Study On Mechanism And Prevention Of Floor Type Rock Burst In Inclined Slicing And Section Mining Of Large Dip Angle Ultra-Thick Coal Seam

Rock burst is a kind of dynamic failure phenomenon in coal seam and rock mass which releases elastic energy instantaneously.Its occurrence mechanism is complex and diverse,and the disaster effect is different under different mining conditions.Therefore,it is of great theoretical significance and practical value to study the mechanism of rock burst mining in large dip angle and extra-thick coal seam.This paper adopts theoretical analysis,numerical simulation and engineering practice,and takes Dongxia Coal Mine as the background to study the mechanism and prevention countermeasures of floor rock burst in inclined sublevel mining of large dip angle ultra-thick coal seam.The research results are as follows:The basic situation of Dongxia Coal Mine and 37221-1 working face is introduced.The ground stress test and bursting liability identification of coal seam and roof and floor are carried out.The positioning errors under the three-dimensional microseismic monitoring network are studied,and the characteristics of shock appearance and the distribution characteristics of large energy mine earthquakes in the mining process of medium-layer working face are analyzed.The distribution characteristics of mining stress in section mining are analyzed,and the reason of frequent earthquakes in upper roadway trough mine is theoretically revealed.In this paper,the force characteristics of the mining in large dip coal seam are studied,the fracture form of strong mine earthquake is determined by using the method of moment tensor focal mechanism inversion,and the shear failure conditions of the rock mass in layered mining are deduced.The numerical simulation study on the mining of inclined stratified and sublevel coal seam with large dip angle and thick seam is carried out to explore the influence characteristics of the key factors of shear failure under mining conditions.The results show that:compared with the upper and lower slicing,the middle slicing has the strongest burst risk.The influence of dip angle on rock burst has a critical value,which makes it reach the maximum value under the same condition.The ground stress and the strength of floor rock are the main factors that cause the accumulation of elastic energy of floor,which provides a high dynamic load source for the occurrence of strong ore earthquake in upper roadway.With the increase of the width of coal pillar in the stage,elastic nuclei are generated inside the coal pillar,and then the upper roadway in the middle layer is located in the high shear stress area,which provides a high static load source for the occurrence of mine earthquake in this area.A method of analyzing the disaster effect of mine earthquake by combining theoretical analysis,field data and numerical simulation is proposed.Based on the propagation characteristics of vibration wave,the attenuation model of mine earthquake is established.The dynamic load characteristics of mine earthquake propagating to roadway surface are studied by FLAC^3D numerical simulation,and the critical PPV of roadway resisting impact is determined.The disaster causing model of floor type mine earthquake on roadway is established,and the disaster causing effect of mine earthquake with different energy on roadway is analyzed.This method can solve the maximum energy that the roadway can resist the shock when the mine earthquake is at different distance from the roadway.It provides a new method and a new idea for evaluating the disaster effect caused by dynamic burst and roadway support check.According to the floor type burst mechanism of inclined sublevel mining in large dip angle ultra-thick coal seam,the depressurization design of large diameter borehole under strong tectonic stress is proposed,the floor blasting measures under high dynamic load and coal body blasting measures under high static load are implemented,and the evolution trend of energy and frequency of mine earthquake before and after the stress-relief measures are analyzed.The results show that the charge amount of single hole blasting in the construction of floor on upper roadway should be no less than 30kg,and the spacing should be no less than 15m,and the pressure relief measures should be continuously implemented along with the mining,in order to basically ensure the safety requirements of rock burst prevention.There are 72 figures,19 tables and 139 references in this thesis.