Introducing displacement softening in the contact model has been shown to be effective in increasing the compressive over tensile strength ratio as large as ~ 30 in DEM modeling with bonded spherical particles (Ma and Huang, 2018a). In our previous work, bonds between particles are allowed to fail only in the normal direction. Here this assumption is relaxed. Both shear and normal bond failures are allowed. The effect of shear bond failure on the micro- and macro-scale behaviors, in particular, the UCS/UTS ratio, is investigated. Formulation of the displacement-softening contact model is first introduced. Numerical simulations are conducted to examine the role of the shear bond failure by varying the shear over normal bond strength ratio and the softening coefficient. Finally, implications of the numerical results in the context of how to calibrate the material properties in DEM modeling are discussed.

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