| Water bursting from coal floor rock mass is a major hidden danger to the safe production of Chinese coal mines.With the increasing mining depth and the high-intensity mining of lower coal seam,the prevention and control of coal mine floor water bursting disasters has become a major technical theoretical subject that is urgently needed to be resolved.Research on the control mechanism of mining damage and water inrush of floor rock mass is much related to the coal production safety and coal resource recovery,which can transform the mining area environmental protection of Chinese coal industry.Mining coal under pressure,evaluating water bursting possibility,forming strongly engineering measures are the key to the safe operation g in confined water,whose key is the control mechanism research on damage floor rock mass water bursting of longwall caving mining.Taking some mine in Northern Shaanxi as the research object,the theoretical analysis and numerical analysis to study the failure law of broken floor rock mass is as below.(1)Analyzing main water bursting factors.Combined with the hydrological and geological data of some coal mine,the influencing factors of water bursting from the floor rock mass are analyzed,including the advancing step distance,the thickness of the floor,the integrity of the floor,and the depth of the floor failure.(2)Research on floor rock mass.Pressure distribution characteristics and propagation law of floor rock mass during mining are studied by failure stress analysis of coal mining face floor under stress-damage conditions.Lastly the broken floor depth theoretical calculation formula under stress damage and structural surface are derived.(3)Damage numerical simulation research.Considering the water pressure,mining height,floor thickness,floor integrity and the changing characteristics of the rock under mining action,numerical simulation are focused on different change trend and plastic zone distribution of floor rock mass under stress-damage conditions.The larger the advancing step of the coal mining face,the worse the integrity of the floor,the thinner the thickness of the floor,the greater the change of the stress and displacement of the stope floor,and the larger the damage range of the plastic zone.(4)Floor water inrush prevention.Combined previous numerical simulation,the grouting floor rock mass is carried out to determine the reformation degree of water bursting.Generally,this method can effectively increase rock mass density and internal friction angle,decrease god floor heave and peak bearing pressure,which can ensure the resisting layer integrity and the safely mining under pressure.(5)Studying floor damage indexing.Combined with the on-site measured data,grey correlation analysis are applied,whose descending degree is: inclination angle> oblique length>floor damage indexing> mining thickness> mining depth. |
