Use of explosives to investigate liquefaction resistance of aged sand deposits

• Current liquefaction prediction methods are overly conservative in aged deposits.
• Major disturbances, i.e. earthquakes or explosions, reset a deposit's “geological age”.
• Explosive compaction projects are used to correct liquefaction resistance for age.
• The method proposed predicts a ~ 20% gain in liquefaction resistance per log cycle.

Current methods of predicting liquefaction potential were largely developed using data from relatively young deposits or deposits that have been frequently disturbed (i.e., areas of high seismicity). While engineers recognize that these prediction methods are overly conservative for assessing liquefaction potential in geologically aged deposits, there is no widely accepted method for quantitatively accounting for age in these assessments. Because a major disturbance, such as an earthquake or explosion that causes liquefaction, resets a deposit's “geological age,” data from explosive compaction projects in aged deposits are used herein to provide information about both the aged and fresh deposits. A recent explosive compaction project performed in Griffin, IN, as well as four other explosive compaction projects, is used to develop an aging correction relationship for liquefaction resistance. Using a log-linear trend frequently proposed in previous studies, the method proposed herein predicts an approximate 20% gain in liquefaction resistance per time log cycle. The proposed relationship can be used directly if the time since deposition or last disturbance is known or in conjunction with the measured-to-estimated-velocity-ratio (MEVR) relationship proposed by Andrus et al. if the deposit's age is unknown.