Acoustic emission(AE) characteristics of fine sandstone and coarse sandstone fracture process under tension-compression-shear stress

The use of TAW-2000KN press, TYJ-500KN press and SH-II acoustic emission(AE) system, coarse sandstone and fine sandstone under uniaxial compression, Brazil splitting and variable angle shear experiment on crack propagation mechanics characteristics and AE in the process of research. The experiment results show that the tensile strength and shear strength of sandstone and coarse sandstone can be compared with that of the approximate equivalent shear strength ratio and the ratio of shear strength to shear strength is larger than that of the single axial compressive strength. The AE characteristics of the fine sandstone and the coarse sandstone are obviously different. The variation law of AE count curve of fine sandstone under the action of shear stress: ①-I-②-II-③(the mark express region by"-"), shear stress gritrock regularity of AE count curve: ①-I-II-III-②. The characteristics of AE energy characteristics are as follows, fine sandstone:present the bending "Chinese character" type, coarse sandstone:present the bending"S"type. The curves of stress-strain curves are completely consistent. Fine sand and coarse sand rock tensile failure process of AE characteristic differences, The variation law of the AE count curve of fine sandstone under the action of tensile stress:①-I-②-II-③-III, the action of tensile stress gritrock regularity of AE count curve: ①-I-②-II-③-III;AE energy features for fine sandstone:local instability damage exists, the complexity of the path curve growth, coarse sandstone:a linear trend growth. From the point of view of failure analysis, the difference between the two types of rock is that the sound emission count and the slow growth of energy before the destruction of fine sandstone, the occurrence of a certain period of stability after the destruction. Coarse sandstone loading period, high count signal and low count signal alternately, failure and failure early stage of high count signal and low count signal mixed sparse. Fine sandstone and coarse sandstone uniaxial compression process of AE characteristics of different AE count features, fine sand: ①-I-②-II-③, coarse sand: ①-I-II-②-③; AE energy features for fine sandstone:present the bending "S" type, coarse sand:present the bending "Z" type. The RA value of AE and the average frequency can reflect the type of crack, tensile failure and shear failure are in line with the objective reality. The uniaxial compression damage form given crack types of positive feedback, it is shown the application of AE technology to determine the crack type effective and feasible. © 2016, Science Press. All right reserved.