To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element i...To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity （or supply） of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.展开更多
Riverbed modeled rockfill material from Noa Dehing dam project, Arunachal Pradesh, India and blasted quarried modeled rockfill material from Kol dam project, Himachal Pradesh, India were considered for this research. ...Riverbed modeled rockfill material from Noa Dehing dam project, Arunachal Pradesh, India and blasted quarried modeled rockfill material from Kol dam project, Himachal Pradesh, India were considered for this research. Riverbed rockfill material is rounded to sub-rounded and quarried rockfill material is angular to sub-angular in shape. Prototype rockfill materials were modeled into maximum particle size （dmax） of 4.75 mm, 10 mm, 19 mm, 25 mm, 5O mm and 80 mm for testing in the laboratory. Consolidated drained triaxial tests were conducted on modeled rockfill materials with a specimen size of 381 mm in diameter and 813 mm in height to study the stress-strain-volume change behavior for both rockfill materials. Index properties, i.e. uncompacted void content （UVC） and uniaxial compressive strength （UCS）, were determined for both rockfill materials in association with material parameters. An elasto- plastic hardening soil （HS） constitutive model was used to predict the behavior of modeled rockfill materials. Comparing the predicted and observed stress-strain-volume change behavior, it is found that both observed and predicted behaviors match closely. The procedures were developed to predict the shear strength and elastic parameters of rockfill materials using the index properties, i.e. UCS, UVC and relative density （RD）, and predictions were made satisfactorily. Comparing the predicted and experi- mentally determined shear strengths and elastic parameters, it is observed that both values match closely. Then these procedures were used to predict the elastic and shear strength parameters of large- size prototype rockfill materials. Correlations were also developed between index properties and ma- terial strength parameters （dilatancy angle, ~, and initial void ratio, einit, required for HS model） of modeled rockfill materials and the same correlations were used to predict the strength parameters for the prototype rockfill materials. Using the predicted material parameters, the stress-strain-volume change behavior of prototype rockfill material was predicted using elastoplastic HS constitutive model. The advantage of the proposed methods is that only index properties, i.e. UCS, UVC, RD, modulus of elasticity of intact rock, Eir, and Poisson＇s ratio of intact rock, Vir, are required to determine the angle of shearing resistance, Ф, modulus of elasticity, E50^ref and Poisson＇s ratio, , of rockfill materials, and there is E50＆ref no need of triaxial testing. It is believed that the proposed methods are more realistic, economical, and can be used where large-size triaxial testing facilities are not available.展开更多
In recent years,regional floods and typhoons have occurred in the Yangtze Estuary.Changing dynamic conditions and dramatic reduction of sediment discharge in the basin are affecting the dynamic equilibrium pattern of ...In recent years,regional floods and typhoons have occurred in the Yangtze Estuary.Changing dynamic conditions and dramatic reduction of sediment discharge in the basin are affecting the dynamic equilibrium pattern of the Yangtze Estuary.Based on the field measurement data and theoretical derivation,this paper analyzed the changing process of runoff-sediment discharge into the sea after the operation of the Three Gorges Project(TGP),and the tidal dynamics and sediment variation characteristics of the Yangtze Estuary.The erosion of South Branch mainly occurs in the channel below-10 m contour,and the riverbed volume below contours 0 m and-10 m has a good correlation with the sediment discharge of Datong Station in the previous year.On this basis,the ratio of the horizontal distance from the starting point to the section centroid below the average water level(B_c)and the water depth at the section centroid(H_c)was proposed to describe the change of the section shape.The relationships between the water-diverting ratio,the sediment-diverting ratio and the water-diverting angle,the conditions of runoff and sediment discharge from the upper reach and the characteristics of the riverway section were established,and the theoretical calculation equations of the water-diverting ratio,the sediment-diverting ratio and the diverting angle of each bifurcation were also established.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
