下分层综放工作面上覆岩层结构特征

我国综放开采技术是在分层综采技术的基础上发展起来的,对于一直采用分层综采的一些大型厚煤层生产矿井,面临着顶分层采后下分层综放开采技术问题,这个问题与一次采全厚整层综放开采矿压显现有所不同.下分层综放开采时,二次垮落的直接顶岩层碎胀系数较小,垮落带高度与采高的比值将增加,造成顶分层开采时下位老顶岩层垮落后转化为规则垮落带,成为下分层综放工作面的上位直接顶,促使下分层综放工作面的老顶“砌体梁”式平衡结构向更高层位岩层发展.上位直接顶岩块强度较高、块度较大,容易形成“岩-矸”半拱式平衡结构.该结构的周期性失稳和垮落,造成采场出现小的周期来压现象;而“砌体梁”平衡结构的周期性失稳和垮落,将导致采场出现大的周期来压现象.

Character of Overlying Strata Structure for Fully Mechanized Coal Face with Sublevel Caving in Lower-slicing

Based on fully mechanized mining in slicing,fully mechanized mining with sublevel caving or FMMSC has been developed.With fully mechanized mining in slicing,some large-production coal mines are confronted with problems of FMMSC in lower-slicing while top-slicing of thick seam has been excavated.Behaviors of ground pressure of FMMSC in lower-slicing have some different from that in whole-seam.Owing to expansion factor of re-caving roof-strata being smaller while lower-slicing seam is excavated with FMMSC,the ratio of caved zone height to mining height will increased.Former Basic roof-stratum while top-slicing seam was excavated,has being translated into caved zone and has become upper-immediate roof stratum.So,it is the equilibrium structure with stacked layer of blocks in basic roof with FMMSC in lower-slicing that moves into a higher stratum.Since lump size of upper-immediate roof is large,a semi-arch equilibrium structure of the stratum-rock sometimes can be formed.Periodic destabilization and caving of the structure will lead to a small periodic weighting in coal face.While destabilization and caving of the equilibrium structure with stacked layer of blocks will cause of large periodic weighting.