Abstract
The stability of panel floor, which is above confined water, is the key to determine the water inrush from the panel floor. Based on the characteristics of “lower three zones” of the panel floor, the mechanics analysis model of a floor water-resisting rock beam is established. Then, by the principle of virtual work and energy functional variational conditions, the trends of deflection and internal stress are researched in the effective water-resisting rock beam under the combined action of mining stress and water pressure. And how to determine its stability is acquired. According to the geological and mining conditions of A3 coal seam in Panxie mining area of Huainan Mining Group, three factors influencing on the stability of the floor rock beam are analyzed, such as elastic modulus, coefficient of viscosity, and water pressure. It is shown that the elastic modulus plays the most important role on the deformation of the rock beam. So, for improving the mechanical properties of the rock beam, the reinforcing floor technique has been proposed. On the one hand, it is contributed to improve the ability for resisting floor deformation. On the other hand, it can increase the coefficient of rock viscosity in water damage zones and reduce the speeds of loading and deformation in the whole rock beam. Hydrophobic decompression can effectively reduce the stress on the boundary of the rock beam, and the stability is enhanced. The research results have a guiding significance for determining whether there are water inrush risks in the panel above the confined aquifer.
Highlights
China is one of the countries that have been affected seriously by damage caused by water in coal mines. e increase in mining depth and widespread application of comprehensive mechanized coal mining and top coal caving have resulted in an increase in floor breaking and water disaster due to mining over pressurized water [1]. ree zones similar to the overlying rock by mining can be found inside the coal floor [2,3,4]. ese are the water-guiding zones broken by mining on the top and the central complete rock, the water-flowing zone on the bottom artesian water, and the water-resisting zone on the central complete rock, which plays an important part in resisting water inrush from the seam floor
Panel floor rock instability is the direct cause of artesian water inrush. erefore, the jointed rock mass damagecoupling mechanical model [5,6,7], jointed rock mass
Floor water inrush is the process that results in crack initiation, extension, connection, and eventual failure. e combined action between mining dynamic pressure and hydraulic pressure should be considered in the systematic investigation of the stress and deformation of an e ective water-resisting rock beam
Summary
China is one of the countries that have been affected seriously by damage caused by water in coal mines. e increase in mining depth and widespread application of comprehensive mechanized coal mining and top coal caving have resulted in an increase in floor breaking and water disaster due to mining over pressurized water [1]. ree zones similar to the overlying rock by mining can be found inside the coal floor [2,3,4]. ese are the water-guiding zones broken by mining on the top and the central complete rock, the water-flowing zone on the bottom artesian water, and the water-resisting zone on the central complete rock, which plays an important part in resisting water inrush from the seam floor. Ese are the water-guiding zones broken by mining on the top and the central complete rock, the water-flowing zone on the bottom artesian water, and the water-resisting zone on the central complete rock, which plays an important part in resisting water inrush from the seam floor. The thicknesses of the water-guiding and water-flowing zones differ for different mining conditions. Panel floor rock instability is the direct cause of artesian water inrush. E combined action between mining dynamic pressure and hydraulic pressure should be considered in the systematic investigation of the stress and deformation of an e ective water-resisting rock beam. Based on the three zones of the panel oor, this paper takes the water-guiding zone broken by mining as a viscoelastic body and the e ective water-resisting rock beam as an elastomer. Under the combined action of mining dynamic and hydraulic pressures, the resistance to bending decreased with the time accumulated for the amount of growth. e de ection and stress of the complete rock beam in the oor change, and a comparison of the maximum bearing capacity of rock mass can determine its stability
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