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UBC Theses and Dissertations

Stress path dependency of dilatancy and stress-strain response of sand Sasitharan, Sabanayagam


The drained loading behaviour of water pluviated Erksak sand is investigated in the triaxial apparatus by varying consolidation history, stress path and loading direction (compression or extension). It is shown that, under identical minor effective principal stress, anisotropically consolidated sand has a higher tangent modulus than the isotropically consolidated sand in the initial stages of the shearing phase. This difference in the tangent modulus reduces as the sand approaches failure. The modified hyperbolic model, in which the increment in the deviator stress after consolidation is considered as the stress variable, is shown to represent satisfactorily the stress-strain response of anisotropically consolidated sand. The small strain response of anisotropically consolidated sand also shows a hyperbolic variation which is different from the large strain one. The elastic tangent modulus, at a given stress state, of water pluviated isotropically consolidated sand is not unique. It varies with stress path and direction of loading. Thus, the incremental elastic modeling based on hyperbola under conventional stress paths is shown not applicable for other stress paths and loading direction. The failure strength of sand is uniquely related to maximum rate of dilatancy d∈[sub v]/d∈[sub a] regardless of the relative density, minor effective principal effective stress at failure and stress path for both compression and extension loading. The failure strength depends only on the normal stresses at failure and relative density and is not affected by consolidation history or stress path. The water pluviated sand yields a higher failure strength under compression loading than under extension loading.

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