Design Vertical Breakwater

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DESIGN OF VERTICAL BREAKWATERSBy Shigeo TAKAHASHIPORT and AIRPORT RESEARCH INSTITUTE, JAPANAugust 31, 1996 (Revised in Jully, 2002 Version 2.1)Revised Version of Reference Document No.34, PHRIDESIGN OF VERTICAL BREAKWATERS*by S. TAKAHASHI**1. INTRODUCTION2. TYPES OF BREAKWATERS AND THEIR HISTORICALDEVELOPMENT2.1 Structural Types2.2 Historical Development of Breakwaters3. RECENT FAILURES OF VERTICAL BREAKWATERS4. DESIGN OF CONVENTIONAL VERTICAL BREAKWATERS4.1 Example of Vertical Breakwaters4.2 Wave Transmission and Reflection of Vertical Walls4.3 Wave Forces on Vertical Walls4.4 Design of Rubble Mound Foundations4.5 Evaluation of Sliding Distance5. DESIGN OF NEW VERTICAL BREAKWATERS5.1 Perforated Walls5.2 Inclined Walls6. DESIGN OF HORIZONTALLY COMPOSITE BREAKWATERS6.1 Typical Cross Section of Horizontally Composite Breakwaters6.2 Wave and Block Forces on a Vertical Walls6.3 Stability of Wave Dissipating Concrete Blocls7. PERFORMANCE DESIGN OF COPMOSITE BREAKWATERS7.1 History and Definition of Performance Design7.2 New Framework for Performance Design7.3 Deformation-Based Reliability Design7.4 Extended Performance DesignREFERENCES13263468738796* A lecture note for Coastal Structures Short Course, 25t hInternational Conference on CoastalEngineering, Orlando, USA, September 31, 1996. Revised as the version 2.1 for Short Course ofHydraulic Response and Vertical Walls, 28thInternational Conference on Coastal Engineering,Cardiff, Wales, UK, July 7,2002** Director of Marine Environment and Engineering Department, Port and Airport ResearchInstitute, Independent Administrative Agency, Japan, 3-1-1, Nagase, Yokosuka, Japan 239-0826Phone +81-468-44-5036 Fax +81-468-44-1274, email. takahashi_s@pari.go.jp1. INTRODUCTIONBreakwaters are constructed to provide a calm basin for ships and to protect harbor facilities.They are also sometimes used to protect the port area from the intrusion of littoral drift. In fact,for ports open to rough seas, breakwaters play a key role in port operations.Since sea waves have enormous power, the construction of structures to mitigate such power is noteasily accomplished. The history of breakwaters, therefore, can be said to be one of much damageand many failures. On the other hand, maritime technology has progressed a great deal, especiallysince 1945, and this has gradually made it possible to construct breakwaters having high stabilityagainst waves.There are two main types of breakwaters: rubble mound and composite breakwaters. Rubblemound breakwaters have a rubble mound and an armor layer that usually consists ofshape-designed concrete blocks. Due to the development of these blocks, modern-day rubblemound breakwaters can strongly resist the destructive power of waves, even in deepwaters.Composite breakwaters consist of a rubble foundation and vertical wall, and are therefore classifiedas vertical breakwaters. By using caissons as the vertical wall, composite breakwaters provide anextremely stable structure even in rough, deep seas. Such strength has led to their use throughoutthe world.In this book, different types of breakwaters are introduced and their historical development isdescribed in order to understand the advantages and disadvantages associated with each type ofbreakwater. The failures of breakwaters are then discussed to demonstrate crucial points in theirstability design. Finally, the design methods used for vertical are explained including a new designconcept of performance design for vertical breakwaters. Since the design methodology for rubblemound breakwaters has been addressed in many textbooks, the design of vertical breakwaters willbe concentrated on here.Sincere gratitude is extended to the authors of many references, especially the following:1) Ito, Y. : A treatise on historical development of breakwater design, Technical Note of Port andHarbour Research Institute, No. 69, 1969, 78 p. Gn Japanese).2) Horikawa, K. : Coastal Engineering, University of Tokyo Press, 1978,402 p.3) Goda Y. : Random Seas and Design of Maritime Structures, University of Tokyo Press, 1985,323p.4) Tanimoto, K. et al.: Structures and Hydrodynamic Characteristics of Break waters, Report of Portand Harbour Research Institute, Vol. 25, No. 5. 