Stress threshold identification of progressive fracturing in Bukit Timah granite under uniaxial and triaxial stress conditions

Abstract

This paper reports the results of an extensive study of the deformation and fracturing of Bukit Timah granite in Singapore under uniaxial and triaxial loading conditions. In the investigation, the stress fracturing thresholds (crack initiation, crack coalescence and crack damage) were determined using stress-strain and stiffness curves and the acoustic emission (AE) detection technique. Crack initiation was found to be best determined by the volumetric strain curve in both uniaxial and triaxial compression tests. The subjectivity of determining the crack closure region and these stress thresholds can be overcome and the results validated by the AE technique by simply observing the cumulative curve of the AE count plotted against deviator stress, which showed four distinctive zones of fracturing. Furthermore, AE detection in the loading stage was found to be a powerful method for determining the phenomena of stable and unstable crack propagation, which are helpful in predicting the rockburst phenomenon. Finally, a comprehensive petrographical analysis using a petrological microscope and a scanning electron microscope was performed to identify the mode of cracking and the characterisation of the cracking pattern.

The Influence of Confining Pressure and Preexisting Damage on Strain Localization in Fluid‐Saturated Crystalline Rocks in the Upper Crust

“…These fracture networks are often diffusely distributed, with several fractures extending from the top to the bottom of the core (e.g., Akdag et al., 2021; Basu et al., 2013; Hu et al., 2021). Under higher confining pressures, the rock cores fail through the development of one or a few macroscopic shear fractures, perhaps as a pair as conjugate shear fractures (e.g., Lee & Rathnaweera, 2016; Paterson, 1958). Although these fractures may develop from the coalescence of many small fractures, the final fracture geometry identified following the maximum stress consists of a few system‐spanning fractures.…”

Mechanical Properties and Acoustic Emission Characteristics of Karst Limestone under Uniaxial Compression

“…Compression. According to previous studies, the failure process of brittle rock can be generally divided into five stages: crack closure, elastic deformation, fracture initiation and stable growth, fracture damage and unstable growth, and failure and post peak [44][45][46]. According to the experimental results, the stress-strain curves of karst limestone samples under uniaxial compression were showed in Figures 6-8.…”

Microscopic Identification of Progressive Fracturing in Granite Under Triaxial and Uniaxial Stress Conditions from Bátaapáti Radwaste Repository

“…But the previously mentioned parallel, overlapping and non-overlapping flaws (or pre-existing cracks) are presents in the Figs. 12-14. In [44], the numerically simulated results demonstrated that rock heterogeneity and inclination of the pre-existing flaw are important factors that could affect the crack patterns and peak uniaxial compressive strength of rock specimens. To investigate the propagation and coalescence of nonpenetrating surface flaws and their effect on the strength of soft rock material, gypsum was selected for the experimental investigation.…”