Finite Element Modeling of Frictional Contact Between a Blunt Tool and Rock with Anisotropic Damage

The mechanism is investigated for frictional contact between a wear flat and rocks. A brief review focuses on the governing parameters of frictional contact on different types of rocks. Anisotropic damage is taken into account using an anisotropic elasto-plastic-damage model, as demonstrated by a single-element test in uniaxial compression. Anisotropic damage is controlled by a compressive damage coefficient ζ, which can be interpreted as the ratio of axial damage to lateral damage in a special case of uniaxial compression. Tool-rock frictional contact is investigated using a finite element model consisting of a slightly inclined tool and a quasi-brittle rock with induced anisotropic damage. The nature of frictional contact is predominantly governed by three dimensionless parameters: the elastoplastic parameter η, the brittleness number ξ, and the anisotropic compressive damage coefficient ζ. The dimensionless average contact stress (equation) increases with the elastoplastic parameter η, and then slightly varies before leveling off. The contact stress (equation) generally decreases with an increase in the brittleness number ξ. Additionally, the contact stress (equation) increases with a decrease in the damage coefficient ζ from isotropic to anisotropic damage. The numerical results of (equation) are generally consistent with typical experimental results. 1 INTRODUCTION Tool-rock interactions have important applications in various subsurface operations, such as hydrocarbon production, geothermal exploration, and carbon sequestration (DePaolo and Cole, 2013; Phelan et al., 2022; Li et al., 2023). Different types of tool-rock interactions have been extensively studied from various perspectives, including tool wear, rock failure modes, and material characterization. A wear process is influenced by three components, including the cutting tool, rock properties, and interfacial properties (Hamzaban et al., 2023). The wear of tools increases with increasing applied loads and travel distances, resulting in reduced cutting efficiency (Rostami et al., 2014; Zhou et al., 2017). Different failure modes in rock cutting have been revealed through extensive laboratory tests with both sharp and blunt cutters (Rostamsowlat et al., 2019; Zhang et al., 2022). The mechanisms of tool-rock frictional contact have been investigated using various constitutive models for rocks in numerical modeling (Zhou and Detournay, 2014; Voyiadjis and Zhou, 2019; Zhou and Voyiadjis, 2021). Tool-rock interaction tests also provide a way to characterize material properties of rocks, including uniaxial compressive strength and internal friction angle from scratch tests (Rostamsowlat et al., 2022; Zhang et al., 2022), elastic modulus and hardness from nanoindentation in shales (Liu et al., 2016), and hydraulic diffusivity from indentation in poroelastic and poroelastoplastic rocks (Liu and Huang, 2021).