Application and Study on Mechanism of Pressure-relief and Permeability Improvement of Overlying Strata During Mining Lower-protective Seam

In order to master changes of the protected seam permeability cofficient and coal seam gas content after mining lower-protective seam, according to rel ative location between Guozhuang Mine and No.2 Coal Seam of Sihe Mine, the authors adopted the combination of similar material simulation and field practice, deter mined the changes of overlying strata permeability coefficient after protective seams exploitation, obtained the spatial variation of permeability coefficient of overlying st rata in the mining process:from the original value 4. 40 m2/ (MPa2.d) , increased to about 4.89 m2/ (MPa2.d) firstly, then reduced to about 3.91 m2/ (MPa2.d) , and then rapidly increased to the maximum value 85.00 m2/ (MPa2 d) , and finally reduced to about 28.00 m2/ (MPa2.d) .The results indicated that the permeability coefficient w as a dynamic proces, namely the original value-increase-reduce-sharp increase-steady decrease (more than the original value) .