小清河河口航道治理方案研究

小清河河口航道治理是当地港口发展的必要条件。通过分析小清河河口治理的理论与实践研究成果,研究了小清河河口航道治理的措施和主要方案。研究表明,小清河河口航道治理必须采用整治与疏浚相结合的办法;整治防沙堤宜采用双导堤;航道轴线采用北槽与南槽方案技术差别不大,应结合环保、海域使用等非航运条件综合确定轴线方案。     

长江深水航道整治技术研究及发展

航道整治工程是利用整治建筑物调整和控制水流,具有稳定有利河势、增加航道水深以及改善水流流态的功能。在长江下游,一般采用新建导堤、潜堤、丁坝、锁坝等结构,实现“导流、挡沙、减淤、护滩”的作用。1998年,长江口深水航道整治工程一期工程开工建设,标志着我国深水航道整治工程的开端。历经20余a的建设和发展,深水航道施工技术不断取得新突破,解决了深水航道整治工程面临的诸多施工难题,形成了包括水下基础处理、深水砂被铺设、40 m深水软体排护底施工、水下基床抛石整平和半圆体预制、出运及安装等多项核心关键技术和船机装备,填补了我国航道整治施工领域的技术空白。本文主要介绍在五大国家重点深水航道整治项目中5项关键技术的研究及发展历程、工艺简介以及取得的施工成果,供同行交流借鉴。     

河口海岸底部边界层和细颗粒泥沙过程??

水动力、细颗粒泥沙过程是淤泥质河口海岸变化的重要物理过程 ;并具有这样的特征 :强密度梯度、高度不稳定和非均匀流、高浓度泥沙、底床与流相互作用、难确定的底床／水界面。淤泥质河口海岸水动力、细颗粒泥沙过程的研究主要起因于：１）海洋科学的基础理论研究 ;２）港口航道的建设、维持（整治、疏浚）、海岸防护工程实践等需要。就淤泥质河口海岸水动力、细颗粒泥沙过程而言 ,水流最重要的部分是底部边界层。为计算河口海岸水流中的底床切应力 ,必需考虑边界层。在淤泥质河口海岸底部边界层内 ,强劲的潮流、波致流可以引起淤泥底床沉积…     

广利港河道水位变化及河口拦门沙地形变化分析研究

根据1984年和2007年两次对广利港航道水深测量的结果,分析研究了广利港航道内的水位变化规律,以及河口拦门沙的地形特征。结果表明广利港航道内水位变化复杂,拦门沙形态改变,水深变浅,原有的航道已经消失。     

不同高度潜堤减淤效果水槽实验研究

潜堤高程是淤泥质海岸潜堤设计的关键要素之一。为了确定潜堤高程,首先根据已建潜堤工程的经验分析得出潜堤减淤的主要机理,即主要是阻挡了浮泥或底部高含沙水体直接进入航道和缩短了含沙水体进入航道的时间,进而在长水槽中开展了一系列比对实验,主要研究不同堤顶高程时的水流紊动、堤前浮泥起动、浮泥层厚度变化、堤后航道泥沙落淤情况等,并以此作为比选堤顶高度的基本依据。实验结果表明当相对高度即潜堤高度与堤前水深之比为0.2～0.5时,便有较好的减淤效果。     

灌河口外航道整治模型试验研究

灌河口外为粉沙淤泥质海岸,口外沙嘴发育,形成主、副槽,拦门沙浅区水深仅2 m左右,波浪掀沙作用强烈,水沙运动复杂。利用波、流共同作用下物理模型试验研究灌河口外拦门沙深水航道整治后水动力变化及航槽回淤,特别是台风浪情况下航道骤淤问题。研究表明:灌河口外海域动力条件、泥沙环境以及工程涉及问题复杂,双导堤配合航槽疏浚整治工程能有效发挥减淤效果,通过双导堤间过流断面积补偿能有效降低工程对新沂河排洪的影响,正常条件下航道开挖年回淤约190~330万方,台风浪骤淤约为180万方,建议导堤根部加高以减少口门附近航道回淤。     

