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1.
Facilities for handling large draft vessels, modern container ships and tankers have become essential due to the rapid growth in marine traffic. A pile supported skirt breakwater (PSSB) is one of the most promising concepts that could fulfill this requirement as PSSBs are environment friendly and economical for locations where tidal fluctuations are large and soil conditions are poor compared to other types of conventional breakwaters. The structure consists of an impermeable barrier piercing the free surface and extending up to a certain depth of submergence. The barrier which is responsible for attenuating the incident waves through partial reflection is supported on closely spaced concrete or steel piles. The barrier would consist of pre-cast elements that are connected to the piles on site. A numerical model based on the Eigen function expansion theory for linear waves to investigate the reflection and transmission characteristics of a PSSB consisting of single and double rows has been developed. The wave run-up on the skirt of the front row as well as the oscillation of the water surface in between the two rows was also computed. The results on the above stated parameters are reported as a function of wave and structural parameters in a dimensionless form. The numerical results are compared with experimental results and the agreement in general is found to be good. 相似文献
2.
Understanding the sediment transport and the resulting scour around coastal structures such as pile breakwaters under local extreme wave conditions is important for the foundation safety of various coastal structures. This study reports a wave-flume experiment investigating the scour induced by solitary waves at a pile breakwater, which consists of a row of closely spaced large piles. A wave blacking gate with a simple operation procedure in the experiment was designed to eliminate possible multiple reflections of the solitary wave inside the flume. An underwater laser scanner and a point probe were used in combination to provide high-resolution data of the bed profile around the pile breakwater. Effects of incident wave height and local water depth on the maximum scour depth, the maximum deposition height and the total scour and deposition volumes were examined. An existing empirical formula describing the evolution of the scour at a single pile in current or waves was extended to describe the scour at the pile breakwater under the action of multiple solitary waves, and new empirical coefficients were obtained by fitting the formula to the new experimental data to estimate the equilibrium scour depth. It appears that the maximum scour depth and the total scour volume are two reliable quantities for validation of numerical models developed for the scour around pile breakwaters under highly nonlinear wave conditions. 相似文献
3.
O.S. Rageh 《Ocean Engineering》2009,36(14):1112-1118
The efficiency of the breakwater, which consists of caissons supported on two or three rows of piles, was studied using physical models. The efficiency of the breakwater is presented as a function of the transmission, reflection and the wave energy dissipation coefficients. Regular waves with wide ranges of wave heights and periods and constant water depth were used. Different characteristics of the caisson structure and the supporting pile system were also tested. It was found that, the transmission coefficient (kt) decreases with increasing the relative breakwater draft D/L, increasing the relative breakwater width B/h, and decreasing the piles gap-diameter ratio G/d. It is possible to achieve kt values less than 0.25 when D/L≥0.1. The reflection coefficient takes the opposite trend especially when D/L≤0.15. The proposed breakwater dissipates about 10-25% of the incident wave energy. Also, simple empirical equations are developed for estimating the wave transmission and reflection. In addition, the proposed breakwater model is efficient compared with other floating breakwaters. 相似文献
4.
The behavior of a self-supported earth-retaining wall with stabilizing piles was investigated using a numerical study and field tests in urban excavations. Special attention is given to the reduction of lateral earth pressures acting on a retaining wall with stabilizing piles. Field tests at two sites were performed to verify the performance of the instrumented retaining wall with stabilizing piles. A number of 3D numerical analyses were carried out on the self-supported earth-retaining wall with stabilizing piles to assess the results stemming from wide variations of influencing parameters such as the soil condition, the pile spacing, the distance between the front pile and the rear pile, and the embedded depth. Based on the results of the parametric study, the maximum horizontal displacement and the maximum bending moment are significantly decreased when the retaining wall with stabilizing piles is used. In engineering practice, reducing the pile spacing and increasing the distance between the front pile and the rear pile can effectively improve the stability of the self-supported earth-retaining wall with stabilizing piles. 相似文献
5.
