Effects of cubical specimen sizing on the uniaxial compressive strength of etna volcanic rocks (Italy) [Effetti della dimensione di provini cubici sulla resistenza a compressione monoassiale delle rocce vulcaniche etnee (Italia)]

Etna is the tallest active volcano in Europe; its lava flows, occurred from 500 ky ago, made the volcanic rock very widespread in the eastern sector of Sicily. Because of its good mechanical strength, this type of rock has various applications and, for this reason, there are numerous quarries scattered all over the area. With the purpose of evaluating the uniaxial compressive strength (UCS) of these rocks, massive lava blocks have been sampled from outcrops of Etna. From these blocks, 55 cubical specimens, differently sized, have been carved and tested by a press trough the uniaxial compression test, so to obtain the direct value of UCS. This paper aims to investigate the UCS variability among cubical specimens of volcanic rocks, in dependence of their size. The estimated values have been correlated against the specimens geological and textural features. The results show how, by varying the specimen size until a side length of 85 mm, UCS increases; conversely for larger cubes, with lengths up to 115 mm, the trend is reversed. This relation has been described by some equations, leading us to estimate the most suitable specimen size for the mechanical characterization of these rocks, so that the texture would not influence the UCS.