Microscopic Damage Mechanism of Coal Sample Under Uniaxial Compression Test Under Different Creep Pre-damage

In this paper, the coal rock is taken as the research object, and the saw-2000 rock servo test system is used to creep pre damage the coal sample, and the uniaxial compression failure test is carried out. The fracture surface of coal sample after uniaxial compression was observed by xpv-900e computer transmission and reflection polarizing microscope, and the meso images of the fracture surface under different magnification were collected. The meso images obtained were binary processed by ImageJ software and the fractal dimension was calculated. The test results show that: with the increase of creep pre damage degree, the damage degree of coal increases; the peak strength first increases and then decreases; the overall change trend of elastic modulus first increases and then decreases; the micro cracks of coal sample first close and then expand with the increase of creep pre damage degree; the fractal dimension value decreases with the increase of the multiple of mirrors, and then decreases with the increase of damage degree.