Soil Elastic Modulus Determined by Ultrasound Tests

The elastic constants obtained through conventional destructive (triaxial and resilience) tests can present great variability, even for soils with the same classification. Thus, a test is necessary to determine the elastic constants of soils in a reliable and replicable way. The ultrasonic technique is used to characterize rock and several construction materials (wood, cementitious matrices, metals), including the elastic parameters (elastic modulus, shear modulus, and Poisson's ratio). The aim of this study was to verify the correlation between the elastic modulus obtained through ultrasonic testing and through a simple unconfined compression test on compacted clayey soil. Test specimens were molded at normal compression energy with three moisture contents; the specimens were exposed to air and packed with plastic wrap for 120 days. After this period, we performed ultrasonic and compression tests. The technique presented great potential to study the mechanical behavior, with correlation coefficients over 0.97 for both parameters (compressive strength and static elastic modulus). We also verified that the ultrasonic testing is influenced mainly by the moisture content.