Kolsky Compression Bar for Dynamic Triaxial Experiments

Triaxial experiments are commonly performed under quasi-static loading conditions on pressure-sensitive materials. In such an experiment, a cylindrical specimen is placed inside a pressure chamber where hydrostatic pressure is applied. Further axial pressure is then applied to measure the material response in terms of principal stress difference verses pressure or axial strain. A compression Kolsky bar can be modified through integration of pressure chambers such that further axial load is applied dynamically after hydrostatic pressure on the specimen. This chapter describes the design principle of a dynamic triaxial test system consisting of a Kolsky bar and two pressure vessels, the instrumentation for pressure and specimen deformation measurement inside a pressure chamber, and an example of using such a system to characterize the dynamic compressive response of sand under various hydrostatic pressures. In addition to the pressure boundary conditions on the lateral surface of the specimen, snug-fit sleeve can be used to supply dynamic triaxial load through displacement boundary conditions during a Kolsky compression bar experiment. Examples are given to determine the mechanical responses of an EPDM rubber and an epoxy syntactic foam under such dynamic lateral confinement.