methods in Mines
### Optimization of Structural Parameters of the Stope  
MIDAS is a finite element system that can be better applied to the calculation of mining subsidence and the stability of the mining hollow area in three-dimensional situations, which provides a favorable tool for the calculation and analysis of the stability of the rock body in mining engineering. In this section, MIDAS, a finite element analysis software, is used to simulate the stress and deformation of the roof plate and filling body of the mining field with different structural parameters of the mining field to determine the structural parameters of the mining field suitable for the technical conditions of mining in Luohe iron ore body. Figure 5: Satellite map of the vicinity of the Luohe Iron Mine. When choosing a constitutive model, MIDAS provides many constitutive model options, such as modified Mohr-Coulomb, Mohr-Coulomb, modified Cambridge clay, etc. Since the Mohr-Coulomb constitutive model shows the shear failure and the change of compressive strength of materials such as surrounding rocks and rocks and soils around the ore body in underground mines during the stress process, the Mohr-Coulomb constitutive model is selected for this numerical simulation. The yield function of the Mohr-Coulomb theory model (average stress \(p\) and generalized shear stress q):  
\[p\,\sin\varphi+\tfrac{1}{\sqrt{3}}\Big{(}\cos\theta_{\varphi}-\tfrac{\sin \theta_{\varphi}}{\sqrt{3}}\sin\varphi\Big{)}q=c\,\cos\varphi \tag{1}\]  
In the formula: \(p=(\sigma_{1}+\sigma_{2}+\sigma_{3})/3\);  
\[q=\frac{1}{\sqrt{2}}[(\sigma_{1}-\sigma_{2})^{2}+(\sigma_{2}-\sigma_{3})^{2}+( \sigma_{3}-\sigma_{1})^{2}]^{\frac{1}{2}};\]  
1. Material parameters  
The parameters of the filling dynamics refer to the relevant data of similar mines in China (see Table 2). 2. Model construction  
This simulation is mainly aimed at the ore body at the \(-455\) to \(-560\) m stage. Combined with the current situation map of the mine, the model size was established as X \(\times\) Y \(\times\) Z = 400 m \(\times\) 620 m \(\times\) 500 m. The model is shown in Figure 6.  
3. Simulation scenarios and structural parameters \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \begin{tabular}{c} **Mineral** \\ **Rock Type** \\ \end{tabular} & \begin{tabular}{c} **Modulus of** \\ **Elasticity \(\times\) 10\({}^{4}\)** \\ **(Mpa)** \\ \end{tabular} & \begin{tabular}{c} **Compressive** \\ **Strength** \\ **(Mpa)** \\ \end{tabular} & \begin{tabular}{c} **Tensile** \\ **Strength** \\ **(Mpa)** \\ \end{tabular} & \begin{tabular}{c} **Poisson’s** \\ **Ratio** \\ \end{tabular} & \begin{tabular}{c} **Cohesive** \\ **Force** \\ **(Mpa)** \\ \end{tabular} & \
\begin{tabular}{c} **Friction** \\ **Angle** \\ **(\({}^{\circ}\))** \\ \end{tabular} &
\begin{tabular}{c} **Capacity** \\ **KN (m\({}^{3}\))** \\ \end{tabular} \\ \hline Ore body & 5.9 & 148.6 & 6.43 & 0.20 & 14 & 57.3 & 37 \\ \hline Roof & 5.6 & 49.2 & 3.43 & 0.22 & 7.4 & 50.5 & 25 \\ \hline Floor & 5.6 & 120.8 & 4.35 & 0.22 & 9.6 & 53.5 & 28.4 \\ \hline Filling body & 0.021 & 1.59 & 0.39 & 0.15 & 0.47 & 44.7 & 28.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Table of mechanical parameters of the ore rock. Figure 6: Numerical model map and grid distribution. 5. Analysis of numerical simulation results  
By analyzing the above charts, the following conclusions can be drawn:  
Figure 8: Model 2 tensile and compressive stress analysis. Figure 9: Model 3 tensile and compressive stress analysis. (a) The maximum tensile stress of the roof of the surrounding rock on the upper wall of each stope and the direct roof of the ore body is 2.98 MPa (model 3 condition 2), and the maximum compressive stress of the direct roof of the ore body is 19.2 MPa (model 3). However, the maximum tensile stress of each model does not exceed the tensile strength of each model and is in a relatively stable state.