Dynamic Evolution and Identification of Bed Separation in Overburden During Coal Mining

Bed separation's evolution plays a crucial role in mining safety. Accurate identification of bed separation location is necessary to prevent disasters caused by bed separation. However, conventional methods such as theoretical calculation and in situ investigation cannot comprehensively reflect the dynamic evolution of the bed separation during mining. In this study, bed separations were classified as either supported or unsupported based on the stress state of the strata below a given bed separation. Furthermore, a theoretical method (PDLS-method) for identifying the dynamic location and aperture of bed separations during mining was proposed. In addition, in situ investigation was carried out to determine the internal movement of overlying strata and evolution law of bed separation. Monitoring results indicate that the internal movement of overlying strata has characteristics of "group movement" and "differential settlement". The rock layers in a strata group move synchronously, and adjacent strata groups move independently. Bed separations occur along the interfaces of those strata groups. The evolution of bed separation can be divided into four stages of emergence, rapid growth, stability, and recession. The biggest aperture of bed separation at investigation borehole was 1.56 m. The feasibility of the PDLS-method was verified by observed data. The results can be used in research regarding bed separation and prevention of secondary hazards.