Rheology of Flocculated Suspension in Turbidity Currents

Turbidity currents are generated as a result of various processes such as dredging and deep-sea mining. In this work, we generate a turbidity current in a lock exchange setup [1] by using 100 g/l illite, as shown in figure 1. Two different flocculant dosages (0.25 mg/g & 0.75 mg/g of clay) were used with this illite. The material was mixed in the mixing section of the lock exchange before the lock gate was opened. Experiments were done both in fresh and salt water. The samples were collected after the end of the experiment, and their rheological properties were measured using a HAAKE MARS I rheometer (Thermo Scientific, Germany). Rheological studies were carried out using Couette geometry with a gap of 1mm. The sample was gently stirred before rheological measurements.

Higher yield stress values were observed in freshwater experiments compared to saltwater experiments, which can be attributed to a larger floc size in freshwater. In addition, the structural recovery of the flocs was also found to be higher in freshwater than in salt water.