Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

M. Hesham El Naggar

Abstract

The liquefaction behaviour and dynamic properties of reconstituted natural carbonate-silica silty sand samples were investigated in a series of monotonic and cyclic triaxial tests. The critical state parameters of the mixtures with different levels of fines were obtained through monotonic triaxial compression tests. Bender element tests were performed at the consolidation stage to characterize soil’s initial state and small strain properties. The results demonstrated that soil contraction capacity, liquefaction potential and undrained brittleness increase by increasing the state parameter. A general correlation between shear wave velocity and state parameter was established. The susceptibility and triggering of liquefaction under cyclic loading were discussed considering soil’s composition and state. It was revealed that increase in state parameter decreases the cyclic resistance. The results showed that under constant level of stress, the tested silty sands were susceptible to flow liquefaction rather than cyclic mobility because of their loose states in most of the ranges of their densities. To evaluate the liquefaction potential, the cyclic resistance and energy capacity of the specimens were determined. Liquefaction triggering curves were developed by relating the cyclic resistance and energy capacity to the state parameter and normalized shear wave velocity. Comparing the obtained liquefaction triggering curves with those available in the literature demonstrated that the tested carbonate-silica silty sands have lower liquefaction resistance and energy capacity compared to other silty sands. The developed liquefaction triggering curves might be helpful for preliminary liquefaction assessment of silica-carbonate silty sands.

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