EXPERIMENTAL RESEARCH ON DYNAMIC MECHANICAL CHARACTERISTICS OF LAYERED COMPOSITE COAL-ROCK
USING THE SEPARATE HOPKINSON PRESSURE BAR TEST DEVICE, A SERIES OF DYNAMIC IMPACT TESTS WERE CARRIED OUT ON THE SINGLE COAL AND WHITE SANDSTONE NEAR THE INCIDENT BAR. WHEN THE STRESS WAVE PROPAGATES IN A COMPLEX WITH DIFFERENT WAVE IMPEDANCE MATCHING EFFECTS, ITS DYNAMIC MECHANICAL PROPERTIES CHANGE, ENERGY DISSIPATION LAW AND DAMAGE CHARACTERISTICS ARE STUDIED. THE RESEARCH RESULTS SHOW THAT: (1) WITH THE INCREASE OF IMPACT VELOCITY, THE PEAK STRESS AND DIF OF LAYERED COMPOSITE COAL-ROCK INCREASE LINEARLY. AT THE SAME SPEED, WHEN THE STRESS WAVE CHANGES FROM HARD TO SOFT, THE PEAK STRESS AND DIF ARE LARGER THAN THE STRESS WAVE FROM SOFT TO HARD. (2) THE DISSIPATED ENERGY DENSITY OF LAYERED COMPOSITE COAL-ROCK INCREASES IN A QUADRATIC FUNCTION WITH THE INCREASE OF THE INCIDENT ENERGY DENSITY, AND THE COMPOSITE BODY WITH BETTER WAVE IMPEDANCE MATCHING EFFECT HAS A HIGHER DISSIPATED ENERGY DENSITY. (3) THE FRACTAL DIMENSION AND THE DEGREE OF FRACTURE
OF LAYERED COMPOSITE COAL-ROCK INCREASE WITH THE INCREASE OF THE SPEED. THE WHITE SANDSTONE COMPONENT IS MOSTLY SHEAR FAILURE, AND THE COAL COMPONENT IS MOSTLY CRUSHED.
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