Masters Thesis

Evaluating the Shear Strength of Overconsolidated Clays in Mineralogical Framework with Shansep and Hvorslev's Theories

Undrained shear strength is important in the evaluation of the stability of both natural and man-made slopes. Some researchers have proposed methods such as SHANSEP to evaluate the undrained shear strength of fine grained soils. However, the impact of plasticity characteristics and mineralogical composition on the undrained shear strength has not been widely studied. to do so, the SHANSEP technique was extended to include the interpretation of the normalized undrained strength ratio in this study. to determine the normalized undrained strength ratio, the undrained strength ratio for a sample at any over-consolidation ratio (OCR) is normalized by the value of undrained strength ratio for a normally consolidated sample of the same soil. This study will also focus on calculating the true friction angle and the true cohesion of various mixtures. in this study, five mixtures of montmorillonite with quartz and three mixtures of kaolinite with quartz were used. Unique relationships dependent on the mineralogical composition were developed between the normalized undrained strength ratio with the OCR. the results also showed that the true friction angle decreases with an increase in plasticity index for soils with plasticity indices less than 60% and liquid limit in soils with liquid limits less than 125%, beyond which there are negligible changes in the true friction angle. the base friction angle increases with an increase in plasticity index and liquid limit in soils with kaolinite as the clay mineral, but does not change significantly in soils with montmorillonite as the clay mineral.

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