Statistical and regression analysis of sand and clay stiffness in triaxial tests

Triaxial tests are the common laboratory methods for studying the mechanical properties of soils. According to international practice, it allows determining the reliable strength and stiffness properties. This paper describes the results of statistical analysis of the deformation parameters of sand and clay soils, obtained from triaxial tests. The research focused on sand and clay deposits of the Quaternary, Cretaceous, Jurassic and Carboniferous periods of diverse genesis. The results of 2000 consolidated isotropic drained triaxial tests on sand and clay soils in Russia (Moscow) and Belarus (Minsk) were analyzed. More than 50% of the tests were carried out under unloading/reloading conditions. As a result, empirical equations enabling evaluation of the effects of physical properties and stress state on stiffness of soils with different age and genesis were proposed. The proposed equations can be applied for provisional FEM calculation of the stiffness parameters and can be used in geotechnical models that consider variability, horizontal and vertical distribution of stiffness. Generally, geotechnical engineers may utilize the obtained results to apply them to design of complex soil models.