Investigation of microcracking behaviors in brittle rock using polygonal grain‐based distinct method

Abstract

The failure process in brittle rocks is an important topic in rock mechanics, whose good understanding assists in predicting the strength and deformation characteristics of rocks. Because it is difficult to directly observe microcracks in laboratory tests, a numerical model is a useful tool for investigating microcracking behaviors. However, the mechanism of microcrack evolution is still unclear at the grain scale considering the microscopic heterogeneities. This paper proposes a polygonal universal distinct element code grain‐based model to solve this problem. Compared with other grain‐based models, this model is different in that mineral grains are subdivided into polygon blocks. The grain size, composition, and bond types of the contacts are incorporated, and both inter‐ and intra‐grain cracks are mimicked. Subsequently, micro‐parameters of the blocks and contacts are carefully calibrated according to the laboratory results. Following this, the calibrated model is employed to study the microcracking behaviors of granite in unconfined compression, confined compression, and Brazilian splitting tests. Both the cumulative numbers and locations of microcracks in different grains are recorded, and the types of macroscopic fractures are identified. The modeling results show that tensile cracks dominate the generated microcracks in the low confined compression tests, and the macroscopic fracture pattern is axial splitting. Shear cracks are dominant in the high confined compression tests, and the macroscopic failure pattern is X‐type shear failure. The simulated results are consistent with those observed in the laboratory tests, and thus, may assist in improving rock acoustic emission monitoring and understanding the damage process of rock.

Experimental and Numerical Investigation of the Tensile Performance and Failure Process of a Modified Portland Cement

“…Numerical simulation was conducted, because it is powerful in revealing the microscopic failure behaviour of materials (Chen et al, 2019;Wang et al, 2021). In addition, numerical simulation was able to reproduce the tensile failure process of the cement paste.…”

Laboratory Earthquakes Simulations—Typical Events, Fault Damage, and Gouge Production

“…Various approaches inspired by the Bonded‐Particle‐Model (Potyondy & Cundall, 2004) have been proposed in order to represent in the same numerical framework an initially elastic medium which can progressively damage and fracture (Asadi et al., 2012; Hazzard & Young, 2000; Kim & Buttlar, 2009; Park & Min, 2015; Potyondy, 2007; Wanne & Young, 2008). A recent trend in rock mechanics is to enrich the traditional circular/spherical representation of grains by considering an initial assembly of polygonal bodies (Saksala & Jabareen, 2019; Z. Wang et al., 2021). This geometry allows to consider samples without any initial porosity, and to represent more accurately the nucleation and the development of fractures and microcracks and the associated dilatancy.…”

Prediction of the post‐failure behavior of rocks: Combining artificial intelligence and acoustic emission sensing

“…Recent studies have shown how DEM simulations can be used as a powerful tool to study the characteristics of AE events in rocks (and concrete) before, during, and after failure. [23][24][25][26][27] The complex and somewhat stochastic post-failure response and its correlation with the pre-failure characteristics evade the current rock-mechanics frameworks. This is the domain where artificial intelligence (AI) and machine learning (ML), and particularly DL methods 28 can provide powerful tools for capturing temporal correlations in AE and stress-strain data to predict the post-failure responses.…”

“…In particular, it is possible to track the energy release in the form of AE when a cohesive bond breaks. Recent studies have shown how DEM simulations can be used as a powerful tool to study the characteristics of AE events in rocks (and concrete) before, during, and after failure 23–27 …”