Wireless Sensor Network (WSN) is a special type of communication medium through distributed sensor nodes. Popular wireless sensor nodes like ZigBee have splendid interoperability after IEEE 802.15.4 standardization in...Wireless Sensor Network (WSN) is a special type of communication medium through distributed sensor nodes. Popular wireless sensor nodes like ZigBee have splendid interoperability after IEEE 802.15.4 standardization in the domain of wireless personal area network (WPAN). ZigBee has another great feature mobility that makes the ZigBee network more versatile. The mobility feature of ZigBee mobile nodes has a greater impact on network performance than fixed nodes. This impact sometimes turns into more severe because of network structure and mobility model. This study mainly focuses on the performance analysis of the ZigBee mobile node under Random and Octagonal mobility management model with the Tree routing method. The Riverbed academic modeler is used to design, implement and simulate the ZigBee network under certain conditions. This study also presents a competitive performance analysis based on ZigBee mobile nodes transmitter and receiver characteristics under the observation of the mobility model. This indicates that Octagonal mobility model exhibits better performance than the Random mobility model. This study will constitute a new way for further designing and planning a reliable and efficient ZigBee network.展开更多
The energy dissipation of boundary resistance is presented in this paper based on the flow resistance.Additionally,the river morphology responses to the resistance energy dissipation are explored using the Gaocun-Taoc...The energy dissipation of boundary resistance is presented in this paper based on the flow resistance.Additionally,the river morphology responses to the resistance energy dissipation are explored using the Gaocun-Taochengpu reach in the lower Yellow River as a prototype.Theoretical analysis,measured data analysis and a one-dimensional hydrodynamic model are synthetically used to calculate the energy dissipation rate and riverbed morphological change.The results show that the energy dissipation rate along the channel will increase in both the mean value and the fluctuation intensity with increasing discharge.However,the energy dissipation rate will first decrease and then increase as the flow section or width-depth ratio increases.In addition,the energy dissipation rate has a significant positive correlation with the riverbed stability index.The results imply that the water and sediment transport efficiency of the river channel can be improved by optimizing the cross-sectional configuration to fulfil the minimum energy dissipation rate of the boundary resistance under stable riverbed conditions.展开更多
在水文学的探索过程中,对河槽演变的研究是揭示河流流量变化、河流水势变化与研究流域自然地理演变的基础。在中国国内对黑龙江(阿穆尔河)流域的研究中,关于河槽演变的成果和分析不多。《Formation of the Riverbed Relief and River Ba...在水文学的探索过程中,对河槽演变的研究是揭示河流流量变化、河流水势变化与研究流域自然地理演变的基础。在中国国内对黑龙江(阿穆尔河)流域的研究中,关于河槽演变的成果和分析不多。《Formation of the Riverbed Relief and River Banks》一书是由俄罗斯科学院远东分院水生态研究所(IWEP FEB RAS,文中简称IWEP)副所长阿雷克谢·尼古拉耶维奇·马奇诺夫教授为第一作者编著的,该书从东亚的地区特征出发,对黑龙江(阿穆尔河)河床地貌的形成与河槽演变过程作了详细的说明。全书共分为五章,共172页,附图片44张(9张是实景彩图),并有英语和俄语两版简介与结论。该书对黑龙江河槽演变的研究具有一定的参考价值。展开更多
Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement ...Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement projects.Toward this end,we utilized the Yangzhong reach in the lower reaches of the Yangtze River as a case study and evaluated runoff,sediment content,and topographical data measured over the past 70 years(1951–2021).With the decrease in the amount of incoming sediment in the river basin,the Yangzhong reach exhibited a continuous state of scouring.The cumulative riverbed scouring volumes of the low-water and flood channels from 1981 to 2021 were 3.97×10^(8)and 4.14×10^(8)m^(3),respectively,with the riverbed scouring volume of the low-water channel accounting for 95.9%of that of the flood channel.Under quasi-natural runoff–sediment conditions,the evolution of the central bars in the Yangzhong reach was highly correlated with the amount of scouring or deposition.In particular,the Luochengzhou reach could be characterized as a meandering river with scouring on concave riverbanks and deposition on convex riverbanks.In the context of reduced incoming sediment,the beach area of the Yangzhong reach decreased by approximately 9.9%(from 2003 to 2021)and the central bars of the straight section areas decreased.Moreover,following operation of the Three Gorges Reservoir,both the Luocheng central bar and Jiangyin beach areas could be characterized as meandering rivers with convex riverbanks and beaches.In the quasi-natural period before the implementation of the waterway improvement project,the trend of high scouring intensity and increased fluid diversion ratio in the right branch of the Luocheng central bar was in accordance with the law that the short branch of the length is in a developing state under the condition of decreasing river sediment volume.With the control of riverbank protection and the construction of waterway improvement projects in the Yangzhong reach,the shapes of the riverbanks and central bars were effectively stabilized,and the linkage relationship formed in the quasi-natural period was interrupted.Overall,these findings provide a strong foundation for understanding riverbed scouring or deposition and the evolution of central bars under the influence of natural conditions and human activities,and will inform future river management and waterway dimension planning.展开更多
