Evaluation of strength and stiffness of compacted geo-materials considering strain influence factors

This study aimed to evaluate the strength and stiffness characteristics of geo-materials for construction under various field compaction conditions and establish reliable relationships between the elastic modulus and geotechnical properties. For comprehensive site characterization, multiple in situ tests were conducted, including the soil stiffness gauge (SSG), unrepetitive plate load test (uPLT), light falling weight deflectometer (LFWD), dynamic cone penetrometer (DCP), and crosshole-type dynamic cone penetrometer (CDP). The elastic moduli (EuPLT, ELFWD, and ESSG), estimated from field test results, were compared with depth-dependent geotechnical properties such as the penetration index (NDCP) and shear wave velocity (Vs). To improve the reliability of the correlations, strain influence factors were considered in the analysis, and a comparative evaluation was conducted between arithmetic averaging and weighted averaging methods. EuPLT and ELFWD exhibited relatively strong correlations with NDCP, which reflects large-strain strength characteristics, as both values are indicative of stiffness properties under large-strain conditions. In contrast, ESSG showed a close correlation with shear wave velocity (Vs), which represents small-strain stiffness characteristics, since the SSG test evaluates soil stiffness under relatively small-strain conditions. Furthermore, the weighted average values of NDCP and Vs calculated using strain influence factors exhibited more accurate correlations with the corresponding elastic moduli. This study demonstrated that this data-based approach can be effectively used to estimate various engineering properties by considering the factors influencing the strain.