波浪周期对防波堤护面块体稳定性影响的试验分析

波浪对斜坡堤护面结构的冲刷破坏作用受诸多因素的影响,如波浪要素、水深条件、坡面角度、护面块体型式等。在进行某项有关斜坡堤护面块体的课题研究中发现,当防波堤断面结构确定后,护面人工块体的稳定性主要取决于波高及波周期的变化。在进行这方面内容设计计算中,通常波高的取值都能给予足够的重视,但波周期对护面块体稳定性的影响容易被忽视。本研究通过物理模型试验,针对波浪周期对斜坡堤护面块体稳定性的影响进行了总结分析,为防波堤设计提供参考。     

扭王字块体护面斜坡堤越浪量试验研究

针对现行规范中缺少扭王字块体护面斜坡堤越浪量的计算方法,考虑波陡、相对水深、相对堤顶超高、相对坡肩宽度、相对胸墙高度和相对块体尺寸等影响因素,通过波浪水槽物模试验,运用多元回归方法,给出了扭王字块体斜坡堤越浪量中护面结构影响系数和平均越浪量的计算公式。与试验值和其它计算公式进行了验证对比,结果基本吻合,具有一致性的规律。研究成果丰富了规范内容,对斜坡堤工程设计具有重要参考意义。     

波浪作用下斜坡上护面块体内部应力分布数值模拟

基于3D FEMDEM方法建立三维原型尺度数值模型,模拟波浪荷载作用下斜坡上护面块体内部的应力分布。波浪作用下结构物的水动力荷载采用微幅波理论模拟,护面块体之间的运动、碰撞接触以及块体内部的应力变化采用3D FEMDEM方法模拟。块体之间的接触力采用基于势函数的罚函数法计算,有限元的变形采用中心差分的显式方法求解。应用该数值模型与ANSYS软件程序对自重作用下混凝土扭王字块的内部应力分布特性进行了比较分析,验证了数值模型应力计算的可行性和计算精度。通过数值模拟计算给出了波浪作用下斜坡上护面块体之间的相对运动和块体内部的应力分布及应力历时曲线,探讨了块体内部应力变化特性。     

污水深海排放工程整体与断面模型试验

在断面模型试验与整体模型试验的基础上 ,确定了扭工字护面块体的稳定重量。通过断面模型与整体模型试验结果的比较 ,以及试验结果与理论计算结果的比较 ,分析了特殊地理条件对波浪传播的影响以及斜向波浪和沿堤水流对护面块的影响 ,阐述了工程试验在工程建设中的重要性。     

斜向和多向不规则波在斜坡堤上的单波越浪量的实验研究

通过三维物理模型实验对斜坡堤上斜向和多向不规则波的单波越浪量进行了研究.实验考察了入射方向为0°~45°的斜向波和方向分布宽度为0°~25°的多向波以及混凝土和扭工字块体两种护面形式.在混凝土护面堤上用Weibull分布函数拟合了单波越浪量的累积频率分布,在影响因素不同的条件下确定了分布函数中的系数和越浪比例,给出了计算单波越浪量的公式,同时对扭工字块体护面堤上大约100个波中最大的单波越浪量进行了估算.     

深水斜坡式防波堤人工垫层块体稳定性及反射系数研究

船舶大型化的趋势导致港口设施向深水发展。而对于深水防波堤,在较大设计波浪作用下,护面块体和垫层块石的重量往往超出现行技术规范的要求,针对大型天然块石垫层选料和施工困难,大量的开山选石损害自然环境等问题,本文总结了国内外人工块体的研究成果,阐明了人工块体垫层代替大型块石垫层的可行性,遴选了3种类型人工块体作为垫层,进行护面块体稳定性试验,经对比分析得出扭王字护面下带槽方块垫层的新结构,并确定其重量比值关系对护面稳定性的影响;对比传统垫层块石,给出遴选人工块体垫层的K_D值、堤前反射系数经验公式及波浪爬高糙渗系数推荐值。通过物理模型试验证明了深水斜坡防波堤通过采用人工垫层块体代替大型天然垫层块石的方法是可行的,为港口工程技术规范的修订提供了参考。     

斜向和多向不规则波在斜坡堤上的平均越浪量的试验研究

通过三维物理模型试验研究了在斜坡堤上斜向和多向不规则波在非破碎条件下的平均越浪量与波浪参数及堤参数的关系.着重考察了波浪以小角度(0°~30°)斜向入射时平均越浪量的变化情况,肯定了多向波的越浪量在这一范围内有所谓“小角度斜向增加”的现象,但否定了单向波也具有这一现象.在考察波浪的方向分布影响时发现波浪斜向入射时多向波的越浪量往往要比单向波的大.比较了已有的相关研究成果,给出了适用于混凝土护面和扭工字块体护面斜坡堤上斜向和多向不规则波的平均越浪量的估算公式.     

