DBPapers
DOI: 10.5593/SGEM2015/B12/S2.023

CHARACTERIZATION OF A SCHIST USING LABORATORY TESTS

F. Loureiro, I. Fernandes, M. A. Ribeiro, J. Neves, M. Quinta-Ferreira
Friday 7 August 2015 by Libadmin2015

References: 15th International Multidisciplinary Scientific GeoConference SGEM 2015, www.sgem.org, SGEM2015 Conference Proceedings, ISBN 978-619-7105-32-2 / ISSN 1314-2704, June 18-24, 2015, Book1 Vol. 2, 171-178 pp

ABSTRACT
The study of metasedimentary rocks using laboratory test methods is presented. Field work revealed a highly weathered yellowish metasedimentary quartz-pelitic rock characterized by very close discontinuities. The Schmidt hardness values obtained at an excavated slope were low. The rock mass was studied in depth for the excavation of a tunnel with the execution of mechanical exploration and tests. The macroscopic examination of the samples revealed that the drill cores were mainly fresh to slightly weathered. In most of the cores, the foliation made a very low angle with the axes of the boreholes. A soft cleavage was the main foliation. It was parallel to the stratification, which was sub-vertical, locally superposed by a smooth crenulation cleavage. Samples were selected at various depths. Thin sections were used for the petrographic study allowing to identify the constituents and texture of the rock. Test specimens were prepared for the mechanical characterization of the rock. The laboratory tests included sound velocity tests, point load tests and uniaxial compression tests. Possible correlations between the different tests were investigated, seeking also to compare results obtained with others already published for the same metasedimentary sequence. The higher values for the mechanical properties corresponded to the silica-rich specimens and the lower values to the specimens of pelitic composition. The results of the uniaxial compression strength test corresponded to moderately hard to hard rock, according to the ISRM. Due to the anisotropy of the rock and the fact that there were quartz-richer portions intercalated in the pelitic layers, the correlation between laboratory tests was quite weak, although higher for the quartz-richer specimens.

Keywords: Metasedimentary rocks, Petrography, Mechanical tests, Anisotropy.