Research On The Inoculation Mechanism Of Geological Discontinuity Rock Burst In The Bifurcation Area Of Coal Seams

In recent years,geological discontinuity have caused frequent occurrences of rock burst accidents.Researchers have done more research on large-scale geological discontinuity such as faults,but less on the mechanism of coal seam bifurcation areas.This article uses coal seam bifurcation in Zhaolou Coal Mine.As the research background,the occurrence of the area is analyzed from three aspects: the stress field of the initial rock,the stress evolution characteristics of the surrounding rock during the mining process,and the mechanical response of the geological geological discontinuity,and the following research results are obtained:(1)The initial rock stress field in the bifurcation zone of the coal seam is composed of the self-weight stress field and the residual tectonic stress field.The initial rock stress is mainly affected by the change of coal thickness and the geological discontinuity;the two factors of the original rock stress and the mining disturbance in the bifurcation zone of the coal seam are derived.The analytical formula of stress distribution and the sliding criterion of the geological discontinuity of coal and rock under this condition,the mechanical model of coal mining face passing through the bifurcation zone of the coal seam is established,the analytical formula of the load intensity on the bifurcated coal pillar is obtained,and the influence factor is determined.The main controlling factors for the occurrence of slippage instability in the fork area are the angle of the fork,the range of the fork area and the direction of the mining face passing the fork area.(2)In the process of mining the bifurcation zone of the coal seam at the working face,the coal and rock mass at the junction of the upper bifurcation coal and rock at the geological discontinuity and the coal seam bifurcation line are more sensitive to the mining disturbance,and the coal and rock mass in this area is more prone to stress concentration.,And there are obvious stress gradient changes;the lower direct roof is affected by the geological discontinuity,and the triangular wedge between the upper and lower bifurcated coal seams slips and loses stability or the caving step is rapidly reduced,which is the basic top hard rock strata and the upper direct roof of the working face.The roof provides strain space,the overhanging area gradually increases,the squeezing and clamping effect on the coal in front of the working face is enhanced,and the impact risk of the working face is increased.(3)Compared with advancing from coal seam to bifurcated coal seam,during the process of advancing from bifurcated coal seam to coal seam through the bifurcation zone of coal seam,the support stress and horizontal stress peak level of the coal in front of the working face are higher,and the triangle wedged into the rock block It is easier to "activate" along the geological discontinuity of the upper bifurcation coal and rock,and the impact risk of mining through the bifurcation area at the working face is higher.(4)The bifurcation angle and the range of the bifurcation zone have similar effects on the mining process in the bifurcation zone.When the bifurcation angle or the range of the bifurcation zone is larger,the initial rock stress abnormality zone is larger,and the coal supporting stress and the horizontal stress peak value are higher in front of the working face,and the impact risk of the working face passing the bifurcation zone is stronger.The effect of the change of the bifurcation angle on the stress evolution of the surrounding rock and the mechanical response of the geologically geological discontinuity is stronger than the change in the range of the bifurcation zone.The greater the bifurcation angle,the integrity of the triangular wedged rock block sliding along the geological discontinuity,resulting in slippage The greater the impact strength of instability and the greater the range of the bifurcation zone,the sliding of the triangular wedged rock block along the geological discontinuity will change from overall sliding to partial sliding.(5)The leading factors for rock bursts induced by coal mining in the bifurcation zone of the working face are respectively the impact induced by the geological discontinuity slippage instability,the impact induced by the instability of the coal of the working face,and the impact induced by the breaking of the hard roof.This paper involves 65 figures,1 tables,and 80 references.