Research On Weakening Mechanism Of Fully Mechanlzed Top-coal Caving In Horlzontal Section Of Steep Inchined Ultra Thick Seam

The mining process, when faced the hard coal seam during the mechanized top-coalcaving in horizontal section of steep inclined ultra thick seam, it is difficult to the top-coalcaving and drawing rely on the role of ground pressure. So we need the artificial weakening tothe hard top-coal. It is important to study the mechanism on top-coal weakening for solvingthe problem of top-coal caving and drawing, and enhancing the recovery coefficient.In this thesis, mechanism of water-infusion softening was studied specifically formechanized top-coal caving in horizontal section of steep inclined ultra thick seam, by meansof theoretical analysis , physical and mechanical tests, numerical experiments, and fieldmeasurement.First, establish the force model of roof and floor of steep inclined coal seam. Study thedestruction rules, obtain the factors that affect the rock deflection of roof and floor. Then,analysis of different rules for arch structure under the condition of different layer thicknessaccording numerical simulation calculation. And compared to the displacement and pressurebefore and after water-infusion. It is indicate that the water injection pressure of the holeoutward extension fracturing, making the seam soft. So, it increases the displacement of thetop-coal and roof, the more developed cracks, the easier emit of the top-coal. Determinate thephysical and mechanical parameters such as porosity, moisture content, water absorption andwater-coal contact angle of the coal specimen. On the basis of the results for effective porevolume coal in water, obtain the absorbent of the specimen weak or strong, and compare theresult to the experiment, theory certainly that there is a strong possibility of artificialweakening. Then observe the intensity change before and after water-infusion, and the effectof water-infusion according uniaxial compressive strength test. And compare the curve of stress-strain before and after water-infusion, it is declare that the strength of the coal specimenweakened after water-infusion. At last, application site for steep inclined work face, verify theconsistency of research results and on-site.