Abstract
Brittle failure of rock is characterized by the initiation, propagation and coalescence of micro- and macro-cracks. To study the macro-crack evolution of rocks, a parallel long strain gauge measurement apparatus was developed, which was composed of multiple long axial strain gauges and linear variable differential transformers (LVDTs). Using the developed strain measurement apparatus, conventional triaxial compression (CTC) tests were carried out on Linghai granite specimens. The results showed that a) using the radial strain of rock specimens monitored by LVDT as the servo feedback signal, the strain gauges can obtain the local complete stress–strain curves of the specimen. b) Macro-cracks often formed in the areas with large pre-peak axial strain (ε 1) values, but not in the areas with small pre-peak ε 1 values. c) There were three typical cracking patterns in Linghai granite: rapid tensile cracking, slow tensile cracking, and rapid shear cracking, among which rapid tensile cracking was the most common. d) The macro-crack evolution process can be deduced through the fracture sequence of the strain gauges and the failure pattern of the specimen. In addition, the typical crack propagation velocity of Linghai granite under a confining pressure of 80 MPa was approximately 667 m/s.
Published Version
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