带胸墙斜坡堤越波量的试验研究 总被引：1，自引：0，他引：1
带胸墙斜坡式防波堤堤顶标高的合理确定，有赖于越波量的正确计算。本文基于水力学中流量系数的概念，建立越波量的计算公式。对影响流量系数的几个主要因素：波高、波陡、胸墙高、平台宽度、相对水深和护面结构等，进行了较系统的试验和讨论，提出了确定流量系数的经验公式。另外，还根据越波量的大小及越波波态，将堤分为：不越水堤、少量越水堤、越水堤及半潜堤四类，可作为合理确定堤顶标高时参考。 相似文献
6.
《Coastal Engineering》2001,44(2):117-139
In this paper, laboratory data for free surface displacements and velocity fields in front of a caisson breakwater covered with wave-dissipating blocks, together with wave pressures acting on the caisson, are presented and discussed. The core of the breakwater is made of a concrete caisson with a vertical front wall. The caisson is protected by a thick layer of tetrapods and is supported by a rubble mound. The breakwater is placed on the 1/25 impermeable slope. Two types of incident waves are used in the experiments: nonbreaking waves and spilling-type breaking waves. In the breaking wave case, the incident wave breaks offshore before it reaches the breakwater. The velocity data are obtained by using both the Laser Doppler Velocimeter (LDV) and the Electromagnetic Current Meter (EMCM). The raw data are analyzed using a numerical-filtering scheme so that turbulent fluctuations are separated from the phase-dependent wave motions. The vertical profiles of the time-averaged (over a wave period) turbulent velocity components at several vertical cross-sections in front of the breakwater are then analyzed. The spatial variations of the time-averaged turbulence velocity suggest that turbulence is generated inside the protective armor layer and transported into the flow region in front of the breakwater. The wave pressures on the vertical face and on the bottom of the caisson are also reported. 相似文献
7.
波浪破碎是海洋中最常见的现象之一,其能够对海洋中的结构物产生巨大的波浪力作用。本文在大比尺波浪水槽通过聚焦波的方法生成了极端波浪和不同破碎阶段的破碎波浪,并对其冲击桩柱过程中的点压力进行了测量,进而采用连续小波变换的方法,对桩柱上点压力的分布及大小进行了细致分析。结果表明,多次重复试验下,相比非破碎极端波浪,破碎极端波浪产生的点压力离散性更强;波浪破碎程度越大,测点位置越靠近波峰,则点压力离散程度越大;破碎波的最大点压力出现在1.2倍的最大波面附近,且其大小可达3倍的最大静水压力;基于点压力小波谱,不同破碎阶段破碎波产生冲击作用不同,对于波浪作用桩柱前波浪已经发生破碎的情况,其冲击区域更大,点压力分布更复杂;而对于桩面破碎的情况,其造成的波浪总力更大。 相似文献
8.
基于1987年和1988年夏季在古镇口港直立堤前的实测资料,对波浪和波压力连续记录进行了统计分析和谱估计,研究了在堤前海浪不发生破碎条件下,堤前波浪和堤面不同高程上压力波的波面高度概率分布、堤前波浪波高和周期与波压力幅度和周期的概率分布特征、入射波行近提前过程中的谱变化及堤面不同高程上压力谱的变化特征。主要结果总结在本文最后一节。 相似文献
9.
A Numerical Investigation of the Reduction of Solitary Wave Runup by A Row of Vertical Slotted Piles
To improve the current understanding of the reduction of tsunami-like solitary wave runup by the pile breakwater on a sloping beach, we developed a 3D numerical wave tank based on the CFD tool OpenFOAM in this study. The Navier Stokes equations were applied to solve the two-phase incompressible flow, combined with an LES model to solve the turbulence and a VOF method to capture the free surface. The adopted model was firstly validated with existing empirical formulas for solitary wave runup on the slope without the pile structure. It is then validated using our new laboratory observations of the free surface elevation, the velocity and the pressure around a row of vertical slotted piles subjected to solitary waves, as well as the wave runup on the slope behind the piles. Subsequently, a set of numerical simulations were implemented to analyze the wave reflection, the wave transmission, and the shoreline runup with various offshore wave heights, offshore water depths, adjacent pile spaces and beach slopes. Finally, an improved empirical equation accounting for the maximum wave runup on the slope was proposed by taking the presence of the pile breakwater into consideration. 相似文献
10.