河口拦门沙航道整治方案及效果研究

在分析射阳港拦门沙航道一期整治工程建设后航道回淤特征的基础上,通过潮流泥沙数学模型分析研究了二期不同整治方案建设后的水流、含沙量及淤积分布特征,论证了不同方案的整治效果。研究表明:现状条件下由于导堤为潜堤,受越堤水流、口门回流等影响,一期工程建设后航道沿程普遍淤积。在一期导堤的基础上将导堤加高后有利于减小口门段航道淤积;将导堤延长后,淤积最严重的部位年淤强度有所减小,但在新的口门附近航道淤积仍然较严重;将口门宽度缩窄后,口门附近的淤积强度有所减小,但幅度有限;在航道内增加丁坝后,口门段泥沙淤积强度有所减小,但对改善中段航道淤积有限。     

河口整治工程建筑物局部冲刷试验研究

采用正态系列模型延伸法,通过试验研究了长江口深水航道治理一期工程丁坝坝头、北导堤头部的局部冲刷深度和范围,试验结果预报了丁坝坝头和北导堤头部的冲刷深度,并得出了合理的防护范围,随着长江口深水航道治理工程实施,试验结果得到较好的实践检验。分别采用稳定流和潮汐往复流试验方法,比较了不同试验水流条件的丁坝坝头冲刷深度,通过原型沙和轻质沙的比较试验,比较了系列模型延伸法采用不同模型沙得出试验结果。     

长江口12.5米深水航道南坝田挡沙堤加高工程总平面方案研究

长江口12.5米深水航道2010年贯通后,发挥了巨大社会经济效益,同时航道回淤量大、维护压力大、维护费用高的问题突出。本研究基于北槽四边界水沙通量观测成果,分析提出了北槽航道回淤泥沙来源;针对回淤原因,在已建减淤工程经验总结的基础上,提出了本次减淤的研究思路,优化了减淤工程方案的比选指标体系;采用三维潮流泥沙数模、清水动床物模、经济技术综合分析等手段,通过"加高范围"、"加高高程"及"加高位置"比选,研究推荐了减淤工程方案。利用实测回淤量分析了工程减淤效果。研究结果表明,南导堤越沙是洪季北槽的重要泥沙来源,对北槽高浓度含沙量场有一定贡献。提出了可通过加高北槽南侧的导堤,实现减少通过南导堤越堤进入北槽的泥沙量,从而减小北槽含沙量水平,同时改善北槽下段流态,降低水沙横向输移,进而降低航道回淤的减淤思路。研究推荐的长江口12.5米深水航道减淤工程为南坝田挡沙堤加高工程及先期工程方案。先期工程位于S4～S9丁坝坝田,在现有南坝田挡沙堤的基础上加高S4～S8区段,并延长至S9丁坝,工程全长约23.8 km,高程+3.5 m。工程于2015年11月开工建设,2016年7月主体工程完工,工程减淤效果显著,2016—2018年年均减淤量约954×105m3/a,近三年已节省航道维护疏浚费用约5亿元。     

空心方块斜坡堤整治效果试验研究

河口整治工程的实施效果与堤坝的结构型式密切相关,在河工模型上直接研究局部复杂结构对整治效果的影响有较大难度。以长江口深水航道治理二期工程北导堤NⅡC区段空心方块斜坡堤结构为个例,采用水槽试验和动床模型相结合方法,通过水槽试验确定可以在特定河工模型上使用的概化透水结构,使在模型上精确模拟局部复杂结构对整治效果的影响成为可能。研究成果认为,二期工程NⅡC区段2 600 m导堤不建对北槽出口段的整治效果有明显影响,NⅡC区段导堤高程降低1 m或采用空心方块斜坡堤透水结构对整治效果影响不大。     

Effect of the Twin Jetties as A Regulating Structure at the Tao-er Estuary

The phase one project of the twin jetties at the Tao-er Estuary yields no effect on the flow, and there is a large area of deposition. A numerical model is employed to simulate the flow field, and the scouring and silting in the channel be-tween the two jetties are analyzed. The results show that the effective tidal flux between the two jetties is reduced due to the notch located at the heel of the east jetty, and the effect of contraction-flush is not obvious. As for the regulation of this kind of estuary under the tide action, the capability of tidal flux should be fully used.     

