## 3 Numerical Simulation of Full-Columnar Overburden
### Simulation Results of Models with Different Mining Widths  
Figure 10 shows the cloud diagram of overburden displacement change in Scheme 4 during the mining process. When the working face advances to \(50\) m behind the NLC, a \(0.4\) m thick separation layer appears below KSI in the NLC. As the working face continues to advance, the separation layer below KS2 and KS3 tends to close, and the maximum thickness of the separation layer below KS3 is \(1.0\) m. When the working face advances to \(200\) m behind the NLC, the separation layer below KS1 and KS2 tends to close, and the separation layer below KS3 is approximately \(1.2\) m. No obvious separation layer is observed below KS4 throughout the whole process. Figure 11 shows the monitoring data curves of displacement and stress obtained from measuring points of each key stratum in NLC in Scheme 4. As is shown in Figure 11, when the working face advances past NLC by \(200\) m, the subsidence of KS1 tends to be stable and reaches \(4.32\) m. Figure 11 shows that when the working face advances ahead NLC \(70\) m, stress concentration is generated remarkably within the range of KS1 to KS3, and the peak stress reaches \(17.35\) Mpa. When the working face continues to advance to right below NLC, obvious fractures appear in KS1, and the stress of this stratum is depressurized to \(0\) Mpa sharply. When the working face advances past NLC by \(50\) m, KS2 and KS3 are fractured completely; the stress of the corresponding strata is depressurized to \(0\) MPa. Meanwhile, stress relief occurs from KS4 to PKS, but the stress does not drop down to \(0\) MPa, indicating that there is no fracture. Figure 9: Displacement and stress curves of each measuring point in NLC in Scheme 3: (**a**) Displacement curves; (**b**) Stress curves. Figure 12 shows the cloud diagram of overburden displacement change in Scheme 5 during the mining process. When the working face advances to 50 m behind the NLC, a 0.2 m-thick separation layer appears below KS1. When the working face advances to 150 m behind the NLC, the separation layer below KS2 and KS3 is approximately 0.1 m, and the separation layer below KS3 and KS4 is 0.8 m and 0.1 m, respectively. When the working face advances to 200 m behind the NLC, the separation layer below KS1 to KS4 tends to close. Figure 13 shows the monitoring data curves of displacement and stress obtained from measuring points of each key stratum in NLC in Scheme 5. Figure 11: Displacement and stress curves of each measuring point in NLC in Scheme 4: (**a**) Displacement curves; (**b**) Stress curves. Figure 12: Cloud Diagram of displacement change of Scheme 5 when the working face advances to a range of 200 m behind the NLC: (**a**) 50 m; (**b**) 150 m.  
As is shown in Figure 13a, when the working face advances past NLC by 200 m, the subsidence of KS1 tends to be stable and reaches 4.35 m. Figure 13b shows that when the working face advances ahead NLC 90 m, stress concentration is generated remarkably within the range of KS1 to KS3, and the peak stress reaches 18.19 MPa. When the working face continues to advance to right below NLC, obvious fractures appear in KS1 and KS2; the stress of this stratum is depressurized to 0 MPa sharply. When the working face advances past NLC by 50 m, KS3 and KS4 are fractured completely; the stress of the corresponding strata is depressurized to 0 MPa. As the working face advances past NLC 150 m, KS5 is fractured completely, and its stress drops down to 0 MPa. Meanwhile, stress relief occurs from KS6 to PKS, but the stress does not drop down to 0 MPa, indicating that there is no fracture. Based on a comprehensive analysis of the simulation results of the above five models, the main indicators were analyzed, and the statistical data obtained are shown in Table 3. Generally speaking, there is no separation in the overlying strata in the advance stage of working face.