A Fast Triaxial Shear Device
The fast triaxial shear device (FTRXD) loads a 1.9-cm (0.75-in.) diameter by 3.8-cm (1.5-in.) long soil specimen, deforming it axially at a very rapid rate. The specimen is deformed by a piston-cylinder assembly driven by compressed nitrogen. Load and displacement at the top of the specimen and load at the bottom are measured; the specimen is subjected to a confining pressure up to 6.9 MPa (1000 psi). The shortest times to failure to date have been 0.5 ms. Soil from the CARES-Dry Luke Gunnery Range in Arizona was used in the evaluation. It is a clayey sand (SC) in the Unified Soils Classification System. The moving upper load cell is sensitive to specimen inertia and FTRXD dynamics; the stationary lower load cell is much less so. Both load measurements and the displacement of the specimen top are needed for wave analyses of the specimen and assessment of FTRXD dynamics.