Research On Safe Anti-sand Coal And Rock Pillar Set Up In Coal Mining In Thin Bedrock Area Under Quaternary Loose Aquifer

Based on the comprehensive study of Quaternary lithology,color,aquifer,electricity,stratum thickness and watery,the article divides Quaternary loose layer and Quaternary lower stratum containing water barrier layer,and discusses the possibility of drying the bottom aquifer of Quaternary lower formation and the feasibility of setting up safe anti-sand coal and rock pillar;The deformation and failure characteristics of overburden rock in Baodian thin bedrock area 3 coals are simulated and analyzed by numerical analysis method under three conditions: slicing mining,fully mechanized caving mining under net and fully mechanized caving mining;The height of caving zone is calculated by using relevant regulations,codes and empirical formulas in mining area,and the reserved size of safe anti-sand coal and rock pillar is calculated.The main conclusions are as follows:(1)The average thickness of the middle Quaternary strata is 84.78 m,mainly composed of gray clay,sandy clay and clay sand,with several layers of clay-bearing sand.The bottom is a clay layer,with a thickness of 1.55-13.90 m,generally 5-8m,and an average of 6.70 m.It is a regional aquiclude layer group with good water-resistant performance,resulting in poor vertical recharge conditions of the lower aquifer.(2)The lower group of the Quaternary system is divided from top to bottom into upper segment(1 containing,1 separated)and lower segment(2 containing,2 separated,3 containing,3separated).Among them 1 containing and 1 intervals are isolated in the whole region,2 containing and 2 intervals are isolated in the middle and northern part of the region,and 3 containing and 3intervals occur in the northern part of the region.The average thickness of 1 compartment is 7.24 m,and the whole area exists,which can effectively prevent the water supply from the 1 containing and overlying aquifer.It can effectively block the downward recharge of the 2 containing and overlying aquifers.The lower strata 1 containing?2 containing?3containing have low water-richness,and the replenishment conditions are poor.Affected by mine drainage,the water level has dropped significantly,and the bottom aquifer of the lower group is possible to be drained,and the mining level of the water body is level II,which meets the requirements of setting up safe anti-sand coal and rock pillar.(3)Based on the numerical simulation of the deformation and failure characteristics of overlying rock in three kinds of mining of thin bedrock slicing mining,fully mechanized caving under net and fully mechanized caving in Baodian Coal mine of Yanzhou mining area,The quantitative parameters of deformation and failure characteristics of mining-induced overburden under three mining modes are obtained,It is concluded that the height of the two zones caused by slicing mining is minimum,the caving ratio of the third layer is the lowest in the maximum stratification of the two zones caused by fully mechanized caving,the first layer has the largest cave-production ratio,safe anti-sand coal and rock pillar is 26.1m;(4)Fully mechanized caving mining of 3 coal seam in the study area,the safety anti-sand coal and rock pillars in no.5,no.6 and No.8 mining areas are 43.6m,43.3m and 46.1m,respectively,safe anti-sand coal and rock pillar is 26.1m.Fully mechanized caving mining of 3 upper coal seams in eight mining areas,the top layer of 3 coal of fully mechanized coal seam and the undernet fully mechanized caving mining,the safe anti-sand coal and rock pillars in no.5,no.6 and No.8 mining areas are 34.2m,33.8m and 35.5m,respectively.3 coal fully mechanized coal seam mining in layers,the fifth and sixth mining are divided into three layers,mining thickness of 2.9m,the thickness of safe anti-sand coal and rock pillar is 22.5m,eight mining is divided into four layers,mining thickness of 2.3m,the thickness of safe anti-sand coal and pillar is 21.6m.