Coupled thermo-mechanical growth of multiple fractures in brittle heterogeneous rocks during thermal shock and resulting aperture distributions

Understanding the mechanisms that control the development of fractures in complex thermally deformed media, as well as how they interact with smaller-scale and larger-scale heterogeneiies in material properties, is relevant to a number of natural and engineered processes. In this study, we investigate the results of numerical simulations of thermal shock and the resultant fracturing of brittle rock slabs in the context of a fracture growth benchmark. The benchmark, based on multiple laboratory experiments, induces the non-planar formation of multiple fractures due to thermal shock on ceramic mm-scale slabs. The benchmark experiment tracks fracture geometries for a series of shock temperatures and is used to directly validate our numerical approach, which utilises a three-dimensional in-house finite element code to simulate thermo-mechanical deformation. The ensuing damage and spatially variable fracture apertures are quantified, as well as the resulting fracture network patterns. In our approach, fractures are represented as NURBS surfaces, which are discretised using quadrilaterals and triangles. The matrix is discretised using isoparametric tetrahedral and hexahedral elements. We show in our results how thermal shock affects the fracture aperture distributions, and how these aperture distributions depend on the initial heterogeneities in the modelled slab. We discuss how the simulated fracture interactions are self-organising, and compare well to the proposed multi-fracture benchmark. Additionally, we discuss the manner in which geometry, scale, and heterogeneity influence the resulting fracture pattern and aperture distribution.