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Quasi-static Compression of Granular Materials (Sand) at High Pressures (~ 3 Gpa)

Subramanian, Vijay Krishnan
This investigation presents the results on the static behavior of confined sand (from Eglin Air Force Base) subjected to axial compressive stresses up to 3 GPa. A self-aligning compression fixture was developed to statically compress sand specimen in a cylindrical steel confinement using tungsten carbide pins. A strain gage was mounted on the confining cylinder to measure the circumferential strain. Using axial stress, axial strain, and hoop strain the multi axial behavior of the confined sand is investigated. Compressive tests were conducted up to axial strains of 35%. The static response of the dry sand was tested at four different initial densities, namely, 1.55, 1.60, 1.65, and 1.75~g/cm$^3$. Effects of particle size, primarily classified as coarse and fine, were investigated. The effect of moisture was also investigated at four different degrees of saturation, namely, 0%, 20%, 40%, and 100%. The dense sand provided a much stiffer response than the loosely packed ones. The coarse sand grains showed significant crushing of particles followed by compaction of the powdered grains.