The new wave overtopping database for coastal structures     

Jentsje W. van der Meer  Hadewych Verhaeghe  Gosse Jan Steendam 《Coastal Engineering》2009

Significant effort has been made to generate a homogeneous database on wave overtopping consisting of more than 10,000 irregular wave overtopping tests from more than 160 independent projects or test series, each described by means of 31 parameters. Many coastal structures, including dikes, rubble mound breakwaters, berm breakwaters, caisson structures and combinations have been considered and have been schematised for inclusion in the database. All these overtopping tests are represented by over 300,000 numbers in the database.  相似文献   

燕山水库的主要环境工程地质问题     

杨锋  杨裕云  刘佑荣 《河南国土资源》1998,(1)

本文在简要介绍燕山水库工程地质环境的基础上,分析论述了可能产生的环境工程地质问题。指出水库淹没及浸没、水库诱发地震、坝基渗透变形及膨胀土体稳定问题是该水库的主要环境工程地质问题,并提出了进一步研究的途径。  相似文献   

一次突发性中尺度暴雪天气过程分析   总被引：10，自引：0，他引：10       下载免费PDF全文

高松影  李慧琳  孙连强 《气象与环境学报》2006,22(5):32-35

对2004年12月丹东地区一次突发性中尺度暴雪天气过程的成因进行了分析。结果表明:造成此次暴雪天气过程的影响系统除天气尺度的冷锋外,其直接影响系统是中尺度海岸锋,它在有利的天气尺度环境下发展加强并向内陆移动,其上的中尺度环流形成的低云与冷锋云系的叠加是产生暴雪的主要原因。  相似文献   

A note on the deflection of a baroclinic current by a continental shelf     

Y. Hsueh  Liejun Zhong 《地球物理与天体物理流体动力学》2013,107(5):393-415

The deflection, at a step-shelf fronted coast, of a constant potential vorticity current in a reduced-gravity, inviscid model ocean is studied theoretically. The step shelf, with a depth smaller than the reservoir depth, forces the uplifting of the approaching current and causes water column foreshortening, leading to relative vorticity generation that enhances current deflection to the right (facing the coast). As a consequence, in comparison to the case of a vertical wall coast, the proportion of the transport to the right is increased. For normal incidence for a shelf-depth/reservoir-depth ratio of 0.3 and shelf width to deformation radius ratio of 1.5, more than 90% of the approaching current transport goes to the right and less than 10% to the left. In addition, the (barotropic) dynamic pressure at the coast is low to the right and high to the left (with the highest pressure at the stagnation point). In the vertical wall case, the wall pressures on the flank are equal. For oblique incidence from the left, the deflection to the left is drastically reduced. In fact, there is practically no steady-state flow diverted to the left (less than 2%) when the approach angle is greater than 60° to the left of normal. In the vertical wall case, the same angle would have to be 90° for the flow to the left to vanish, namely only when the approach current is parallel to the coast to the right.  相似文献   

Seasonal cycle of surface circulation in the coastal North Indian Ocean     

S R Shetye  S Satheesh Chandra Shenoi 《Journal of Earth System Science》1988,97(1):53-62

Monthly-mean winds and currents have been used to identify the driving mechanisms of seasonal coastal circulation in the North Indian Ocean. The main conclusions are: (i) the surface circulation off Arabia is typical of a wind-driven system with similar patterns of longshore current and wind stress; (ii) circulation off the west coast of India is consistent with the dynamics of a wind-driven eastern boundary current only during the southwest monsoon. During the northeast monsoon it is possible that the influence of the interior flow is important. (iii) There are at least three mechanisms that influence the surface circulation off the east coast of India: wind-stress, influence of fresh-water run off and contribution of the interior flow. It is difficult at present to assess the relative importance of these three processes.  相似文献   

Areal extent of the 1988 flood in Bangladesh: How much did the satellite imagery show?     

