| Abstrakt: |
In rock engineering, size effects have been a topic of extensive research since the early 1960s, and despite many advances over the years, our understanding of size effect remains incomplete, especially for weak, porous, homogeneous rocks. Indeed, the vast majority of studies related to size effect have specifically considered low porosity rocks (generally crystalline). To bridge this gap in knowledge, we conducted unconfined compression tests on cubic limestone blocks ranging in size from 0.1 to 0.9 m. Texas Cream Limestone, which is a porous, homogeneous, weak rock, was chosen for this study. As this rock has not previously been studied in the literature, conventional compression tests and indirect tensile strength tests on cylindrical specimens were completed prior to testing the cube specimens. For the largest specimens, 3D digital image correlation (3D-DIC) was employed to track the surficial displacements as a function of the applied load. The tests revealed a lack of size effect for the entire range of block sizes considered. To evaluate size effects more broadly, data from prior studies on sedimentary rocks were compiled, and a tendency for the magnitude of the size effect on strength to decline with increasing porosity was noted. Some hypotheses regarding this trend are presented and evaluated based on strain-field heterogeneity metrics obtained from the 3D-DIC analysis. Highlights: Unconfined compression tests were conducted on limestone blocks ranging in size from 0.1 m to 0.9 m side length. Negligible size effect on strength was observed in this weak, porous, homogeneous limestone. 3D-Digital Image Correlation analysis was performed to obtain strain fields as a function of applied load for the two largest specimens. Contrary to low-porosity rocks, more heterogeneity in strain field was noted in the axial direction in comparison to the lateral direction A compilation of data from the literature indicates that increased porosity may dampen size effects. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink