Thermally Induced Microcracks in Granite and Their Effect on the Macroscale Mechanical Behavior

Abstract

Owing to changes in temperature with time in active tectonic setting, for example, melt migration and magma-chamber formation, vast volumes of crustal rock will develop extensive microcracks in response to thermal loading (Johnson et al., 2021), which has a significant influence on their physical and mechanical properties. The damage horizon might occur at depths of 5 km geothermal fields or at greater depths where thermal gradients can reach >120°C/km (Marini & Manzella, 2005). Since granites are considered the target formation for deep geothermal energy, understanding and controlling the mechanical behavior of granites under thermal loading are critical for geothermal exploration from hot dry rock (Aghahosseini & Breyer, 2020;Salimzadeh et al., 2018). Thermally induced cracking has been identified as the cause of the reduced strength and enhanced permeability of rock at high temperatures (Nasseri et al., 2009). Furthermore, the reduction of friction coefficient (Du et al., 2022) at elevated temperatures and pore fluid pressures may potentially promote fault destabilization

Impact of soft minerals on crack propagation in crystalline rocks under uniaxial compression: A grain‐based numerical investigation

“…Thus, in GBM numerical simulation of crystalline rocks, it is essential to accurately determine the mechanical properties of different minerals via approaches such as nanoindentation. 58 For crystalline rocks containing hard and soft minerals, it is necessary to calibrate micro-parameters pertaining to the hard and soft minerals independently to enhance the performance of modeling.…”

“…As the content increases from 5% to 30%, the proportion of microcracks in soft minerals grows from the initial 9% to 62% with an amplitude as much as 85.5%, indicating that the content of soft minerals significantly affects the crack propagation in crystalline rocks. Thus, in GBM numerical simulation of crystalline rocks, it is essential to accurately determine the mechanical properties of different minerals via approaches such as nanoindentation 58 . For crystalline rocks containing hard and soft minerals, it is necessary to calibrate micro‐parameters pertaining to the hard and soft minerals independently to enhance the performance of modeling.…”

Mechanical properties of minerals in lunar and HED meteorites from nanoindentation testing: Implications for space mining

“…This necessitates methods to extrapolate microscale (mineral-level) properties to macroscale (rock-level) phenomena. Xu et al (2023) exemplify this by studying thermally induced microcracks in granite, analyzing mineral heterogeneity and thermal stress effects on granite's macroscale mechanical integrity using high-temperature microscopy and accurate grainbased modeling (AGBM). Conversely, Tang et al (2023) employ microscale rock mechanics experiments and AGBM to determine asteroid rocks' Young's modulus, bridging mineral and interphase-level analyses to a comprehensive macroscale understanding.…”

Study on the Evolution of Physical Parameters and Dynamic Compression Mechanical Properties of Granite after Different Heating and Cooling Cycles

“…Sun et al [ 9 ] studied the effect of temperature on the physical properties of granite such as quality and surface color. Xu et al [ 10 ] and Zhou et al [ 11 ] investigated the thermal microcrack extension of granite using optical microscopy, thin section observation and scanning electron microscopy (SEM). Zhang et al [ 12 ] and Hao et al [ 13 ] investigated the effect of temperature on the physical and mechanical properties, as well as the intrinsic structure relationship, of granite.…”