... ABSTRACT: The existence of the overlying compound key strata would cause stress distribution in surrounding rock, breaking of the key strata and the periodic weighting of a mining face, which are also related to variation of the mining height. Based on the compound key strata theory...

... coal mine district of Northern Shaanxi. The result shows that: after the mining of the lower s-1 seam at this coal, overburden presents the typical characteristics of "three zones"; after the sixth peri- odic weighting, ascending crack through strata, which is located above 3-1 seam at about 60 m...

... initial mining stage more violent than normal mining stage, main roof was broken after hydraulic support was moved when the main roof reached the maximum span, so the hydraulic support must be sliding advance of support during periodic weighting. The lead abutment pressure peak was located in front...

... of covering loose layer and broken bedrock layers occurs (Holla & Buizen 1990). weighting interval bearing structure characteristic loose layer metals & mining strata structure fractured rock bedrock layer distribution characteristic breakage main roof stress bearing structure...