Abstract
The crack propagation and failure of 3D-printed samples with prefabricated K–S fissures (a kinked fissure and a straight fissure) were observed under uniaxial compression, and the strain and displacement of the sample surface were quantified by the digital image correlation (DIC) method. The experimental results show that the branch inclination angle of the kinked fissure is an important factor affecting the crack initial position, and the evolution of the strain field during the failure process of the sample can better reflect the cracking law of the internal fissures. Furthermore, two coalescence modes are classified: Mode I is a tension–shear composite failure formed by the penetration of the tension–shear composite crack; Mode II is a tensile failure that penetrates the whole samples during the failure process without rock bridge damage. In addition, the numerical simulation results were well consistent with the cracking and failure modes.
Highlights
For a preexisting fissure, new cracks form and subsequently coalesce with other preexisting fissures due to a disturbance, which causes the failure of the rock bridge and eventually causes overall damage [1,2,3,4,5]
The failure mode of the rock bridge between fissures plays an essential part in predicting the failure process of preexisting fissures when they are subjected to external load
Sagong and Bobet [6] carried out compression experiments on samples containing two to 16 fissures, and the results indicated that the crack propagation in the multiple-fissure samples was similar to those that contained two fissures
Summary
New cracks form and subsequently coalesce with other preexisting fissures due to a disturbance, which causes the failure of the rock bridge and eventually causes overall damage [1,2,3,4,5]. Many scholars have conducted experimental studies [6,7,8,9] and numerical analysis [10,11,12] on the crack propagation and failure behavior of the rock bridge for samples containing prefabricated straight fissures. The software RFPA2D produced by Tang et al [39] has been recognized and applied in the research of crack propagation, the numerical simulations of non-straight fissures are in good agreement with the experimental results [17]. Six inclination angles of the branch in the kinked fissure were selected, and uniaxial compression loading of these samples was performed using a rock mechanics servo-controlled testing system. The strength, crack initiation, and propagation process of the sample and the coalescence of the rock bridge between prefabricated fissures were studied.
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