Ultrasonic pulse velocity as a way of improving uniaxial compressive strength estimations from Leeb hardness measurements

Abstract

Uniaxial compressive strength (UCS) is one of the most important parameters in rock mechanics. Nevertheless, there are instances when it is not advisable to perform UCS standardised tests, because it is not possible to sample or because it is not feasible to obtain a significant enough set of results. Leeb hardness (LHD) is used for estimating UCS non-destructively and, currently, most research is focussed on improving its quality as UCS estimator by either increasing the number of samples or combining several sets of samples to obtain better fitting curves. This paper analyses if combining LHD with ultrasonic pulse velocity (UPV) improves UCS estimations obtained from LHD alone, analogously to what is already proven for SonReb methods. This is done considering how different lithology and, particularly, porosity impact on UCS estimations obtained from LHD. Results show that combining ultrasonic pulse velocity and Leeb hardness is an effective way to improve UCS estimations through portable and non-destructive techniques in non-porous polymineral rocks, in which Leeb hardness leads to relatively poor (R2 = 0.779) UCS estimations if used on its own.