Fundamental research on the dynamic behaviour of soils and the seismic stability of earth structures.

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This research addresses two related topics; (A) the fundamental aspects of the dynamic behaviour of soil and (B) the seismic stability of earth structures. Topic A : Despite extensive research, there are aspects of each of these topics where there exist considerable uncertainty and further research is necessary to increase our understanding with the objective of improving evaluation procedures and thereby advancing the state of the practice.Natural soils and hydraulically deposited fills (e.g. tailings) are often characterized by layering of finer and coarser material (silt and sand). Instrumented seismic table testing will be used to characterize the dynamic response of such deposits and provide recommendations for their evaluation in engineering practice. Due to conflicting research on the effect of confining stress on liquefaction, the effect of confining pressure on normally and over-consolidated hydraulically-deposited soils will be evaluated using cyclic triaxial testing. This research may lead to revised correction factors for the evaluation of liquefaction in such soils.Topic B: Due to advances in the state of the practice and regulations, numerical analysis is increasingly to evaluate the seismic stability of earth structures. The utility of these analyses are restricted by the limitations of the constitutive models used to simulate material behaviour. A constitutive model that incorporates critical aspects of dynamic behaviour will be developed and implemented. The model will be based on correlations with widely used laboratory and in situ testing procedures and will consider: a hyperbolic stress-strain relationship, the effects of fines content, initial static shear and degree of consolidation, and post-liquefaction strength loss.Numerical and analytical methods will be compared to validate the use of the pseudo-static method and the Newmark displacement method for earth structures composed of materials subject to strength loss and liquefaction. Basic guidelines for dynamic numerical analysis will be developed.