Numerical study of mechanical properties and microcrack evolution of double-layer composite rock specimens with fissures under uniaxial compression

• Published in: Engineering fracture mechanics 2023-09, Vol.289, p.109403, Article 109403
• Main Authors: Ma, Qing, Liu, Xiaoli, Tan, Yunliang, Elsworth, Derek, Shang, Junlong, Song, Danqing, Liu, Xuesheng, Yan, Fayuan
• Format: Article
• Language: English
• Subjects: Composite samples; Layered rock mass; Mechanical behaviour; Pre-existing fissures; Uniaxial compression
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2023.109403

•We complete a suite of numerical (granular mechanics) and complementary physical compression experiments on layered rocks containing fissures in different modalities where the overlying layer is both stronger and stiffer.•We complete this to understand the impact of local specimen and system stiffness on ultimate strength and modes of failure (stability).•We systematically examine the influence of fissure angles, lengths and positions on the mechanical response, including observations of microcrack evolution and tendency for instability (i.e. rock bursting), constrained by acoustic emission (AE). Layered and heterogenous fissured rock masses are ubiquitous in nature. Fissures exert significant influence as release surfaces and nucleation sites for failure in layered rock masses. However, key mechanisms controlling microcrack initiation and extension in layered and heterogenous rock masses remain unclear. We complete a suite of numerical (granular mechanics) and complementary physical compression experiments on layered rocks containing fissures in different modalities where the overlying layer is both stronger and stiffer. We complete this to understand the impact of local specimen and system stiffness on ultimate strength and modes of failure (stability). We systematically examine the influence of fissure angles, lengths and positions on the mechanical response, including observations of microcrack evolution and tendency for instability (i.e. rock bursting), constrained by acoustic emission (AE). Peak strength and overall elastic moduli vary in a predictable and systematic manner. The strengths and stiffnesses of the double-layer composite specimens fall between those of the homogeneous weak and strong single layer specimens. The AE counts, micro crack growth and failure characteristics of the double-layer composite specimens are closely related to the fissure angles, lengths and positions. Whether the weak rock or the strong rock contains fissures, the rock burst tendency of the double-layer composite specimens decreases in varying degrees–defining the potential of pre-blasting/fracturing to soften the mass. Fissure angles and lengths do not have to be too large. Additionally, failure in the double-layer composite specimens results not only from crack propagation in the weak layer, but also failure of the entire specimen when the length of the fissure in the strong layer is sufficiently large. These observations provide a reference for stability evaluati