| Drainage systems,as an important urban infrastructure,play a key role in the prevention and control of urban water pollution and urban flood control,but sediment deposition have a serious impact on the operation of drainage pipelines.Studies have shown that there are significant differences in the particle size,density and organic matter content of pipeline sediments,and different types of organic sediments show different incipient motion under the action of microorganisms,but there is still a lack of systematic research on the incipient motion and incipient motion discriminatory formulae for different types of sediments under the action of microorganisms.Therefore,this study investigates the incipient motion and initiation formulae of different types of organic sediments under the action of microorganisms through microscopic observation experiments and open channel flushing experiments.The main research contents are as follows:(1)Samples of organic sediments were selected from artificial configurations of inorganic sand of different densities and organic matter,and the influence of the density of the main sediment on the laws of incipient motion of organic sediments under the action of microorganisms was investigated by open channel flushing experiments The results show that the higher the sediment density,the slower the erosion rate increases with water flow shear stress and the higher the critical shear stress.The increase in sediment density increases the base shear stress in the main sediment,and at the same time causes microorganisms to produce more EPS between sediment particles,enhancing the bioadhesive additional shear stress in the sediment.Under the combined effect of both,the erosion resistance of organic sediments under microbial action increases with increasing density.(2)The effect of sediment particle size on the laws of incipient motion of organic sediment under microbial action was investigated by open channel flushing experiments with different particle sizes sand and organic matter in artificial configurations of organic sediment.The results show that the larger the sediment particle size is,the faster the erosion rate increases and then decreases,and the critical shear stress decreases and then increases.On the one hand,the increase in sediment size increases the base shear stress of the sediment.On the other hand,it weakens the microbial activity,which reduces the EPS content in the sediment and weakens the linkage of biofilm,resulting in a reduction of the bioadhesive additional shear stress.Under the combined effect of the two,the erosion resistance of the sediment shows a pattern of decreasing and then increasing as the particle size increases.(3)Based on the results of the open channel flushing experiments,the effects of sediment grain size,density and organic matter content on the bio-viscosity coefficient of different types of organic sediments were investigated.The results show that the bioadhesion coefficient decreases slowly with the increase of organic matter content,decreases with the increase of sediment size and then increases with the increase of density.At the same time,the response surface method and intelligent algorithm were used to establish the empirical equation of critical starting shear stress for different types of organic matter content sediments under the action of microorganisms and the BP neural network model.The comparison of the prediction performance of the two shows that the response surface empirical formulation has smaller error values and higher accuracy. |
