Study on the zoning characteristics of strata behaviors during the primary mining of mining face under contiguous goaf

According to severe strata behaviors occur frequently during the primary mining of the panels under contiguous goaf,In Shendong mining area and it is urgent to know about its reasons.the strata behavior characteristics and its mechanism in different regions during the primary mining are analyzed based on field test and relevent theories.The results show that compared with conventional panels in the upper coal seam,strata behavior of the lower coal seam has obvious aperiodicity and zoning characteristics.Moreover,the weighting positions during the primary of the panel in close-distance goaf coincide with the top coal pillar and the first fracture position of the overlying key strata,and then based on that,the strata behaviors during primary mining are zoning.Strata movement structure and mechanical models in different strata behavior regions during the primary mining are established and the mechanisms of those regions are analyzed.For the region passing the overlying one-side mining pillar,the strata behavior is under the coupling effect of the breaking of key strata and the distance between coal seams,and it is the distance that leads to the eccentric strata behaviors along the panel.For the rest regions under the overlying goaf,the broken coal and rock mass has little influence on the strata behaviors during the weighting ,but has a great influence on that of non weighting period.Some effective control measures are given finally.choosing the open-off cut position and increasing the advancing speed reasonably.