Research Information System
the International Symposium on Geomechanics from Micro to Macro, IS-Grenoble, Grenoble, France, 23 - 27 September 2024, pp.103-104
The construction of engineering structures within rocks exposes these materials to secondary
stresses, leading to consequential deformation and potentially irreversible damage. Over a century,
researchers have focused on unraveling the microscale deformations that initiate subsequent
mesoscale and macroscale rock damage (e.g. Griffith 1921; Bieniawski 1967; Tapponnier and Brace
1976; Horii and Nemat-Nasser 1986; Martin and Chandler 1994; Eberhardt et al. 1998; Renard et al.
2009; Dinç Göğüş and Avşar 2022, etc.). While these investigations denote evolving interest,
underscoring the concerted effort to elucidate fundamental mechanisms governing rock deformation,
acquiring quantitative insights remains imperative for advancing our comprehension of rock damage
mechanisms within the context of engineering applications.
In this research, we aim to quantitatively investigate the roles of textural properties, and
mineralogical composition on micro and mesoscale mechanical rock behaviors by combining
different methodologies such as laboratory experiments, discrete element modeling, mineralogical
examinations, and fractal analysis (Figure 1). For this purpose, we focused on the initiation and
propagation of cracks spanning from microscale to mesoscale in different rock types, diabase,
ignimbrite, and marble. Firstly, the key macro mechanical parameters such as uniaxial compressive
strength (UCS), tensile strength (UTS), elasticity modulus (E), and Poisson's ratio (ν) were
determined through laboratory experiments (Figure 1a). Secondly, discrete element methodology
(DEM) was employed to generate numerical models representing the stress-strain behaviors of real
rocks. Critical stress thresholds (σci, σcd, σpeak) marking microscale cracking leading to meso fractures
were identified within these models. Subsequently, core samples were subjected to uniaxial loading
up to these critical stress levels, followed by thin section preparation for microscopic analysis—
examination under a polarizing microscope allowed for inspecting mechanisms governing crack
propagation (Figure 1b). Finally, a quantitative assessment of rock damage evolution was conducted
through fractal analysis on crack patterns, calculating fractal dimensions (DB) of cracking intensity at
each stress level (Figure 1c). Diabase exhibited the highest DB values on sections parallel to the
loading direction, while ignimbrite and marble manifested equivalent DB values. Conversely, diabase
displayed the least tendency for cracking on sections perpendicular to the loading direction, followed
by marble, with ignimbrite exhibiting the highest cracking intensity. The results show that postcritical stress (σcd) reveals the emergence of textural properties as first-order factors dictating the
extent of rock damage, with mesoscale fractures aligning under mineralogical composition.
The insights derived from this research provide efficient numerical data for predicting
deformation and damage mechanisms in brittle rocks during rock engineering applications. This
integrative approach, combining laboratory experiments, numerical modeling, and microscopic
investigations, advances our understanding of the complex interplay between mineralogical and
textual controls on stress-induced fractal rock damage.