DBPapers
DOI: 10.5593/SGEM2014/B12/S2.118

THE INFLUENCE OF LOADING SPEED IN THE CLASSICAL BRAZILIAN TESTS ON AN ESTIMATE VALUE OF FRACTURE TOUGHNESS INDICATOR (KIC) FOR EXAMPLE POLISH FLYSCH SANDSTONES

A. Dziedzic, L. Pieczara
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-08-7 / ISSN 1314-2704, June 19-25, 2014, Book 1, Vol. 2, 921-928 pp

ABSTRACT
The article presents the results of research of fracture toughness of flysch sandstones (Krosno Sandstones) from the Polish part of the Western Carpathians, with characteristic laminar structure. The research was realized as suggested by the ISRM method Chevron Bend (CB), marking KIC CB1 in Level 1 and a classical Brazilian test (BR) to give a tensile strength  and on this basis denoting the indicator KIC BR. The sample loading speed in the CB method was in accordance with the recommendation of ISRM. In Brazilian method, rock samples were compressed transversely in two variants of speed: according to the Polish Industry Standard – 7.5 kN/min and with reference to the speed of CB tests - 400 kN/min. It is important that in Brazilian method the obtained results, are comparable to the values of KIC from CB tests carried out at 400 kN/min. Using in the BR tests recommended, standard speed (7.5 kN/min) causes, that the value of KIC BR7,5 differs significantly from the value of the indicator from CB Level 1 (KIC CB1). The influence of the rock sample loading speed is therefore important to estimate the value of KIC BR in the classical Brazilian method.

Keywords: Chevron Bend, fracture toughness, Brazilian method, geomechanics, cracking of rocks, anisotropy