Multi-Modal Synthesis and Variable Modulus Effects in Resonant Column Tests by Random Excitations

To extend current measurement and data synthesis techniques for resonant column testing, random vibration transfer functions measured using a modified 6 inch (152.4 mm) diameter Drnevich free-free resonant column device are evaluated against viscoelastic theories of homogeneous and heterogeneous soil models. By means of the transfer function approach, it is found that the first four resonant peaks of the soil column response can be captured experimentally with some instrumental adaptations. By calibration against theoretical transfer functions, the ability to characterize the modulus and damping properties of the soil samples over a broad range of frequencies is demonstrated. As a generalization of the analytical theory for resonant column tests to a number of practical applications, the sensitivity of the experimental procedure to the specimen’s vertical material heterogeneity is examined for a linear variation in shear modulus. The feasibility of applying the experimental and analytical techniques to investigations of the frequency-dependence of damping properties is demonstrated. Calibration of theoretical models against measured resonant column soil behavior over a wide range of frequencies is anticipated to lead to more accurate material characterization across the spectrum of frequencies encountered in seismic and foundation vibration applications

Quantifying Repeatability Reproducibility Sources of Error and Capacity of a Measurement: Demonstrated Using Laboratory Soil Plasticity Tests

The repeatability, reproducibility, and sources of error inherent in a given measurement are important considerations for potential users. To quantify errors arising from a single operator or multiple laboratories, most testing standards uses a one-way analysis of variance- (ANOVA-) based method, which utilizes a simple standard deviation across all measurements. However, this method does not allow users to quantify the sources of error and capacity (i.e., the precision to tolerance ratio). In this study, an innovative two-way ANOVA-based analysis method is selected to quantify the relative contributions of different sources of error and determine whether a measurement can be used to check conformance of a measured characteristic to engineering specifications. In this study, the standardized Atterberg limits tests, fall-cone device Atterberg limits tests, and bar linear shrinkage tests widely used for determining the soil plasticity were selected for evaluation and demonstration. Comparisons between results of the various testing methods are presented, and the error sources contributing to the overall variations between tests are discussed. Based on the findings of this study, the authors suggest use of two-way ANOVA-based R&R analysis to quantify the sources of measurement error and capacity and also recommend using the fall cone device and ASTM standardized thread rolling device for determining liquid and plastic limits of soils, respectively