Research on Fracture Propagation and Fracture Instability Precursors of Coal under Different Loading Rates
In the process of coal mining,cracks will be generated inside the coal rock under the action of mining stress,and the expansion of cracks will eventually cause the fracture and instability of coal rock.It is of great theoretical value for the safe mining of mines to study the fracture propagation characteristics of loaded coal rock and the omen of fracture instability precursors.The uniaxial compression tests of coal rock specimens with different loading rates were carried out.Based on the a-nalysis of acoustic emission energy characteristics,the crack propagation direction of loaded coal rock was analyzed,and the crack propagation law and instability precursor of coal rock under different loading rates were discussed.The results show that the main cracks of coal rock specimens are connected by multiple micro-cracks at low loading rate,and the main cracks of coal rock specimens are connected by a few cracks at high loading rate.The evolution trend of the proportion of horizontal cracks and vertical cracks in coal and rock specimens in each loading stage is opposite,and the change curve is conjugate distribu-tion.During the loading process of coal rock,the shear failure dominates in the coal rock,and the correlation dimension of the crack propagation direction can reflect the degree of damage inside the coal rock.During the loading process,the correlation di-mension of the crack propagation direction of coal rock shows a trend of decreasing first and then increasing.The correlation di-mension of the crack propagation direction of coal rock can be taken as the minimum value as the instability precursor of coal rock.
NETL
NSTL
万方数据
