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Volume 47, Issue 3 (October 2018)
Special Issue Paper
Microwave Technology for In Situ Determination of Void Ratio and Compactness in Saturated Soils
(Received 19 December 2017; accepted 13 July 2018)
Published Online: 16 October 2018
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Void ratio and compactness are two of the principal parameters used for the geotechnical characterization of soils. Among others, these factors determine the soil expected quality and performance as a foundation. Direct measurement of the natural void ratio is particularly challenging, since it requires undisturbed specimens. Because of it, commonly used indirect methods, such as the standard penetration test or cone penetration test, have been developed and are widely practiced during the initial site investigation phase. However, such indirect methods have their limitations and often fail, especially with heterogeneous soils. Results are interpreted by indirect correlations, which are often affected by uncertainty. Extraction of undisturbed specimens or the use of geophysical methods are typically not considered in the first place due to overall project schedule and costs. Similar measurement principle systems such as crosshole georadar produce 2-D/3-D images by means of image reconstruction algorithms. The proposed system produces a 1-D value, which is the mean dielectric constant between two antennas. The application need a quick, simple to use, and more reliable and flexible approach that allows a direct quantitative measurements. This new approach uses microwave technology. With a crosshole measurement arrangement, it is comparable to various other georadar setups. The main difference from the already existing geophysical approaches is the output in terms of an average value of the dielectric constant at a certain depth at greater measurement distances. The developed technique provides instantly the direct determination of a soil-water percentage in saturated soils. The testing procedure it is simple and time effectiveness, allowing measurement with reduced effort and cost. The device functionality and robustness has been proven by means of laboratory and fileld tests. The developed SCT device already exists in a beta version and is being applied to projects on an international level.
Lombardi Engineering Ltd., Minusio, TI
SUPSI University of Applied Sciences and Arts of Southern Switzerland, Manno, TI
Stock #: JTE20170764
Title Microwave Technology for In Situ Determination of Void Ratio and Compactness in Saturated Soils