GEOTECHNICAL PROPERTIES OF SEDIMENT SUBJECT TO ULTRASOUNDS

The paper reports the comparison of the results of laboratory tests conducted on reconstituted samples of lagoon sediment before and after ultrasonic treatment. The purpose of the work was to evaluate the effects of ultrasonic treatment, on compressibility and velocity of sedimentation and consolidation. In the natural state, sediment may be classified as a high plasticity soil with a clay fraction of between 20% and 30% and activity index values typical of active soils. 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 particles was noted. The mechanical effect of sonication produced a reduction in coarse particles, with enrichment of the silty fraction. Different oedometer consolidation tests were conducted on reconstituted samples of sediment treated with ultrasounds: oedometer with standard loading sequence (SLS), with small stress increments (SSI) and with constant rate of strain (CRS). Comparison of the results confirms an appreciable increase in the compression index and a reduction in permeability of sonicated samples.