Liquefaction is one of the biggest nightmares for engineers, when designing in seismic-prone areas. The determination of the liquefaction risk in such areas is indispensable, often presenting a “Go or No-go” criterion already at the feasibility stage of a project.
Two of the principal parameters used for the corresponding geotechnical characterization of soils are: void ratio, and compactness. Among others, these factors determine the expected soil quality and performance as a foundation. Direct measurement of the natural void ratio is particularly challenging, since it requires undisturbed samples. Because of this, indirect methods are commonly used, such as the standard penetration test or the cone penetration test, which have been developed and are widely applied during initial site investigation phases. 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 samples, or the use of geophysical methods are typically not considered as a first choice due to overall project scheduling and costs.
This situation has led Lombardi engineers, together with industry and university partners, to develop a quick, simple to use and more reliable and flexible approach, that allows a direct quantitative measurement of the void ratio, and thus of the relative density.
This new approach uses microwave technology with a crosshole measurement arrangement, and instantly enables the direct determination of a soil-water percentage in saturated soils. The testing procedure is simple and time effective, allowing measurements to be made with little effort and costs. The device functionality and robustness has been proven by means of laboratory and field tests. The developed SCT device already exists in a beta version, and is being applied to projects internationally.
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