Abstract: Many scholars in China and abroad have carried out a lot of experimental researches and analysis on the formula of single particle sedimentation. In view of the 10 times difference between single particle sedimentation rate and group settlement, current formulas of sediment settlement are mostly empirical expression. In this paper, based on the perturbation theory and the least square method, a new calculation model for the settlement of sediment group is proposed. The influence of coarse and fine particle sizes are considered. Through calculations and fittings of field measured data and flume experiment data, and compared with other classical formulas, the present model is found to be superior to classical formulas. Results show that taking the sizes of coarse and fine particles into account is an effective way to calculate sediment deposition.

Key words: sediment group settlement, formula of sediment settlement, perturbation theory, lease square method, coarse and fine particles, single particle velocity