Analysis and measured of strata behavior law and mechanism of 8.8 m ultra- high mining height working face

In view of the problem of strong strata behavior appearing at ultra-high mining height working face in shallow buried depth,based on the on-site monitoring of support pressure,the law of ground pressure at 8.8 m ultra high mining height face in Shangwan coal mine was studied.The results show that the first weighting step of the main roof in 8.8 m ultra-high mining face is 45 m,while the average step distance of periodic weighting cycle is 13.5 m.The average dynamic load coefficient is 1.6.Cyclic weighting in super high mining face has the characteristics of short weighting steps,long duration of pressure,obvious regional weighting and strong dynamic rock pressure and so on.According to the analysis of the overlying roof structure on the working face,it is concluded that the main reasons for the strong ground pressure in the working face with shallow buried depth and super high mining height are as follows:the high mining strength of the working face,intense roof activity,single key layer structure,low occurrence horizon,easy slipping and instability and integral breakage of overlying roof.