A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a poten...A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a potential order of metal availability in seven sludge samples was proposed： Cd 〈 Cu 〈 Zn, and samples S1 , S2, and S4 were used for the determination of total Zn content, and sample S3 used for the determination of total Cu content in the mobile and the mobilizable fractions showed the highest pollution risk. The results with regard to metal mobility in sludge samples were confirmed by the individual and global contamination factors that were calculated from the nonresidual and residual metal contents. The results obtained from metal-release experiments after exposure of sludge to environmental conditions agreed well with those obtained from both SSEP and the individual and global contamination factors, indicating that the maximum metal release could be an additional factor to evaluate the heavy metal availability in contaminated sludge. A substantial time saving was achieved by using the metal-release method in the present study.展开更多
Laboratory study of three riverbed soil samples denoted as A, B and C have been carried out by determining the soils Porosity, Hydraulic conductivity, Permeability and also investigating if there are points of converg...Laboratory study of three riverbed soil samples denoted as A, B and C have been carried out by determining the soils Porosity, Hydraulic conductivity, Permeability and also investigating if there are points of convergence between the discharge rate and angle of tilt for the above mentioned samples. The experimental results for Porosity were approximately within 34% - 37%, Hydraulic conductivity was within 3.02 × 10-5 - 9.70 × 10-5 (m/s) and Permeability was within 2.74 × 10-12 - 8.80 × 10-12 (m2). Pressure generally increases as distance of flow increases for θ = 5° - 25° but there was decrease in pressure as distance of flow increases for all three samples when θ = 0°. The points of convergence for the discharge rate ranged from 0.001 × 10-10 - 4.54 × 10-10 (m3/s), while the angle of tilt convergence points ranged from 0.1° to 3.6°. There was increase in discharge rate as angle of tilt increases for all three samples.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
基金National Natural Science Foundation of China Under Grant No.50878147
文摘To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity （or supply） of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.
文摘Riverbed modeled rockfill material from Noa Dehing dam project, Arunachal Pradesh, India and blasted quarried modeled rockfill material from Kol dam project, Himachal Pradesh, India were considered for this research. Riverbed rockfill material is rounded to sub-rounded and quarried rockfill material is angular to sub-angular in shape. Prototype rockfill materials were modeled into maximum particle size （dmax） of 4.75 mm, 10 mm, 19 mm, 25 mm, 5O mm and 80 mm for testing in the laboratory. Consolidated drained triaxial tests were conducted on modeled rockfill materials with a specimen size of 381 mm in diameter and 813 mm in height to study the stress-strain-volume change behavior for both rockfill materials. Index properties, i.e. uncompacted void content （UVC） and uniaxial compressive strength （UCS）, were determined for both rockfill materials in association with material parameters. An elasto- plastic hardening soil （HS） constitutive model was used to predict the behavior of modeled rockfill materials. Comparing the predicted and observed stress-strain-volume change behavior, it is found that both observed and predicted behaviors match closely. The procedures were developed to predict the shear strength and elastic parameters of rockfill materials using the index properties, i.e. UCS, UVC and relative density （RD）, and predictions were made satisfactorily. Comparing the predicted and experi- mentally determined shear strengths and elastic parameters, it is observed that both values match closely. Then these procedures were used to predict the elastic and shear strength parameters of large- size prototype rockfill materials. Correlations were also developed between index properties and ma- terial strength parameters （dilatancy angle, ~, and initial void ratio, einit, required for HS model） of modeled rockfill materials and the same correlations were used to predict the strength parameters for the prototype rockfill materials. Using the predicted material parameters, the stress-strain-volume change behavior of prototype rockfill material was predicted using elastoplastic HS constitutive model. The advantage of the proposed methods is that only index properties, i.e. UCS, UVC, RD, modulus of elasticity of intact rock, Eir, and Poisson＇s ratio of intact rock, Vir, are required to determine the angle of shearing resistance, Ф, modulus of elasticity, E50^ref and Poisson＇s ratio, , of rockfill materials, and there is E50＆ref no need of triaxial testing. It is believed that the proposed methods are more realistic, economical, and can be used where large-size triaxial testing facilities are not available.
