Consolidation and strength evolution ofCaland-Beer Channel mudMeasurement report on laboratory experiments

摘要

Many harbours in the world suffer from high siltation rates in their basins. To guarantee safeshipping, harbour authorities have to maintain the navigable depth by having dredged largeamounts of mud. Some authorities relate the navigable depth to a depth at which the densityis equal to a certain value, e.g. 1200 kg/m3. However, the shear strength might be a moredirect criterion to relate the navigable depth to.A research project is conducted to develop a model to describe the consolidation behaviourand strength evolution of mud layers. The second series of experiments for this project,executed at Delft University of Technology, are described in this report. The analysis of thedata is left for future work.The sedimentation and consolidation of Caland-Beer Channel mud was simulated in seg-mented consolidation columns. The use of segments made it possible to obtain well-definedand undisturbed samples of the mud bed. For this reason, more accurate shear vane mea-surements of the samples could be done than if conventional consolidation columns had beenused.Four segmented consolidation columns and one conventional consolidation column wereset up. To study the time evolution of the strength of the mud bed, the segmented columnswere dismantled at different times. After the dismantling, shear vane tests could be carriedout and density measurements could be done with a conductivity probe. The density profilesof the mud layer in the conventional column were measured with a γ-ray densimeter. Porewater pressures were measured at several times. From these measurements effective stressesand permeabilities were calculated. Various rheological parameters were derived from fourdifferent types of shear vane measurements. Flow curves were also measured.It turned out that the effective stresses could be approximated by a power law. Further-more, the rheological parameters turned out to be approximately linearly interrelated, eventhough the parameters were derived from different types of rheological experiments. Smallmodifications of the experimental set-up are recommended for future experiments.