Water-reducing mining technology for fully-mechanized top-coal caving mining in thick coal seams under ultra-thick sandstone aquifer

Binchang Mining Area is a typical intensive full-mechanized top-coal caving mining area.However,mine production is faced with the influence and threat of water inflow from Luohe formation ultra-thick sandstone of coal roof,for a long time.Therefore,water-reducing mining is the main problem in the sustainable development of mining area.This paper summarized general characteristics of vertical heterogeneity of ultra-thick aquifer,based on hydrogeological condition fine expedition of ultra-thick sandstone aquifer.And these characteristics were regarded as water-reducing basic hydrogeology of Binchang mining area.In addition,overburden failure general law of fully-mechanized top-coal caving mining area was summarized according to exploration results of water-conducting fracture zone height.Then,we analyzed the main controlling factors of water inflow including aquifer thickness,water yield property and overburden rock thickness.And a P evaluation model,mining area affected by roof water index,was established.Based on this model,influence of roof aquifer on mining was divided into three grades including weak influence zone,medium influence zone and strong influence zone,and influence partition indexes were provided.Besides,we first proposed the concept of wedging ratio,and analyzed its basic theory and application condition.And three water-reduction patterns including water reduction control,height-width limit,isolation-grouting modes were established according to the influence degree dividing zones.Using this technology,typical coal mines all conduct fully-mechanized top-coal caving water-reducing mining,and this technology makes aquifer level recover in weak influence zone,increase of water inflow decrease in medium influence zone after mining(basically within 100 m2/h),water inflow decrease after grouting and insulating.On the whole,the practical application results are satisfactory.