Parametric Analysis and Experimental Study on Local Flexibility of TY-Type Tubular Joints     

XuHantao Chen Bozhen HuYuren Pan Hao 《中国海洋工程》1996,(1)

Loal flexibility of tubular joints has important effect on the static and dynamic behaviour of offshore platforms, therefore, the determination of it becomes an important research subject in the field of offshore engineering. In this paper, the local flexibility of TY-type tubular joints, which are widely used in offshore platforms, is calculated by using semi- analytical method. Based on the calculated results, parametric formulae for evaluating element in the local joint flexibility matrix of TY- type tubular joints are derived by regression. A test on PVC models of TY-type tubular joints to measure the local joint flexibility is also reported. A comparison of the results calculated from the parametric formulae presented in this paper with those measured from the model test shows that the parametric formulae are reliable. It is recommended that these formulae be used in the global structural analysis of offshore platforms.  相似文献   

粤西水东弧形海岸海滩剖面的地貌状态     

陈子燊  李春初 《热带海洋学报》1993,(2)

对粤西水东弧形海岸长时段重复测量海滩剖面的因子分析说明了各特征岸段剖面的主要地貌状态。频域分析反映了各岸段海滩体积的月周振动峰值和对波能的响应特征。实测海滩剖面波动过程的计算则指示了当前各剖面的蚀积状态。  相似文献   

褚岛连岛沙坝的形成与演变     

张海启  朱而勤 《中国海洋大学学报(自然科学版)》1993,(3)

本文运用沉积动力学的理论和方法,对褚岛连岛沙坝的形成与演变进行了动力机制方面的探讨。  相似文献   

Wave reflection characteristics of plane, dentated and serrated seawalls     

S. Neelamani  N. Sandhya 《Ocean Engineering》2003,30(12):1507-1533

The hydrodynamic performance of vertical and sloped plane, dentated and serrated seawalls were investigated using physical model studies. Regular and random waves of wide range of heights and periods were used. Tests were carried out for different inclinations of the seawall (i.e. θ=30, 40, 50, 60 and 90°) and for a constant water depth of 0.7 m. The wave reflection was measured to assess the dissipation character of the seawalls. It was observed that the serrated seawall was superior to the plane and dentated seawall in reducing the wave reflection. Even for the vertical case, the coefficient of reflection due to regular waves for dentated seawall ranged from 0.6–0.99 and for the vertical serrated seawall it was 0.45–0.98, whereas for the vertical plane wall, it was almost 1.0. It was found that the characteristic dimension of the seawall (i.e. L/W) and the relative water depth (i.e. d/L) were better influencing parameters compared to the conventionally used surf similarity parameter ‘ξ’ (ξ=tan θ/(H_i/L)^0.5) in predicting the reflection from the dentated and serrated seawall, where L is the local wave length, W the width of the dent along the length of the seawall slope, d the water depth at the toe and H_i is the incident wave height. A similar trend was observed for the random waves too. The reduction in the wave reflection due to random waves for the dentated seawall as compared to the plane seawall was about 18% and for the serrated seawall, it was 20%. It was observed that the reflection due to random waves was lesser for all the three different walls than the regular waves, due to the mutual interaction of random waves. Multiple regression analysis on the measured data points was carried out and predictive equations for the reflection coefficient were obtained for both regular and random waves. This study will be useful in the design of energy dissipating type vertical quay walls in ports and harbours, sloped seawalls for shore protection from erosion and sloped caisson as breakwaters. Comparison of predictive formulae with the experimental results revealed that the prediction methods were good enough for practical purposes.  相似文献   

烟台海滨潮间带岩岸环境无脊椎动物群落特性的初步研究   总被引：1，自引：0，他引：1  

庄树宏 《海洋科学进展》1997,(3)

本文所研究的烟台沿海潮间带岩带环境无脊椎动物群落的最小样方面积为4m3。石沟屯的无脊椎动物群落种的多样性与蛇们岛和雨岱山两地的无脊椎动物群落种的多样性存在显著差异（P＜0．01），以石沟屯的多样性指数最高（Shannon－WienerIndexH＝0．888），生物密度最大（6702个体／m），且石沟屯的无脊椎动物群落的结构与崆峒岛和雨岱山的存在明显差异。水体一定程度的富营养化和风浪的影响是造成所研究的岩岸环境无脊椎动物群落的结构与多样性差异的主要原因。所研究的三地无脊椎动物群落都以东方小藤壶为绝对优势种，以东方小藤壶、黑荞麦蛤和短滨螺3个优势种决定着所研究的烟台岩岸环境无脊椎动物群落的结构和外貌。  相似文献   

