# Research on the Laws of Overlying Rock Fracture and Energy Release under Different Mining Speeds
## 4 Numerical Simulation of Influence of Mining Speed on Energy Release in Mining Field  
### Numerical Simulation and Scheme  
The simulation employs borehole columnar data from the 2-2 coal seam in a mine located in Shaanxi Province. The 112201 fully mechanized mining face has a buried depth ranging from 313 to 400 m, and its overall trend aligns north-south. A numerical simulation model diagram is constructed based on these conditions. The working face extends 1047 m in strike and 200 m in dip, with a buried depth varying between 313 and 400 m. A three-dimensional model is established using Ansys, adhering to the geological conditions of the coal seam. The simulation encompasses a range of 400 m in length, 400 m in width, and 150 m in height. Figure 12 displays the model diagram, and Table 2 presents the mechanical parameters of the coal and rock mass.  
In this calculation, the D-P yield criterion is employed to assess the failure of the rock mass [40; 41; 42]. Both sides and the bottom of the model are firmly constrained. The model's  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Rock**} & \multirow{2}{*}{**Thickness/m**} & \multicolumn{2}{c}{**Volumetric Weight/**} & \multirow{2}{*}{**Elastic Modulus/ GPa**} & \multirow{2}{*}{**Poisson Ratio**} & \multirow{2}{*}{**Cohesion/MPa**} & \multirow{2}{*}{**Friction Angle/°**} & \multirow{2}{*}{**Tensile Strength/MPa**} \\  & & & & & & & \\ \hline Silstone & 4.2 & 2.36 & 27.02 & 0.19 & 2.9 & 38.65 & 1.44 \\ Fine sandstone & 13.5 & 2.36 & 16.53 & 0.23 & 2.5 & 30.56 & 1.2 \\ Mudstone & 10.71 & 2.42 & 23.16 & 0.2 & 2.85 & 38.88 & 1.41 \\ Medium sandstone & 35.29 & 2.28 & 24.03 & 0.18 & 2.26 & 35.14 & 1.22 \\ Fine sandstone & 3.37 & 2.38 & 19.18 & 0.21 & 2.24 & 35.49 & 1.33 \\ Coal & 6 & 1.33 & 9.52 & 0.21 & 0.99 & 37.41 & 0.5 \\ Fine sandstone & 5 & 2.38 & 19.18 & 0.21 & 2.24 & 35.49 & 1.33 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The table shows the mechanical parameters of coal and rock mass.  
Figure 12: The figure shows a three-dimensional geological model.  
bottom is restricted to vertical displacement, and a uniform load of 4.25 MPa, equivalent to the gravity of the overlying rock, is applied to the top of the model.  
The model's size and the node traversal unit program impose constraints; if the size division is overly dense, calculations can become exceedingly slow or even impractical. Given that the focus is on exploring the difference in elastic energy before and after each unit time step iteration, a differentiated approach to grid sizing is adopted. The coal seam unit close to the mining field employs a square grid with a 2 m edge length, while the rock layer situated farther from the coal seam uses a square grid with an 8 m edge length.  
Utilizing the model's equilibrium time step size for simulating the process of stress transfer and energy release can qualitatively delineate the temporal evolution of stress adjustment in actual mining activities [43; 44; 45; 46]. This study examines the impact of mining speed on the elastic energy release in the mining field, considering two critical parameters: the single excavation amount and the balanced time step. The simulation scheme is articulated as follows: the single excavation amounts are designated as 5, 10, 15, and 20 m, respectively. Correspondingly, the single time steps are established at 300, 600, and 900 s, respectively. The total excavation amount is constrained to 40 m, resulting in continuous excavation times of 8, 4, and 2, respectively. The goal size is maintained at 50 m in all scenarios.