MEASURING ANISOTROPIC ELASTIC PROPERTIES OF SAND USING A LARGE TRIAXIAL SPECIMEN

An advanced automated triaxial testing system developed to characteriz e elastic behavior of soils is described. Small axial and lateral stra ins of a large rectangular prismatic specimen were measured locally at various stress states along a specified stress path, which was achiev ed by automatically controlling axial load and confining pressure. Ela stic deformation was measured by applying very small cycles of axial o r lateral stress at each given neutral stress state. Typical test data for air-dried sand are presented. It is observed that the elastic You ng's modulus is a rather unique function of the normal stress in the d irection of the major principal strain increment, and therefore elasti c deformation characteristics of sand become anisotropic under anisotr opic stress conditions.