Enhanced Portable Device for Subgrade and Granular Base Characterization

Principal Investigator:

Bojan Guzina, Associate Professor, Civil, Environmental and Geo-Engineering

Project Summary:

In this study, the accuracy of the stiffness estimate from portable deflectometer devices was investigated, based upon the example of a particular device, the Portable Falling Weight Deflectometer (PRIMA 100). A laboratory calibration setup, assembly consisting of a simply supported steel beam of variable span, was designed to verify the calibration of the device (sensors and data interpretation method). Associated with the tester apparatus, an enhanced setup for the portable device was examined. By verifying the stiffness estimated from the portable device against the known stiffness of the beam, inconsistencies in the data interpretation method using peak values of load and displacement time histories were pointed out. An alternative method using Frequency Response Functions, spectral average, Single Degree of Freedom System analog, zero frequency estimates and curve fitting was then proposed to extract the static stiffness from PRIMA measurements. Test results showed good agreement between estimates stemming from the modified analysis and true beam stiffness. A baseline for the application of both the alternative method and the enhanced device setup to quality control field measurements was proposed.

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