Comprehensive Prediction And Prevention Of Impact Hazards In Thick And Hard Roof Working Face In Dongtan Coal Mine

With the increase of mining depth and intensity of coal resources in China rock burst has become one of the most serious disasters in the process of deep mining of coal resources.Dongtan coal mine has entered the stage of deep mining which is affected by the increase of buried depth and in-situ stress,the possibility of impact rock pressure is greatly increased,and the presence of thick hard roof on the top of the 3 coal further increases the possibility of gas impact rock pressure.Therefore,it is particularly important to study the early warning and prevention of the impact hazard of working face under the condition of thick roof.the research methods such as theoretical analysis,field investigation,numerical simulation and engineering practice have been adopted to systematically study the hazard source and lure mechanism,the comprehensive prediction and the prevention and control method of impact risk of the thick hard roof working face of Dongtan coal mine,and the following achievements have been obtained:(1)According to the engineering geology of the 6304 working face in Dongtan coal mine,the impact risk factors in the mining process of the working face were analyzed,and an accurate identification of the impact hazard source on the working face was performed.Through the establishment of mechanical model of hard top slate beam in working face,the mechanism of rock burst induced by working face of thick and hard roof was analyzed.The study concludes:the risk sources of rockburst in 63up04 working face of Dongtan coal mine mainly include factors such as depth of mining,nature of roof and floor,activity of thick and hard roof,and geological structure.(2)Using FLAC3D numerical simulation software,simulation revealed different progress from the push face hard roof thick elastic strain energy distribution law of distribution of the support pressure thereto,both having a large degree of similarity,showed semi-elliptical distribution,should be closer to the center position of the face.strain energy density and peak pressure peaks than the support ends from the coal.farther wall,the larger the peak value,the front face thick and hard rock breaking point ahead of the highest degree of energy accumulation region.and the higher the risk of impact to the face forward when it was square.(3)Based on the identification results of the impact hazard sources of the working face,the comprehensive index method,the possibility index method and the "three condition" discriminant method were used to synthetically predict and determine the impact risk of the 63up04 working faces in Dongtan coal mine,and It was considered that 63up04 face had moderate impact risk.According to the evaluation result of the impact hazard grade and considering the influence of geological structure conditions and mining conditions,the grade division and regional delineation of the dangerous ground pressure area of the working face were carried out,which provided an important basis for the fine monitoring and control of hazard rockburst on the next work face production.(4)Based on the result of dividing the dangerous area of rock burst in working face and combining with the specific situation of the working face,the combined monitoring and early warning method of micro-seismic monitoring and drilling chip method was put forward.The distribution law of large energy microseismic events and its precursory characteristics during the mining face were analyzed.It was concluded that the breaking motion of the hard roof above the working surface was easy to produce larger microseismic energy events,and the hazad risk was higher.The method of using large diameter borehole to release pressure and treating the dangerous area of percussive ground pressure by stages were put forward,and blasting was adopted to break the roof of the hard roof above the working face,and good results were obtained.