Differences in the dynamic evolution of surface crack widths at different locations in the trench slope area and the mechanisms: a case study

Coal seams were buried extremely shallowly in the trench slope area, which is prone to inducing surface cracks, seriously threatening the surface environment and mine safety production. The development of surface mining cracks varies at different locations in the trench slope area. In this research, we aimed to study the dynamic characteristics and laws of surface crack widths at different mining locations in the trench slope area and reveal the evolution mechanism of surface crack widths. Taking the 125,203 working face in Anshan Coal Mine in Shaanxi Province, China, as the geological prototype, we analyzed the full-cycle dynamic change law and planar distribution law of the surface crack widths in the trench slope area by combining the unmanned aerial vehicle remote sensing technology and field actual measurements and revealed the dynamic evolution mechanism of surface mining cracks in the trench area. The research results showed that the dynamic changes of surface crack widths varied at different locations of the slope. The surface crack width in the downslope area increased first and then stabilized with the advance of the working surface; the crack width at the bottom of the trench shows the dynamic change characteristic of increasing–decreasing–slightly increasing–stabilizing with the continuous advance of the working surface. The surface crack width in the upslope area showed the dynamic change of increasing–decreasing–stabilizing with the continuous advance of the working surface. Influenced by the surface morphology, the development mechanisms of surface mining cracks were different. The research results can provide practical guidance for selecting the best treatment time for surface cracks in different areas.