Modeling of the Changes in Flow Velocity on Seawalls under Different Conditions Using FLOW-3D Software

Seawalls are among protective structures that are constructed for decreasing the level of wave force and/or protecting from other structures. In this regard, more accurate investigation of these structures takes great importance from different perspectives. This research investigates the change of the velocity on seawall crown by considering the obstacles in different layouts and slopes. FLOW-3D has been used in this research for modeling. The results of the modeling show that the existence of obstacles has a determinative role in decreasing flow rate in the crown of seawalls. Also, as it was expected, the slope factor on upstream seawalls is very determinative in decreasing this rate such that the lowest velocity on the wall occurs in D-state layout and the slope of 45°.

Experimental investigating on the reflected waves from the caisson-type vertical porous seawalls

The hydrodynamic efficiencies of caisson-type vertical porous seawalls used for protecting coastal areas were calculated in this study. Physical models were developed to compare the wave reflection from vertical plane, semi-porous, and porous seawalls caused by both regular and random waves. Tests were carried out for a wide range of wave heights, wave periods, and different water depths (d=0.165, 0.270 and 0.375 m). The performance regarding the reflected waves from porous and semi-porous seawalls showed improvement when compared with those from the plane seawall. The reflection coefficients of the porous and semi-porous seawalls were calculated as 0.6 and 0.75, respectively, while the coefficient for the fully reflecting plane vertical wall was significantly higher (0.9). It was also observed that the reflection coefficient decreases with increase in wave steepness and relative water depth. In addition, the reduction in the reflection coefficient of porous and semi-porous seawalls, as compared to that of a plane seawall, was observed for both regular and random waves. New equations were also proposed to calculate the reflection coefficient of different types of seawalls with the aid of laboratory experiments. By verifying the developed equations using some other experimental data, it was validated that the equations could be used for practical situations. The results of the present study can be applied to optimize the design of vertical seawalls and for coastal protecting schemes.

A Calculation Method for Incidence and Reflection of Irregular Waves Along Seawalls

Some researches have been made in this aspect. In the method by Walton Jr.(1992), incident waves are supposed to be the overlapping result of M component waves with different frequencies which may take different directions, the direction of incident waves should be available in advance, but in fact the direction of incident waves is not available. In our study, incident waves are supposed to be composed of M overlapping component waves with different frequencies, and different frequencies have different directions. Based on the irregular wave reflection theory, the calculation formulas of wave direction, complex amplitude of incident waves, and complex amplitude of reflected waves in surface which are composed of component waves are derived by means of discrete Fourier transform. Then, the frequency spectra of incident waves and reflected waves and the reflection coefficient of waves with corresponding frequencies are obtained. Verification of the method and the calculation results from in-situ measured data indicate that the method is reliable and highly accurate.

Wave Height Transformation and Set-up Between A Submerged Permeable Breakwater and A Seawall

In this study, we investigated wave transformation and wave set-up between a submerged permeable breakwater and a seawall. Modified time-dependent mild-slope equations, which involve parameters of the porous medium, were used to calculate the wave height transformation and the mean water level change around a submerged breakwater. The numerical solution is verified with experimental data. The simulated results show that modulations of the wave profile and wave set-up are clearly observed between the submerged breakwater and the seawall. In contrast to cases without a seawall, the node or pseudo-node of wave height evolution can be found between the submerged breakwater and the seawall. Higher wave set-up occurs if the nodal or pseudo-nodal point appears near the submerged breakwater. We also examined the influence of the porosity and friction factor of the submerged permeable breakwater on wave transformation and set-up.

Enlightenment and Reflection on the Leap of "Butterfly Change" in Cultural Features of the Ancient Seawall in the New Era

At first, the overview and value of cultural relics of Xiaoshao Seawall were introduced, and then the confusion of daily management and comprehensive improvement were analyzed. Finally, the enlightenment and reflection on the "butterfly change" of the seawall were discussed.

