ABSTRACT
Two free-field downhole array seismic records are now available to document the underlying site liquefaction response mechanisms. Records of acceleration and pore pressure at the Wildlife Refuge (Imperial County, CA, USA) reflected liquefaction during the 1987 Superstition Hills earthquake. In 1995, liquefaction at Port Island (Kobe, Japan) was documented by a four-accelerometer downhole array during the Hyogoken-Nanbu earthquake. Using these records, the associated shear stress-strain response is identified and employed as a guideline for development of liquefaction countermeasure techniques. A number of these techniques are discussed in view of the identified response mechanisms. Furthermore, results of a recent centrifuge testing program are employed to illustrate the beneficial effects of four different countermeasure techniques applied to a liquefiable foundation layer underlying an earth embankment.
