Air, water and vacuum pluviation of sand specimens for the triaxial apparatus

A device is presented for reconstituting sand specimens directly onto the triaxial apparatus by pluviation in air, water or under vacuum. The sand is delivered by means of a uniform rain covering the whole specimen cross section and target density is achieved by changing fall height and depositional intensity. The apparatus was calibrated using Ticino River sand, for which water and vacuum pluviations provided the lowest and highest densities, respectively. Whilst the density of loose samples was similar to that obtained using Kolbuszewski (1948) and ASTM minimum density methods, much denser specimens were obtained with vacuum pluviations as compared to vibration compaction methods (similar to ASTM maximum density method). The resulting maximum relative density, referred to the limits from standard tests, was as high as 140%. Water pluviation density is independent of both depositional intensity and fall height. For other target density best results in terms of sample uniformity are achieved by vacuum pluviation with an appropriate selection of depositional intensity and fall height. This provides also an extremely high reproducibility of target density.