大亚湾波高计算及分析

波高是海堤设计需要考虑的重要因素,它直接影响海堤的堤顶高程、结构及投资。对此,以大亚湾海堤为例,基于海域地形、风向、风速、波浪、潮位等条件,构建研究区域数值模型,分析大亚湾波高变化规律,计算确定海堤堤前设计波高。结果表明:东大亚湾波高值整体较西侧大;鹏城东段海堤、东山段海堤和杨梅坑段海堤堤前各计算点的波高SE向较S向大;随着潮位的降低,各段海堤计算点的波浪强度均呈逐渐减弱的趋势。波高计算结果可为开展大亚湾海堤达标加固设计工作提供参考。

考虑应力罗德角的修正剑桥模型在ABAQUS中的数值实现及其在海堤工程中的应用

基于有限元软件ABAUQS提供的UMAT用户材料子程序接口,考虑应力罗德角对黏土力学特性的影响,改进了修正剑桥模型中的临界状态线。采用相关联流动法则,通过引入剪胀比推导了弹塑性矩阵,从而开发了考虑应力罗德角影响的修正剑桥模型UMAT子程序。运用该子程序模拟了正常固结土的静三轴和真三轴试验,并分析了应力罗德角改变引起的海堤最终沉降量的变化。模拟结果表明,考虑应力罗德角的修正剑桥模型能够较好模拟土体的应力-应变特性;应力罗德角变化对海堤最终沉降量的影响随地基深度增加而降低,对海堤-地基交界处的最终沉降量影响最为显著。

粤港澳大湾区防风暴潮生态海堤核心技术研究及应用

在大湾区灵山岛北岸防风暴潮生态海堤工程的设计中,为解决城市防洪潮和滨海景观生态海堤亲水性的矛盾,在技术理念上由传统单一的防潮海堤向多元化滨海景观生态海堤转变,创新提出了多级消浪平台技术和滨海景观带迎水面系统排水技术来解决消浪与排水的问题,在实践中提出“横向换纵向”“外水外排,内水内排”的理念,打破传统海堤对海浪的“挡”和“抗”硬对硬模式,采用横向多级消浪平台技术消减越浪,并设置多级排水系统实现越浪自排,对迎水面海浪采用“通”和“排”的柔性衔接,可有效降低纵向堤顶高程以破解“堤防围城”的难题,实现海堤成为滨海生态景观的目的。研究成果已应用在该项目中,经过数次风暴潮检验证明达到了预期效果,灵山岛在韧性城市方面尤其是生态堤设计上,以宽度换高度,既能防洪同时又满足亲水、休闲、景观要求,为岭南地区的生态建设乃至中国滨海河口地区同类型建设提供了经验和参考。

悬挑框架式海堤不规则波浪力特性研究

以浙江温州浅滩二期生态堤为例,在波浪港池中开展物理模型试验,探究悬挑框架式海堤在不规则波作用下的受力特性。测量不同入射波条件下海堤直立墙和悬挑的波压强值并分析其随时间变化特性,得到各工况下海堤结构上波压强的分布特征,并探讨结构受力的主要影响因素,对结构所受波浪总力及其影响因素进行冗余分析(RDA)。结果表明:海堤直立墙在波峰作用下,水平方向不同位置受力存在相位差,且潮位以上、以下部分受力过程差异较大;极端工况下海堤直立墙与悬挑连接处所受压强最大;结构整体所受最大竖向总力为5653.125 kN,约为最大水平总力的70%;有效波高相较于潮位与结构受力的相关性更大。在悬挑框架式海堤设计中,应保证直立墙与悬挑连接处的强度,充分考虑波浪竖向荷载以及最大波高出现情况对整体稳定的影响。

Different responses of two adjacent artificial beaches to Typhoon Hato in Zhuhai,China

