Mechanical behavior and failure analysis of brittle sandstone specimens containing combined flaws under uniaxial compression

YANG Sheng-qi(杨圣奇)^{1, 2}, JING Hong-wen(靖洪文)¹, XU Tao(徐涛)³

(1. State Key Laboratory for Geomechanics and Deep Underground Engineering
(China University of Mining and Technology), Xuzhou 221008, China;
2. Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province,
Wuhan University, Wuhan 430072, China;
3. Center for Rock Instability & Seismicity Research, Northeastern University, Shenyang 110819, China)

Abstract:Based on the axial stress-axial strain curves, the effect of fissure angle on the strength and deformation behavior of sandstone specimens containing combined flaws is analyzed. The mechanical parameters of sandstone specimens containing combined flaws are all lower than that of intact specimen, but the reduction extent is distinctly related to the fissure angle. The results of sandstone specimens containing combined flaws are obtained by the acoustic emission, which can be used to monitor the crack initiation and propagation. The ultimate failure mode and crack coalescence behavior are evaluated for brittle sandstone specimens containing combined flaws. Nine different crack types are identified on the basis of their geometry and crack coalescence mechanism (tensile crack, hole collapse, far-field crack and surface spalling) for combined flaws. The photographic monitoring was also adopted for uniaxial compression test in order to confirm the sequence of crack coalescence in brittle sandstone specimens containing combined flaws, which recorded the real-time crack coalescence process during entire deformation. According to the monitored results, the effect of crack coalescence process on the strength and deformation behavior is investigated based on a detailed analysis for brittle sandstone specimens containing combined flaws by using digital photogrammetry.

Key words:brittle sandstone; combined flaws; strength; crack coalescence; acoustic emission (AE)