Geotechnical properties of sediment subjected to ultrasound

The paper reports the comparison of the results of laboratory tests conducted on reconstituted samples of high-plasticity lagoon sediment before and after ultrasonic treatment. The purpose of the work was to evaluate the effects of ultrasonic treatment on the compressibility and velocity of sedimentation and consolidation. The improvement of these geotechnical characteristics may lead to the storage of a greater volume of dredged material in the confined disposal facilities. Tests in a sedimentation column were performed in salt water to investigate the influence of ultrasonic treatment on the occurrence of two different sedimentation processes: zone settling and compression settling. The zone settling velocity of sediment subject to ultrasonic treatment was six times slower than that of natural soils and a significant variation of grain size of the particles was noted. The mechanical effect of sonication produced a reduction in coarse particles, with enrichment of the silty fraction. Different methods of consolidation testing were conducted on reconstituted samples of sediment treated with ultrasound: oedometer with standard loading sequence, with small stress increments and with constant rate of strain. Comparison of the results confirms an appreciable increase in the compression index and a reduction in the permeability of sonicated samples.