Major differences in beach erosion between two neighboring artificial beaches Xiangluwan Beach(XL beach)and Meiliwan Beach(ML beach)in Zhuhai,China,were studied after Super Typhoon Hato.In this study,a fully nonlinear Boussinesq wave model(FUNWAVE)-Total Variation Diminishing(TVD)was used to distinguish the main impact factors,their relative contributions,and the hydrodynamic mechanisms underlying the different beach responses.Results show that compared to the ML beach,the main reason for the relatively weak erosion on Xiangluwan(XL)beach was the smaller beach berm height(accounting for approximately 75.9%of the erosion response).Regarding the beach with a higher berm,the stronger wave-induced undertow flow,along with the higher sediment concentration,led to a higher offshore sediment transport flux,resulting in more severe erosion relative to the beach with a smaller berm height.The second most important reason explaining the weak erosion on XL beach was the absence of seawalls(accounting for approximately 17.9%of the erosion response).Wave reflection induced by the seawall could cause higher suspended sediment concentration,resulting in a toe scouring near the seawall.The offshore submerged breakwater protected XL beach slightly(accounting for approximately 6.1%of the erosion response).Due to the higher water level induced by storm surge,most of the wave energy could penetrate through the submerged breakwater.The effect of the larger berm width of XL beach was negligible.Compared to the beach with a larger berm width,the erosion/deposition regions in the beach with a narrower berm width showed shoreward migration,without significant changes in the erosion/deposition extent.Despite of this,the larger berm width could reduce the wave energy reaching the shoreline.This study of the storm stability of artificial beaches may be applied to beach restoration design.

不同的沉降计算方法在长江盾构穿越海塘中的应用

本文以轨道交通工程崇明线长江盾构穿越海塘为例,将经验公式与有限元分析两种不同的计算方法应用于海塘沉降预测中,经验公式有清晰的计算原理,计算方便、结果容易收敛;有限元计算结果能够提供应力场、位移场,可以方便应用于预测沉降趋势、总结规律。两者结合能够为穿堤工程的沉降预测提供数据支撑,也为后续类似工程问题的管理提供了很好的方向。

海堤迎潮侧护面结构全生命周期碳排放研究

我国建筑业全生命周期碳排放占全国的51.2%,已成为实现“双碳”目标的关键因素。以浙江省常见的两种海堤为例,以迎潮侧护面结构碳排放为目标,基于全生命周期理论对其进行研究。通过设定护面结构碳排放阶段、确定材料与机械设备碳排放系数、计算不同材料性质的结构碳排放系数、统计护面结构工程量,最终计算形成生产建造阶段、使用维护阶段、拆除阶段及全生命周期的碳排放。分析可知,研究目标具有对以合成材料为主的结构工程量最为敏感、主要发生在生产建设阶段、受拆除阶段材料回收率及回收量影响较大等特点。

应对极端风暴潮的粤港澳大湾区海堤建设研究

海堤是防御风暴潮侵袭、减轻海洋灾害的重要工程措施。在海平面上升和风暴潮加剧的双重影响下,大湾区海堤防潮能力被动降低,防潮安全备受挑战。通过现场调查梳理了大湾区海堤典型破坏形式,有防浪墙倾覆、迎水坡损毁及背水坡垮塌等,其中案例中背水坡破坏占比近1/2。为应对极端风暴潮灾害,迫切需要对大湾区海堤进行提标加固,但以提高堤顶高程为主的传统提标方式与城市亲水景观需求矛盾突出,基于此提出大湾区海堤建设应由防浪防潮垂向一体式向防浪防潮横向分离式转变,即利用堤身“挡高潮”,利用堤前措施和堤身“消大浪”。相较于传统提标方法,该方法实现了不抬高堤顶高程却提升防潮能力的目标,成果可为粤港澳大湾区海堤建设提供借鉴。

钱塘江海塘文化遗产构成及活化利用研究

钱塘江古海塘是凝聚先民智慧的伟大防洪工程,孕育及衍生出丰富的物质文化遗产及非物质文化遗产,其形式多样、特征鲜明,价值突出。采用文献研究法和实地调研法,对钱塘江海塘文化遗产的载体形式进行了梳理分类,分析了其价值及保护与利用现状,进而明确了“以古为核、承古创新”的钱塘江海塘文化遗产活化利用原则,并从展示建筑工程文化、传承治水精神文化、融合区域特色文化、运用现代科技文化4方面提出了建设举措。

