Study of Soil Compaction Using X-Ray Computed Tomography

The maximum dry density and optimum moisture content obtained from the laboratory compaction curve have been used customarily to characterize the field behavior of compacted soils. It is well known, however, that the microstructure of compacted soils is dependent on the method of compaction. The structure has an important influence on the engineering behavior of compacted soils. Therefore, in order to provide a better description of compacted soils, methods that can quantify the changes in microstructure are needed. In this study, compacted specimens at various densities and water content were scanned using X-ray Computed Tomography (CT). It has been found that there is direct correspondence between the CT numbers, soil dry density and moisture content. The scanning observations showed also the development of shear planes parallel to the surface of the compacted soil, and changes in structure of the soil towards a more uniform arrangement around the point of optimum moisture content. Compaction of the soil beyond the optimum moisture content appears to disperse soil particles with an overall uniform structure.