Experimental Study on the Impact of Salinity on the Settling Velocity of Fine Sediment in Static Water

Ou Yangming, Li Ran, Qin Leilei, Liu Zhonghao

Monday 29 june 2015

17:57 - 18:00h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling, Poster pitches

Parallel session: Poster pitch: 3A. Sediment - Erosion

Salt concentration can increase the flocculation of fine-grained sediments in suspension; many relationships between salinity and settling velocity have been developed in the previous studies. However, these unique relationships typically have been limited in their appalicability due to their specific conditions. Salt concentration on the impact process of flocculation and settling for smaller particle and non-natural sand was rarely studied. In this paper, kaolinite is the constituent mineral of the sediment sample (D10=1 ; D50=5 ; D90=29 ). The experiments were conducted in a 1.5m high settling column, for different initial concentration of sediment (0.6~17.0 g l-1) and different NaCl concentration (0~20 g l-1). For each case, samples were collected at 8 times (0, 30, 60, 120, 180, 240, 360 and 1320minutes); settling velocities were calculated on the basis of the time evolution of suspended sediment concentrations. Settling velocity in direct relation with the increase in NaCl concentration and sediment concentration, after reaching the best-flocculation NaCl concentration (5.0~7.0 g l-1) and best-flocculation sediment concentration (4.5~7.0 g l-1), the velocity will decrease before tending to stability.