Study on crack evolution law of overburden strata and stability of interlayer rock in upward coal mining

In order to study the feasibility of a upward coal mining in Dongmao Mine of Northern Shaanxi Province,a study method with the similar material simulation test was applied to simulate and study the overburden rock crack evolution law and the interlayer rock stability condition. The results showed there were 10 cracks passing through the upward cracks in the top No. 3-seam occurred in 328 m pushing process of the coal mining face in the low No.5-2seam of Dongmao Mine. During the mining process of the coal mining face in No.3-seam,when the coal mining face was pushed forward passing through those upward cracks in the strata,there was no sliding falling and instability and no bench subsidence phenomenon occurred. The mining in No. 5-2seam would not cause a serous deformation failure in No. 3 seam,the mining in No. 3-2seam would cause the stress variation from the interlayer rock less influence to No. 3-2seam,thus the mining in No. 3-seam would be ensured in a stable floor and the practices showed that the upward mining practiced in Dongmao Mine was feasible.