A well-established 3D phase-averaged beach morphodynamic model was applied to investigate the morphodynamics of a typical artificial beach,and a series of discussions were made on the surfzone hydro-sedimentological p...A well-established 3D phase-averaged beach morphodynamic model was applied to investigate the morphodynamics of a typical artificial beach,and a series of discussions were made on the surfzone hydro-sedimentological processes under calm and storm events.Model results revealed that the nearshore wave-induced current presents a significant 3D structure under stormy waves,where the undertow and longshore currents exist simultaneously,forming a spirallike circulation system in the surfzone.Continuous longshore sediment transport would shorten the sediment supply in the cross-shore direction,subsequently suppress the formation of sandbars,showing that a typical recovery profile under calm waves does not necessarily develop,but with a competing process of onshore drift,undertow and longshore currents.Sediment transport rate during storms reaches several hundreds of times as those under calm waves,and two storm events contribute approximately 60%to the beach erosion.Sediment transport pattern under calm waves is mainly bed load,but as the fine sands underneath begin to expose,the contribution of suspended load becomes significant.展开更多
Dune riocks are aeolian sands cemented ty calcium carbonate under subaerial conditions. They have been found in many of the coastal belts of Fujian, Guangdong and Hainan Provinces in South China. The grain composition...Dune riocks are aeolian sands cemented ty calcium carbonate under subaerial conditions. They have been found in many of the coastal belts of Fujian, Guangdong and Hainan Provinces in South China. The grain composition of the dune rocks is mainly quartz sands and shell fragments. The quartz sands are medium and fine sized, relatively well sorted and positively skewed. Their surface texture formed in aeolian environments is characterized ty dishshaped depressions, meniscus depressions and V-shaped depressions with rounded edges. The most common bedding type of the rocks is larg (thickness>1.5m), steeply dipping (32--40°) with cross strata tolaner and convex upward). Mg and Sr contents are very low in the rock chemical composition which is classified into low Mg and low Sr category. The typical species of microfossils in the dune rocks are mainly freshwater ones and lack of typical saltwaer or semi-saltwater ones with incomplete assemblage of marine species. The cement minerals in the rocks are mainly low-Mg calcite and the common cement fabrics are meniscus cement and gravitational cement in response to impermanent water in vadose zones. Therefore, the dune rocks may be apparently distinguished from the beach rocks.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51779112 and 51879096)Research Innovation Fund of Tianjin Research Institute for Water Transport Engineering(Grant Nos.TKS20200401 and TKS180405).
文摘A well-established 3D phase-averaged beach morphodynamic model was applied to investigate the morphodynamics of a typical artificial beach,and a series of discussions were made on the surfzone hydro-sedimentological processes under calm and storm events.Model results revealed that the nearshore wave-induced current presents a significant 3D structure under stormy waves,where the undertow and longshore currents exist simultaneously,forming a spirallike circulation system in the surfzone.Continuous longshore sediment transport would shorten the sediment supply in the cross-shore direction,subsequently suppress the formation of sandbars,showing that a typical recovery profile under calm waves does not necessarily develop,but with a competing process of onshore drift,undertow and longshore currents.Sediment transport rate during storms reaches several hundreds of times as those under calm waves,and two storm events contribute approximately 60%to the beach erosion.Sediment transport pattern under calm waves is mainly bed load,but as the fine sands underneath begin to expose,the contribution of suspended load becomes significant.
文摘Dune riocks are aeolian sands cemented ty calcium carbonate under subaerial conditions. They have been found in many of the coastal belts of Fujian, Guangdong and Hainan Provinces in South China. The grain composition of the dune rocks is mainly quartz sands and shell fragments. The quartz sands are medium and fine sized, relatively well sorted and positively skewed. Their surface texture formed in aeolian environments is characterized ty dishshaped depressions, meniscus depressions and V-shaped depressions with rounded edges. The most common bedding type of the rocks is larg (thickness>1.5m), steeply dipping (32--40°) with cross strata tolaner and convex upward). Mg and Sr contents are very low in the rock chemical composition which is classified into low Mg and low Sr category. The typical species of microfossils in the dune rocks are mainly freshwater ones and lack of typical saltwaer or semi-saltwater ones with incomplete assemblage of marine species. The cement minerals in the rocks are mainly low-Mg calcite and the common cement fabrics are meniscus cement and gravitational cement in response to impermanent water in vadose zones. Therefore, the dune rocks may be apparently distinguished from the beach rocks.
