Correlatıon of Sand Fabrıc and Constraıned Elastıc Modulus (Ec)

Abstract

The Constrained Modulus of Soil (Ec) is a key parameter for assessing soil compressibility and calculating consolidation settlements. The Ec values obtained from laboratory and in-situ tests are influenced by various factors. This study investigates the variations in Ec with respect to selected sample characteristics. To this end, four sand samples were utilized: three of marine origin and one collected from a riverbed. Only clean sands were considered in the testing program. In order to evaluate the influence of mineralogy, the samples were chosen to represent magmatic, metamorphic, and sedimentary origins. Their mineralogical compositions were identified through X-Ray Diffraction (XRD) analyses. To better examine the effects on the elastic modulus, loose specimens representing shallow deposits and dense specimens representing deeper layers were prepared. Accordingly, the physico-mechanical properties of the sands were also determined. The metamorphic sand, rich in mica, exhibited the lowest specific gravity (2.74) and the highest void ratio, whereas the magmatic sand containing iron compounds showed the highest specific gravity (3.44) and the highest minimum void ratio. In this study, oedometer tests were conducted on sand specimens prepared at different relative densities under applied stresses of 200, 400, 800, 1600, and 3200 kPa, and the Constrained Modulus (Ec) values were calculated. The experimental results indicated that the sands exhibited similar behavior up to 3200 kPa, but differences emerged at this stress level. The lowest Ec values were obtained in sands with high mica content. The findings reveal that the genetic and mineralogical differences of sands have a significant influence on the constrained modulus.