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1.
The short communication presents application of the conventional Van der Meer stability formula for low-crested breakwaters for the prediction of front slope erosion of statically stable berm breakwaters with relatively high berms. The method is verified (Burcharth, 2008) by comparison with the reshaping of a large Norwegian breakwater exposed to the North Sea waves. As a motivation for applying the Van der Meer formula a discussion of design parameters related to berm breakwater stability formulae is given. Comparisons of front erosion predicted by the use of the Van der Meer formula with model test results including tests presented in Sigurdarson and Van der Meer (2011) are discussed. A proposal is presented for performance of new model tests with the purpose of developing more accurate formulae for the prediction of front slope erosion as a function of front slope, relative berm height, relative berm width, method of armour stone placement, and hydraulic parameters. The formulae should cover the structure range from statically stable berm breakwaters to conventional double layer armoured breakwaters. 相似文献
2.
1 .IntroductionTheslopingbreakwateriswidelyusedintheprotectionofcoastalstructures ,withrubblemoundtoebermbuiltatthefootofthewave attackingslope .Thefunctionofarubblemoundtoestructureis ,inadditiontodecreasingthequantityofmainarmorstoneused ,toprovidestaticsupporttothemainarmorlayer,avoidingtherollingdownofmainarmorstonesandprotectingtheapronstonesfromero sion .TheweightoftoebermstonesisdecidedaccordingtotheCodeofBreakwaterDesignandBuildingformulatedbytheMinistryofCommunicationsofChina .When… 相似文献
3.
The toe structure of a breakwater provides support to the armour layer and protects the structure from damage due to scour at the toe. Often a toe structure consists of rock material. Several design formulae exist to predict the amount of damage to the toe structure under wave loading. These design formulae for the required rock size include effects of the wave height and the water depth above the toe structure. Here, rock toe stability has been studied by means of physical model tests to provide information on the required rock size in the toe structure. The tests and analysis are focussed not only on the influence of the wave height and the water depth above the toe structure, but also on the influence of the width of the toe structure, the thickness of the toe and the wave steepness. The wave steepness, width of the toe and the thickness of the toe appear to affect the damage to the toe; these parameters need to be taken into account in order to derive accurate predictions of the damage to the toe structure. Based on the test results a prediction formula has been derived including these effects. The formula can be used to determine the required rock size in the toe of rubble mound breakwaters within the ranges of the performed tests. 相似文献
4.
In this study, waves with the heights higher than H1/3 in an irregular wave train are called as extreme waves and defined with the help of extreme wave parameter, αextreme. In order to see the effect of extreme waves on the design weight of armour stone, stability analysis is carried out based on the hydraulic model test results. The test results of high αextreme cases (HE) and low αextreme cases (LE) are compared with currently used van der Meer's formulae with permeability factor P=0.4 and 0.45 and Hudson formula by using H1/3 and H1/10 in terms of the design weight of armour stone. As a result of the comparison, it is found that Hudson formula by using H1/3 underestimates the necessary armour weight. Usage of H1/10 instead of H1/3 in Hudson formula doubles the weight which seems overestimated when Irribaren number is away from the transition zone in which both wave run-up and run-down forces become effective. However, it seems underestimated near the transition zone where experiment case HE gives higher armour weights. When the design weight of armour stone is calculated by van der Meer's formulae with P=0.4, it may be necessary to increase the weight up to 30% in the case of high extreme waves. On the other hand, van der Meer's formulae may overestimate the weight 14% when the extreme waves are low. 相似文献
5.
Sun Jingshi Zhu Yiming
Research Professor Tianjin Research Institute of Water Transport Engineering Tianjin
Associate Professor Dalian Aquatic Product Institute Dalian 《中国海洋工程》1995,(1)
Through hydraulic model experiment and site investigation, this paper has derived a calculation formula of dry-laid stone armour layer thickness of rubble mound breakwaters for fishery harbours. The influences of the friction force between stone blocks and the variations of wave length or period and water depth are considered in the formula. The calculated results of several existing structures are in good agreement with field data. This formula is more practical than those ever published both at home and abroad, and has been adoptted by the technical standards of aquatic projects published by the Ministry of Agriculture of China. It is applicable for the calculation of dry-laid stone armour layer of breakwater for small- or medium-size harbours. 相似文献
6.
