Measuring shear wave velocity in laboratory to link small-and large-strain behavior of soils

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Current geotechnical practice relies on empirical relationships with in situ tests to determine the effective stress strengt;h parameters for dense, cohesionless soils. Although these methods work reasonably well in practice, they cannot account for in situ effects related to time, fabric, and cementation. These factors are especially important for brittle or sensitive soils, such as loess and cemented sands. To develop methods that can predict strengt;h in these types of soils, a better understanding of the link between small-and large-strain behavior is needed. The objective of this paper is to evaluate the hypothesis that a unique relationship exists between the small-strain shear modulus (G0) and the effective stresses at failure (σ'1) for dilatant soils. To accomplish this objective, isotropically consolidated-drained triaxial compression tests were performed, with shear wave velocity measured throughout the tests. The soils tested in this study included a quartz sand and nonplastic silt, and the results were compared with previous studies by the authors on weakly cemented sands. The findings showed that the G0/σ'1 ratio was approximately 200 ± 20 for the three soils tested and was independent of density, degree of cementation, and confining stress. If true for other soils, this finding could have important implications for evaluating staged construction on sensitive soils and estimating the strengt;h of dilative soils in situ.

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Transportation Research Record