# An Experimental Study of Industrial Site and Shaft Pillar Mining at Jinggezhuang Coal Mine
## 7 Discussion  
Energy consumption has increased significantly owing to rapid economic development in the last thirty years. The annual coal production in China is approximately 3.68 billion tons [26]. This has caused coal resource exhaustion in numerous colleries in East China. A few colleries must face bankruptcy and be closed. For most colleries, the engineering site and shaft area pillars are the only remaining coal resources. The excavation of these pillars can not only provide economic benefits and prolong the life of colleries but also reduce the wastage of coal resources. The following three aspects should be considered for pillar excavation:  
1. The most important aspect is that excavation should not be carried out before a shaft is closed. In addition, mechanical analysis may be required in a few cases.
2. Mine subsidence should be predicted to determine the influence of surface subsidence on engineering facilities and buildings.
3. For deformation sensitive facilities, deformation monitoring and warning are the best methods of preventing loss of life and economic damage. This study used the PIM for predicting mine subsidence. The parameters obtained from the field-measured  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Building**} & **Subsidence** & **Tilt** & **Curvature** & **Displacement** & **Strain** & \multirow{2}{*}{**Damage Level**} \\  & **(mm)** & **(mm/m)** & **(mm/m2)** & **(mm)** & **(mm/m)** & \\ \hline CB & 322 & 6.96 & \(-\)0.015\(\sim\)0.111 & 473 & \(-\)1.13\(\sim\)7.45 & IV \\ FD & 341 & 6.97 & \(-\)0.026\(\sim\)0.104 & 472 & \(-\)1.85\(\sim\)6.95 & IV \\ HT & 165 & 3.99 & \(-\)0.015\(\sim\)0.076 & 272 & \(-\)1.06\(\sim\)5.16 & III \\ HR2 & 34 & 0.82 & 0.017\(\sim\)0.021 & 55 & 1.20\(\sim\)1.38 & I \\ FR & 25 & 0.89 & \(-\)0.003\(\sim\)0.027 & 58 & \(-\)0.21\(\sim\)1.79 & I \\ AuS & 6 & 0.18 & 0.004\(\sim\)0.005 & 12 & 0.25\(\sim\)0.38 & Subsidence \(<\)10 mm \\ MS & 2 & 0.00 & 0.000\(\sim\)0.003 & 5 & 0.01\(\sim\)0.21 & Subsidence \(<\)10 mm \\ AS & 0 & 0.00 & 0.000\(\sim\)0.000 & 0 & 0.00\(\sim\)0.00 & Subsidence \(<\)10 mm \\ \hline \hline \end{tabular}
\end{table}
Table 4: Deformation parameters of buildings at engineering site.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Level**} & \multicolumn{4}{c}{**Surface Deformation**} & \multirow{2}{*}{**Classification**} \\  & **(mm/m)** & **(mm/m2)** & **(mm/m)** & \\ \hline I & \(\leq\)2 & \(\leq\)0.2 & \(\leq\)3 & Minor \\ II & \(\leq\)4 & \(\leq\)0.4 & \(\leq\)6 & Mild \\ III & \(\leq\)6 & \(\leq\)0.6 & \(\leq\)10 & Moderate \\ IV & \(>\)6 & \(>\)0.6 & \(>\)10 & Serious \\ \hline \hline \end{tabular}
\end{table}
Table 3: Reference damage level for brick-masonry buildings.  
data were reliable and robust. However, as it is based on the discrete medium theory, it is difficult to calculate the stress and strain inside the rock. Therefore, if shafts are influenced by pillar mining, further analysis based on mechanical simulation is necessary. The major challenge is to balance economic benefits and safety.  
Until the closure of the colliery in December 2017, 2.54 million tons of coal resources were extracted from the mining of pillar 0091 in 2008. This provided not only economic benefits but also sufficient time to resettle industrial workers in an orderly manner.