Investigations of Rheological Flow Properties Based on Lab Data of Fluid Mud Samples and an Extended Model Approach

摘要

Fluid mud parameters like mass concentration, yield point and apparent viscosities are derived by means of fluid mud sampling along the tidal reach of river Ems and subsequent lab analysis regarding suspended sediment concentration, bulk density and rheological parameters. Equilibrium flow curves were obtained for every sample by means of constant-rate analysis with a high resolution lab rheometer. Comparisons of samples from different locations show good correlation between fluid mud mass concentration and yield point. A reliable method for yield point detection based on creep and recovery rheometer tests and a semi graphical approach was found to deliver the best results. In order to reproduce the large spread of viscosities occurring in reality, the Toorman model was extended by means of an empirical fit with respect to suspended sediment mass concentration. The comparison shows a good correlation between model results and measured constant-rate-test data. Also the thixotropic behavior due to weakening and strengthening as a result of disintegration and build-up of the internal floc structure is reproduced.