Cone Penetration Testing before, during, and after Blast-Induced Liquefaction

To investigate the consequences of liquefaction with regard to foundation performance, subsurface blasting was used to induce liquefaction around a test shaft for a major foundation load testing program in Charleston, South Carolina, USA. Cone penetration test data were recorded before blasting, immediately following two blast-induced liquefaction events while pore pressures were still elevated, one month after the blasting, and again, seven years after the blasting. All testing was located inside of the blast array (i.e., within the liquefied area). Tip resistance, sleeve friction, and u₂ porewater pressure measurements were all lower in the two soundings that were performed while the sands were still liquefied. The post-blast soundings performed one month later and again seven years later indicated that the upper portion of the liquefied deposit (immediately below an impermeable clay cap) had been loosened. There was little change between the data collected one month after blasting and those data collected 7 years after blasting. Densification was not apparent. However, the sand was Pleistocene Age and the destruction of aging effects may have countered blast-induced densification effects in the CPT data.