The velocities of propagating elastic waves can be used to determine the amount of damage in form of induced microcracks in rock materials and other materials. An increasing number of microcracks yields lower propagation velocities. To assess the damage, e.g. around tunnels caused by the excavation, is of interest since the damage affects the material properties, such as mechanical and thermal properties and permeability.

A new ultrasonic testing system ULT-100 from GCTS (Geotechnical Consulting and Testing Systems), aimed for measurement of p- and s-wave velocities, was evaluated. Reference cylindrical specimens in aluminium with different sizes were manufactured and a series of tests were conducted in order to find suitable wave arrival picking methods and to determine equipment specific constants which are needed to be determined. The procedure to do this was according to an ASTM standard.

Expanded measurement uncertainties for the wave velocity measurements were calculated according to Guide to the Expression of Uncertainty in Measurement (GUM).

Equipment such as sensor holders and fixtures were manufactured in order to be able to conduct repeatable measurement on specimens. One test rig was made to carry out tests on nearly unloaded specimens in one direction and another was made for tests on axially loaded cylinders in a standard load frame with measurements in the axial plus two lateral directions.

A Round Robin test was carried out on the three different types of testing equipment, one at SP, one at Swedish Cement and Concrete Research Institute (CBI), and one at Finnish Geological Survey (GTK) in Finland to evaluate the measurement results on p-wave velocity measurements. The results of the measurements were mainly in line with the calculated measurement uncertainties.

The report is directed to persons working with wave velocity measurements using ultrasonics with particular interest of quality assurance of the measurements, which includes calibration, validation and uncertainty estimation.