This paper presents a mathematical model which computes the hydrodynamic characteristics of a curtainwall–pile breakwater (CPB) using circular piles, by modifying the model developed for rectangular piles by Suh et al. [2006. Hydrodynamic characteristics of pile-supported vertical wall breakwaters. Journal of Waterway, Port, Coastal and Ocean Engineering 132(2), 83–96]. To examine the validity of the model, laboratory experiments have been conducted for CPB with various values of draft of curtain wall, spacing between piles, and wave height and period. Comparisons between measurement and prediction show that the mathematical model adequately reproduces most of the important features of the experimental results. The mathematical model based on linear wave theory tends to over-predict the reflection coefficient as the wave height increases. As the draft of the curtain wall increases and the porosity between piles decreases, the reflection and transmission coefficient increases and decreases, respectively, as expected. As the relative water depth increases, however, the effect of porosity disappears because the wave motion is minimal in the lower part of a water column for short waves. 相似文献
11.
基于开源程序REEF3D,通过建立高精度二维数值波浪水槽,系统研究了聚焦波浪在浅堤上传播变形的规律,着重分析了聚焦波浪通过浅堤的水动力过程及能量变化规律,讨论了不同波浪要素对聚焦波浪传播特性的影响。除此之外,还考虑了双浅堤布置对聚焦波浪传播变形的影响。研究结果表明:极端波浪通过浅堤时,堤顶水深越小,波浪主频能量衰减越显著。在给定堤顶水深条件下,聚焦点与浅堤的相对位置对聚焦波浪能量的衰减影响较小。在双浅堤布置条件下,随着浅堤间距的增加,上下游浅堤的相互影响逐渐减弱,高频段的波浪能量也随之减小。 相似文献
12.
Wave induced forces around buried pipelines 总被引：1，自引：0，他引：1
This work refers to an experimental investigation carried out to analyze wave induced pressures on a pipeline buried in a permeable seabed. In this investigation, the model tests were performed on a pipeline buried in the soil test bed. The wave flume used was 30 m long, 2 m wide and 1.7 m deep, 96 number of tests were conducted with waves generated for different wave heights. A pipeline 200 mm in diameter was buried in the sandy bed at different burial depth ratios. The pipeline was laid perpendicular to the wave direction, pressure was measured with 12 transducers along the outer circumference of the pipeline. The results show that wave induced pressures are significantly controlled by the wave period analyzed in terms of the scattering parameter (ka). Higher pressures were recorded at the top and the lower pressures were recorded at the bottom. 相似文献
13.
The wave transmission characteristics and wave induced pressures on twin plate breakwater are investigated experimentally in regular and random waves.A total of twenty pressure transducers are fixed on four surfaces of twin plate to measure the wave induced dynamic pressures.The spatial distribution of dynamic wave pressure is given along the surface of the twin plate.The uplift wave force obtained by integrating the hydrodynamic pressure along the structure is presented.Discussed are the influence of different incident wave parameters including the relative plate width B /L,relative wave height /i H a and relative submergence depth s /a on the non-dimensional dynamic wave pressures and total wave forces.From the investigation,it is found that the optimum transmission coefficient,t K occurs around B /L 0.41 ~ 0.43,and the twin plate breakwater is more effective in different water depths.The maximum of pressure ratio decreases from 1.8 to 1.1 when the relative submergence depth of top plate is increased from 0.8to +0.8. 相似文献
14.
A new approach to the analysis of pile foundations, developed recently for the analysis of a pile supported offshore structure, is described. The method uses a coupled soil-pile analysis which takes into account the non-linear resistance of the pile to lateral deformation and the effect of progressively increasing pore water pressures on that resistance. The analysis allows also for radiation of energy away from the site. Typical of results given in the paper are: (1) the effect of pore water pressure increases on the API cyclic loading curves, (2) the degradation in lateral stiffness due to pore pressure increases for piles with fixed and free heads, (3) variations in deflections and moments with depth due to pore water pressure from those predicted using current API procedures. 相似文献
15.
为研究水流作用下斜桩周围局部冲刷特性及流场变化并掌握斜桩同垂直桩的差异,本研究在不同流速条件下开展了包含反斜桩、垂直桩、正斜桩等多种工况的水槽试验,测量分析了斜桩的冲刷历时曲线、床面形态、沿程流速分布、最大冲刷深度等数据.结果表明:清水条件下斜桩周围局部冲刷坑及桩后沙丘尺度明显减小;斜桩桩前最大冲刷深度随倾角的增加而逐... 相似文献
16.
