Development of a dynamic triaxial Kolsky bar

We present a confined Kolsky bar device capable of applying hydrostatic confining pressures and dynamic axial shear loads to right-circular cylindrical samples. The conventional Kolsky bar apparatus is modified by adding a high-pressure hydraulic chamber capable of applying radial confining pressures up to 400 MPa to the test specimen. An additional pressure chamber is added to the free end of the transmission bar and applies the axial portion of the hydrostatic pressure to the specimen. Once confinement is achieved, a striker bar impacts the incident bar to apply a dynamic, axial shear load to the test specimen. Pulse shaping techniques are employed in this device to generate the desired incident pulse necessary to achieve stress equilibrium in the sample and strain the sample at a nearly constant rate. We present data for an Indiana limestone tested at confining pressures up to 200 MPa and strain rates of 400 s(-1), and compare results to quasi-static data.