Evaluation of laboratory Schmidt Hammer tests on carbonate rocks

Being quick, inexpensive, non-destructive and handy, the Schmidt Hammer (SH) test has been widely used to determine hardness and to predict the unconfined compressive strength (UCS) of rocks. However, a review of empirical equations recommended for determination of the USC of rocks based on the SH rebound number (N) suggests that one unique formula cannot be representative for all types of rocks. Even though the obtained relationship is a useful and quick reference to assign a preliminary value for UCS, geological features such as composition, texture and mineralogy influence the mechanical properties of rock masses and these factors should be carefully evaluated. In the work presented here, a case study was chosen to demonstrate and discuss the effectiveness of particular geological circumstances on laboratory SH test results concerning different carbonate rocks. Three different types of limestones, chalky, marly and dolomitic are available in the Tertiary carbonate sequence at the studied area which is Jabal Hafit, south of Al Ain city, United Arab Emirates (UAE). The results clearly show that rapid changes in carbonate rocks composition, texture and mineralogy always create problems in generalizing the mechanical properties which are essential parameters in geological and engineering practices.