A comprehensive blast
densification field study was conducted at a test site in South Carolina to
densify a loose soil layer at a depth between z=8–13
m. The study included extensive laboratory and field characterizations and four
carefully monitored blast events. Results revealed that densification is not an
instantaneous phenomenon; underlying time-dependent processes involve
resedimentation, drainage of excess pore pressure as the granular skeleton
deforms and the effective stress recovers, and secondary settlement effects, which
do not involve excess pore pressure dissipation. The degree of densification
decreased in successive blasting events, and the soil gradually evolved toward
an asymptotical terminal density associated with blast densification. The
blasting sequence and detonation delays appeared to have a minor effect on
shear-induced movements. The increase in penetration resistance manifested 2
years after four blasting-drainage events. Instead, surface settlement using
standard surveying techniques, subsurface deformation assessment, and subsurface
pore fluid pressure monitoring provided valuable, real-time indicators of the
soil response to the blasting events.