Numerical modelling of flow around coastal structures and scour prediction     

K. Jyothi  J. S. Mani  M. R. Pranesh 《Ocean Engineering》2002,29(4):417-444

The nearshore circulation and the wave characteristics are important parameters, which control coastline morphology. The interaction of nearshore circulation with coastal structures, modify the wave characteristics and seabed topography, often resulting in scour near the foundation of the structures. This paper deals with the numerical prediction of nearshore circulation induced due to wave setup in the nearshore region with and without the structure [(i) structure resting on seabed (ii) structure raised above the seabed]. It is also helps understand the deficiencies in studying the coastal characteristics by describing the flow field due to the wave velocity potential alone. Comparison of the results of both nearshore circulation and the wave potential model are discussed and the importance of the study and its prototype applications are highlighted.  相似文献   

Devonian lacustrine shore zone architecture: Giving perspective to cliff exposures with ground penetrating radar          下载免费PDF全文

Steven D. Andrews  Julien Moreau  Stuart Archer 《Sedimentology》2016,63(7):2087-2105

Lake margin sedimentary systems have been the subject of only limited study. The cyclic Middle Devonian lacustrine succession of Northern Scotland contains repeated developments of shore zone sandstones and thus provides an ideal location for the study of these units. The cycles comprise deep lake, shallow lake, playa and shore zone facies. Detailed field observations are presented alongside ground penetrating radar data which has aided large‐scale and three‐dimensional characterization of the shore zone sand bodies. Loading and discrete channel forms are recognized in thin‐bedded sandstones within the lower portion of the lake shore zone successions. Up‐section, the sandstone beds appear to become amalgamated, forming subtle low angle accretionary bar complexes. Where imaged on the radar profiles, the repeated development of shoreward migrating features succeeded by more shallow angled lakeward accreting surfaces is recognized; these are ascribed to washover and swash–backwash processes, respectively. The orientation of these features is similar to palaeocurrent measurements from oscillation ripples, suggesting an alignment of the shore zone bars perpendicular to the prevailing wind direction. Further loaded sandstone beds and sand‐filled shallow channel features overlie the bar forms. The context of the shore zone facies allows the controls on its formation to be examined. The shore zone sandstones overlie playa facies which contain abundant desiccation horizons, reflecting the most arid phase in the climatically controlled lacustrine cycle. As climatic conditions ameliorated, the rejuvenation of fluvial systems resulted in the transport of sand out into the basin. Initial deposition was limited to intermittent events where sediment was laid down on a water‐saturated substrate. High resolution fluctuations in lake level resulted in periodic short‐lived reworking events along the lake margins which produced amalgamated sands, forming low relief bars. Shore zone reworking is likely to have occurred over a wide  area as the lake margin migrated back and forth, and gradually transgressed.  相似文献   

Cordilleran front range structural features in northwest Montana interpreted from vintage seismic reflection data     

《Journal of Structural Geology》2016

Industry seismic reflection data spanning the Rocky Mountain Cordillera front ranges of northwest Montana were reprocessed and interpreted in this study. Five seismic profiles represent 160 km of deep reflection data collected in 1983 that span the eastern Purcell anticlinorium, Rocky Mountain Trench (RMT), Rocky Mountain Basal Décollement (RMBD), and Lewis thrust. The data were reprocessed using modern techniques including refraction statics, pre-stack time migration (PSTM), and pre- and post-stack depth migration. Results indicate the RMBD is 8–13 km below the Earth's surface and dip 3–10° west. Evidence for the autochthonous Mesoproterozoic Belt and basal Cambrian rocks beneath the RMBD is present in all of the profiles and appears to extend east of the RMT. The Lewis thrust was identified in the seismic profiles and appears to sole into the RMBD east of the RMT. The RMT fault system has a dip displacement of 3–4 km and forms a half graben filled with 1 km of unconsolidated Tertiary sedimentary deposits. The RMT and adjacent Flathead fault systems are interpreted to be structurally linked and may represent a synthetic, en echelon fault system.  相似文献   

