(1. State Key Laboratory of Mine Disaster Prevention and Control，Shandong University of Science and Technology，Qingdao，Shandong 266590，China；2. School of Energy Science and Engineering，Henan Polytechnic University，
Jiaozuo，Henan 454003，China)
Abstract：Based on the independently developed coal(rock) pressure water immersion test device，combined with Scanning Electron Microscope and XTDIC 3 D full-field strain measurement system，we carried out the Brazilian split test of four groups of coal samples under 0，3 and 5 MPa pressure water immersion(immersion time is 10 d)，and studied the tensile characteristics of coal samples under pressure water immersion. The results show that the uniaxial tensile strength and post-peak axial stress decline trend with the increase of water immersion pressure，and the plastic failure of coal samples increases at the same time. At the early stage of loading，the distribution of the maximum principal strain field of the coal sample is almost irregular. With the increase of the water immersion pressure，the strain isometric lines of the coal sample strain gradually become dense. The coal sample first produces stress concentration at the original macroscopic crack，forming the deformation localization zone. With the axial stress loads to the peak stress，the macro master control crack is generated in the middle of the coal sample，and the strain isometric line gradient increases，and gradually close to the control of the main macro tensile crack deformation localization zone area contraction. At the same time，the evolution of displacement mismomentum in the deformation localization zone of coal samples is related to the development，expansion and penetration of the localization zone，and the displacement mismomentum in the deformation localization zone at the stress peak increases with the increase of the water-immersion pressure. The increase of water immersion pressure intensifies the water-coal rock action，destroys the initial energy storage structure of coal samples，its pre-peak energy storage capacity gradually decreased，and the mechanical energy loaded to the coal samples by the test machine decreases. Compared with the dry coal samples，the average mechanical energy under 0，3 and 5 MPa pressure water immersion decreases by 29.93%，44.90% and 57.14%，respectively. As the immersion pressure increases，coal fracture morphology from relatively flat to "honeycomb" shape，measured its average porosity，pore maximum area and probability entropy，indicating that the internal damage of coal samples increased，which leads to its uniaxial tensile strength，and the tensile characteristic deterioration effect enhancement. The above research results are of great significance to the reasonable retention and stability guarantee of coal(rock) column in coal mine.
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2023, Vol. 42 
