Parameter Estimation for Evaluation of in Situ Density and Moisture Content by using Elastic and Electromagnetic Wave Propagation

Abstract

Soil density and moisture content are two essential properties in the quality control and quality assurance of projects that involve soil compaction. However, current field practices either are destructive and time-consuming (i.e., sand cone or water balloon for soil density and oven drying for moisture content) or include hazardous substances that require special handling and operating procedures (i.e., nuclear density gauge). Therefore, new robust, reliable, and nonnuclear techniques for the determination of in situ density and moisture content would assist in quality control and quality assurance processes and would allow more measurements to be performed in a shorter time. A methodology for the in situ determination of density and moisture content by using the propagation of elastic and electromagnetic waves through soils was evaluated. It is based on a semiempirical model that relates elastic wave velocity through soils to the water content, porosity, and degree of saturation. An experimental program was used to verify the model and examine its range of applicability. It was also used to examine the accuracy and limitations of the suggested methodology. An analysis was made of the experimental assessment, along with a detailed numerical study of the inversion procedure used to calculate the density and moisture content. Although the parametric and experimental study shows that the methodology can provide an estimate of density and water content rapidly and non-destructively, there are inherent accuracy and precision limitations that need to be solved. These results also show that combined elastic and electromagnetic wave propagation measurements can help in the development of a methodology that may assist in solving inconsistencies in stiffness measurements.