Brazilian splitting characteristics and weakening mechanism of coal under the influence of water content
Using abandoned mine goaf as water storage space plays an important role in the ecological environment and economic development of mining areas.However,under the influence of different moisture content,the strength of coal and rock mass will weaken,which will further affect the stability of underground storage.In this paper,the weakening degree of Brazilian splitting strength,splitting fail-ure characteristics and acoustic emission evolution law of coal samples with different water content are studied.The coal samples were taken from-710 m mining level,3# coal seam of closed Datai Mine.With the help of CT scanning of pore characteristics of coal samples before and after water immersion,the internal influence mechanism is explored.The results show that the main fractures of dry coal samples disc exist along the splitting plane,while the fractures of saturated samples deviates from the splitting plane,resulting in many irregular shear fractures.With the increase of water content,the flat-ness of the splitting fracture on the samples disc surface decreases.From dry to saturated,the fractal di-mension of splitting fracture on the sample increases from 1.066 to 1.298.The tensile strength of coal samples decreases linearly with the increase of moisture content,but the peak strain increases first and then decreases parabolically.The cumulative count of acoustic emission in coal samples decreases gradu-ally with the moisture content increasing.In the failure stage,the coal samples with low moisture content produce tension-shear composite fractures with large scale,while the coal samples with high moisture content produce small-scale tension fractures.With the help of CT scanning,it is found that the main fracture of coal samples expand after water immersion,and the porosity increases by 2.55％.The in-crease of the porosity of the coal samples accelerates the damage development of the coal samples,which leads to the formation of through fractures more easily in the splitting process.The existence of water weakens the cementation strength of the main fracture,and then makes the splitting fracture expand along the joint fracture surface with less strength.The decrease of new fractures also reduces the intensity of acoustic emission.
万方数据
维普
