Since 1958,there have been significant changes in the Yangtze River estuary.Due to extensive reclamation and con-struction of ports and channels,the water area has drastically decreased,resulting in corresponding chan...Since 1958,there have been significant changes in the Yangtze River estuary.Due to extensive reclamation and con-struction of ports and channels,the water area has drastically decreased,resulting in corresponding changes in hydrodynamics and riverbeds at the mouth of the river.According to the analysis of measured topographic data and Delft3D-FLOW model for seven typical historical periods since 1958 at the Yangtze River Estuary,this study investigates the characteristics of riverbed evolution and tidal flow dynamics.From 1958 to 2019,driven by strong human activities,the total area of the Yangtze River Estuary decreased from 2084km^(2)to 1403km^(2),with a decrease of 32.7%,while the total volume of the corresponding river channel changed slightly and remained stable.Com-pared with 1958,the volume of the Yangtze River Estuary in 2019 only increased by 345 million m^(3),with an increase of about 4.1%.The tidal dynamic change of the Yangtze Estuary is closely related to the riverbed evolution of each reach,which not only shapes the estuary landform,but also is affected by the riverbed evolution.Tidal level,tidal range and water area change are closely related.With the decrease of water area in the Yangtze River Estuary,tidal range tends to increase.Tidal prism change is closely related to channel volume.In the past 60 years,the tidal vol-ume at the mouth of the Yangtze River has decreased by 8%.The research findings will provide technical support for enhancing flood control and tide resistance measures at the Yangtze River Estuary,as well as formulating compre-hensive management plans for estuaries,contributing to the protection and sustainable development of the Yangtze River Estuary.展开更多
It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by waterflood disa...It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by waterflood disasters.In order to clarify the evolution law of the riverbed near un-derwater crossing line pipes and its negative effects,this paper conductedflume model experiments on underwater crossing line pipes.The physical process of riverbed evolution near pipes was observed and the effect of hydrodynamic conditions on the local pipe scour was studied.What's more,the formation mechanism of local scour at underwater crossing line pipes was revealed.And the following research results were obtained.First,when the waterflow is slow,the riverbed evolution process near underwater crossing line pipes is mainly divided into six stages,including riverbed undercutting,pipe exposure,micro-pore formation,scour hole propagation,pipe suspension and scour equilibrium.Second,vortex and seepageflow are the reasons for the local scour of underwater crossing line pipes.Before pipes are exposed,the silt around the pipes is reduced by vortex.After pipes are exposed,micro-pores occur at the pipe bottom under the joint action of vortex and seepageflow.And thus,local scour is formed.Third,flow velocity and water depth jointly influence the riverbed scour duration of each stage and the maximum scour depth at the pipe bottom.When the Froude number(Fr)is in the range of 0.306e0.808,with the increase of Fr,waterflow gets fast,the maximum scour depth at the pipe bottom increases,the duration for scour equilibrium decreases,the riverbed undercutting depth increases and the riverbed topographically getsflatter.The maximum scour depth at the pipe bottom is 0.9e1.6 times the pipe diameter,and the duration for scour equilibrium is between 1650 min and 2620 min.In conclusion,the experimental results provide important reference for predicting the burial depth of underwater crossing line pipes and ensuring their safe operation.展开更多
The Inner Mongolia reaches of the Yellow River face problems of severe sedimen-tation caused by a variety of complex factors.The sedimentation process in those reaches has been characterized using the sediment balance...The Inner Mongolia reaches of the Yellow River face problems of severe sedimen-tation caused by a variety of complex factors.The sedimentation process in those reaches has been characterized using the sediment balance method,and the key factors affecting the process have been analyzed using the correlation analysis method.The results show that during the period 1952-2012 the Bayangaole(Bayan Gol)to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation,then relative balance,and then accumulative sedimentation once again.The total annual sedimentation is 12.0341×10^(8)m^(3),of which accumulations from July to October account for 95.1%and the reaches from Sanhuhekou to Toudaoguai account for 98.5%.The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition.The critical conditions for equilibrium are an incoming sediment co-efficient〈0.007 kg·s·m^-6 and a flow discharge〉700 m^(3)·s^(-1).The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream.The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m^(3)·s^(-1)and a comprehensive incoming sediment coefficient〈0.005 kg^(-3)·m^(-6).The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1×10^(8)t.The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches,but the latter contributes the most.展开更多
基金funded by the National Key R&D Program of China(2023YFC3208500).
