The Research On The Development Of "Three Zones" On Mechanized Coal Faces And Its Impact On Aquier Structures

The balancing of stresses of overlying strata is broken in mining process and it results to the separation,deformation and fracture of stratum.As a result,fracture between aquifers and aquiclude changes,so that the original aquiclude becomes a water passage or storage space.With the evolution of aquiclude's fracture,the composition relationships of original aquifers would be changed,which will lead to the changes of aquifer structures.Besides,due to the barrier pillar,the aquifer structure between two working faces is not similar to the changes of gob.Previous studies on these changes often starts from the point of water inrush and little of them have researched from the property variation of aquiclude.Through studying the overlying strata destruction caused by coal mining and the structure variations of the aquifer,this thesis adopts a series of research methods including field geological investigation,geophysical field investigation,indoor simulation experiment,computer numerical simulation and theoretical analysis to study the fracture evolution of aquiclude and its influences on water conductivity of aquiferous medium.It takes Yuwu Coal Mine of Shanxi LuAn Mining Group as research district and focuses on studying the fracture evolution of water-conducting zone when the mutual contact zones between two working faces superpose with each other and its influences on aquifer's structure.The main research results are as follows:1.Through geophysical field investigation,w discover that overlying strata will fall,subside after mining and strati-graphic structure would become disorganized.Besides,the 120 mm strata destruction above coal roof is serious.There is no falling above the keeping coal pillar and goaf rises.The transverse border of circled water-conducting fracture zone is larger than the scope of goaf,which indicates that mining fracture has extended.Between two working faces,the height of water-conducting fracture zone is higher than that of a single face.2.Through indoor simulation experiment,this research thinks that fractures which are perpendicular to coal seam profile and closed to open-off cut and working face are well developed.The middle fracture on goaf is compacted by gravity action of overlying strata.The distribution density of boundary fractures is two to four times of middle face recompaction area and it is distributed in elliptic paraboloid zone.The lateral fracture between two working faces does not develop and monitoring point's displacement decreases from the bottom up.3.Through computer numerical simulation,this research discovers that the middle fracture of goaf has higher degree of compaction.Its two sides is based on vertical fracture development and its top part is based on abscission fracture development,which is in accord withindoor simulation experiment.According to this research,fractures develop not only above the goaf but also extend to the above of coal pillar.This study found that the extended distance of goaf is about 33.5 meters.And according to simulation result,the height of water-conducting fracture zone is higher than that of a single face,which conforms with the analysis result of geophysical field investigation4.Through indoor simulation experiment,computer numerical simulation and geophysical field investigation,this research thinks that the height of water-conducting fracture zone in single face is 101 meters and its lateral extended distance is 33.5 meters away from goaf area.When two working faces superpose with each other,the height of water-conducting fracture zone above the coal pillar is about 130 meters.5.According to research,influenced by mining activities,the anisotropy in aquifer itself and between aquifers changes.Due to the existence of mining fractures,previous aquiclude becomes water passage or storage space,making previous aquifers with low hydraulic connections become united aquifers with high hydraulic connections.The fracture development of the new aquifer shows zonation from bottom up and clear partition from outside to inside.Besides,its storage capacity and the size of the aquifer becomes larger.From the structural point of view,the aquifers in relative level become an aquifer above the goaf.From the point of aquiter structure distribution,previous horizontal aquifer evolves into alveilate aquifer.