ABSTRACT
Project developments in areas where the soil conditions consist of sand require assessments of in-situ density and strength/deformation parameters. Due to the difficulty of obtaining undisturbed samples, the usual practice is to estimate in-situ relative density, Dr, from CPT cone resistance and to reconstitute specimens in the laboratory to the estimated Dr before carrying out triaxial or other laboratory tests. In order to calculate Dr of the reconstituted sand specimen it is necessary to determine the maximum and minimum dry densities, often expressed as maximum dry unit weight, γdmax, and minimum dry unit weight, γdmin. Depending on the country where the project is developed different standards or methods are used. In addition, some geotechnical laboratories (including NGI, Geolabs and Fugro) have developed their own in-house methods. There are large differences in the measured γdmax and γdmin values according to which standards or methods used, e.g. Tavenas (1973). As an example, a comparison study of three different methods used in a German DONG Energy project showed a large variation in the results. A triaxial specimen was reconstituted with a dry unit weight of 16.4 kN/m3; Table 1 lists the corresponding representative values of γdmin and γdmax as measured with three different methods as well as the resulting relative density.
