Experiment Study Of Key Stratas' Movement Characteristics In Fully-mechanized Sublevel Caving Mining Of Extremely Thick Coal Seam And It's Application

Full thickness mining in extremely thick coal seam cased many different strong strata behavior problems,such as emerging support crushing disaster per hundred meters and severe destruction of roadway on gob side when mining the lower coal seam in Datong mining area.These problems are closely related to the broken and instability of the strata in far field.The characteristics of far strata are closely related to prone to overhang size,which do not be studied by using two-dimensional planar similarity simulation device.In order to change the present situation,three-dimensional similar simulation experiment system was been developed,and was used to do some basic experiments,which provides basic experimental research methods for the mechanism and prevention and control of strong strata behavior in large space stop for extremely thick coal seam.Three-dimensional similar simulation experiment system was been designed and developed.It can change the width flexibility,fulfil requirements of loading evenly and adjustment of coal seam mining height within 30 meters,and can been used to simulated mining of single or double mining working face,also it achieves the monitor of strata movement,pressure transfer between stratums,pressure in goaf and occur process of fractures.Combined with the geological and mining condition in Datong mining area,broken feature of simplified key layer was studied by three-dimensional similar simulation experiment system.The result shows that the periodic weighting is caused by the inconsistent rotation of several broken plates of near key layer above the extent of working face.The study founds the occurrence and breaking features of “horizontal O-X” in first weighting and “horizontal “U-Y” in periodic weighting of far key layer.After that,making the manufacture of cement block with the shapes of horizontal “O-X” and “U-Y” to reproduce the instability process of curved triangle block and trapezoidal block.Based on these results above,the instability of curved triangle block may caused strong strata behavior suddenly,and the rotation of trapezoidal block may caused the large-scope deformation of roadway on gob side,which matches the field measurement.