Study on movement law of extremely thick strata and triggering mechanism of mine earthquakes

Mine earthquake are unnatural seismic activities during mining. In the Ordos mining area in North China, the Jurassic coal seam is commonly overlain by the extremely thick cretaceous sandstone strata. It is easy to trigger strong mine earthquakes when the fracture and slip of the extremely thick strata occur caused by the coal extraction. The movement characteristics and the dynamic response of the extremely thick strata are the basis for mine earthquake prevention and control. Based on Vlasov’s theory, this paper used data from surface boreholes, surface subsidence and seismic monitoring to investigate the structure evolution law and movement characteristics of the extremely thick strata in fully-mechanized caving mining of an Ordos coal mine, aiming to reveal the triggering mechanism of the mine earthquakes. The results showed that in the retreating period with no goaf nearby, a small goaf area behind the longwall was presented, and the low roof collapsed rapidly with fracture angles between 64° and 72°, an