Study on the influences of rock bridge dip angle and mineral structure on coal damage and failure at three-dimensional scale
In order to explore the effects of rock bridge inclination angle and mineral structure on coal body damage and failure at a three-dimensional scale,uniaxial loading tests are carried out on double-crack samples prefabricated from raw coal with different rock bridge inclination angles,and phased scanning of the compression failure process is carried out with CT scanning equipment.Image processing techniques such as threshold segmentation,3D reconstruction and digital volume correlation methods were used to analyze the dynamic evolution of internal cracks and deformation and damage characteristics of coal samples,and the PFC3D simulation program was used to explore the internal stress distribution characteristics at different stages of the loading process.The results show that the macro-strength of coal samples decreases gradually with the increase of rock bridge angle.The evolution characteristics of the displacement fields in X,Y and Z directions are different due to the influence of prefabricated fractures on coal samples.The local high displacement area in X direction shifts from the rock bridge area to the end with the loading,while the local high displacement area always drifts around the rock bridge area and the prefabricated fracture in the whole loading process of Y direction,and the Z direction displacement field presents obvious stratification at each loading stage.The displacement is small and uniform.According to the crack propagation path and the stress characteristics of the failure surface,the failure mode of coal samples with rock bridge angles of 0° and 90° is tensile failure,and the failure mode of coal samples with rock bridge angles of 30° and 60° is tensile shear compound failure.The relationship between the growth of new crack and the occurrence state of mineral mainly includes three types:encapsulation propagation,around gravel propagation and through gravel propagation.Among them,through gravel propagation is the most frequent and wrapped propagation is the least.The simulation results show that the stress characteristics of coal samples with double cracks in each direction are different at the peak stage.When the slice position extends from the outside of the sample to the inside of the sample,the Y,Z and total stress values show a trend of gradual increase,while the X stress values show a phenomenon of first decreasing and then increasing.
rock mechanicsangle of rock bridgemineral structureCT scanparticle flow simulationdamage and failure
万方数据
维普
