Time-space evolution regularity of mining deformation and failure of overlying strata with the long-wall fully mechanized coal face

After coal is excavated as working face advances,overlying strata starts to separate,break and collapse to form caving zone and fractured zone whose range have great influence on the coal mine safe production. In this paper,we take Guqiao Coal Mine 1116( 1)face as the engineering background. Overlying strata is divided into six groups combining the properties and mechanical index of the rock mass. Focusing on the 11-2 coal seam of Huainan Mining Area,we intend to study the regularity of its strata movement and failure by the numerical simulation and parallel electric-testing technology. Investigation and simulation results show that zones characteristics of overlying strata over the goaf are obvious in the vertical direction.The zone is in turn bidirectional tensile stress failure zone,the tensile fracture zone,the shear failure area and the undamaged area from above to bottom. The maximum height of the caving zone accounts for 11. 5-14. 5 m with the fissure zone being 45-47. 5 m. The resistivity of the rock in the caving zone remains high on the whole,perhaps over 10 times than that of the background resistivity. With working face advancing,the transmitting current goes down continually and finally comes to be stable. The rock resistivity of water flowing fracture zone is uneven and is 10 times higher than the background resistivity. The zone with high resistivity is discontinuous.With working face advancing,the transmitting current varies greatly from high-low-high-low. Compared to the background resistivity,the resistivity of the rock layers vary but the change is not 2 times higher than the background resistivity. With working face advancing,the maximum current is 90 mA and minimum current is 50 mA. The final form of the strata failure become a saddle shape,the strata failure scope around the goaf would develop greater than the scope in its central section and the failure scope of overlying strata is greater than mining scope in the horizontal direction. The above results of our investigation and simulation can be expected to provide a certain theoretical basis for the mine water-prevention and gas control in the similar geological and mining conditions.