“Vertical Three Zones” Determination of Overburden Based on Tracer Gas Method

According to the present situation of the “vertical three zones” determination technology of the overburden strata in coal mine, the tracer gas method was proposed to determine the “vertical three zones”, and the SF₆ acted as the tracer gas; the failure process of the high level boreholes in the process of coal seam mining was analyzed and the technical principle of using the SF₆ to determine the “vertical three zones” of the overburden was determined, and the experimental scheme of the “vertical three zones” was designed with multiple boreholes comparison. The field tests showed that the upper and lower boundaries of the fractured zone determined by the 1^# to 4^# boreholes were almost the same, the fractured zone range of the 15203 working face overburden was 35.8 m to 71.2 m, the fully developed strata of the fracture zone was 54.1 m to 58.5 m, the curve subsidence zone range was more than 71.2 m, and the caving zone range was less than 35.8 m. The accurate determination of fracture zone can provide guidance for the high level boreholes design, reduce drilling works and improve the coal mine production efficiency.