Distribution Characteristics of Overburden EH-4 Electric Conductivity in Full Mechanizd Caving Face

To understand the situation of overburden damage and water filling after mining to ensure safety mining under reservoir,EH-4 electric conductivity imaging system was used to forecast overburn damage in N1S1 coal face of Daping coal mine.It can be obtained from the image data of rock strata conductivity that overlying strata above goal forms a arched high resistance zone with high resistance when advancing length of working face is 22 m,the height of the arched zone is about 90 m which is as 7.2 times as mining height when strata conductivity is more than 800 Ω.When advancing length of working face is 92 m,the height of the arched low resistance zone is about 300 m which is as 24.2 times as mining height and strata conductivity decreases to less than 30 Ω.When the angle range of working face advancing is about 70°,strata is destroyed and water filled and conductivity decreases.When working face length advances 160~190 m,strata conductivity is normally between 10 Ωto 20 Ω,and strata shows water filling characteristics.