文摘Since 1958,there have been significant changes in the Yangtze River estuary.Due to extensive reclamation and con-struction of ports and channels,the water area has drastically decreased,resulting in corresponding changes in hydrodynamics and riverbeds at the mouth of the river.According to the analysis of measured topographic data and Delft3D-FLOW model for seven typical historical periods since 1958 at the Yangtze River Estuary,this study investigates the characteristics of riverbed evolution and tidal flow dynamics.From 1958 to 2019,driven by strong human activities,the total area of the Yangtze River Estuary decreased from 2084km^(2)to 1403km^(2),with a decrease of 32.7%,while the total volume of the corresponding river channel changed slightly and remained stable.Com-pared with 1958,the volume of the Yangtze River Estuary in 2019 only increased by 345 million m^(3),with an increase of about 4.1%.The tidal dynamic change of the Yangtze Estuary is closely related to the riverbed evolution of each reach,which not only shapes the estuary landform,but also is affected by the riverbed evolution.Tidal level,tidal range and water area change are closely related.With the decrease of water area in the Yangtze River Estuary,tidal range tends to increase.Tidal prism change is closely related to channel volume.In the past 60 years,the tidal vol-ume at the mouth of the Yangtze River has decreased by 8%.The research findings will provide technical support for enhancing flood control and tide resistance measures at the Yangtze River Estuary,as well as formulating compre-hensive management plans for estuaries,contributing to the protection and sustainable development of the Yangtze River Estuary.
基金supported by the National Natural Science Foundation of China"Soil-pipe-water coupling effect and seismic damage mechanism of buried water pipeline"(No.:51478403)PetroChina Major Science&Technology Project"Sudy and application of key technology for maintaining 30 billion cubic meters of production in Southwest Oil and Gas Field(No:2016E-0610).
文摘It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by waterflood disasters.In order to clarify the evolution law of the riverbed near un-derwater crossing line pipes and its negative effects,this paper conductedflume model experiments on underwater crossing line pipes.The physical process of riverbed evolution near pipes was observed and the effect of hydrodynamic conditions on the local pipe scour was studied.What's more,the formation mechanism of local scour at underwater crossing line pipes was revealed.And the following research results were obtained.First,when the waterflow is slow,the riverbed evolution process near underwater crossing line pipes is mainly divided into six stages,including riverbed undercutting,pipe exposure,micro-pore formation,scour hole propagation,pipe suspension and scour equilibrium.Second,vortex and seepageflow are the reasons for the local scour of underwater crossing line pipes.Before pipes are exposed,the silt around the pipes is reduced by vortex.After pipes are exposed,micro-pores occur at the pipe bottom under the joint action of vortex and seepageflow.And thus,local scour is formed.Third,flow velocity and water depth jointly influence the riverbed scour duration of each stage and the maximum scour depth at the pipe bottom.When the Froude number(Fr)is in the range of 0.306e0.808,with the increase of Fr,waterflow gets fast,the maximum scour depth at the pipe bottom increases,the duration for scour equilibrium decreases,the riverbed undercutting depth increases and the riverbed topographically getsflatter.The maximum scour depth at the pipe bottom is 0.9e1.6 times the pipe diameter,and the duration for scour equilibrium is between 1650 min and 2620 min.In conclusion,the experimental results provide important reference for predicting the burial depth of underwater crossing line pipes and ensuring their safe operation.
文摘The Inner Mongolia reaches of the Yellow River face problems of severe sedimen-tation caused by a variety of complex factors.The sedimentation process in those reaches has been characterized using the sediment balance method,and the key factors affecting the process have been analyzed using the correlation analysis method.The results show that during the period 1952-2012 the Bayangaole(Bayan Gol)to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation,then relative balance,and then accumulative sedimentation once again.The total annual sedimentation is 12.0341×10^(8)m^(3),of which accumulations from July to October account for 95.1%and the reaches from Sanhuhekou to Toudaoguai account for 98.5%.The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition.The critical conditions for equilibrium are an incoming sediment co-efficient〈0.007 kg·s·m^-6 and a flow discharge〉700 m^(3)·s^(-1).The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream.The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m^(3)·s^(-1)and a comprehensive incoming sediment coefficient〈0.005 kg^(-3)·m^(-6).The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1×10^(8)t.The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches,but the latter contributes the most.