Bridge scour is recognized as one of the key factors that causes structure failures, which in turn leads to economic and life loss. In this study, flume tests of four typical arrangements of pier groups embedded in sand under steady clear water conditions were carried out to observe the process and maximum depth around piles of scour. The investigation included single pile, tandem piles, side-by-side piles, and 3 × 3 pile groups. Different conditions including different pile spacing, flow velocity, and water depth are considered. Moreover, the evaluation of design methods from the United States, New Zealand, and China was analyzed and compared through experimental and mathematical methods. The experimental results show that shielding and jetting effects are obvious in pile groups, which become less obvious with the increase of pile spacing. The dynamic process of scour around single pile and pile groups are quite different. Meanwhile, most of the predicted scour depths by these equations tend to be much larger than those from field data, which may lead to overdesign and consequently high construction cost. In addition, data from this study and some laboratory experiment data from previous work were used to derive the correction factors of a new scour prediction equation, which can be used to estimate the scour in a sand bed and agree well with the observations. 相似文献
17.
港口靠船桩工作性状计算的双参数法 总被引：8，自引：0，他引：8
港口靠船桩是承受重复性荷载或多循环荷载的一种横向承载桩。双参数法能较好地描述靠船桩 (单桩、群桩 )的桩土工作性状。用双参数法进行计算时 ,所给的地面条件必须由重复荷载或多循环荷载作用下实测出来。根据现场试桩资料 ,标定桩土参数 ,即k =mx1/n的指数l/n、桩土相对柔度系数α、桩土综合刚度EI等值 ,可以用来设计试桩附近局部地区同类条件下的其它长桩。对于没有进行试桩的某些工程 ,可以联合运用双参数法和p -y曲线法进行桩的分析 相似文献
18.
Response of a porous seabed around breakwater heads 总被引：1，自引：0，他引：1
The evaluation of wave-induced pore pressures and effective stresses in a porous seabed near a breakwater head is important for coastal engineers involved in the design of marine structures. Most previous studies have been limited to two-dimensional (2D) or three-dimensional (3D) cases in front of a breakwater. In this study, we focus on the problem near breakwater heads that consists of incident, reflected and diffracted waves. Both wave-induced oscillatory and residual liquefactions will be considered in our new models. The mistake in the previous work [Jeng, D.-S., 1996. Wave-induced liquefaction potential at the tip of a breakwater. Applied Ocean Research 18(5), 229–241] for oscillatory mechanism is corrected, while a new 3D boundary value problem describing residual mechanism is established. A parametric study is conducted to investigate the influences of several wave and soil parameters on wave-induced oscillatory and residual liquefactions around breakwater heads. 相似文献
19.
The shaft resistance of rock-socketed piles depends not only on the properties of its surrounding rock, but also on the radial force induced by the load imposed on the top of the pile. This paper deduced a plastic zone of rock around a single pile and obtained the shaft resistance of a rock-socketed pile based on the theories of cavity expansion and shear strength. The research results showed that the magnitude of the radial force in the socketed portion of a rock-socketed pile was related to the pile diameter, Poisson’s ratio, and properties of the surrounding rock. The influence area of rock decreased with increasing pile diameter. The radial force and lateral friction decreased with the increasing relative stiffnesses of the pile and rock. The radial stress on the elastic–plastic interface can be analytically determined based on the rock properties and depth. A field test was used to validate the proposed method, and a good agreement was obtained between the field data and predicted results of the proposed method. The research results in this paper are beneficial to guide actual practice. 相似文献
20.
The semicircular breakwater (SBW) is a composite breakwater consisting of a semicircular caisson resting on a rubble mound. The SBW function as a barrier dissipates the incident wave energy and creates tranquillity on its leeside. The dynamic pressures due to regular waves exerted on seaside perforated SBWs with 7 and 11% of exposed surface area with perforations were measured. The measured pressures are compared with those exerted on impermeable SBWs. In addition, the forces exerted on the caisson alone are measured. The reflection coefficient, measured total forces on the caisson of the models, and the pressures are presented as functions of relative water depth. The effect of the water depth and the percentage of perforations on the above stated variables are examined, details of which are reported in this paper. 相似文献