# Study on the Evolution Law of Overlying Rock Collapse Induced by Mining Based on BOTDR
## 6 Conclusions  
1. To monitor the collapse of overlying strata, a collapse model was established, and three distinct collapse modes--single collapse, articulated collapse, and composite collapse--were systematically analyzed. Based on this model, an analytical expression was derived to describe the relationship between overlying strata displacement and horizontal fiber strain. Laboratory fiber tensile tests demonstrated a significant positive correlation between fiber strain and the collapse slope of the overlying strata, providing a theoretical basis for quantitative monitoring of the collapse process.
2. Horizontal fiber monitoring results indicate that fiber strain can accurately capture the evolution of overlying strata collapse, with strong agreement between the measured strain and actual displacement height. At 115 m and 155 m of advancement, the rock strata primarily experienced stress adjustments with minimal failure. At 195 m, the collapse zone expanded, leading to a substantial increase in strain. By 240 m, the roof experienced severe failure, forming a complete caring zone in the goat. Fiber strain effectively detects rock deformation and identifies fracture locations, verifying its feasibility in coal seam mining monitoring and providing reliable technical support for roof stability assessment and mine safety management.
3. Vertical fiber monitoring clearly delineated the dynamic evolution of the \"three-zone\" structure in the overlying strata. Throughout the working face advancement, strain exhibited a staged variation characterized by three phases: compressive strain, tensile strain, and stabilized compaction. In the caving zone, fiber strain fluctuated intensely due to the rotation and extrusion of collapsed rock blocks before eventually stabilizing. In the fracture zone, fiber strain exhibited continuous tensile characteristics, indicating gradual fracture expansion while maintaining structural integrity, revealing the progressive nature of failure. In the bending subsidence zone, fiber strain remainedrelatively small and stable, suggesting that the rock mass retained overall continuity and was primarily influenced by bending deformation.
4. The study results demonstrate that during coal seam mining, the collapse height and evolution of the overlying strata exhibit distinct staged characteristics, which can be classified into three zones: caving zone, fracture zone, and bending subsidence zone. Fiber strain monitoring provides an effective method for detecting rock deformation and accurately identifying fracture locations. This approach offers scientific insights into overlying strata collapse mechanisms and serves as a critical technical tool for mine safety monitoring, roof stability evaluation, and hazard early warning in coal mining operations.  
C.H.: methodology, investigation, writing--original draft. C.M.: conceptualization, formal analysis, writing--review and editing. H.Z.: conceptualization, supervision, visualization, investigation, funding acquisition. Q.X.: conceptualization, resources, supervision, writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This work was funded by the State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Blasting Engineering, grant number (No. PBSKL2022B01).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors declare no conflicts of interest.