基金financially supported by the Key Laboratory of Estuarine&Coastal Engineering,Ministry of Transport Open Research Program (Grant No.KLECE202001)CRSRI Open Research Program (Grant No.CKWV20221007/KY)+4 种基金the National Natural Science Foundation of China (Grant No.51979172)Jiangsu Provincial Water Conservancy Technology Project (Grant Nos.2020002,2021025,and 2021029)Fundamental Research Funds for Central Public Welfare Research Institutes (Y223002)Innovation Team Project of Estuarine and Coastal Protection and Management (Grant No.Y220013)the Major Scientific Projects of the Ministry of Water Resources (Grant No.SKS-2022087)。
文摘In recent years,regional floods and typhoons have occurred in the Yangtze Estuary.Changing dynamic conditions and dramatic reduction of sediment discharge in the basin are affecting the dynamic equilibrium pattern of the Yangtze Estuary.Based on the field measurement data and theoretical derivation,this paper analyzed the changing process of runoff-sediment discharge into the sea after the operation of the Three Gorges Project(TGP),and the tidal dynamics and sediment variation characteristics of the Yangtze Estuary.The erosion of South Branch mainly occurs in the channel below-10 m contour,and the riverbed volume below contours 0 m and-10 m has a good correlation with the sediment discharge of Datong Station in the previous year.On this basis,the ratio of the horizontal distance from the starting point to the section centroid below the average water level(B_c)and the water depth at the section centroid(H_c)was proposed to describe the change of the section shape.The relationships between the water-diverting ratio,the sediment-diverting ratio and the water-diverting angle,the conditions of runoff and sediment discharge from the upper reach and the characteristics of the riverway section were established,and the theoretical calculation equations of the water-diverting ratio,the sediment-diverting ratio and the diverting angle of each bifurcation were also established.
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.
文摘Wireless Sensor Network (WSN) is a special type of communication medium through distributed sensor nodes. Popular wireless sensor nodes like ZigBee have splendid interoperability after IEEE 802.15.4 standardization in the domain of wireless personal area network (WPAN). ZigBee has another great feature mobility that makes the ZigBee network more versatile. The mobility feature of ZigBee mobile nodes has a greater impact on network performance than fixed nodes. This impact sometimes turns into more severe because of network structure and mobility model. This study mainly focuses on the performance analysis of the ZigBee mobile node under Random and Octagonal mobility management model with the Tree routing method. The Riverbed academic modeler is used to design, implement and simulate the ZigBee network under certain conditions. This study also presents a competitive performance analysis based on ZigBee mobile nodes transmitter and receiver characteristics under the observation of the mobility model. This indicates that Octagonal mobility model exhibits better performance than the Random mobility model. This study will constitute a new way for further designing and planning a reliable and efficient ZigBee network.
基金National Natural Science Foundation of China,No.51979185,No.51879182,No.52109097。
文摘The energy dissipation of boundary resistance is presented in this paper based on the flow resistance.Additionally,the river morphology responses to the resistance energy dissipation are explored using the Gaocun-Taochengpu reach in the lower Yellow River as a prototype.Theoretical analysis,measured data analysis and a one-dimensional hydrodynamic model are synthetically used to calculate the energy dissipation rate and riverbed morphological change.The results show that the energy dissipation rate along the channel will increase in both the mean value and the fluctuation intensity with increasing discharge.However,the energy dissipation rate will first decrease and then increase as the flow section or width-depth ratio increases.In addition,the energy dissipation rate has a significant positive correlation with the riverbed stability index.The results imply that the water and sediment transport efficiency of the river channel can be improved by optimizing the cross-sectional configuration to fulfil the minimum energy dissipation rate of the boundary resistance under stable riverbed conditions.
