Ductility Criterion for Evaluating Remedial Measures to Increase Liquefaction Resistance of Sands

Abstract

This technical note discusses from the viewpoint of “ductility” the performance of two soil improvement methods for liquefaction remediation: sand compaction piles and gravel drains. The sand compaction pile method is judged a viable remedial measure for liquefaction protection because the compacted sand shows ductile behavior in that strain amplitude in the sand increases only moderately when the intensity of earthquake ground motion is increased significantly beyond a design value. For sands having moderately high initial liquefaction resistance, a gravel drain system can improve their capacity to resist earthquake ground motions that are stronger than usual design values. On the other hand, loose sands for which improvement is attempted by the use of gravel drains show nonductile behavior in that the pore pressure in the sand increases considerably even when the earthquake ground motion is slightly increased beyond a design value.