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Geomechanics and Engineering Volume 8, Number 4, April 2015 , pages 541-557 DOI: https://doi.org/10.12989/gae.2015.8.4.541 |
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An experimental study on fracture coalescence characteristics of brittle sandstone specimens combined various flaws |
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Sheng-Qi Yang
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| Abstract | ||
| This research aims to analyze the fracture coalescence characteristics of brittle sandstone specimen (80 × 160 × 30 mm in size) containing various flaws (a single fissure, double squares and combined flaws). Using a rock mechanics servo-controlled testing system, the strength and deformation behaviours of sandstone specimen containing various flaws are experimentally investigated. The results show that the crack initiation stress, uniaxial compressive strength and peak axial strain of specimen containing a single fissure are all higher than those containing double squares, while which are higher than those containing combined flaws. For sandstone specimen containing combined flaws, the uniaxial compressive strength of sandstone increase as fissure angle (α) increases from 30° to 90°, which indicates that the specimens with steeper fissure angles can support higher axial capacity for α greater than 30°. In the entire deformation process of flawed sandstone specimen, crack evolution process is discussed detailed using photographic monitoring technique. For the specimen containing a single fissure, tensile wing cracks are first initiated at the upper and under tips of fissure, and anti-tensile cracks and far-field cracks are also observed in the deformation process; moreover anti-tensile cracks usually accompanies with tensile wing cracks. For the specimen containing double squares, tensile cracks are usually initiated from the top and bottom edge of two squares along the direction of axial stress, and in the process of final unstable failure, more vertical splitting failures are observed in the ligament region. When a single fissure and double squares are formed together into combined flaws, the crack coalescence between the fissure tips and double squares plays a significant role for ultimate failure of the specimen containing combined flaws. | ||
| Key Words | ||
| brittle sandstone; experiment; combined flaws; crack coalescence; strength | ||
| Address | ||
| (1) State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, PR China; (2) Deep Earth Energy Research Laboratory, Department of Civil Engineering, Monash University, Melbourne, Victoria 3800, Australia. | ||