This paper deals with the following two shortcomings of the smooth joint contact model (SJCM) used in the particle flow code (PFC): (a) Use of a constant value for joint normal stiffness instead of allowing actual non-linear behavior between the joint normal deformation and joint normal stress; (b) The so called “interlocking problem”. The first one is solved by imposing a linear relation between the joint normal stiffness and the normal contact stress in a new modified smooth-joint contact model (MSJCM). A good agreement obtained between the results from the experimental tests and the numerical modeling of the compression joint normal test, shows the accuracy of this new model. The second shortcoming occurs due to a lack of an updating procedure in the PFC software related to the contact conditions of the particles that lie around the intended joint plane during high shear displacements. This problem increases the shear strength of the joint when the shear displacement of the joint exceeds a specific value and creates unwanted fractures around the intended joint plane. To solve this problem a new approach termed joint side checking (JSC) is proposed. Numerical modeling of the direct shear test shows JSC can solve the interlocking problem and proves to be more consistent with the theory compared to the regular approach.

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