Research On Resuspended Flux Of Sediment In The Yellow River Subaqueous Delta

Based on the existing studies of the National High Technology Research and Development Program of China (863 Program) (Contract No.2008AA09Z109), the research on resuspended flux of sediment (F) in the Yellow River subaqueous delta was done, funded by the project of National Nature Science Foundation Project"Study on Consolidated Sediment Re-suspension and Transportation in the Yellow River Estuary"(Project Number, 40876042).In this dissertation, the research contents include following aspects: (1) The mechanism of sediment resuspention and a calculate formula of F under wave loading was created from a seabed-dynamic-response standpoint, which was applied to Chengdao sea; (2) A wave flume experiment was conducted with silt taken from the Yellow River delta, which studied changes of F with varied wave parameters, different consolidation degree, artificial destruction and bioturbation; (3) Changes of resuspension characteristics of sediment around the Yellow River delta were discussed, and effects of bioturbation on sediment resuspension characteristics were studied using a recirculating flume.The main conclusions are as follows:(1) F in Chengdao sea Calculated using the formula area under wave with 5⁵0 years recurrence interval (Y) is 15³0kg·m^-2·s^-1, which seems roughly to fit the facts; sediment in Chengdao sea is mainly resuspended by shear failure induced by wave with 5⁵0 Y; Fmin and the ratio of vertical transporting sediment flux caused by liquefaction seepage are induced by wave with 50 Y at 9¹0 m water depth(W) as a whole.(2) The calculated value is far more than flume test result, the calculate formula is more suitable for F induced by storm; as wave height increases, F of 20cm and 40cm W increases; F of 20cm W is larger than which of 40cm W with the same wave height; Fmax can be reached of 40cm W is larger than which of 20cm W; F and clay content of deposition sediment on the bed increases as consolidation time of seabed increases; Artificial destroyed the seabed before the flume experiment, surging layer in the seabed and high concentration layer near bottom will be found, F will significant uplift, but the stable value of F will be smaller than which is without artificial destruction. Biological activities increase water content, decrease strength of sediment, and markedly increase F; As wave height increases, the growth amplitude of F after bioturbation is bigger than before; a large quantity of fine sediment will be produced by zoobenthos, but they are not the major part of suspended sediment.(3) F on-site increases with increasing flow velocity; resuspended coefficient of the Yellow River delta is about 0.002⁰.014 kg·m^-2·s^-1, which in north is the biggest, and near current estuary is the smallest. Biological activities increase vertical transporting sediment, make sediment finer, but have little effect on clay content; as a whole, strength of surficial sediment decreases and other parameters change little with increasing degree of bioturbation; the above-mentioned will make sediment erodibility which is defined by critical erosion velocity and critical erosion shear stress decreases, increase resuspended coefficient and F of on-site sediment in the Yellow River delta.