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Wave overtopping pressures and spatial distribution behind rubble mound breakwaters
Get PDFCurrently, there is no widely accepted method to determine the pressure profiles induced by wave overtopping behind the crest of a breakwater other than physical modelling. In this experimental study, the spatial distribution of overtopping pressures on a vertical structure is investigated at various distances behind a rubble mound breakwater with a crown wall. A 2D physical modelling study in presented in an attempt to derive a practical method for estimating these overtopping pressures. The variability of overtopping wave pressures behind the crest of a breakwater is also discussed. Rule of thumb guidelines are proposed which will contribute to better concept and schematic structural designs in advance of physical model testing
ICE Themes: Flood Resilience
No full textICE Themes: Flood Resilience focuses on identifying novel solutions to the risks of flooding. Manuela Escarameia and Andrew Tagg have curated existing research into sections identifying and planning for flood risks, understanding the problems associated with flood resilience in urban areas and building in resilient flood measures in design. It is underpinned by international case studies and practical advice
Determination of erosion parameters of coarse-grained materials using a small flume
Get PDFOvertopping is one of the major causes of dams and levees failure. There is uncertainty in estimation of the erosion parameters especially for coarse- grained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, results from a box test performed on three coarse grained materials in a 0.3-meter wide flume are discussed. The three materials share the same median grain size D50 of 2 mm, however, they vary in fines content between zero to 20%. The box measured 0.3 m wide x 0.6 m long x 0.15 m deep. Each of the three materials was compacted in the box at near optimum moisture content and dry density as determined from standard Proctor test. Each material was tested at varying hydraulic loadings to determine the erosion rate after equal time intervals. The water depth and velocity were measured at each hydraulic loading using Pitot tubes and the acting bed shear was calculated. The effect of fines content and level of acting shear stresses is discussed in the paper
Ice overtopping of embankments: ice-tank experiments and field observations
Get PDFIce-sheet overtopping poses a problem for embankments adjoining large water bodies in cold regions. The problem is akin to wave loading and overtopping, though the water level is well below embankment crest level. Wind drives ice sheets, imparting large momentum, causing ice sheets to severely impact and possibly overtop embankments. Additionally, swift water currents in large rivers, especially during ice-cover break-up during spring weather, may drive ice against embankments such as flood-protection levees. Wind- or current-drive ice-sheets place unforeseen loads on embankments and the various erosion-protection methods intended to shield embankments. This paper briefly reviews the present state-of-knowledge regarding ice overtopping of embankments and reports the findings of ice-tank laboratory tests and field observations. Of interest are the influences of embankment geometry and ice-sheet properties on embankment overtopping. Also, of interest are the ice effects on riprap rock stability; and ice loads exerted against structures on embankments (e.g., a parapet wall)
Erosion resistant dikes thanks to soil treatment with lime
Get PDFLime treatment is a well-known technique of earthworks, for soil improvement and stabilization, its applications are mainly roads, railways, airports and platforms construction. In addition, some positive past experiences of lime treatment were related to solve erosion problems of dispersive and non-cohesive soil in hydraulic structures. The interest of the hydraulic works community regarding this technique is currently growing. During the last decade, the benefits of lime treatment and appropriate application technologies were evidenced for earthworks execution, for the improvement of mechanical properties and stability, high internal and external erosion resistance of treated materials and the possibility to maintain low hydraulic conductivity values. These have been shown in the laboratory and for some properties with full scale experiments.
The conferred soil properties can lead to innovative earthfill dams and dikes designs by addressing some of the typical designer’s problems, such as stability, watertightness, internal erosion, surface protection and flood control. However, lime treated soil external erosion resistance was still to be quantified in the field for proper designing and dimensioning of lime treated soil external erosion protection or spillways. With this purpose, an experimental earthfill dike was built along the river Vidourle (south of France) in July 2015, in the frame of the French R&D program “DigueELITE”. This 50 m long and 3,5 m high dike is made of lime treated silty soil and is provided with sensors (suction, water content and temperature) and piezometer in order to be monitored. It also was tested against surface erosion (JET testing) and real scale overflow testing. The in situ methodology and equipment for assessment of overflow resistance, and the benefits of lime-treatment against overflow are described. Eventually, proposals for dike design perspectives thanks to soil treatment with lime are opened
Engaging stakeholders in research to address water–energy–food (WEF) nexus challenges
No full textThe water–energy–food (WEF) nexus has become a popular, and potentially powerful, frame through which to analyse interactions and interdependencies between these three systems. Though the case for transdisciplinary research in this space has been made, the extent of stakeholder engagement in research remains limited with stakeholders most commonly incorporated in research as end-users. Yet, stakeholders interact with nexus issues in a variety of ways, consequently there is much that collaboration might offer to develop nexus research and enhance its application. This paper outlines four aspects of nexus research and considers the value and potential challenges for transdisciplinary research in each. We focus on assessing and visualising nexus systems; understanding governance and capacity building; the importance of scale; and the implications of future change. The paper then proceeds to describe a novel mixed-method study that deeply integrates stakeholder knowledge with insights from multiple disciplines. We argue that mixed-method research designs—in this case orientated around a number of cases studies—are best suited to understanding and addressing real-world nexus challenges, with their inevitable complex, non-linear system characteristics. Moreover, integrating multiple forms of knowledge in the manner described in this paper enables research to assess the potential for, and processes of, scaling-up innovations in the nexus space, to contribute insights to policy and decision making
Revetment failure tests in the River Experiment Center
