Microstructure evolution on sandstones with different degrees of cementation

Fonseca, J., Bésuelle, P. & Viggiani, G. (2013). Microstructure evolution on sandstones with different degrees of cementation. Paper presented at the Workshop on Experimental Micromechanics for Geomaterials (ISSMGE TC101-TC105), 23-5-2013 - 24-5-2013, Hong Kong.

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Abstract

This study investigates the grain scale mechanisms that lead to failure by strain localisation in specimens of Fontainebleau sandstone with different degrees of cementation. While the effects of inter-particle bonding on the mechanical behaviour of granular geomaterials, including soft rocks, have been largely studied, the physical micro-scale mechanisms governing the material deformation are still poorly understood. In this study, laboratory techniques have been developed to allow a non-invasive investigation of the internal deformation of sandstones during triaxial compression to failure. The material investigated was Fontainebleau sandstone, a quartzite formation from the Paris Basin (France) which can be found as very hard, tightly cemented sandstone or more permeable and less cemented material. Specimens with porosities 6% and 21% were investigated. Triaxial compression tests at confining pressures of 2MPa and 7MPa were conducted on dry cylindrical specimens of 11mm diameter by 22mm height. Three-dimensional images of the full specimen were obtained by carrying out x-ray micro-tomography scans at key points throughout the test. The high-resolution tomographic images have a voxel size of 8.5um (0.033d50) allowing a clear identification of the grains. The analysis suggests that dilatancy of the material which depends on the degree of bonding between grains, plays a fundamental role on the failure mode of the granular media.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: fabric-structure of soils, soft rock, laboratory tests, x-ray micro-tomography
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: School of Engineering & Mathematical Sciences > Engineering
URI: http://openaccess.city.ac.uk/id/eprint/12098

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