It was hundred years ago, when Theodore von Kármán (born as Tódor Kármán) designed and developed the first triaxial cell for investigating the behavior of brittle rocks. He carried out researches on Carrara marble and Mutenberg sandstone with different confining pressure up to 330 MPa, showing first how a brittle material become ductile and work hardening. The goal of this paper is to tribute this centenary, which has a great influence for the mechanics, rock engineering and geophysical sciences. After a short historical overview of this research the published data are re-calculated using different empirical failure criteria. For the calculation and description of Kármán's triaxial tests the original Hungarian paper was used.
Hundred years ago Tódor Kármán (Theodore von Kármán1) published his results on triaxial tests of brittle rocks. First it was published in Hungarian in the Journal of Hungarian Engineers andArchitects in 1910 (Kármán, 1910) and a year later it was published in German (von Kármán, 1911), as well. Kármán was born in Budapest in 1881. He graduated as mechanical engineer at the Royal Joseph University (now Budapest University of Technology and Economics) in 1902. Followed by a short (but very useful) practical period in Hungary, he moved to Heidelberg, where he worked at the University as the assistant of Prandtl. At that time, the professor of Geology in Heidelberg was E. Heyn who pointed out that, contrary to logical conclusions, mountains which consist of brittle rocks are deformed as plastic material (Kármán & Edison, 1967). Kármán became interested in this problem, therefore he designed the first triaxial test chamber (named "bump", by Kármán)whichwas manufactured by the company Krupp in Essen. The first triaxial samples had a diameter of 40mm and a height of approximately 100mm (i.e. diameter/height ratio was around 1:2.5).