Study on failure characteristics of overburden in extra thick coal seam mining

Detecting the development height of the water-flowing fractured zone in the overburden of coal seam is of great significance for the overburden safety of working face with developed sandstone and thick loose layer. In this paper, the dual-mode parallel electrical method was used for dynamic monitoring of overlying rock in shallow and large mining height working face. Under the influence of mining, the apparent resistivity of initial mining fracture was high. The apparent resistivity began to decrease after the crack was understood by water entering the surrounding rock, and the apparent resistivity of fracture water-flowing to goaf was high again. According to the apparent resistivity monitoring results, the maximum height of the water-flowing fracture was 122 m. The ratio was 11.1 between the fractured zone and mining height. The numerical simulation results showed that the height of the water-flowing fractured zone above the working face was 122 m. The field monitoring results and numerical simulation results verify each other. With the influence of mining, the loose layer near the surface above the working face was cracked. There would exist a series of geological problems, such as soil erosion and ground subsidence.