Use of Stiffness for Evaluating Compactness of Cohesive Geomaterials
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2002-12
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University of Hawaii at Manoa
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There has been a recent push towards adoption of the in-place soil stiffness as a means of assessing compactness of pavement geomaterials. The Humboldt GeoGauge is a relatively new and promising instrument that is portable, that provides instantaneous results and that does not require handling of radioactive materials. Unlike the nuclear gage, which yields the soil unit weight and water content, the GeoGauge yields soil stiffness corresponding to very low strains. Based on a series of low-strain soil stiffness measurements made under controlled laboratory conditions on compacted silts from Oahu, the variation of modulus with water content, dry unit weight, degree of saturation, volume change upon wetting, shear strength and soil plasticity is discussed. These results help advance the understanding of the role of stiffness in assessing compactness of cohesive soils. For compacted partly saturated soils, the dry unit weight can be related to stiffness and water content. This relationship is derived herein. Using this relationship, measured values of stiffness and water content can then be used to predict the dry unit weight in the field. This work involved testing of tropical soils, which can undergo irreversible changes upon drying, resulting in permanent alterations in soil properties. Upon drying, the tropical cohesive soils tested became less plastic, coarser (downward shift in grain size and higher sand equivalent), and exhibits a higher maximum dry unit weight and lower optimum water content.
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x, 87 leaves
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Civil Engineering; no. 3755
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