Stability formulae for armour layers of rubble mound breakwaters are usually being applied assuming perpendicular wave attack. Often the effects of oblique waves are neglected. This is however a conservative assumption since the stability of armour slopes generally increases for oblique waves. New wave basin tests have been performed to assess the effects of oblique waves on the stability of rock slopes and the stability of cube armoured rubble mound breakwaters. The physical model tests were focussed on wave directions between perpendicular (0°) and parallel (90°). The test programme included tests with long-crested waves and tests with short-crested waves. The results show that for rock slopes the influence of oblique waves is larger for long-crested waves. Based on the test results a design guideline is provided to account for effects of oblique waves on the stability of rock slopes, armour layers with a double layer of cubes, and armour layers with a single layer of cubes. 相似文献
7.
Physical model tests have been performed in two different wave flumes to analyse the threshold of stone movement and quantify the frequency and length of displacements due to head-on wave attacks at a reshaping breakwater. Data on stone movements were obtained from the observation of cumulative displacements at the end of each wave attack and from video records during the attack. Threshold conditions, frequency of movement and displacement length are expressed as function of a suitably modified stability number.A simple model is defined relating longshore transport due to oblique wave attack to stone mobility. The transport model is based on the assumption that movement statistics is affected by obliquity only through the appropriate mobility index and that stones move during up- and down-rush in the direction of incident and reflected waves. Without any calibration, results compare favourably with experimental data available in literature in the range of low mobility conditions where movement statistics was observed. A calibration is provided in order to obtain an accurate transport formula valid in a wide mobility range i.e. for reshaping breakwaters and up to gravel beaches. 相似文献
8.
9.
Ocean waves can be destructive as steeper waves due to their high energy eroding the sandy beaches. During storm surge or high tide, the water level rises and if large waves occur, they will break closer to the beach, releasing enormous amount of energy resulting in strong currents. This causes heavy loss of beach material due to large-scale erosion. If these waves are made to break prematurely and away from the beach, they can be attenuated so as to reduce beach erosion. The reef, which is a homogeneous pile of armour units without a core, breaks the steeper ocean waves, dissipates a major portion of their energy and transmits attenuated waves. This paper experimentally investigates the armour stone stability of the submerged reef and the influence of its varying distance from shore and crest width on ocean wave transmission. 相似文献
10.
护面是海堤和护岸的重要结构,直接抵御波浪作用,可采用人工块体、块石等,种类繁多。采用紧密排列方块石作为护面结构是一种景观性较好的型式,依据方块石厚度不同能抵御不同大小的波浪作用。干砌条石及干砌块石护面曾有一些规范给出过计算方法,但现行规范没有相关内容可供设计参考,已有计算方法的理论分析还存在不足。当波浪与斜坡堤相互作用时,方块石护面出现位移或脱落可能发生在波浪回落最低阶段、波浪破碎打击阶段及破后爬高水流作用阶段,通过研究得到了不同阶段波浪对方块石护面作用力的计算方法。在波浪回落最低阶段,考虑了护面及其下方垫层渗透性影响,通过理论分析建立了低渗透护面浮托压强计算模型,采用物模试验将计算结果与试验测量值进行了对比分析,结果表明总体趋势符合,量值接近;在波浪破碎冲击阶段,基于射流冲击作用原理,提出了波浪在斜坡面破碎冲击压强计算方法,通过试验分析了波浪破碎水深波高比与破波相似参数的关系,利用浅水波理论计算了波浪破碎冲击水流流速;在爬高水流作用阶段,提出了水流引起的方块石护面垂直浮托力及水平拖曳力的计算方法,通过试验结果拟合了浮托力系数和拖曳力系数,验证了水流作用下护面的受力特征。最后,针对方块... 相似文献
11.
《Coastal Engineering》1987,11(3):219-239
New practical design formulae have been developed which describe the stability of rubble mound revetments and breakwaters under random wave attack. The formulae are based upon a series of model tests. More than two hundred and fifty tests have been performed in order to ensure that all the relevant variables could be varied systematically. As a result of the present series of investigations the main shortcomings in Hudson-type formulae have been solved. Stability formulae are given which include the influence of wave period, number of waves, armour grading, spectrum shape, groupiness of waves and the permeability of the core. A clearly defined damage level parameter is introduced in the formulae. 相似文献
12.
