Coarse Estuary Mouth Ballast Gravel Deposits: A Sourcing Case History

Pebbles and cobbles along the channel margin of the Tayport-Tentsmuir tidal flats rest on eroded surfaces of layered sands. Their origin and source have been hitherto unexplained, although they are evidently relatively local. The compositional assemblage of the well-rounded clasts is compared with those of pebbles in the tills and fluvio-glacial deposits of Fife and Tayside, in the River Earn and in the River Tay at Perth. The closest similarity is with the latter site. It is suggested that the material was transported to Tayport as ballast for lighters prior to trans-shipping of cargoes for Perth from larger vessels moored off Tayport. A sloop or brig of 100 tons would have carried about 20 tons of ballast. Trading by one vessel per week over a time period of a century could have accounted for the transport of 100000 tons of the material concerned. Removal of the ballast by barge from Tayport enabled the building of Lucky Scalp island. Attempts to improve the underfoot conditions for salmon fishing are believed to have been responsible for the spreading of ballast along the outer margin of the tidal flats.     

Sediment macrobenthos off eastern Waiheke Island,Hauraki Gulf,New Zealand

Aspects of sea-bed structure and benthic-macroinvertebrate species composition, distribution, richness and diversity in coastal waters off eastern Waiheke Island, Hauraki Gulf, are reported. In contrast to the sole historical account of sea-bed community structure from this same region, no widely distributed assemblages of species are recognised throughout it; no two sites share the exact same complement of species; and almost all sites are less than 80% similar in their taxonomic composition, most considerably so. Species richness and diversity are reported to vary with substratum type and depth, and spatially; species occurring within muds are the least diverse and species rich, followed by those of muddy gravels, and then gravels; many taxa prove common to the three substratum types; and dominance of taxa is recognised to decrease with an increase in substratum complexity, from muds to gravels, and species richness. With the exception of invasive marine species, apparent changes in the composition of assemblages throughout this region over the eight-decade period that data span are considered artefacts of the way in which such assemblages were historically defined. We recommend historical accounts of sea-bed community distributions throughout Hauraki Gulf be interpreted with caution, especially when attempting to use such schematic depictions to determine whether changes have occurred in assemblage composition.     

黄河三角洲区域水动力条件下岸滩侵蚀研究

An ideal nature system for the study of post-depositional submarine mass changing under wave loading was selected in the intertidal platform of the subaqueous Huanghe River Delta, a delta formed during period from 1964 to 1976 as the Huanghe River discharged into the Bohai Gulf by Diaokou distributary. A road embankment constructed for petroleum recovery on the inter-tidal platform in 1995 induced the essential varieties of hydrodynamic conditions on the both sides of the road. With both sides sharing similarities in （1） initial sedimentary environment, （2） energetic wave loading, （3） differential hydrodynamic conditions in later stages, （4） enough long-range action, and （5） extreme shallow water inter-tidal platforms; the study is representative and feasible as well. Two study sites were selected on each side of the road, and a series of measurements, samplings, laboratory experiments have been carried out, including morphometry, hydrodynamic conditions, sediment properties, granularity composition, and fractal dimension calculation of the topography in the two adjacent areas. It was observed that in the outer zone, where wave loading with high magnitude prevailed, the tidal flat was bumpy and exhibited a high erosion rate and high fractal dimension. Further, the fractal dimension diminished quickly, keeping with the enlarging of calculative square size. However in the inner zone, where the hydrodynamic condition was weak, the tidal fiat was fiat and exhibited a low erosion rate and low fractal dimensions; the fractal dimension diminished with the enlarging of calcu- lative square size. The fractal dimensions in the different hydrodynamic areas equalized increasingly as the calculative square size accreted to threshold, indicating that the hydrodynamic condition plays a significant role in topography construction and submarine delta erosion process. Additionally, the later differentiation of sediment properties, granularity composition, microstructure characteristics, and mineral composition     

多波束条带测深仪的增益控制方案

分析了海底混响的特点以及多波束条带测深仪的工作原理，提出了信号幅度归一化方法－滑动窗TVG方法和自动增益控制方法。     

Sea-bed characterisation and classification from the power spectra of side-scan sonar data

This work is concerned with the automatic characterisation and classification of the sea-bed for side-scan sonar trace power-spectra.A parametric model of side-scan sonar trace power-spectra is developed from the equation for the magnitude frequency response of a Butterworth filter. The model's parameters are optimised to give a least squares fit with observed spectra. Three of the optimised parameters are used to define features.     

大直戏薄壁管线浅海铺设的空间形态和应力分布数值计算与分析

利用非线性大直径薄壁铺设变形和应力计算模型，对水中铺设的典型工况进行了空间形态和应力分布的模拟计算，分析了实际工程中的两种铺设方案－采用刚性托架和托架船辅助铺设及仍采用刚性托铺设，并计算了水中铺设时的纵向水流对铺设时的管线空间形态和应力分布的影响，对计算结果作了定性的分析，提出了相应工况时该管道铺设工程中应该注意的考虑的问题。