Mechanical behavior of rock-like jointed blocks with multi-non-persistent joints under uniaxial loading: A particle mechanics approach

• PFC3D is used to study the mechanical behavior of blocks with finite size joints.
• UCSB and DMB depend heavily on the joint dip angle (β) & joint size (k).
• Jointed blocks produced three types of stress–strain curves (Types I–Type III).
• A relation exists between the types of curves and β and k values.
• Four failure modes were observed (splitting, plane, stepped path, intact material).

By selecting appropriate micro-mechanical parameter values through a trial and error procedure, the computer code PFC3D was used to study the macro-mechanical behavior of jointed blocks having multi-non-persistent joints with high joint density under uniaxial loading. The focus was to study the effect of joint orientation, size and joint mechanical properties on jointed block strength, deformability, stress–strain relation and failure modes at the jointed block level. Both the uniaxial compressive strength of the block, UCSB, and block deformability modulus, DMB, were found to depend heavily on the joint dip angle, β, and joint continuity factor, k. The joint particle stiffness was found to play a minor to a significant role on UCSB depending on β and k values. The joint particle stiffness was found to play a negligible to a moderate role on DMB depending on β and k values. The jointed blocks produced three types of stress–strain curves labeled as Type I through Type III. A relation seems to exist as explained in Section 4 of the paper between the types of curves and β and k values. The dominance of tensile failures over the shear failures was observed for all three types of curves based on the micro-mechanical parameter values used in the paper. The UCSB, rate of bond failures and the number of bond breakages were found to decrease as the curve type moves from Type I to Type III through Type II. The jointed blocks resulted in 4 failure modes as follows: (1) splitting failure; (2) plane failure; (3) stepped path and (4) intact material failure. The main features of each failure mode and possible relations between the failure modes, UCSB and β and k values are given in Section 5 of the paper.