Triaxial testing under high confining pressures

A first attempt at triaxial testing was carried out in Prague in 1892 by F. Kick, as mentioned in the previous chapter. Shellac, sulfur, molten alum, stearin or olive oil was employed as the soft material embedding the brittle specimen in a copper or brass tube. One of Kick’s attempts is shown in Figure 2.1 . A marble sphere was embedded in fused alum inside a thick-walled copper tube ( Fig. 2.1a ), and the tube was compressed between parallel plates together with alum and the marble sphere by means of a hydraulic press. Then, the marble sphere was deformed as shown in Figure 2.1b . The confining pressure is applied to the marble sphere through alum when it is compressed in the tube. Deviating compressive stress is applied to the marble sphere for further compression which simultaneously increases the confining pressure. Kick’s experiment is the first attempt at triaxial testing as well as the first experimental confirmation of the brittle-ductile transition. It was, however, only qualitative. After many investigations (e.g. Adams 1910 ), quantitative experimental work was first carried out by Karman (1911).