G.W. Timco 《Coastal Engineering》1984,8(2):161-170
A new empirical stability criterion for dolos-armoured, rubble-mound breakwaters is proposed. This criterion is based on an analysis of the energy level at which dolos armour units fracture and break in a breakwater environment. The input information has been obtained from ten different prototype breakwaters. The present analysis indicates the ratio of the wave energy to size (mass) of the armour units at which dolos units break. 相似文献
13.
Hocine Oumeraci 《Ocean Engineering》2011,38(1):159-170
A systematic armour stability and the hydraulic performance, including wave reflection, wave transmission, experimental study in the twin-wave flumes of Leichtweiss-Institute (LWI) is performed on a geocore breakwater and a conventional rubble mound breakwater in order to comparatively determine the wave run-up and wave overtopping. The geocore breakwater consists of a core made of sand-filled geotextile containers (GSC) covered by an armour made of rock. The geocore is more than an order of magnitude less permeable than the quarry run core of a conventional breakwater. As expected, the core permeability substantially affects the armour stability on the seaside slope, the wave transmission and the wave overtopping performance. Surprisingly, however, wave reflection and hydraulic stability of the rear slope are less affected. Formulae for the armour stability and hydraulic performance of the geocore breakwater are proposed, including wave reflection, transmission, run-up and overtopping. 相似文献
14.
The berm recession of a reshaping berm breakwater has a very important role for the stability of this kind of structure. Based on a 2D experimental modeling method in a wave flume, the recession of the berm due to sea state and structural parameters has been studied. Irregular waves with a JONSWAP spectrum were used. A total of 215 tests have been performed to cover the impact of sea state conditions such as wave height, wave period, storm duration and water depth at the toe of the structure, and structural parameters such as berm elevation from still water level, berm width and stone diameter on berm recession. In this paper, first a new dimensionless parameter is introduced to evaluate the combined effect of wave height and wave period on berm recession using results of the experimental work. Then, a formula that includes some sea state and structural parameters is derived using the new dimensionless parameter for estimating the berm recession. A comparison is made between the estimated berm recessions by this new formula and formulae given by other researchers to show the preference of using the new dimensionless parameter. The comparison shows that the recession estimated by the new formula has not only a better correlation with the present experimental data, but also has an improved correlation with other experimental results within the range of parameters tested. Outside the range of parameters tested the Lykke Andersen (2006) formula performed best. 相似文献
15.
灾害性波浪是中国沿海地区最具破坏性的自然灾害之一。采用开源程序OpenFOAM中interFoam求解器,对低顶海堤（在风暴潮和海平面上升情况下所面临的不利工况）的孤立波越浪特性开展数值模拟研究。通过孤立波冲击海堤的基准算例,验证模型在模拟波浪爬升和越浪过程中大变形波面以及剧烈波浪力方面的精度。基于验证的数值模型,对孤立波在低顶海堤上的越浪特征以及防浪墙高度对越浪的影响开展参数化研究。结果表明堤顶超高减小导致更为剧烈的越浪。针对尚无低顶海堤孤立波越浪量经验公式的问题,提出新的适用于堤顶超高小或为0的孤立波越浪量经验公式。此外,研究发现增加防浪墙高度可有效减少越浪,但防浪墙所受的波浪力也增大。综合考虑防浪墙减少越浪以及自身所受波浪力,针对文中研究采用的海堤截面和波浪条件,建议无量纲防浪墙高度取为1.00。 相似文献
16.
Gu Hanbin Sun Jingshi
Engineer Tianjin Research Institute of Water Transport Engineering Tanggu: Professor Tianjin Research Institute of Water Transport Engineering Tanggu: 《中国海洋工程》1995,(4)
This paper introduces a new kind of armour block - hexagon multihole block on sloping breakwater. It has great characteristics such as good interlocking, strong resistance against waves and saving concrete. Through the hydraulic model test, the mechanism of stability of the block has been proved and the relations between stability and wave height, wave period, water depth, slope, laying method, porosity and cushion have been found. The effect of weight on steadiness have also been discovered. Finally, the method of design and some formulas are given. 相似文献
17.
