Response of soils under generalised loading and drainage conditions

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Behaviour of soils is typically assessed under either fully drained or fully undrained conditions, and along specific loading paths. However, in reality the deformation is dependent on the three dimensional stress state that exists in the field, and would invariably involve simultaneous changes in both pore volume and pore pressure.The drained, and undrained approximations work well under certain situations, but may not yield satisfactory results when evaluating the post-earthquake response of soils. A proper characterization should consider the fact that both pore volume and pressure change simultaneously in actual field problems. The proposed experimental research will provide an insight into the shear-deformation characteristics of soils when subjected to simultaneous changes in pore volume and pressure. Triggering of liquefaction will be considered not only due to undrained loading, but also due to pore water migration.Seismic provisions in the new National Building Code of Canada (NBCC2005) are stricter, and designers will have to deal with higher levels of earthquake shaking. The empirical approach typically used to evaluate cyclic resistance is based on data at lower shaking levels than those specified by NBCC2005. Proposed research will contribute to this aspect by studying the effect of three dimensional stress state on the cyclic resistance of soils, and on the post-cyclic deformation characteristics. Outcome of the research will allow us to evaluate currentdesign methodologies, and propose improved cyclic resistance assessment techniques. Better understanding of the rheology of the liquefied soils is key to confidently predict earthquake induced displacements.There is significant potential for economic benefits if current practice is determined to be conservative.  Proposed research will improve our understanding of the mechanical behaviour of soils, and enhance the reliability of numerical models, and current design methodologies. It will lead to more confident designs, and economic solutions.