Sduty On Mechanism Of Floor Fault Activation And Water Inrush In Confined Water Mining

Most of mine accidents are caused by water inrush from seam floor with fault structure.Cracks in the fault zone will develop and expand under the stope pressure.The fault dislocation movement of upper and lower plates will happen when shearing and stretching action occurs along fault planes,which called "mining fault activation".The mining fault activation will reduce the distance between the floor and the aquifer when the fault cut through the coal seams and aquifers,which reduces the thickness of aquiclude and increases the probability of water inrush.Cracks in the rocks connect to each other,form water inrush channels and cause serious water inrush accidents.Therefore,study on fault activation and water inrush mechanism under mining support pressure and water pressure is of great significance to reduce and solve the water inrush problems.Combined the influence of the fault factors on the fault activation,the theoretical analysis,numerical simulation are used to study the cracks growth,mining fault activation and water inrush channels.The mining fault activation and water inrush mechanism is revealed.(1)Consider the distribution law of support pressure on the bottom of a stope and the effect of water pressure in the aquifer,the mechanical model of fault activation mechanism of stope floor is improved.Based on elastic mechanics,normal stress and shear stress formula of any point on the fault is deduced.The mechanical criteria of fault activation and aquiclude failure are obtained.(2)Fault activation characteristics in different propulsion distances,fault dip,fault fall,and thrust direction are analyzed through numerical simulation software FLAC3D.Because the fault zone has a lower strength than the surrounding rock formations,the plastic zone and shear stress of the stope increase gradually with the advance of the work surface.The greater the fault drop,the easier the fault will be to activate.Small-angle faults are prone to shear failure and crack development.(3)The evolution process of floor water inrush channel during mining is simulated and the seepage flow characteristics of coal seam floor are analyzed.The greater the fault fall,the wider the waterproof pillars,the smaller the fault dip,the wider the waterproof pillar.