Skip to main content

Size effects on strength properties of sedimentary rocks

Size-dependent mechanical properties have been extensively investigated with rocks (e.g., basalt, granite, norite and marble) through compression experiments. However, the obtained empirical correlations of these rock strength properties (UCS and Young’s modules) with sample sizes show discrepancies with the ones obtained from the same experiments with some sedimentary rocks (e.g., limestone and sandstone). There is a lack of microstructural understanding of size effects. In this study, we combine petrographic analyses and uniaxial compression experiments with Rotliegend sandstone to shed light on the controlling mechanism of size-dependent rock strength. Cylindrical samples with diameters of 25, 38, 50, and 75 mm and length/diameter aspect ratio between 1.6 and 2.1 were prepared. UCS and Young’s modulus of different-size samples are systematically compared. Thin section analyses including the initial intact samples and some selected failed samples were performed to link the microstructure with the rock strength at different scales. Additionally, P-wave velocity and porosity were also measured to have comprehensive results. The ongoing experiments indicate UCS between 52.9 and 72.2 MPa, and Young’s modulus between 12.9 and 15.5 GPa. We will also make a comprehensive comparison with published results of different rock types. Understanding size effects in strength properties of sedimentary rocks may contribute to the upscaling of the laboratory results, and may also indicate the reliability of experiments performed with a smaller sample size (e.g., 25 mm in diameter), which is the most common dimension of plugs prepared from drill cores.

Details

Author
Yonghui Chen1, Chaojie Cheng1, Benjamin Busch1, Christoph Hilgers1
Institutionen
1Structural Geology and Tectonics, Institute of Applied Geosciences, Karlsruhe Institute of Technology, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/94q0-xt12