Effects of the MV Rena oil spill on intertidal rocky reefs in the Bay of Plenty,New Zealand     

DR Schiel  PM South  SA Lilley 《新西兰海洋与淡水研究杂志》2016,50(1):70-86

In the weeks following the 2011 Rena oil spill, a series of surveys was initiated on eight rocky intertidal reefs to describe the distribution of oil and to assess the impacts of oil on ecological communities. Consistent but relatively low cover of oil occurred at two sites (Mt Maunganui and Moturiki). The area covered by oil had decreased by c. 90% after 5 months due to natural weathering processes. There were immediate effects of oil fouling on the mussel Limnoperna pulex and its associated fauna, with reductions in the number of mussels and infaunal taxonomic richness. However, no ecological effects on any of the communities were detectable after 1 month. Overall, the ecological effects of the Rena oil spill on rocky shore intertidal communities were small and not long-lasting, but we stress that this does not consider potential sublethal effects and their consequences on organisms.  相似文献   

Carboniferous palaeomagnetism of the Rocky Creek Block,northern Tamworth Belt,and the New England pole path     

C. T. Klootwijk 《Australian Journal of Earth Sciences》2013,60(2):375-405

Palaeomagnetic, rock magnetic and magnetic fabric results are presented for a Carboniferous (Visean to Westphalian) succession of felsic, mainly ignimbritic, volcanic and volcaniclastic rocks from the Rocky Creek Block of the northern Tamworth Belt, southern New England Orogen. Detailed thermal demagnetisation of 734 samples from 64 sites show three groups of magnetic components with low (<300°C), intermediate (300–600°C) and high (500–680°C) unblocking temperature ranges. Well‐defined primary magnetisations have been determined for 28 sites with evidence of four overprint phases. The overprints arise from a mid‐Tertiary weathering event (or possibly recent viscous origin), and from fluid movements associated with the Late Cretaceous opening of the Tasman Sea, thrusting during the Middle Triassic main phase of the Hunter‐Bowen Orogeny, and latest Carboniferous — Early Permian formation of the Bowen‐Gunnedah‐Sydney Basin system. Rock magnetic tests establish that the primary magnetisation carriers in the volcanic rocks are mainly magnetite (predominantly single domain, or pseudo‐single domain, and little or no multidomain) and hematite. Optimal magnetic cleaning is achieved at high to very high temperatures, with subtle, but systematic, directional and statistical differences between primary components derived from the mainly hematite fraction and pseudo‐components derived from the mainly magnetite fraction. The 28 primary magnetisation results are presented as six mean‐site results, summarised below and representing 25 sites, and three single‐site results. Fold tests could be applied to five mean‐site results. These are all positive, but one of these results may represent a secondary magnetisation. The primary magnetisation results define a Visean to Westphalian pole path. This long pole path indi cates extensive latitudinal and rotational movement for the Rocky Creek Block, and potentially for the New England Orogen, as follows: (i) Yuendoo Rhyolite Member (Caroda Formation, Visean) pole 235.8°E, 27.7°S, ED₉₅ = 9.0°, n = 3; (ii) Peri Rhyolite Member/Boomi Rhyolite Member (Clifden Formation, Namurian, 318.0 ± 3.4 Ma) pole 177.4°E, 63.4°S, ED₉₅ = 5.2°, n = 3; (iii) tuffaceous beds above Boomi Rhyolite Member (Clifden Formation?, Namurian) pole 162.2°E, 59.1°S, ED₉₅ = 10.2°, n = 3; ((iv) upper Clifden Formation/lower Rocky Creek Conglomerate (Namurian/Westphalian) pole 95.3°E, 49.6°S, ED₉₅ = 8.1°, n = 3 (possible overprint)); (v) Rocky Creek Conglomerate (Westphalian) pole 136.5°E, 57.6°S, ED₉₅ = 5.3°, n = 5; (vi) Lark Hill Formation (Westphalian) pole 127.0°E, 50.4°S, ED₉₅ = 4.8°, n = 8.  相似文献