Cracking Processes and Failure Modes of Rock-Like Specimens with a Set of Non-persistent Joints

To gain a better understanding of the cracking process and failure mode of rock mass with a set of coplanar non-persistent joints, the uniaxial compression tests were carried out for 15 cylindrical rock-like specimens with different joint inclination angles (alpha) and rock bridge lengths (L-r) prepared through a self-developed method. Results obtained from the laboratory experiments are as follows, (1) five types of failure modes of specimens are observed: tensile failure mode (T-mode), tensile dominated tensile/shear complex failure mode (TDM-mode), tensile/shear equally complex failure mode (TSEM-mode), shear dominated tensile/shear complex failure mode (SDM-mode) and shear failure mode (S-mode); (2) The failure mode of specimen is T-mode or TDM-mode at alpha = 15 degrees, and that of specimen is S-mode and SDM-mode at alpha = 60 degrees; and the transitional failure modes occur as alpha increases from 15 degrees to 60 degrees and from 60 degrees to 75 degrees; (3) a greaterL(r)will strengthen the tension effect and mitigate the shear effect on the failure of specimen; in general, the representative value of failure mode increases asL(r)increases from 10 to 30 mm. Numerical modeling by the discrete element method efficiently simulates the cracking process and fracturing behavior of the five types of failure modes in laboratory experiments.