Meikuang Anquan (Sep 2023)
Damage test and model study of soft and hard interbedded rock based on piezoelectric ceramics and DIC
Abstract
In order to explore the damage evolution law of soft and hard interbedded rock after failure, three groups of rock-like test blocks (soft rock, interbedded rock and hard rock) were made by using the similar model theory. In addition to uniaxial compression of rock-like test blocks, piezoelectric ceramic test and digital image correlation (DIC) technology are used to detect rock internal and external damages in real time, and analyze its failure state and damage evolution law. The test results show that the strength and deformation characteristics of soft and hard interbedded rock are between those of soft and hard rock. Before reaching the peak point, the mechanical law is similar to that of soft rock with certain expansion deformation, but after failure, the mechanical property is similar to that of hard rock with brittle failure. By combining the time domain signal of piezoelectric ceramics and DIC strain images with the process of rock loading to failure, it is found that all kinds of rocks present an “S” shaped damage evolution law, which is gentle at the beginning, accelerated at the middle stage and slowed down at the end. The time domain signal attenuation amplitude of piezoelectric ceramics is positively correlated with the early stage of rock damage, while the strain variation characteristics of DIC images are closely correlated with the middle and late stage of rock damage. In the early stage, the damage accumulation is mainly caused by the deformation of the soft rock and the development of a small number of cracks in the hard rock, while in the late stage, the damage accumulation is mainly caused by the interconnecting and transfixating of microcracks in the hard rock. The damage accumulation is finally manifested as the crushing of the soft rock and the obvious transfixating cracks in the hard rock. Combined with the damage monitoring characteristics of piezoelectric ceramics and DIC technology, the abrupt change interval and abrupt change intersection in rock damage curves were quantified based on the abrupt change theory, and the abrupt change intersection was taken as the subsection point of rock internal and external damage. A rock constitutive model combining internal and external damage was proposed.
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