一种新型双曲弧面海堤护坡结构的防浪消能效果

研发新型海堤护坡结构对守护人民生命安全、提高海堤工程稳定性具有重要意义。针对钱塘江河口潮流强劲,而传统海堤护面光滑,难以对强大冲击浪进行有效缓冲的工程问题,设计研发了一种具有双曲弧面结构的海堤护坡结构,采用室内水力试验和数值模拟等手段对其防浪效果、压强分布特征进行分析。研究结果表明,新型海堤护面结构通过有效引导、改变冲击浪的流向及流态,既能起到较好的消能作用,又能增强钱塘江大潮的观景效果,为复杂水流条件下海堤护坡结构设计提供了新的工程思路。

钱塘江海塘文化遗产的研究、保护与传承

钱塘江海塘研究中,针对其工程技术的研究极为深入,但针对海塘非物质文化遗产的研究却相对薄弱;在海塘文化宣传方面,工作既不成规模,也不成体系,且由于缺少学术研究的支持,文化宣传也缺乏深度。对比西湖等世界文化遗产的成功案例,分析上述钱塘江海塘文化遗产的研究与文化宣传现状,认为进行海塘文化的遗产研究可以促进申遗,申遗又可以推动对文化遗产的保护。因此,建议加强对钱塘江海塘非物质文化遗产的深入挖掘和研究,并且将宣传工作进一步规模化、系统化、深刻化,通过增加“海塘文化”的宣传途径、建设钱塘江海塘文化长廊等举措保护、传承钱塘江海塘文化遗产。

城郊区域古海塘保护与风貌提升设计——以萧绍海塘益农段为例

萧绍海塘文化形态多样、人文内涵丰富、地域特色明显,具有传承治水理念、工程技术、人文精神的重要价值。然而随着城市化进程的推进,当前萧绍海塘文化遗产存在海塘本体及海塘管理设施遗存遭受破坏,环境风貌差、安全隐患突出、文化展示缺失等问题,如何在此背景下对其进行有效的保护与风貌提升,成为了关注的焦点。以萧绍海塘益农段改造为例,探讨了城郊区域古海塘的保护与风貌提升策略。通过梳理地域风貌格局及特色元素,查找短板问题,明确特色定位、整体格局和整治提升的重点区域,对廊道界面、建筑控制、色彩指引、绿化提升、管控机制等方面进行深化落实。

南沙地区海堤迎海侧堤岸生态防护结构体系研究

南沙区位于珠三角的河网地带,全区整体防洪(潮)体系基础骨干框架已形成,但绝大部分海堤为传统海堤,需按照国家级自贸区的建设要求进一步进行生态化改造。根据南沙地区各水道的水文规律,按照设计洪潮水位、多年平均高潮位、多年平均低潮位等特征洪潮水位,以及区域动植物群落分布与海堤迎海侧堤岸的相对竖向关系进行生态结构分层,不同的分层采用不同的生态防护结构,形成适用于南沙地区的独特海堤生态防护结构体系。在不同的海堤建设条件和不同的水位条件下,可以组合运用,形成南沙独特的海堤生态风貌风格,冀可为以后该地区海堤生态化建设能提供借鉴。

“附近”的历史:《何兆瀛日记》呈示的晚清镜像

晚清名士何兆瀛现存的日记保留了他人生几个重要阶段的记录。特别是在京师生活五十载后,何兆瀛以浙江杭嘉湖道、两广盐运使的身份分别去到浙、粤二地,作为相关事务的亲身参与者,他深度接触到攸关国家命脉的科举、海塘、盐务等要项。他以日记书写的“附近”,是普通人和多数官员不曾经历的“远方”,密切关联着当时的国情前沿,如同一面镜子,映现出独特的晚清镜像。

探地雷达在滩海构筑物检测中的应用

根据探地雷达原理和滩海构筑物结构特点,对探地雷达用于滩海构筑物检测进行可行性分析,并结合工程实例介绍探地雷达的应用效果。工程实例表明,探地雷达用于滩海构筑物工程质量检测和内部淘蚀空洞、脱空、松散等结构隐患,探测效果良好,为滩海地区滩海构筑物日常安全检测和维修加固质量评估等提供检测手段,对非滩海区域的海堤、防波堤等构筑物的检测维护具有参考价值。