Modified joint element constitutive model for FDEM to simulate the nonlinear mechanical behavior of rocks

Abstract

The closure behavior of fractured rock, which is a crucial characteristic, is challenging to simulate accurately using commonly employed numerical models. To address this issue and accurately replicate the nonlinear mechanical behavior of rock, we propose a modified joint element constitutive model for the finite-discrete element method (FDEM). The modified model resolves the stress on both sides of the crack by considering the aperture of the broken joint element instead of contact. Additionally, Joint elements with virtual opening, which are referred to as preprocessed joint elements (Pre-JEs), are implemented in this model. We extensively discuss two parameters associated with Pre-JEs to elucidate their impact on the nonlinear mechanical behavior of rock. Our findings demonstrate that the incorporation of Pre-JEs leads to a reduction in the compressive strength of rock. Furthermore, increasing the thickness of Pre-JEs results in the softening of the elastic modulus. Moreover, we have made improvements to the conventional calibration procedure for input parameters in FDEM. By employing our enhanced methodology, we successfully reproduce the crack closure behavior and peak strength of Lac du Bonnet granite using the proposed model.