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| Factors | Class |
| Class I | Class II | Class III | Class IV |
|
| Assign a value | 1 | 2 | 3 | 4 |
|
| Structural types of rock mass X1 | Loose surrounding rock | The surrounding rock is broken showing small pieces | The surrounding rock is a laminated structure | Surrounding rock integrity |
| Geological structure X2 | Fault penetration through the surrounding rock | Located in the lower plate of the fault and the top plate of the empty area is connected to the fault | The roof located in the footwall of the fault is far away from the fault | Located on the upper plate of the fault |
| Mined-out area water X11 | The surrounding rocks in the goaf have seepage for a long time, and the surrounding rocks are affected by the water body | There is seepage in the rainy season in the goaf, and the surrounding rock is affected by the water body | Water traces are visible in the surrounding rocks of the goaf, and the surrounding rocks are less affected by the water body | No seepage and no water traces in the surrounding rock of the goaf, no water body around the surrounding rock |
| Adjacent empty area situation X12 | The surrounding goaf is connected and densely forms a large connected area | The number of goafs in the vicinity of the goaf is high, the area is not large, and they are close to each other | The goaf near the goaf is small, not large, and scattered | Independent goaf |
| Subsequent mining disturbances X13 | The empty area is located in the subsequent proposed goaf | The empty area is located in the proposed goaf mining larger impact range | The vacant area is located in the less influential area of the proposed goaf | The vacant area is located outside the area of influence of the proposed goaf |
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