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Geomechanics and Engineering
  Volume 23, Number 6, December25 2020, pages 587-600

Shear failure and mechanical behavior of flawed specimens containing opening and joints
Yuanchao Zhang, Yujing Jiang, Xinshuai Shi, Qian Yin and Miao Chen

    Shear-induced instability of jointed rock mass has greatly threatened the safety of underground openings. To better understand the failure mechanism of surrounding rock mass under shear, the flawed specimens containing a circular opening and two open joints are prepared and used to conduct direct shear tests. Both experimental and numerical results show that joint inclination (β) has a significant effect on the shear strength, dilation, cracking behavior and stress distribution around flaws. The maximum shear strength, occurring at β=30o, usually corresponds to a unifrom stress state around joint and an intense energy release. However, a larger joint inclination, such as β=90o~150o, will cause a more uneven stress distribution and a stronger stress concentration, thus a lower shear strength. The stress distribution around opening changes little with joint inclination, while the magnitude varys much. Both compression and tension around opening will be greatly enhanced by the 30o-joints. In addition, a higher normal stress tends to enhance the compression and suppress the tension around flaws, resulting in an earlier generation and a larger proportion of shear cracks.
Key Words
    flaws; cracking; stress distribution; acoustic emission; PFC
Yuanchao Zhang and Yujing Jiang: Graduate School of Engineering, Nagasaki University, 1-14 Bunkyo, Nagasaki 852-8521, Japan

Xinshuai Shi and Qian Yin: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China

Miao Chen: College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, China

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