| As a natural material with anisotropic characteristics,rock mass may be damaged under the influence of complex geo-stress environment and its own structural characteristics,thus affecting its geotechnical engineering stability.For rock mass,the process of deformation damage and failure is caused by the crack propagation of a large number of cracks in its structural plane and rock.The acoustic signals generated by the cracking and propagation of these cracks,namely acoustic emission signals,can be detected by professional instruments and equipment.If the moveout positioning method is adopted,that is,multiple acoustic emission probes are arranged and the signal moveout analysis between each probe is used to calculate the spatial position of acoustic wave signal source caused by the cracking and expansion of micro-cracks in rock mass,which will provide the possibility for three-dimensional visualization of the cracking and expansion process of micro-cracks in rock mass during deformation,damage and failure.This article is aimed to use the self-developed meso-shear test equipment for coal rock containing gas combined with AE positioning to study sandstone specimens with different bedding angles.The experimental study of rock shear crack propagation under different normal stress conditions of 0°,30°,60° and 90° and 0 MPa and 3 MPa was carried out.By analyzing of the shear cracking propagation process and the shear cracking propagation characteristics of sandstone with different bedding inclinations under different normal stresses,the influence of different bedding inclinations on the mechanism of shear cracking propagation is revealed.The result has shown:(1)using the acoustic emission test system to collect sandstone shearing process of acoustic emission signals and to calculate the noise emission location map,based on the analysis of acoustic emission location map,different time show that different stratification Angle of sandstone under shear load damage micro cracks are produced by its internal crack extension and gradually formed a macro transfixion crack caused;(2)Under the same normal stress,the crack propagation process of the cracks is affected to some extent by different bedding inclinations.When the lamination dip Angle is small,the crack propagation direction of the microcrack will proceed from top to bottom.When the lamination dip Angle is large,the microcrack will first appear in the middle of the specimen and crack to the upper and lower ends of the specimen.When the bedding dip Angle was 30° and 60°,the cracks showed a certain Angle related to the bedding dip Angle and a large number of cracks.When the bedding dip Angle was 0° and90°,the cracks presented an approximate vertical shape with a small number of cracks;(3)Under the condition of the same bedding inclination Angle,the increase of normal stress increases the shear strength of sandstone,the crack propagation speed decreases but the crack destruction degree increases,and the turning point of the transition from the pore fracture compaction stage to the elastic stage becomes obvious;The existence of normal stress has little influence on the crack propagation direction,but it has obvious influence on the crack propagation characteristic,which changes from the morphology related to the crack characteristic and the bedding dip Angle to the morphology of vertical crack propagation;... |
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