| Shanxi Binchang mining area is a complex environment for deep ground resources,and the large-scale development of Hujiahe mine faces the problem of "three highs and one disturbance".Under the action of high dynamic stress concentration,the coal body accumulates a large amount of elastic energy,which causes the destruction of the coal body and induces the rock bursts.Based on the combination of in situ multi-stress path true triaxial experiments,theoretical analysis,numerical simulation and engineering application,this paper investigates the damage morphological characteristics of cracked coal body after loading,reveals the acoustic emission response law and fractal characteristics,explores the mechanical mechanism of impact destabilization of cracked coal body,determines the key impact prevention areas based on numerical simulation,and proposes engineering prevention and control technology measures.The main findings of the paper are as follows.1.The damage state of the coal specimen is "tensile-shear" type damage through the real triaxial mechanical experiments of the coal body;the characteristics of the fracture morphology of the coal body after the damage by load are analyzed;the bearable peak strength range of the coal is 14-18 MPa;the three periods of damage variables of the damaged coal body are obtained through AE signal analysis,namely In the initial period is 0,in the stable development period is located in the range of 0.04?0.17,in the accelerated development period presents 90° exponential increase;using the fractal principle,obtained the relationship between the fractal dimension and the amount of debris,that is,the path 2 slope is the largest,the corresponding fractal dimension is also larger(1.50?1.59),the greater the degree of coal fragmentation,the more debris,the coal body destruction power rapid lead to coal rock system instability The impact mine pressure is induced.Different stress paths have significant effects on the fractal dimension values of the crushed masses,and for the presence of high stresses weaken the strength of the coal body to some extent.2.Based on the results of the experimental study,the mechanical properties of the coal samples are theoretically verified using the rock burst theory.It is concluded that the coal body is strong and elastic,and the propensity to impact increases,and also depends on the loading method;the influencing factors of rock bursts and the inducing conditions are analysed;the three indicators in the impact propensity experiment are verified by the "three criteria" theory to determine the impact propensity of#4 coal.3.Based on the experimental and theoretical analysis,FLAC3D was used to invert the stress field,displacement field and fracture field evolution characteristics of 401103 working face.Through the stress field evolution,it was determined that the stress concentration areas in the working face,the roadway area and the solid coal side are impact hazards.From the fracture field evolution,it is concluded that the coal body and the roof and floor are "tension-shear" damage.4.Through on-site monitoring of the key rock burst prevention areas in the numerical simulation results,it was determined that the key rock burst prevention area is 5?10m to the left of the return air roadway of the working face.The "regional pressure relief+local pressure relief+anti-scouring support" anti-scouring management model was proposed for the key control area,with the mine group as the study unit. |
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