ONE-DIMENSIONAL HIGH-PRESSURE COMPRESSION OF GRANULAR MEDIA

A series of one-dimensional compression tests was performed at vertical pressures as high as 689 MPa (100,000 psi). Three materials were tested: Ottawa sand, a granulated slag called Black Beauty, and soda lime glass. Glass specimens included three grades of spherical particles and one grade of angular particles. Test results showed how particle crushing is influenced by initial void ratio, particle size, particle angularity, and particle material composition. Three phases of compression behavior were identified: Volume decrease as a result of particle rearrangement at low stresses, characterized by a low ''initial'' constrained modulus; more intense compression as particles crush and are rearranged extensively under higher stresses; and, as the number of contacts between fractured particles increases greatly at very high stresses, an approach to pseudoelastic behavior characterized by very high values of constrained modulus typical of natural sandstones. Even though the tested specimens varied in mineralogy, initial void ratio, median grain size, particle shape and initial moduli, they showed little variation in final constrained modulus.