Preliminary Study on In-Situ Modulus Measurement Using Knocking Ball Test; A Case Study on Setul Limestone

The in-situ elastic modulus ( E ) is a vital parameter for describing rock strength in many engineering projects on rock slopes. The elastic modulus and uniaxial compressive strength ( UCS ) are typically investigated via laboratory tests using core samples. However, the direct determination of E is costly and time-consuming in preparing many intact samples from highly weathered Setul limestone. The knocking ball testing method is a non-destructive test that can quickly and easily obtain the elastic modulus of rock in-situ by striking the surface of a rock mass with a spherical steel hammer. This study presents the relationship between the elastic modulus of knocking ball ( Ekb ) and the uniaxial compressive strength of the Schmidt hammer ( UCS-Schmidt ). Results show that the regression coefficient correlation, R 2 is 0.851, indicating a positive trend with a few outliers. The measured Ekb were also verified with mineral properties and correlated to differential weathering grades to confirm the accuracy of measurement results. The finding compared to previous similar studies tested on several types of rock show a statistically significant. This research highlights the effectiveness of the knocking ball method for determining the modulus of rock slope at different weathering grades. A high elastic modulus corresponds to a high uniaxial compressive strength, verified by the laboratory test. This study shows that the knocking ball can be useful for predicting in-situ elastic modulus.