Harun Rasid  M. A. H. Pramanik 《Natural Hazards》1993,8(2):189-200

This paper presents the methods and results of visual interpretation of satellite imagery for estimating areal extent of the 1988 flood in Bangladesh. The main limitation of this method was that cloud-free images were not available for the peak flood period in the first week of September. Relatively cloud-free images on three selected dates in the last three weeks of September showed that areas of inundation on those dates ranged from 44000 to 60000 km² ± 5% (31 to 42% of Bangladesh). The Government of Bangladesh official estimates of the areal extent of flooding were tentative in nature, since these were based on a choropleth map of relative proportions (percentages) of flooding in different parts of the country. The official estimate of the maximum extent of flooding was 82000 km² (57% of Bangladesh), i.e. 15 to 26% larger than the area shown on satellite imagery. The actual extent of flooding was certainly larger than the estimates from satellite imagery but, perhaps, smaller than the official estimates, since a reduction of 15 to 26% of flood area in one to three weeks seemed unlikely. An alternative method of mapping flood-affected areas by using newspaper-interpreted data was attempted, but the method had limited values because of reporting bias.  相似文献   

闽粤台沿海北西西向最新构造带与大震构造背景   总被引：3，自引：0，他引：3       下载免费PDF全文

毕福志  袁又申 《地震地质》1990,12(2):183-192,T001

闽粤台沿海自台湾运动以来逐渐形成了多条北西西向隆起—拗陷的最新活动构造带,与已知的北东—北北东向隆起、拗陷带构成了区域性镶嵌构造格局。 研究区内除板块相互碰撞、俯冲及上地幔物质上涌形成大震构造背景外,莫霍面隆起或隆起断距大、低速层厚、地壳变薄、近两、三千年地表抬升差异活动显著以及台东近海有北西西向构造活动等,也都是发生大震的重要构造背景  相似文献   

Frost weathering and the saturation of coastal rocks     

A. S. Trenhaile  D. W. Mercan 《地球表面变化过程与地形》1984,9(4):321-331

Measurements were made of the water content in coastal rocks, by simulating tidal oscillations in the laboratory, and by field measurement in eastern Canada. If rapid freezing takes place upon exposure to the air, saturation levels may be high enough to permit frost weathering in fine grained rocks in the lower portions of the intertidal zone. Near the high tidal level, however, it may be dependent upon a supply of water from the ice foot and from melting snow. If freezing is slow, frost action may be inhibited by desorption of the rocks while they are exposed by the ebb tide. There was no evidence of a level of permanent sea water saturation within the intertidal zone. Ambient temperature and humidity may affect the rate of rock desorption.  相似文献   

Simulation of pebble abrasion on coastal benches by transgressive waves     

Gordon E. Bigelow 《地球表面变化过程与地形》1984,9(4):383-390

Tumbler simulations of abrasion processes affecting rocks on basaltic marine benches have clarified the effects of mass and volume of rock fragments on their rate of wear. Several experiments indicate that rate of basalt wear increases with mass in the interval 1 g to 8 g, but is not related to volume of fragments abraded in seawater. Relatively small quantities of rock flour suspended in the immersant seawater substantially reduced the rate of basalt wear. Basalt and calcareous beachrock responded differently in systems with both rock types tumbling together. Examination of the cuttings from these low-energy encounters suggests that abrasion on elevated benches along exposed seacoasts reduces virtually all clastic material to particles of silt size or smaller, producing essentially no sand.  相似文献   

华南沿海沉积盆地的新构造运动及其与地震的关系   总被引：4，自引：0，他引：4  

陈伟光 《华南地震》1995,15(2):55-61

华南沿海大多数中新生代沉积盆地属于断陷盆地，分析这类盆地的演化发育可以将其划分为完成型、继承型和新生型三类，它们的新构造运动特征，尤其是第四纪以来的活动性有明显差异。通过地质地貌方法初步估算了三类盆地的垂直构造运动的速率，在进行对比后认为，其构造运动的强度与地震活动有密切关系。指出三类盆地主要分布地区的两条地质界线对划分我国东南沿海地震可能有一定意义。  相似文献