《Coastal Engineering》2006,53(5-6):395-417
This paper is the second part of the work presented by Garcia et al. [Garcia, N., Lara, J.L., Losada, I.J., 2004. 2-D numerical analysis of near-field flow at low-crested breakwaters. Coastal Engineering 51 (10), 991–1020]. In the mentioned paper, flow conditions at low-crested rubble-mound breakwaters under regular wave attack were examined, using a combination of measured data of free surface, bottom pressure and fluid velocities from small-scale experiments and numerical results provided by a VOF-type model (COBRAS) based on the Reynolds-Averaged Navier–Stokes (RANS) equations. This paper demonstrates the capability of the COBRAS model to reproduce irregular wave interaction with submerged permeable breakwaters. Data provided by the numerical model are compared to experimental data of laboratory tests, and the main processes of wave–structure interaction are examined using both experimental and numerical results. The numerical model validation is carried out in two steps. First, the procedure of irregular wave generation is verified to work properly, comparing experimental and numerical data of different cases of irregular wave trains propagating over a flat bottom. Next, the validation of the numerical model for wave interaction with submerged rubble-mound breakwaters is performed through the simulation of small-scale laboratory tests on different incident wave spectra. Results show that the numerical model adequately reproduces the main aspects of the interaction of random waves with submerged porous breakwaters, especially the spectral energy decay at the structure and the spectrum broadening past the structure. The simulations give good results in terms of height envelopes, mean level, spectral shape, root-mean-square height for both free surface displacement and dynamic pressure inside the breakwater. Moreover, large-scale simulations have been conducted, on both regular and irregular incident wave conditions. The overall pattern of the wave interaction with a large-scale submerged breakwater is adequately reproduced by the numerical model. The processes of wave reflection, shoaling and breaking are correctly captured. The good results achieved at a near prototype scale are promising regarding the use of the numerical model for design purposes. 相似文献
18.
Leopoldo Franco Jimmy Geeraerts Riccardo Briganti Marc Willems Giorgio Bellotti Julien De Rouck 《Coastal Engineering》2009
The paper presents the comparison between the results of small-scale model tests and prototype measurements of wave overtopping at a rubble-mound breakwater. The specific structure investigated is the west breakwater of the yacht harbour of Rome at Ostia (Italy) and is characterized by a gentle seaward slope (1/4) and by a long, shallow foreshore. The laboratory tests firstly aimed at carefully reproducing two measured storms in which overtopping occurred and was measured. The tests have been carried out in two independent laboratories, in a wave flume and in a wave basin, hence using a two-dimensional (2-D) and a three-dimensional (3-D) setup. In the 2-D laboratory tests no overtopping occurred during the storm reproductions; in the 3-D case discharges five to ten times smaller than those observed in prototype have been measured. This indicates the existence of model and scale effects. These effects have been discussed on the basis of the results of several parametric tests, which have been carried out in both laboratories, in addition to the storm reproductions, varying wave and water level characteristics. Final comparison of all the performed tests with 86 prototype measurements still suggests the existence of scale and model effects that induce strong underestimation of overtopping discharge at small scale. The scale reproduction of wave breaking on the foreshore, together with the 3-D features of the prototype conditions and the absence of wind stress in the laboratory measurements, have been individuated as the main sources of scale and model effects. The paper also provides a comparison between the data and a largely used formula for wave overtopping discharges in the presence of structures similar to the one at hand. The suitable value of a roughness factor that appears in that formula is investigated and good agreement is found with other recent researches on rubble-mound breakwaters. 相似文献
19.
Berm breakwaters are rubble mound structures in which the seaward slope of the initial profile may be reshaped to become more stable under severe wave attack. The stones in the seaward slope move from the initial slope to an equilibrium profile. A 2D experimental study has been carried out in a wave flume at a hydraulic laboratory of Tarbiat Modares University to study the effects of sea state and structural parameters on the reshaped profile parameters of such breakwaters. A series of 287 tests have been performed to cover the effect of various sea state conditions such as wave height, wave period, number of waves and water depth at the toe of the structure, and structural parameters such as berm width, berm elevation above still water level and armor stone size. All the tests have been done employing irregular waves with a JONSWAP spectrum. In this paper, first the reshaped profiles are schematized, and then the key parameters of the reshaped seaward profiles such as step height, step length and depth of intersection point of initial and reshaped profile are investigated, using results of this experimental work. Eventually, formulae that include some sea state and structural parameters are derived for estimation of the reshaped profile parameters. To assess the validity of the proposed formulae, comparisons are made between the estimated parameters of reshaped profiles by these formulae and earlier formulae given by other researchers. The comparisons show that the estimation procedure foretells reshaping parameters well and with less scatter according to the present data and also other experimental results within the range of parameters tested. 相似文献