By means of flumes, experiments have been done in order to determine the effects of consolidation time and particle size on scour rates of cohesive sediment. Experimental results shown dry unit weight increased and sc...By means of flumes, experiments have been done in order to determine the effects of consolidation time and particle size on scour rates of cohesive sediment. Experimental results shown dry unit weight increased and scour rates decreased during the course of consolidation, the resistance to scour was related to consolidation time, but it presented different consolidation properties that depended on particle size. For the finer particle, the consolidation process was longer, the range of dry unit weight altered was greater, the consolidated sediments moved in chunks. On the other hand, based on analysis of the relationship of dry unit weight change with consolidation time, the simplified analytical expressions of dry unit weight and scour rates were derived, the results were checked with experimental data in the same flow situation and good agreements were achieved. Since the effects of different particle size were considered during the process of consolidation, the variations of consolidation properties were well reflected in these formulas.展开更多
When scour occurs beneath a subsea pipeline and develops to a certain extent,the pipeline may experience vortex-induced vibrations,through which there can be a potential accumulation of fatigue damage.However,when a p...When scour occurs beneath a subsea pipeline and develops to a certain extent,the pipeline may experience vortex-induced vibrations,through which there can be a potential accumulation of fatigue damage.However,when a pipeline is laid on an uneven seabed,certain sections may have an elevation with respect to the far-field seabed,e o,at which the development of scour would vary.This work focused on predicting the development of the scour depth beneath subsea pipelines with an elevation under steady flow conditions.A range of pipe elevation-to-diameter ratios(i.e.0≤e o/D≤0.5)have been considered for laboratory experiments conducted in a sediment flume.The corresponding equilibrium scour depths and scour time scales were obtained;experimental data from published literature have been collected and added to the present study to produce a more complete analysis database.The correlation between existing empirical equations for predicting the time scale and the experimental data was assessed,resulting in a new set of constants.A new manner of converting the scour time scale into a non-dimensional form was found to aid the empirical equations in attaining a better correlation to the experimental data.Subsequently,a new empirical equation has also been proposed in this work,which accounts for the influence of e o/D on the non-dimensional scour time scale.It was found to have the best overall correlation with the experimental data.Finally,full-scale predictions of the seabed gaps and time scales were made for the Tasmanian Gas Pipeline(TGP).展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 50679064)the Fund of Ph. D. Student Supervisor of Ministry of Education of China (Grant No. 20050486007)the National Key Project for Basic Research (Grant No. 2003CB415200).
文摘By means of flumes, experiments have been done in order to determine the effects of consolidation time and particle size on scour rates of cohesive sediment. Experimental results shown dry unit weight increased and scour rates decreased during the course of consolidation, the resistance to scour was related to consolidation time, but it presented different consolidation properties that depended on particle size. For the finer particle, the consolidation process was longer, the range of dry unit weight altered was greater, the consolidated sediments moved in chunks. On the other hand, based on analysis of the relationship of dry unit weight change with consolidation time, the simplified analytical expressions of dry unit weight and scour rates were derived, the results were checked with experimental data in the same flow situation and good agreements were achieved. Since the effects of different particle size were considered during the process of consolidation, the variations of consolidation properties were well reflected in these formulas.
文摘When scour occurs beneath a subsea pipeline and develops to a certain extent,the pipeline may experience vortex-induced vibrations,through which there can be a potential accumulation of fatigue damage.However,when a pipeline is laid on an uneven seabed,certain sections may have an elevation with respect to the far-field seabed,e o,at which the development of scour would vary.This work focused on predicting the development of the scour depth beneath subsea pipelines with an elevation under steady flow conditions.A range of pipe elevation-to-diameter ratios(i.e.0≤e o/D≤0.5)have been considered for laboratory experiments conducted in a sediment flume.The corresponding equilibrium scour depths and scour time scales were obtained;experimental data from published literature have been collected and added to the present study to produce a more complete analysis database.The correlation between existing empirical equations for predicting the time scale and the experimental data was assessed,resulting in a new set of constants.A new manner of converting the scour time scale into a non-dimensional form was found to aid the empirical equations in attaining a better correlation to the experimental data.Subsequently,a new empirical equation has also been proposed in this work,which accounts for the influence of e o/D on the non-dimensional scour time scale.It was found to have the best overall correlation with the experimental data.Finally,full-scale predictions of the seabed gaps and time scales were made for the Tasmanian Gas Pipeline(TGP).
