Preliminary Investigation of Unexpected Liquefaction-type Behavior of Fine-Grained Soils in Turkey

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This small grant for exploratory research supports a field investigation to further examine important observations made during a post-earthquake reconnaissance of the 1999 Kocaeli Earthquake in Turkey. Liquefaction-type behavior in the form of strength loss, softening, and settlement occurred in saturated fine-grained soil strata at the Carrefour Shopping Center complex located along Izmit Bay, about 5 km from the ruptured portion of the fault. Construction of the shopping center was underway when the earthquake struck, and the soil beneath the main building had been improved to mitigate soil liquefaction, while most of the site, and all of the surrounding properties, remained on unimproved soil. Significant settlements were observed to occur in two silt/clay (ML/CL) strata and one high-plasticity clay stratum (CH). Cyclic strength loss in these fine-grained materials, especially the CH soils, is unexpected, as they are not considered liquefiable by current liquefaction guidelines. If the settlement data is found to be valid, there are important implications, as it may be shown that current guidelines are not reliable predictors of the seismic behavior of these materials.This further examination of the soil liquefaction at the Carrefour Shopping Center complex is intended to: 1) confirm the previous observations, and 2) gather perishable data that will permit complete documentation of this unique site for the engineering community and allow a future, more comprehensive study. The study will involve field testing and sampling, cyclic triaxial testing, and analytical work. The Carrefour Shopping Complex is being rapidly developed and it is imperative to sample the soils before the data is lost.