A breakable grain-based model for bi-modular rocks

This article proposes a breakable grain scheme and a method to achieve bi-modular elastic material behavior in grain-based models of rocks using the Hybrid Lattice/Discrete Element Method; a version of the Discrete Element Method that employs Rigid Body Spring Network interactions. First, the paper presents both contributions and two validation exercises regarding bi-modular elastic behavior. Subsequently, a set of comprehensive parametric analyses defines the impact that numerical input parameters have on macroscale results, including: crack initiation and damage stresses; unconfined compression and direct tensile strengths; and material's characteristic length. Of note, the analyses investigate the influence of heterogeneity, based on the application of the Weibull probability distribution to compressive and tensile Young moduli and inter and intragranular strength parameters. Afterwards, simulations based on three theoretical rock types show the capabilities of the Hybrid LDEM with the proposed contributions in representing typical macroscale properties of rocks observed in laboratory tests. Lastly, visual comparisons between grain breakage processes from numerical simulations and laboratory thin-section analyses indicate consistent correspondence, which evidences the potential application of the developed methods to future research focused on rocks' microcracking phenomena. This work concludes that the proposed breakable grains and bi-modular material behavior schemes widen the range of macroscale properties that grain-based models can produce while preserving simplicity.