浙江省软土地基海塘的防浪特点研究

根据海塘塘前的波浪条件和台灾后海塘损坏程度,迎潮面的抗浪结构采用砼贴面护面板、埋石砼重力墙和异形块体等,塘顶为砼护面。当海塘越浪量在0.05m3 (m·s)以下时,背坡面采用干砌块石,大于此越浪量的海塘,背水面采用浆砌或灌砌保护。以上护面结构的稳定性经水槽模型验证及台灾的考验。     

堆石防波堤不规则波浪反射系数试验研究

结合物理模型试验,分析斜坡坡度、波陡、相对水深、护面类型和破波参数等因素对堆石防波堤不规则波浪反射系数的影响规律。将常用的Van der Meer公式,Seelig公式,Postma公式和Davison公式计算值和实测值进行比较,并结合试验数据,基于有效波高和平均周期定义的Iribarren数,得出堆石防波堤不规则波浪反射系数经验公式。结果表明,该公式能较好地计算不规则波作用下块石和扭王块体护面堆石防波堤波浪反射系数。     

防波堤断面结构型式及护面块体稳定性模型试验研究——2008北京奥运会青岛帆船比赛基地水工模型试验

为确保2008北京奥运会青岛帆船比赛基地内工程的水工建筑物安全可靠，对给定的2种防波堤断面结构型式及护面块体稳定性进行物理模型试验。准确掌握在极端高水位、设计高水位、设计低水位和极端低水位时．SW向、25a和50a一遇波浪作用下，试验断面所承受的波浪作用力，及SE向50a一遇波浪作用下块体的稳定重量。并绘制各工况1％峰值波压力分布图，得出断面波压力的分布规律。对断面结构和护面块体稳定性进行分析。     

波浪作用下方块石护面稳定性研究

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...     

Experimental analysis of breakwater stability with antifer concrete block

Armor is a pavement made of erosion-resistant materials like a stone or concrete that is constructed to protect breakwater, coasts, and other coastal line features against erosion. These armors are a kind of protective layer made of stone or concrete, used in breakwater constructions or coastal lines, arrayed with specific regular or irregular pattern on the breakwater or the coast. The antifer concrete blocks have almost cubic form, often changed into frustum by adding inclined plates to their sides. One of the most important advantages of these armors is their diversified regular and irregular placement patterns. In this study, using the physical modeling and different tests, the stability level of antifer concrete blocks was evaluated considering the decrease of the armor weight. Results of this study show that by a 10% decrease in the block weight, the failure graph slope is increased and the damage is intensified.     

Alternative placement technique for antifer blocks used on breakwaters

In this study, a placement technique named as “alternative placement technique” was developed for antifer blocks and the results of its application to a breakwater model were presented. This placement technique was compared with the existing techniques such as the “regular placement technique”, the “irregular placement technique” and the “sloped wall placement technique” by experiments. The comparison was carried out considering armor layer stability, prototype placement, clarity of the placement technique’s definition, armor layer cost, and wave runup. As a result of this investigation the “alternative placement technique” was found to be superior to the other existing placement techniques.     

Wave runup on a surging vertical cylinder in regular waves

The wave runup caused by a vertical cylinder surging in regular waves is studied both experimentally and numerically. The so-called DualSPHysics Smoothed Particle Hydrodynamics (SPH) code is used for the 3-D numerical modelling. A wide range of cylinder sizes and wave conditions is investigated with results comparing favourably between the experimental and SPH model under both fixed and forced-surge conditions. The experimental and SPH results are further used to predict the maximum runup amplification, in particular the ratio of the runup caused by the surging cylinder to that of the fixed, over the phase difference between the incident wave and surge motion. This maximum runup ratio has been analysed for its dependence on factors such as wave steepness, wave scattering and surge amplitude. An empirical equation is proposed for predicting the maximum runup ratio from known incident wave and surge conditions. Comparison with results from linear solvers suggests that the linear solvers under-predict the full nonlinear runup by a factor of 1.3–1.5.     

海堤上波浪爬高与越浪计算分析

基于线性波理论,采用VOF法、RNG k-ε的湍流模型,通过FLUENT软件平台的二次开发功能实现了质量源造波。利用多孔介质模型,在动量方程里添加多孔介质源项,对斜坡堤上铺设异型块体时的爬高与越浪进行了数值模拟,并通过模拟爬高值率定出FLUENT中多孔阻力系数与多种异形块体糙渗系数之间的关系,进而建立了可供实际应用的海堤上波浪爬高与越浪数值模型。     

A Study of the Stability Properties in Simulation of Wave Propagation with SPH Method

When ordinary Smoothed Particle Hydrodynamics (SPH) method is used to simulate wave propagation in a wave tank, it is usually observed that the wave height decays and the wave length elongates along the direction of wave propagation. Accompanied with this phenomenon, the pressure under water decays either and shows a big oscillation simultaneously. The reason is the natural potential tensile instability of modeling water motion with ordinary SPH which is caused by particle negative stress in the computation. To deal with the problems, a new sextic kernel function is proposed to reduce this instability. An appropriate smooth length is given and its computation criterion is also suggested. At the same time, a new kind dynamic boundary condition is introduced. Based on these improvements, the new SPH method named stability improved SPH (SISPH) can simulate the wave propagation well. Both the water surface and pressure can be well expressed and the oscillation of pressure is nearly eliminated. Compared with other improved methods, SISPH can truly reveal the physical reality without bringing some new problems in a simple way.