C-SHAPED STRATA SPATIAL STRUCTURE AND STRESS FIELD IN LONGWALL FACE MONITORED BY MICROSEISMIC MONITORING
微震监测揭示的C型采场空间结构及应力场

In order to study the results of relieving pressure above the seam which leads to rockburst while mining the liberation layer,China-Australia co-operation research group used microseismic monitoring techniques in Huafeng Mine of Xinwen Mining Group Co.,Ltd.,Shandong Province.The spatial fracturing rules of surrounding rock in longwall face surrounded by three sides mined areas were observed and researched.On the basis of the achievement of 3D strata fracturing situation and the section plane of microseimic events in different areas,the relationship between the spatial structure of overlying strata and mining pressure field is found,and the conclusions are drawn as follows:(1) the overlying strata forms C-shaped strata spatial structure.Microseimic events distribute in the outside of the C-shaped strata spatial structure and form fracture area of rockmasses.High stress area is in the C-shaped strata spatial structure.The shift of high stress area and the stresses of the different high stress areas are also described.(2) most concave of the C-shaped strata spatial structure lies on the top of the coal pillar when the coal pillar is smallest.The distribution of the supporting stress is that the hard thick rock layers above the main roof fracture near the intake airways,which produces the pressure-relieved area;and the hard thick rock layers above the main roof near the return airways are not fractured,which forms stress concentration area.According to the analysis of the reversal development of pressure,the diversion of high pressure is shown.The differences of pressure in different positions are found;and the areas where the pressure is not relieved are confirmed.So,by monitoring the area of the liberation layer and distinguishing the dangerous areas of rockburst,the measures to control rockburst are taken and succeeded.