${\mathsf{K}}_{\mathrm{0}}$ Compression and Stress Relaxation of Pumice Sand

Pumice sand particles have a vesicular nature, making them light and crushable. Previous research showed that the in situ relative density of pumice deposits cannot be estimated from conventional cone penetration testing. Because of this, a need exsits for more study of the geotechnical properties of this material. First, to distinguish compression behavior of loose and dense sand, $K_0$ compression tests were performed on pumice specimens at various strain rates, from 0.33% to $1,000\%/\min$, until a final compression of approximately 33% of the original specimen length was achieved. Second, after compression, the maximum displacement was held constant for a period of time during which the relaxation of the axial stress was monitored. After unloading, the particle-size distribution was measured to confirm particle crushing. From these results, the magnitude of stress relaxation of loose sand was found to be slightly larger than that of dense sand. On the other hand, dense sand particles exhibited more crushing during loading and less tendency for stress relaxation and particle rearrangement when the axial deformation is held fixed.