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Ground failure in Adapazari, Turkey during the 1999 Kocaeli earthquake (Mw ¼ 7.4) was severe. In four central downtown districts, where more than 1200 buildings collapsed or were heavily damaged, hundreds of structures tilted and penetrated into the ground due in part to liquefaction and ground softening. Based on a multi-institutional subsurface investigation program, soil conditions along four lines in which ground failure was surveyed after the earthquake are classified into four generalized subsurface site categories. This classification is primarily based on the presence or absence of shallow and intermediate depth liquefiable soils. Observations of ground failure are found to correlate well with site categories that are susceptible to liquefaction according to current state-of-the-art methods without strict adherence to the Chinese criteria. Soils that liquefied were found to meet the liquid limit and liquidity index conditions of the Chinese criteria. However, soils that liquefied did not typically meet the clay-size condition for liquefiable soils by the Chinese criteria. q 2002 Published by Elsevier Science Ltd.

The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness resulting in substantial deformations. In many areas of Canada, large structures are constructed on or comprise sandy soils, e.g., some major hydroelectricity earth dams and many tailings impoundments in the mining industry. The behaviour of loose sandy soils can be difficult to predict, but can have a significant financial impact on these types of engineering structures. Consequently, the intent of the CANLEX project was to improve the overall understanding of soil liquefaction. This paper provides an overview of the CANLEX project, outlining the project objectives, major achievements, and conclusions. Four companion papers describe different aspects of the project; thus, together, the five papers provide a summary of the CANLEX project.Key words: geotechnical, liquefaction, CANLEX, collaborative project.

One part of the NEES portfolio is two permanently instrumented field site for monitoring soil-foundation-structure interaction (SFSI), ground motion, ground deformation, and pore-water pressure response to both active and passive seismic sources. The two sites, the Garner Valley Downhole Array and the Wildlife Liquefaction Array, are located in the southern California region. Both sites have many years of previous monitoring history and have been well characterized. These field sites will be used to monitor response generated by local and regional earthquakes and for active experiments using shakers. A reconfigurable steel-framed SFSI test structure is being constructed at the GVDA site and instrumented with sensors installed in the structure, foundation, and underlying soil. The focus of this wimple structure is the study of physics of SFSI without the complexities of "real" structures. This pair of NEES field sites will also provide an excellent bed for new in-situ site characterization techniques and new sensor technologies. Data from both sites will be contributed to the NEES Data repository and the advanced National Seismic System.

The most pervasive and damaging effects of liquefaction generated by the 1983 Borah Peak, Idaho earthquake occurred in the Big Lost River and Thousand Springs Valleys above Mackay Reservoir. Less severe effects occurred in the Big Lost River Valley south of Mackay Reservoir and in the Pahsimeroi Valley. Nearly all of the liquefaction effects developed in floodplain alluvium of late Holocene age. However, the sediment that liquefied beneath the alluvial fans on the east side of the Thousand Springs Valley was deposited in late Pleistocene time. The distance from the fault to the farthest effect of liquefaction was unusually short for an MS = 7.2 event. The distribution of liquefaction effects were consistent, however, with the distribution of MMI intensity and estimated peak ground motion parameters, both of which attenuated more rapidly than is generally expected for an earthquake of this type and magnitude.

Simultaneous measurements of seismically induced pore-water pressure changes and surface and subsurface accelerations at a site undergoing liquefaction caused by the Superstition Hills, California, earthquake (24 November 1987; M = 6.6) reveal that total pore pressures approached lithostatic conditions, but, unexpectedly, after most of the strong motion ceased. Excess pore pressures were generated once horizontal acceleration exceeded a threshold value.