The objective of this study was to present an appropriate method for grain size analysis of sediments flowing into reservoirs. In the numerical simulation of reservoir turbidity, it is important to have accurate data on the particle settling rate. Laser diffraction is typically used for grain size analysis and the settling rate is converted by Stokes formula; however, it has been indicated that the settling rate calculated by this method differs from the actual rate. We conducted grain size analysis using three different methods, i.e., settling cylinder, centrifugal sedimentation and laser diffraction. A comparison of the results led to the following conclusions: (1) Settling cylinder was the most reliable method for obtaining the settling rate of fine particles. (2) Centrifugal sedimentation was a viable alternative to the settling cylinder method. (3) Laser diffraction provided grain size distribution similar to the settling cylinder method by applying supersonic distribution treatment. |