Failure and Fracture Process Characteristics of Layered Slate: Experimental Observation and Discrete Element Modeling

摘要

The thin-bedded slate exhibits the characteristics of strong anisotropy is widely found in underground engineering, where its complex fracture behaviors can easily lead to drastic engineering hazards. Therefore, it is of considerable significance to research its substantial anisotropy fracture characteristics. To this virtue, we present the Brazilian and semi-circular bend (SCB) tests experimentally and numerically to investigate the failure characteristics of layered slate. The study showed that: The experimentally observed tensile strength and mode I fracture toughness gradually decrease with increasing bedding inclination angle, irrespective of the divider-shaped specimens. Further, the empirical relationship was developed as K-IC = 0.094 sigma(t) + 0.036 that fitted from the experimental results. In addition, the mechanical response and final fracture modes predicted by the discrete element method (DEM) are fairly consistent with the laboratory experiments, and the fracture evolutions of the typical numerical slates are reproduced. It was concluded by the systematical DEM simulations that to measure the intrinsic fracture toughness of layered slate by the SCB experiments, a reasonable range of span S/2R should be approximately 0.6 similar to 0.8, which supports the recommendation by ISRM.