Analysis on Partial Roof Falling Causes and Mechanism of No.7131 Coal Mining Face in Qidong Mine

According to the large area spalling and roof leakage problems occurred in the middle and up parts of No.7131 coal mining face in Qidong Mine, the site measurement and FLAC3D numerical simulation software were applied to study the causes of the partial roof falling occurred in No.7131 coal mining face.The results s howed that due to the overlying influences of the lateral support of No.7130 coal mining face and the floor mining stress of No.6130 coal mining face, the roof at the mid dle and upper region of No.7131 coal mining face would form large area solid coal and rock pillars and stress concentration phenomena occurred in the mining and exc avation activities under the solid coal and rock pillars.During the coal mining under the stress concentrated zone, the stress increased zone would be occurred in the up face end of the coal mining face and would not occurred under the whole stress concentrated zone.With the advancing forward of the coal mining face, the scope of the stress increased zone would be reduced and the stress peak would be steadily increased.The stress distribution would develop forward to the up end of the coal mining face.Thus the coal and rock mass in the stress increased zone would have the plastic deformation and the spalling and roof leakage occurred.