Influence of Relative Density of Sands on Their Oedometric Moduli

In laboratory testing, analyzing the influence of various factors on oedometer test results is essential, since the oedometric modulus (Eoed) directly affects e. g. footwear impressions in forensic engineering. This study focused on incremental loading oedometer tests on two types of sand—silty sand (SM) and sand with fine-grained admixture (S-F). For each loading stage, four identically prepared samples were tested at density indices ID = 0.15, 0.65, and 0.85. The Eoed was calculated using both Slovak Technical Standard (STN) and ISO Standard, which differ in evaluating strain increments at each loading stage. The difference in Eoed between ID = 0.15 and 0.85 corresponded to about 1.5 to 5.6 times the Eoed value at ID = 0.15 for SM and about 1.0 to 3.3 times for S-F. Between ID = 0.65 and 0.85, the difference amounted to about 0.18 to 0.63 times the Eoed value at ID = 0.65 for SM and about 0.51 to 1.44 times for S-F. The difference in Eoed between STN and ISO ranged from 0.00003 to 0.067 times the STN-based Eoed value for SM and from 0 to 0.017 times for S-F. Results show a very high linear dependence of Eoed on ID for SM (Pearson R = 0.97–0.99) and high-to-very-high for S-F (Pearson R = 0.83–0.91). Accurate determination of Eoed enables a more reliable and precise assessment of footwear impressions.