# Applicable Conditions of Room-and-Pillar Mining Goal Treatment Methods under a Traffic Load
## 4 Engineering Case Analysis  
The reconstruction and extension project of the Jixi section of the Dan-A national highway is a first-class highway with a design speed of 80 km/h and a roadbed width of 25.5 m. The starting and ending pile numbers of the project are K1600 + 000-K1651 + 498.739,  
Figure 6: Judgment process of the treatment method. (Note: The depth of the goat area is less than 1.5 times the maximum load disturbance depth because it was considered that the coal pillar and roof of the room–pillar goat area had a certain bearing capacity. If its bearing capacity was more than 1.5 times the sum of the dead weight of the overlying strata and the additional stress caused by traffic load, the room-pillar goaf was considered to be capable of remaining stable for a long time under traffic load). and the total length of the route is 51.478 km, among which the old goat areas are K1605 + 000-K1628 + 660 and K1631 + 985-K1647 + 100, with a total length of 38.775 km. The road location map is presented in Figure 7.  
Geophysical exploration, drilling, laboratory tests, and data collection were conducted on the room-and-column goat during the reconstruction and extension project of the Jixi section of the Dan-A national highway. The relevant data for the goat are presented in Table 8. Considering the design documents, the traffic load parameters of the road sections corresponding to the goat areas are presented in Table 9:  
Taking the analysis of the K1631 + 985-K1632 + 035 pile number as an example, this study expounded the applicability analysis of the treatment method of room-and-pillar mining goat areas in detail, in combination with the evaluation process of the treatment method presented in Figure 6. Firstly, the traffic load parameters presented in Table 9 were included in Formula (1), and the maximum load disturbance depth of the road within the service life was calculated to be 14.89 m. In comparison to the depth of the room-and-pillar \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Pile Number Range** & \begin{tabular}{c} **Mining** \\ **Depth (m)** \\ \end{tabular} & \begin{tabular}{c} **Coal Pillar** \\ **Height (m)** \\ \end{tabular} & \begin{tabular}{c} **Coal Pillar** \\ **Width (m)** \\ \end{tabular} & \begin{tabular}{c} **Coal Pillar** \\ **Spacing (m)** \\ \end{tabular} & \
\begin{tabular}{c} **Roof Strength** \\ **(MPa)** \\ \end{tabular} &
\begin{tabular}{c} **Base Plate** \\ **Strength (MPa)** \\ \end{tabular} \\ \hline K1626 + 400–K1626 + 500 & 18 & 1.3 & 10 & 8 & 0.50 & 13 \\ K1627 + 145–K1627 + 423 & 32 & 1.5 & 10 & 8 & 0.50 & 13 \\ K1627 + 945–K1628 + 433 & 20 & 1.8 & 10 & 8 & 0.55 & 13 \\ K1631 + 985–K1632 + 035 & 22 & 1.5 & 10 & 8 & 0.70 & 23 \\ K1633 + 000–K1633 + 160 & 25 & 2.0 & 10 & 8 & 0.70 & 22 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Parameters of goals in sections with room-and-pillar goat areas. Figure 7: Location map of the highway route. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Pile Number Range** & \begin{tabular}{c} **Subgrade Height,** \\ **H(m)** \\ \end{tabular} & \begin{tabular}{c} **Pavement Stiffness,** \\ **E(MPa)** \\ \end{tabular} & \
\begin{tabular}{c} **Maximum Load of** \\ **Vehicle, G(T)** \\ \end{tabular} &
\begin{tabular}{c} **Vehicle Speed,** \\ **V(km/h)** \\ \end{tabular} \\ \hline K1626 + 400–K1626 + 500 & 2.6 & 5000 & 100 & 70 \\ K1627 + 145–K1627 + 423 & 5.4 & 5000 & 75 & 60 \\ K1627 + 945–K1628 + 433 & 3.8 & 5500 & 125 & 80 \\ K1631 + 985–K1632 + 035 & 3.2 & 5000 & 100 & 60 \\ K1633 + 000–K1633 + 160 & 6.2 & 5500 & 75 & 60 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Parameters of traffic load in sections with room-and-pillar goat areas. goaf areas presented in Table 8, which is 22 m, it can be observed that the goat area depth is smaller than 1.5 times the maximum load disturbance depth. Therefore, it was necessary to perform a strength inspection of the roof, coal pillar, and base plate.