Feasiblility Study of Naked Support on K2Limestone Nude Under Hard Roof
|School||Construction Industry Institute|
|Keywords||Hard roof Stability of surrounding rock Bolt support Composite beamtheory Rock classification|
The geology and hydrological geology of the Heng sheng, Heng-Jin Coal is simple relatively, coal seam hosting are more stable. The2nd,9-10coal seam is primary mining coal seam,the immediate roof of9-10coal seam is the K2limestone, and the depth of K2limestone is12.2～15.10meters, average is13.09meters, distributing stability. By the determination on K2limestone roof rock sample, analysis calculation1#rock sample of tensile strength for6.8Mpa, single axis compression situation of compressive strength for91.5Mpa, three axis compression situation of compressive strength is175.6Mpa, friction angle is52degrees, cohesion is15.744Mpa;2#rock sample of tensile strength is6.3Mpa, single axis compression situation of compressive strength is114.8Mpa, three axis compression situation of compressive strength is211.2Mpa, angle of friction is54.3degrees, cohesion is18.465Mpa. It has a high strength、resistance to deformation and a notable feature.Based on the physical and mechanical properties of rock specimen test results, mechanical analysis the nude lane directly by physical and mechanical properties of rock specimens on roof, according to the mine’s existing bare lane calculated width (4.0M) and height (2.5M), even if directly depends on the pressure of overlying strata to take, Clamped beam needed by its maximum thickness of4.68m, calculated on a simply supported beam roof thickness directly required for the5.74m, and the actual roof thickness of13.09m directly in the mine, regardless of the load, in accordance with the constraints directly in the mine roadway roof thickness is greater than the maximum thickness, immediate roof damage does not occur.On this basis, by application FLAC3D program on roadway surrounding rock stress and plastic area of distribution for has numerical simulation, the came roadway top floor is stress reduced area, driving into formed supports pressure is located in two roadways and driving into head must range within, maximum supports pressure stress about for13.72MPa, maximum level pull stress about for0.73MPa, is not over directly roof limestone of anti-pressure, and tensile strength, description limestone directly top rock does not occurs pressure broken and pull crack. Plastic zone mainly located in the roadway, and tunnel two main plastic zone for shear failure, shear failure of roadway within the two0～1.8M. Further on the surrounding rock stress in the bolt support and the distribution of the plastic zone were simulated that the value of the vertical stress in the bolt support and the plastic zone changes little between the two, therefore roof support has little significance.Given constant Heng Sheng coal mine9-10seam directly roof K2limestone is largely thickness, and strength highly, and buried not deeply, roadway face and roadway of is pressure smaller, roadway driving into Shi on top floor of damage is small, analysis came constant Sheng coal mine roadway of support nurse way, and due to two help coal wall not is soft, floor of mudstone strength also larger, so used nude roadway and does not for support nurse is security reliably. Nude of mine roadway support method to save large sums of support costs, more meaningful is to thoroughly solve the contradiction of excavation support, effectively accelerating the driving speed, increase driving efficiency,modernization of to maximize driving efficiencely, promote the building of double high mine.Due to the coal mines around the support form is not so simple, so constant observation of deformation of Shanxi coal mine should be strengthen convergence to set up observatories for observation in Heng Sheng coal. From the observatory, statistical information can be seen, face in mining State, each section of roof, floor Observatory observations is close and the roadway deformation amount of convergence of the two groups are obviously, the two roadway deformations of convergence of the two groups could be a bit larger compared,so when roadway should focus on controlling two strengthen roof support compared.To sum up, the mine overburden of rock engineering geological characteristics, types of Heng Sheng coal are conducive to achieve long-termstability and9-10of coal seam roadway safety green mining, that practice nude roadway is safe、feasible and reliable in technically; in addition, saving the mine roadway support costs and maintenance the costs, have reasonable economic benefits.