The North Branch, separated by the Chongming Island, was once the main channel in the estuary of the Changjiang River. Reclamation and a decrease in runoffto the North Branch had led to the narrowing and shallowing of...The North Branch, separated by the Chongming Island, was once the main channel in the estuary of the Changjiang River. Reclamation and a decrease in runoffto the North Branch had led to the narrowing and shallowing of the channel. The Yuantuojiao Point is located at the intersecting point connecting the North Branch of the Changjiang River and the Jiangsu coastline. Erosion cliffs are developed between the typical silty-muddy tidal flat and the salt marsh occupied by Spartina alterniflorea, and this has changed rapidly over the past few years. The sediment grain size analysis results of the surficial and two core samples indi- cate that the Yuantuoiiao Point tidal fiat experienced continuous accretional processes. Based upon 137Cs analysis results of the YT and YY Cores sampled from the tidal flat at the Yuantuojiao Point, the average sed- imentation rate of the YT Core was 2.30 cm/a from 1963 to 2007, and 2.38 cm/a from 1954 to 2007 for the YY Core. The sedimentation rates of both core locations have declined since the 1960s corresponding to the seaward reclamation at the Yuantuojiao Point. The average sedimentation rates at the Yuantnojiao Point were similar to that of the silty-muddy tidal flat at the northern ]iangsu coast, but lower than that of the south of the Changjiang River Estuary. According to field morphological investigations from 2006 to 2008 on the salt marsh at the Yuantuojiao Point, cliffs retreated markedly by storm surges and disappeared gradu- ally because of the rapid sedimentation on the silty-muddy tidal flat. The maximum annual retreat reached 10 m. The recent sedimentation and morphological changes of the Yuantuojiao Point tidal flat not only displayed the retreat of the salt marsh and the disappearance of cliffs, but also was accompanied by rapid sedimentation of the silty-muddy tidal flat and the salt marsh, indicating the responses to the tidal currents, storm surges, Spartina alterniflorea trapping sediments and large-scale reclamation. The sediment grain size and their trends, southward coastal flow, and sandspits of the longshore bars suggest that the main sediment source at the Yuantuoijao Point, estuary of the North Branch was possibly from the Changjiang River before 1958, since then, it has been from the south of the submarine radial sand ridges of the southern Huanghai Sea （Yellow Sea）.展开更多
A series of physical tests are conducted to examine the characteristics of the wave loading exerted on circular-front breakwaters by regular waves. It is found that the wave trough instead of wave crest plays a major ...A series of physical tests are conducted to examine the characteristics of the wave loading exerted on circular-front breakwaters by regular waves. It is found that the wave trough instead of wave crest plays a major role in the failure of submerged circular caissons due to seaward sliding. The difference in the behavior of seaward and shoreward horizontal wave forces is explained based on the variations of dynamic pressure with wave parameters. A wave load model is proposed based on a modified first-order solution for the dynamic pressure on submerged circular-front caissons under a wave trough. This wave loading model is very useful for engineering design. Further studies are needed to include model uncertainties in the reliability assessment of the breakwater.展开更多
基金The National Natural Science Foundation of China under contract Nos 41071006 and 40676052the Jiangsu Natural Science Foundation under contract No. BK2010050the Research Fund for the Doctoral Program of Higher Education of China under contract No.20100091110011
文摘The North Branch, separated by the Chongming Island, was once the main channel in the estuary of the Changjiang River. Reclamation and a decrease in runoffto the North Branch had led to the narrowing and shallowing of the channel. The Yuantuojiao Point is located at the intersecting point connecting the North Branch of the Changjiang River and the Jiangsu coastline. Erosion cliffs are developed between the typical silty-muddy tidal flat and the salt marsh occupied by Spartina alterniflorea, and this has changed rapidly over the past few years. The sediment grain size analysis results of the surficial and two core samples indi- cate that the Yuantuoiiao Point tidal fiat experienced continuous accretional processes. Based upon 137Cs analysis results of the YT and YY Cores sampled from the tidal flat at the Yuantuojiao Point, the average sed- imentation rate of the YT Core was 2.30 cm/a from 1963 to 2007, and 2.38 cm/a from 1954 to 2007 for the YY Core. The sedimentation rates of both core locations have declined since the 1960s corresponding to the seaward reclamation at the Yuantuojiao Point. The average sedimentation rates at the Yuantnojiao Point were similar to that of the silty-muddy tidal flat at the northern ]iangsu coast, but lower than that of the south of the Changjiang River Estuary. According to field morphological investigations from 2006 to 2008 on the salt marsh at the Yuantuojiao Point, cliffs retreated markedly by storm surges and disappeared gradu- ally because of the rapid sedimentation on the silty-muddy tidal flat. The maximum annual retreat reached 10 m. The recent sedimentation and morphological changes of the Yuantuojiao Point tidal flat not only displayed the retreat of the salt marsh and the disappearance of cliffs, but also was accompanied by rapid sedimentation of the silty-muddy tidal flat and the salt marsh, indicating the responses to the tidal currents, storm surges, Spartina alterniflorea trapping sediments and large-scale reclamation. The sediment grain size and their trends, southward coastal flow, and sandspits of the longshore bars suggest that the main sediment source at the Yuantuoijao Point, estuary of the North Branch was possibly from the Changjiang River before 1958, since then, it has been from the south of the submarine radial sand ridges of the southern Huanghai Sea （Yellow Sea）.
基金financially supported by the Open Fund of the State Key Laboratory of Hydraulic Engineering Simulation and Safety from Tianjin University(Gtant No.HESS-1310)the Natural Science Foundation of Tianjin,China(Gtant No.14JCYBJC22100)+5 种基金the National Natural Science Foundation of China(Gtant No.51509178)supported by the State Scholarship Fund of China Scholarship Council(Gtant No.201308120008)supported by the Physical Oceanography Program of National Science Foundation(Grant No.1436642)the Maine Sea Grant and NOAA for Grant No.NA10OAR4170072part of EFRaCC project funded by the British Council under its Global Innovation Initiativethe open fund research at the State Key Laboratory of Hydraulics and Mountain River at Sichuan University(Grant No.SKHL1311)
文摘A series of physical tests are conducted to examine the characteristics of the wave loading exerted on circular-front breakwaters by regular waves. It is found that the wave trough instead of wave crest plays a major role in the failure of submerged circular caissons due to seaward sliding. The difference in the behavior of seaward and shoreward horizontal wave forces is explained based on the variations of dynamic pressure with wave parameters. A wave load model is proposed based on a modified first-order solution for the dynamic pressure on submerged circular-front caissons under a wave trough. This wave loading model is very useful for engineering design. Further studies are needed to include model uncertainties in the reliability assessment of the breakwater.