Hydrodynamic modeling of Changjiang Estuary: Model skill assessment and large-scale structure impacts

An unstructured grid, Finite Volume Coastal Ocean Model (FVCOM) is used to study hydrodynamics and large-scale structure impacts in Changjiang Estuary. Field measurements conducted after the construction of the large-scale channel-jetty system are used to assess numerical results. The agreements between simulated and measured water levels, depth-averaged current velocities and tidally averaged longitudinal salinity distributions are excellent, as indicated by predictive skills higher than 0.94. The predictive skills for time series of salinity show a large range, from 0.97 to 0.62, in different measurement locations. The impacts of two 50 km long jetties and tens of spurs on the estuarine circulations as well as salinity distribution are investigated using comparisons of numerical results with and without jetty structures. Results reveal that the jetty structures intensify currents in the navigation channel and generate strong shear and vortices in jetty-spur blocks, which enhance turbulent mixing and degrade salinity stratification in the channel. The large-scale structures not only affect the flow field in the northern passage, but also play an important role in redistributing freshwater runoff in the multi-channel system, resulting in estuary-scale adjustments of circulations and salinity distribution.     

Wave Propagation in A Converging Channel of Arbitrary Configuration

A numerical solution was derived to determine wave field in a converging channel bounded by rubble-mound jetties. The solution was achieved by applying boundary element method. The model was applied to analyze the effect of channel convergence, the cross-section of the jetties and their physical and damping properties on wave field in the channel. The study reveals numerous non-intuitive results specific for jetted and convergent channels. The analysis shows that wave reflection is usually low and is of secondary practical importance. Wave transmission strongly depends on the channel geometry and transmitted waves may be higher than incident waves, despite reflection and damping processes. Moreover, wave transmission depends on physical and damping properties of rubble jetties and the results show that wave transmission may increase with the increasing damping properties of jetties, which is a non-intuitive feature of wave fields in jetted channels. The analysis reveals several novel results of practical importance. It is shown that the rubble-mound jetties should be constructed from the material of high porosity, which ensures low transmission. More attention should be devoted to hydraulic properties of porous materials. It is recommended to use the material of moderate damping properties. The material of high damping properties often increases the wave transmission. It is possible, by a selection of rubble-mound material, to obtain lower transmission level for steep waves than for waves of moderate steepness. A series of laboratory experiments were conducted in the wave flume to verify the theoretical results. The comparisons show that theoretical results are in fairly good agreement with experimental data.     

南沙头通道及横沙通道对长江口深水航道的影响分析

根据长江口南沙头通道、横沙通道和南北槽分汊口的断面水深变化及长江口南北港和南北槽的分流比变化实测资料,分析了长江口北槽深水航道淤积的原因。结果表明,北槽深水航道上段淤积受多种因素影响,其中,南沙头通道和横沙通道的发展对深水航道影响最大。南沙头通道的发展在加大落潮流量的同时,对南港南岸会产生一定的冲刷,后经沙洲的阻挡,把泥沙带向南港北岸,在北槽进口段处落淤,直接影响了进入深水航道的落潮量;横沙通道由于直接贯通了北港北槽的水沙交换,因而削弱了南港和北槽之间的水沙交换,促使北槽深水航道上段产生淤积,这也是南槽河道上段刷深的一个主要原因,而南槽河道的发展必然减少了进入北槽的落潮量,进一步加剧了北槽深水航道上段的淤积。同时,科氏力与北槽南导堤分流口鱼咀工程对深水航道也造成了一定的不可忽视的影响。研究成果对治理北槽深水航道淤积问题保障深水航道正常运行具有十分重要的科学实践意义。     

A review of inlet bypassing solutions with nomographs

Bypassing of the coastal sediment at inlets is required to prevent downdrift erosion or the filling in of navigation channels. When coastal structures such as jetties or terminal groins are placed along the inlet boundaries, bypassing is reduced but not eliminated. Bypassing solutions such as Pelnard-Considere (1956) [Pelnard-Considere, R., 1956. Essai de Theorie de l'Evolution des Forms de Rivages en Plage de Sable et de Galets, Fourth Journess de l'Hydralique, les energies de la Mer, Question III, Rapport No. 1, pp. 289–298.] are known although the effect of existing background erosion on such bypassing is not so well known. The occurrence of existing erosion due to offshore sand loss complicates the bypassing situation. The following note reviews existing analytical bypassing solutions and presents a solution and nomograms for solving a bypassed amount when existing erosion occurs along a shoreline and the sand which bypasses the updrift structure is assumed to reach the downdrift shoreline without being trapped in shoals or inlet channel.     

