| Roof water leakage is easy to trigger instability of support in fully-mechanized top caving face with steeply inclined soft coal seam.According to the support dumped accident caused by roof water leakage in No.1125 fully mechanized caving face with steeply inclined soft coal seam of Changshanzi mine,through analyzing the mine hydrogeological and the roof strata structure of coal face,determined the causes of roof water leakage.By using the theoretical analysis and establishment of mechanical model illustrated the influence of roof water leakage on support stability and roof and floor stability,and studied the failure of mechanism and characteristic of roof under water leakage.According to the occurrence condition of coal seam,the FLAC3D numerical simulation was applied to study the distribution law of the complicated stress,displacement and plastic failure.Finally,developed support stabilization and dynamic stability of the dumped support.The main research results are as follows:(1)The sources of roof water in No.1125 workface is Jurassic Xinhe Formation sandstone conglomerate aquifer pore fissure water,the reason resulted in roof water leakage is that the weak roof strata was affected by excavation disturbed,the water-conducting would formed when the fracture penetrates into the sandstone aquifer,which could again lead to the leakage of the local roof water accumulation.(2)The disturbance of roof water supply to the stability of the support is mainly manifested as the roof water washed against the soft and broken roof which finally lead to the roof collapse.And the floor is deformed by water immersion caused the base of support caved in.above two points would lead to a wide range of hollow in the top of support.Floating coal and water spray to form water slime and then resulted in slippery floor,which eventually increased the downward trend of the support.(3)The failure mechanism of roof under water leakage are as follows.With the advancing of the working face,the mining induced fractures continuously developed the loosen zone of roof strata.The roof water weakened the cohesive force between the particles,reduced the shear strength of roof strata,dissolved the cement of the roof stratum,cracked the broken top coal,and reduced the strengtht and stability of roof.The fissure water pressure applied to the loosening zone of the roof water causes the vertical deformation,shear deformation and the displacement,besides,it broken the original balance of roof strata,eventually resulted in roof strata appear the penetrating failure surfac,caused the roof strata instability.(4)FLAC3D numerical simulation results show that under the disturbance of roof water,the distribution of roof vertical complicated stress was uneven and irregular,and the stress perturbation range was larger.Compared with the condition of no roof water interference,the deformation degree of the roof and the plastic failure zone of the roof were significantly increased.(5)The scheme of support stabilization and dynamic stability of the dumped support effectively controled the roof water leakage of the working face and stabilized the support affected by the water.Above two schemes that would provide effective supports for the stability of the fully-mechanized top caving face with steeply inclined soft coal seam.The results of this paper provide a reference for solving the problem of instability of the support surrounding rock system and slow forward of the workface caused by the sudden roof water leakage in fully-mechanized top caving face with steeply inclined soft coal seam.The scheme of support stabilization and dynamic stability of the dumped support provided a guarantee for make sure the workface through the water leakage affected area safely. |
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