文摘在水文学的探索过程中,对河槽演变的研究是揭示河流流量变化、河流水势变化与研究流域自然地理演变的基础。在中国国内对黑龙江(阿穆尔河)流域的研究中,关于河槽演变的成果和分析不多。《Formation of the Riverbed Relief and River Banks》一书是由俄罗斯科学院远东分院水生态研究所(IWEP FEB RAS,文中简称IWEP)副所长阿雷克谢·尼古拉耶维奇·马奇诺夫教授为第一作者编著的,该书从东亚的地区特征出发,对黑龙江(阿穆尔河)河床地貌的形成与河槽演变过程作了详细的说明。全书共分为五章,共172页,附图片44张(9张是实景彩图),并有英语和俄语两版简介与结论。该书对黑龙江河槽演变的研究具有一定的参考价值。
基金National Natural Science Foundation of China,No.52279066Fundamental Research Funds for Central Welfare Research Institutes,No.TKS20230206The CRSRI Open Research Program,No.CKWV2021862/KY。
文摘Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement projects.Toward this end,we utilized the Yangzhong reach in the lower reaches of the Yangtze River as a case study and evaluated runoff,sediment content,and topographical data measured over the past 70 years(1951–2021).With the decrease in the amount of incoming sediment in the river basin,the Yangzhong reach exhibited a continuous state of scouring.The cumulative riverbed scouring volumes of the low-water and flood channels from 1981 to 2021 were 3.97×10^(8)and 4.14×10^(8)m^(3),respectively,with the riverbed scouring volume of the low-water channel accounting for 95.9%of that of the flood channel.Under quasi-natural runoff–sediment conditions,the evolution of the central bars in the Yangzhong reach was highly correlated with the amount of scouring or deposition.In particular,the Luochengzhou reach could be characterized as a meandering river with scouring on concave riverbanks and deposition on convex riverbanks.In the context of reduced incoming sediment,the beach area of the Yangzhong reach decreased by approximately 9.9%(from 2003 to 2021)and the central bars of the straight section areas decreased.Moreover,following operation of the Three Gorges Reservoir,both the Luocheng central bar and Jiangyin beach areas could be characterized as meandering rivers with convex riverbanks and beaches.In the quasi-natural period before the implementation of the waterway improvement project,the trend of high scouring intensity and increased fluid diversion ratio in the right branch of the Luocheng central bar was in accordance with the law that the short branch of the length is in a developing state under the condition of decreasing river sediment volume.With the control of riverbank protection and the construction of waterway improvement projects in the Yangzhong reach,the shapes of the riverbanks and central bars were effectively stabilized,and the linkage relationship formed in the quasi-natural period was interrupted.Overall,these findings provide a strong foundation for understanding riverbed scouring or deposition and the evolution of central bars under the influence of natural conditions and human activities,and will inform future river management and waterway dimension planning.
基金Supported by the National Key Basic Research Priorities Program of China(No. 2004CB3418501).
文摘A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a potential order of metal availability in seven sludge samples was proposed： Cd 〈 Cu 〈 Zn, and samples S1 , S2, and S4 were used for the determination of total Zn content, and sample S3 used for the determination of total Cu content in the mobile and the mobilizable fractions showed the highest pollution risk. The results with regard to metal mobility in sludge samples were confirmed by the individual and global contamination factors that were calculated from the nonresidual and residual metal contents. The results obtained from metal-release experiments after exposure of sludge to environmental conditions agreed well with those obtained from both SSEP and the individual and global contamination factors, indicating that the maximum metal release could be an additional factor to evaluate the heavy metal availability in contaminated sludge. A substantial time saving was achieved by using the metal-release method in the present study.
文摘Laboratory study of three riverbed soil samples denoted as A, B and C have been carried out by determining the soils Porosity, Hydraulic conductivity, Permeability and also investigating if there are points of convergence between the discharge rate and angle of tilt for the above mentioned samples. The experimental results for Porosity were approximately within 34% - 37%, Hydraulic conductivity was within 3.02 × 10-5 - 9.70 × 10-5 (m/s) and Permeability was within 2.74 × 10-12 - 8.80 × 10-12 (m2). Pressure generally increases as distance of flow increases for θ = 5° - 25° but there was decrease in pressure as distance of flow increases for all three samples when θ = 0°. The points of convergence for the discharge rate ranged from 0.001 × 10-10 - 4.54 × 10-10 (m3/s), while the angle of tilt convergence points ranged from 0.1° to 3.6°. There was increase in discharge rate as angle of tilt increases for all three samples.
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.
