Determining Dry and Saturated Strength of Rocks by Using the Schmidt Hammer

Abstract

The main purpose of this research is to determine the dry and saturated strength of different sedimentary rocks including travertine, conglomerate, sandstone and limestone by using the Schmidt hammer test. To determine the strength of the studied rocks, comprehensive geotechnical tests including Brazilian tensile strength (BTS), block punch strength (BPS), point load strength (PLS) and uniaxial compressive strength (UCS) were performed in dry and saturated conditions on prepared standard specimens. Results show under BTS, BPS, PLS and UCS tests, the strength of the studied rocks after saturating is averagely reduced by 24.95, 31.80, 34.36 and 18.97%, respectively. Therefore, under saturated conditions, the strength of the studied samples reduced 27.52% averagely. The correlation between Schmidt rebound hardness and geotechnical properties in dry and saturated conditions was performed by simple regression analysis and experimental equations were obtained with a correlation coefficient from 0.65 to 0.93. For evaluating the performance of predictive models, some statistical parameters including RMSE, VAF, MAPE and PI were calculated and the 45° line and 95% confidence limit curves were also extracted for evaluating the validity of the concluded empirical equations. The results of this research demonstrate that the Schmidt hammer test is a reliable method for estimating the strength of rocks in dry and saturated conditions.