Study On The Movement Rule Of Overlying Strata Of Colliery Stope By Microseismic Monitoring

In the procedure of coal mining, disasters which have close relationship withmovement of overlying strata such as roof fall, roof or floor water inrush, rockburst, coal and gas burst etc occur frequently. Micro seismic (MS) monitoringresults are reliable and prior. MS technology can continuously and dynamicallymonitor the rock mass in big scope. So, it is of great importance not only tothe safety of mining but also to the environment protection to study the movementrule of overlying strata and forecast the fracture of rock mass adopting MStechnology.The theory of MS technology and the research achievements by forerunners onMS technology are introduced firstly. The explosion proof MS "Comise-2002"monitor made by scholars of Shandong University of Science and Technology wasadopted to monitor the movement of overlying strata of 3_over 107 working face inLuxi Colliery. The monitoring method and forecast index on the fracture ofunderground rock mass by MS is presented.Through analysis of the monitoring results on the movement characteristic ofoverlying strata in the vertical direction, it is found that the height offracture zone can be decided by the localization of MS events. The upper limit38m over the 3_over 107 working face which contains 90percent of the MS events isdetermined as the height of water conductivity zone. The actual height of waterconductivity zone surveyed by "two ends sealed water loss monitor" is 36.2m.We find that the actual observation height is a little less than that by MS method,the reason maybe is that the crevasses haven't connected.Through analysis of the monitoring results on the movement character ofoverlying strata in the development direction of working face, it is found thatthe periodic change of MS big events can be used to determine the roof weightingstep distance of basic roof. The basic roof weighting step distance monitoredby MS system is 23.3m, which is almost the same as the result analyzed from groundpressure observation. The rich rock broken precursor information contained in micro seismic eventscan be used to forecast the stability of coal mining overlying strata. The 1-4order variation law of frequency, energy and distance of MS events beforedestabilizing can display the change rule of MS events. According to the variationlaw of the difference of frequency, energy and distance of micro seismic eventsbefore destabilizing, the fracture of rock mass can be precisely predicted. Thisis of great importance for safety of colliery.