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UBC Theses and Dissertations

Effect of particle fabric on the one-dimensional compression response of Fraser River sand Northcutt, Sheri Lynn

Abstract

One-dimensional compression of sand with lateral stress measurement allows for laboratory determination of the coefficient of lateral pressure at rest, Ko. Commonly used to define the initial state of stress in soil where no lateral strain occurs, Ko is calculated as the ratio of horizontal to vertical effective stress. The present study aims to investigate the role of initial particle fabric in one-dimensional compression and to determine the effect of fabric on the coefficient of lateral pressure at rest in Fraser River sand. One-dimensional compression with lateral stress measurement was carried out on reconstituted Fraser River sand specimens using an instrumented oedometer. Laboratory specimen reconstitution methods were developed in order to construct different particle fabrics. Three different techniques were utilized: air pluviation, tamping and vibration. In addition, the effects of initial relative density and loading history on the compression response were evaluated. Each one-dimensional compression test was executed in three distinct phases: virgin loading, unloading and reloading. The key results from the testing program were compared with current methods available for estimation of Ko. The results from the present study show that specimens resulting from different laboratory reconstitution methods (i.e., initial particle fabrics) exhibit different one-dimensional compression responses. For Fraser River sand in one-dimensional compression, air-pluviated specimens yield the highest Ko values, tamped specimens produce the lowest Ko values and vibrated specimens rank intermediate. With increasing initial relative density, regardless of the initial specimen preparation method, the measured Ko values generally decrease. Upon reloading, measured Ko values are slightly reduced from those observed during virgin loading. Furthermore, results from the present study indicate that the current methods commonly used for determination of Ko do not necessarily provide suitable estimations for variable granular particle fabrics arising from different specimen reconstitution techniques. A new method for determination of Ko is proposed, as a function of the constant-volume friction angle, initial relative density and a factor accounting for the initial particle fabric.

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