1987, pp. 11-55.5) Burcharth, H. F. : The Design of Breakwaters, Coastal and Harbour Engineering Reference Book(edited by M. B. Abbott and W. A. Price), Chapter 28, E & FN SPON, 1993.6) Brunn P. : Design and Construction of Mound for Breakwater and Coastal Protection, Elsevier,1985,938 p.7) Proceedings of International Workshop on Wave Barriers in Deepwaters, Port and HarbourResearch Institute, 1994, 583 p.8) Proceedings of International Workshop on Advanced Design of Maritime Structures in the 21st1Century (ADMS21), Port and Harbour Research Institute, 2001, 392 p.9) Technical Standards for Port and Harbour Facilities in Japan: The Overseas Coastal AreaDevelopment Institute of Japan (OCD!), 2002, 599p.10) Manual on the Use of Rock in Coastal and Shoreline Engineering, ClRA special publication 83,CUR Report 154, 1991,607 p.11) Shore Protection Manual: Coastal Engineering Research Center, U.S. Army Corps of Engineers,1984.12) Losada, M. A. : Recent Developments in the Design of Mound Breakwaters, Handbook ofCoastal and Ocean Engineering (edited by J. B. Herbich), Chapter 21, Gulf Publishing Co., 1990.13) Tsinker, G.P.: Handbook of Port and Harbor Engineering,Chapman &Hall, 1996,1054p.22. TYPES OF BREAKWATERS AND THEIR HISTORICAL DEVELOPMENT2.1 Structural TypesThere are many types of breakwater structures used throughout the world. As shown in Table2.1, breakwaters can be classified into three structural types: (1) the sloping or mound type, (2)the vertical type which includes the basic (simple) vertical type and the composite and horizon-tally composite types, and (3) special types. Figure 2.1 shows conceptual diagrams of the dif-ferent types of breakwaters.Table 2.1 Structural types of breakwatersSloping (mound) typeVertical (upright) typeComposite typeHorizontally composite typeRubble mound breakwatersRubble mound breakwaters (multi-layer)Rubble mound breakwaters armored with blocksConcrete block breakwatersReshaping rubble mound breakwaters (berm breakwaters)Reef breakwaters (submerged breakwaters)Monolith concrete breakwatersBlock masonry breakwatersCellular block breakwatersConcrete caisson breakwatersNew caisson breakwatersSpecial (non-gravity) type Curtain wall breakwatersSteel pile breakwatersHorizontal plate breakwatersFloating breakwatersPneumatic breakwaterHydraulic breakwater(1) Sloping or mound typeThe sloping or mound type of breakwaters basically consist of a rubble mound as shown in Fig.2.1(1). The most fundamental sloping type breakwater is one with randomly placed stones (a).To increase stability and decrease wave transmission, as well as to decrease material costs, themulti-layered rubble mound breakwater was developed having a core of quarry run (b). Thestability of the armor layer can be strengthened using shape-designed concrete blocks, whilewave transmission can be reduced using a superstructure (wave screen or wave wall), which canalso function as an access road to the breakwater (c).Breakwaters comprised of only concrete b l o ~ k s (d) are also being constructed, especially for useas a detached breakwater providing coastal protection. Although wave transmission is not re-duced so much for this breakwater type, its simple construction procedure and the relativelyhigh permeability of the breakwater body are advantageous features. Recently, reef breakwatersor submerged breakwaters (e) have been constructed for coastal protection, while not to inter-rupting the beautiful "seascape."3(0)(c);ill vHWL. S7LWL. "7

Fig. 2.1 (2) Vertical typebreakwaters "Z---'------(f)(e)(d) Fig. 2.1 (1) Sloping type breakwatersReshaping breakwaters (f) utilize the basic con-cept of establishing an equilibrium between theslope of the rubble stone and wave action, i.e., therubble mound forms an Se-shape slope to stabilizeitself against wave actions. This breakwater has alarge berm in front, which will ultimately bereshaped due to wave actions, and therefore it iscalled the berm breakwater or dynamically stablebreakwater. It should be noted that this concept isnot new, since ancient rubble mound breakwaterswere all of this type, being naturally reshaped bydamage and subsequent repairs.(2) Vertical type(composite and horizontally composite types)The original concept of the vertical breakwaterwas to reflect waves, while that for the rubblemound breakwater was to break them. Figure2.1(2) shows four vertical type breakwaters havingdifferent mound heights. The basic vertical wallbreakwater is shown in (a), while the others arecomposite breakwaters with a rubble mound foundation,namely, the low-mound (b) and high-mound compositebreakwaters (d). By convention, the high-mound com-posite breakwater has a mound that is higher than the lowwater level (L.W.L.). The former breakwater does notcause wave breaking on the mound, while the latter onedoes. Since the high-mound composite type is unstable dueto wave-generated