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Abstract With the mining of working face，soft rock strata above working face appear obvious separation characteristics，and the rigid thick overlying strata gradually settle. When the working face advances to a certain distance，the huge bed separation provides a certain motion space for the rigid-thick strata，causing the thick overlying strata to be broken. The instantaneous energy release causes a strong impact on surrounding rock，and leading to discontinuous deformation characteristics of the surface，cracks，for instance. The larger surface cracks are located at the position of ground level with larger deformation. As the size of exploitation increases along strike，the width and depth of surface cracks are gradually enlarged，the maximum width is up to 1.5–3.0 m，and the maximum depth is up to 50–70 m. Meanwhile，the overlying strata movement can also lead to surface concentration and stagnant. when the abscission range is larger than the drawing pace of conglomerate body broken，the surface deformation increases，which causes the surface crack. What?s more，the synchronic research of the significant correlation between the surface deformation and the rock burst can provide some auxiliary references for rock burst prediction.
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Received: 17 April 2012
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2012, Vol. 31 