Get PDFThe River Experiment Center (REC) at Korea Institute of Civil Engineering and Building Technology (KICT) is a real scale river experiment facility conducting R&D for river environments and flood response. Located floodplain of the Nakdong River, one of the largest rivers in Korea, the Center has over the total area of 193,051 m2 and three prototype channels with 600 m long and 11 m wide. Artificial floods are generated by large capacity pump with flow rate 10 m3/sec and the maximum velocity generated in the channel is over 5 m/sec. In the study several kinds of environmentally friendly revetments have been tested to find failure patterns and stability limits. Tested revetments are two kinds of concrete blocks with vegetation hole and two kinds of vegetation mats. Test procedure is referred to ASTM (D 7277, D 7276 and D 6460). Real scale revetments are installed in a steep sloped zone of the test channel. Water elevations and velocities are measured in each flow condition to determine the energy slopes. Bed changes in each flow conditions are measured by 3D Lidar and they are used to evaluate the failure condition. From the tests allowable shear stresses and failure patterns of the revetments are suggested. In the concrete blocks with vegetation hole, most damages are happened from the local scour in the vegetation holes. Vegetation mats reinforced by wire mesh show relatively high allowable shear stress
The effect of material zones and layers on breach growth and prediction
Get PDFBreach prediction models have typically focused on the prediction of processes through homogeneous structures (levees and dams), with some allowing for the effects of surface protection layers (such as grass or rock) and in some cases, the effects of simple core structures. Even with these simple models, it can be seen that the effect of surface layers or cores can be significant. The impact of changes in the rate of breach erosion are often magnified by the way in which these changes affect the breach growth timing in relation to the hydraulic load; for example, whether the main breach formation phase occurs as flood levels rise, peak or pass and drop.
The EMBREA model was developed to allow breach prediction through levees and dams constructed from zones of material. The model evolved from the earlier HR BREACH model and combines flow, soil erosion and slope stability calculations. Whilst the model can predict both headcut and surface erosion processes, the zoned behaviour is currently limited to the surface erosion simulation process. Simulations using different zoned geometries shows behaviour that is consistent with aspects of different homogenous breach processes, however, as the different zones erode, the characteristics also change. The effect of integrating erosion and breach growth processes through different zones of material gives results which can differ significantly from breach prediction through simple homogenous structures. This emphasises the importance of modelling real, zoned rather than simplified structures.
Whilst the significance of zoned breach prediction can be seen, the need to understand, refine and validate the way in which we model these processes remains a top priority. As with earlier models, the rate of erosion depends upon the soil erodibility (Kd) for which we need to confirm the most appropriate erosion relationship(s). With zoned structures, the nature of the soil zones can vary from erosion resistant clay cores to highly porous rockfill material. With macro erosion processes changing from headcut to surface erosion to rockfill slumping, the need to understand why and when the erosion process changes in relation to soil type and grading remains very important. To confirm and validate these processes, large scale laboratory and / or field testing of both homogeneous and zoned structures is required
Behaviour of a moveable barrier on revetment for mitigation of disaster by wave overtopping
Get PDFRecently, port city has been gradually expanding near coastal area, and many facilities for the purpose of tour and waterfront have been constructed near the shore. When the storm surge developed by typhoon have occurred, coastal facilities have a lot of damage and failure with loss of life caused directly by the waves. Various barrier de-sign concepts have been suggested to protect property and human life from disasters, they have not been widely applied though. Because they do not satisfy the recent trends that emphasize the surrounding scenery. In this study, a moveable barrier on revetment is proposed against wave overtopping. This moveable barrier has two main functions, sightseeing and protecting. In case of usual day, it is installed on the revetment and used observatory deck for sightseeing. When wave overtopping has occurred by storm surge, it protect coastal area through changing of flat deck to triangular barrier. The hydraulic and the structural performance of the newly proposed movable barrier was investigated through numerical analysis using commercial program. As a results, this structure has good performance. However, it is at a conceptual level, and there are still uncertainties related to aspects such as feasibility and engineering performance
Chapter 7: Models and tools.
No full textWith growing environmental awareness and increasing climate pressures on low-lying deltas, modern-day society puts incredibly strong demands on the sustainability of water infrastructure projects. Classic approaches towards the design and implementation of such projects no longer suffice in satisfying these demands. Recent approaches look beyond the scope of isolated dredging activities and embrace a wider context, by considering water infrastructure development projects as an opportunity to also add value to the (natural and socio-economic) system in order to achieve more sustainable projects. In the past 10-15 years, the international dredging community has embraced this kind of thinking and the approach to dredging has been transformed. From mainly dealing with negative impacts, often at the end of the project design and the start of the construction phase, towards a much more proactive approach where water infrastructure projects are being considered as part of the natural and socio-economic system in which they are situated, and stakeholders are being engaged much earlier in the project development process to facilitate the search for opportunities to create added value. This change in attitude has a huge influence on the initiation, planning and design, execution and maintenance of water infrastructure projects. Comprehensive guidance on how to bring this into practice has to date been lacking. With this book a wide range of professionals have attempted to collect and integrate their experiences and best practices, to deliver this state-of-the-art guidance book on Dredging for Sustainable Infrastructure. Comprised of nine chapters, the book discusses the topics of integrating dredging into sustainable development, sustainability in project initiation, planning and design, assessment and management of sustainability, equipment and methods, dredged material management, models and tools, and monitoring and data