Failure Mode and Spatial Distribution of Damage in Rothbach Sandstone in the Brittle-ductile Transition

Abstract

To elucidate the spatial complexity of damage and evolution of localized failure in the transitional regime from brittle faulting to cataclastic ductile flow in a porous sandstone, we performed a series of triaxial compression experiments on Rothbach sandstone (20% porosity). Quantitative microstructural analysis and X-ray computed tomography (CT) imaging were conducted on deformed samples. Localized failure was observed in samples at effective pressures ranging from 5 MPa to 130 MPa. In the brittle faulting regime, dilating shear bands were observed. The CT images and stereological measurements reveal the geometric complexity and spatial heterogeneity of damage in the failed samples. In the transitional regime (at effective pressures between 45 MPa and 130 MPa), compacting shear bands at high angles and compaction bands perpendicular to the maximum compression direction were observed. The laboratory results suggest that these complex localized features can be pervasive in sandstone formations, not just limited to the very porous aeolian sandstone in which they were first documented. The microstructural observations are in qualitative agreement with theoretical predictions of bifurcation analyses, except for the occurrence of compaction bands in the sample deformed at effective pressure of 130 MPa. The bifurcation analysis with the constitutive model used in this paper is nonadequate to predict compaction band formation, may be due to the neglect of bedding anisotropy of the rock and multiple yield mechanisms in the constitutive model.

Acoustic Emissions Monitoring during Inelastic Deformation of Porous Sandstone: Comparison of Three Modes of Deformation

“…Outside the band, damage is very small. These observations are in agreement with those reported by MENÉNDEZ et al (1996) in Berea sandstone and by BÉSUELLE et al (2003) in Rothbach sandstone.…”

Microstructural Inhomogeneity and Mechanical Anisotropy Associated with Bedding in Rothbach Sandstone

“…Reddish in color, the Rothbach sandstone formed from cross-bedded, fluvial sediments and has been widely used as a building stone. It has been the focus of various studies on mechanical (DAVID et al, 1994;WONG et al, 1997;BÉSUELLE et al, 2003;BAUD et al, 2004) and other physical LOUIS et al, 2005) properties.…”

“…Previous investigations of the damage evolution related to compactive yield are restricted to perpendicular and parallel samples. In a perpendicular sample of Rothbach sandstone failed at 130 MPa effective pressure, the microstructural observations and stereological data ofBÉSUELLE et al (2003) demonstrate the development of several diffuse compaction bands with intense damage that are subparallel to bedding BAUD et al (2004). suggested that the development of each ofFigure 9a.…”

Experimental Investigation on the Strength, Deformability, Failure Behavior and Acoustic Emission Locations of Red Sandstone Under Triaxial Compression

“…Furthermore, knowledge of the mechanical behavior of sandstone is important in geotechnical engineering (e.g., the design of waste repositories) and in petroleum geoscience (e.g., the prediction of reservoir deformation and fluid flow). For this reason, in the last few decades, many experimental studies have investigated the mechanical behavior of sandstone, including its strength, deformation behavior, failure characteristics and time-dependent behavior (Wong et al 1997;Baud et al 2000;Wu et al 2000;Klein et al 2001;Jeng et al 2002;Bésuelle et al 2003;Fortin et al 2006;Tembe et al 2008;Tsai et al 2008;Zorlu et al 2008;Heap et al 2009a, b;Tavallali and Vervoort 2010;Huang et al 2010;Yang and Jiang 2010;.…”