Stability of jetties for channel protection in soft soils at Huanghua Port

This paper presents safety evaluations of jetties found on soft clays at Huanghua Port to protect the channel from deposition due to long shore transport. It is likely to be the most critical for the jetties during construction, as far as excess pore water pressure and its effects on the embankment stability are concerned. A rubble mound jetty and a caisson jetty are considered as design alternatives for comparison. Finite element analysis and limit equilibrium analysis are carried out to evaluate the stability of the jetties during construction. For the rubble mound jetty, effective stresses in the soft clays are calculated associated with consolidation, so as to estimate the shear strength increased thereby. With the effective stresses and shear strength, the critical situation of the rubble mound jetty is revealed by the limit equilibrium analysis. For the caisson jetty, wave action is concerned, which is transformed into distributed forces on the caisson. Both the finite element analysis and the limit equilibrium analysis indicate a potential general shear failure of the caisson jetty and the foundation.     

Regulation of Navigation Channel on Mouth Bar of Guanhe Estuary

-Based on the feasibility study of developing the navigation resources of the Guanhe River and the model test results of the mouth bar regulation, this paper presents some basic principles for the regulation of the channel on the mouth bar, for instance, the direction of navigation channel should be identical with that of the ebb tide current and the main waves, and perpendicular to the bathymetric contours. The principles for regulating mouth bars are also discussed in this paper.     

Hydro-morphological modeling to characterize the adequacy of jetties and subsidiary alternatives in sedimentary stock rationalization within tidal inlets of marine lagoons

Alterations to the tidal inlets shoals, whether natural or anthropogenic, can dramatically influence the hydro-morphological balance of the inlet system in the short and long-term. Jettied inlets, despite typically supported by former technical design reports in curtailing the sedimentology stock, sometimes they require amendments. This paper provides an expository epitome for understanding the role of jetties in concerning the extent of their adequacy to economically and ecologically rationalize the internal siltation within both the western and the eastern tidal inlets of the Bardawil Lagoon, which is situated along the Mediterranean coastline of the Sinai Peninsula, Egypt. The main tool to characterize that role is the hydro-morphological modeling of the inlets system. We used a two-dimensional hydrodynamic circulation model consisting of two steering modules, CMS-Flow and CMS-Wave. In a five-year simulation process, this study emphasized that the sole use of jetties was noticeably insufficient to fulfill the satisfactory stabilization of the sedimentation processes inside the inlets. Consequently, the lake's ecosystem might entirely collapse in the short run due to the progressive deposits fashioning in the form of ebb/flood-tidal deltas. Accordingly, we proposed alternative solutions based on structural modulation scenarios in the vicinity of inlets domain encompassing jetties extension, flow-diverted wall (FDW), sediment trap (ST), random radial channels (RC) and lateral wide channel (LWC). Based upon the results of an optimization model using the Mamdani-type fuzzy inference system, the addition of a lined LWC alongside with jetties proved to be an effective solution over a longer period that rather meets the needs of the majority of stakeholders satisfactorily.     

广利河口拦门沙发育动态和河口航道的选择

根据现场调查和历史资料,获取了广利河口拦门沙水动力特征、海底地形和底质特征,对拦门沙的动态发育和波浪作用下拦门沙运动状态进行了分析,探讨了广利河口的航道选择方案。分析结果认为,广利河槽外航道宜从东偏南向入海。     

潮汐河口坝田长宽比对泥沙淤积特征影响试验研究

在航道治理工程中,往往通过丁坝群来实现其稳定航槽等目的,而坝田作为缓流区,其与主槽的水沙交换主要取决于横向的紊动交换。基于长江口北槽丁坝群实测资料分析和物理模型水槽试验研究发现不同长宽比坝田内的流态、淤积形态、坝田与相邻河段水沙交换的机理均不同,在长江口北槽丁坝群坝田建成后的淤积初期阶段,长宽比为0.30～0.40的坝田内的平均淤积强度最大。水槽试验研究表明,长宽比为0.50的坝田内淤积的主要部位即为主环流所在位置(坝田外侧),而在副环流位置,则出现微淤或冲刷的趋势;而长宽比为0.33的坝田内的淤积分布相对比较均匀。长宽比为0.33的坝田内淤积速率明显大于长宽比为0.50的坝田,长宽比为0.33的坝田达到冲淤平衡的时间较长。坝田淤积强度与随坝田回流强度、坝田与主槽水沙交换系数的增加而增加。