Effects of loading rate on the strength and failure of cemented sand

This study investigates the effects of cement content (CC) and loading rate on the unconfined compressive strength (UCS) of cemented sand. Three CCs (12%, 14%, and 16%) were tested at loading rates ranging from 0.5%-5%/min. In addition, a novel camera vision-based crack detection method was developed to monitor crack-related parameters—crack size and angle—in real-time during testing. The results revealed significant variations in UCS with changes in CC and loading rate. For example, at a loading rate of 0.5%/min, UCS increased by 31% and 102% in the specimens with 12% and 16% CC, respectively. Moreover, UCS consistently increased with increasing loading rate, with increases of 28%, 36%, and 31% observed for CCs of 12%, 14%, and 16%, respectively, within the 0.5%-1%/min range. However, as the loading rate increased above 1%/min, the rate of UCS increase stabilized or decreased, highlighting the importance of selecting appropriate loading rates for accurate strength evaluation. A correlation between normalized UCS and loading rate is proposed based on this study's findings and previous research. Furthermore, the camera-based crack detection method provides detailed insights into the failure behavior of cemented sand and reveals a clear correlation between loading rate, CC, and the angle of the fracture surface. This study highlights the need to adopt a standardized loading rate of 1%/min in UCS testing of cemented sand and demonstrates the potential of camera vision technology to enhance geotechnical monitoring practices.