Abstract

Scale effect in rock mechanics discipline still is an open issue. Estimating rock mass geomechanical parameters starting at laboratory scale has not been completely solved. There are some widely accepted estimations, mainly based on the proposing-authors experience and corroborated with a good number of cases around the world. Indeed, these estimations actually work in most cases, but still there is a lack of knowledge on the reasons why these estimations do not work in some cases. Thus, scale effect needs more research. In this paper, the authors explore the effect of the size of the specimen (from 29 mm to 142 mm in diameter) of a granitic rock coming from the surroundings of the Chuquicamata mine in Northern Chile. The rock mass is very competent, although it is extensively fractured and the specimens also feature a good number of visible filled fissures. These fissures, obviously, have an effect on the behavior of the specimens. Ultrasonic pulse velocity and strength tests on 32 specimens were performed. Results show a clear dependence on the size of the specimen which are in accordance with classic research on the topic