## 5 In Situ Monitoring Result  
### DoFs Data  
DOFS are mainly used to monitor the micro-strain inside the rock strata. However, when a large deformation occurs in the strata, the DOFS may break once the deformation exceeds its strain limit. In that case, the rock deformation below the breakpoint cannot be monitored. On 24 July 2022, the first round of DOFS monitoring was conducted, followed by the second round on 29 July 2022. During this period, the distance between the LC1 borehole and the working face is \(-\)18.4\(\sim-\)0.1 m (negative value indicates advance). Through the analysis of the results obtained in the second round of monitoring, it was found that a strain breakpoint of DOFS occurred at a depth of 475.5 m. This indicated that deformation occurred in the stratum in that position and the deformation amplitude exceeded the strain limit of DOFS. Since the borehole was in an advanced state, the DOFS rupture were caused by the compression deformation of rock strata under the influence of mining advances. The strain monitoring was carried out continuously every day from 30 July to 11 August 2022, during which the working face advanced past the LC1 borehole by 2.9-38.4 m. According to the monitoring results (Figure 5a), the breakpoint depth of DOFS at this stage remained around 475.5 m, with no change. The overburden deformation was not obvious in the drilling range of 0-350 m, while tensile strain segments appeared repeatedly at the borehole depth of 350 m, 390 m, 450 m, and so on. It can be seen from Figure 5a that there is a compression-tensile strain transition zone at a depth of 450-460 m.  
According to the monitoring results obtained on 14 August 2022, a new breakpoint appeared in the DOFS at the depth of 453.7 m (located in the compression-tensile strain transition zone at the depth of 450-460 m in the previous stage). Then, the monitoring was conducted continuously till 16 August 2022, during which the working face advanced past LC1 borehole by 52.6-64.3 m. According to the monitoring results (Figure 5b), the strain of DOFS at this stage was mainly tensile deformation, and the breakpoint depth of DOFS remained around 453.7 m without any change. The overburden deformation was still not significant in the drilling range of 0-350 m, but tensile strain segments appeared repeatedly at the drilling depth of 350 m, 390 m, and so on. It can be seen from Figure 5b that obvious tensile deformation existed at a depth of 385-392 m.  
According to the monitoring results obtained on August 17, 2022, a new breakpoint appeared in the DOFS at the depth of 390.4 m (located in the tensile deformation zone at the depth of 385-392 m in the previous stage). Then, the monitoring was conducted continuously till 24 August 2022, during which the working face advanced past the LC1 borehole by 70.4-101 m. According to the monitoring results (Figure 6a), the strain of DOFS at this stage was mainly tensile deformation, and the breakpoint depth of the strain curve remained around 390.4 m. Slight tensile deformation occurred in the overlying strata in the drilling depth of 0\(\sim\)350 m. However, at the depth of 350 m, the tensile deformation was significantly larger than that of the above overlying strata. In addition, it can be seen from Figure 6a that obvious tensile deformation existed at a depth of 350-360 m.  
According to the monitoring results obtained on 31 August 2022, a new breakpoint appeared in the DOFS at the depth of 351.3 m (located in the tensile deformation zone at the depth of 350-360 m in the previous stage). Then, the monitoring was conducted continuously till 25 September 2022, during which the working face advanced past the LC1 borehole by 70.4-199.8 m. According to the monitoring results (Figure 6b), the strain of DOFS at this stage was mainly tensile deformation, and the breakpoint depth of DOFS remained around 351.3 m. Within the drilling depth of 0-350 m, the overburden deformation was mainly tensile deformation, displaying an overall stable trend.