6 Design of marine structures 1 2 3 4 5 6 7 8 9 10 CIRIA C683 773 6 Design of marine structures CHAPTER 6 CONTENTS 6.1 Rubble mound breakwaters. 778 6.1.1 General aspects . 778 6.1.1.1 Design considerations and overall approach. 779 6.1.1.2 Definitions. 780 6.1.1.3 Selection of breakwater type . 782 6.1.2 Plan layout . 783 6.1.2.1 Influence of the need for berth protection . 785 6.1.2.2 Influence of the need to provide protection to access channel . 785 6.1.2.3 Influence of the need to reduce maintenance and dredging costs . 787 6.1.2.4 Effect of the layout on the breakwater sections. 787 6.1.2.5 Effect of the breakwater sections on harbour layout. 788 6.1.2.6 Cost considerations . 788 6.1.3 Geometry of breakwater cross-section . 789 6.1.3.1 Cross-section concept generation, selection and detailing . 789 6.1.3.2 Data collection and boundary conditions . 790 6.1.3.3 Materials availability . 790 6.1.3.4 Failure analysis . 791 6.1.4 Conventional rubble mound. 793 6.1.4.1 Main dimensions. 793 6.1.4.2 Detailed dimensions . 798 6.1.4.3 Transitions. 801 6.1.5 Rubble mound with monolithic crown wall . 803 6.1.6 Berm or S-slope breakwater . 808 6.1.6.1 Main dimensions. 809 6.1.7 Caisson-type breakwaters . 811 6.1.8 Cost aspects . 814 6.1.8.1 Cost aspects related to the production of armourstone for breakwaters . 815 6.1.8.2 Cost aspects related to design and construction of breakwaters. 817 6.1.9 Construction issues that influence design . 819 6.1.9.1 Construction method . 819 6.1.9.2 Placing tolerances . 820 6.1.9.3 Construction risks . 821 6.1.10 Maintenance issues that influence design. 821 6.1.11 Repair and upgrading of existing structures . 822 6.2 Rock protection to port structures . 823 6.2.1 General aspects and definitions . 823 6.2.1.1 Types of structure . 823 6.2.1.2 Key properties . 825 6.2.2 Plan layout . 826 6.2.3 Cross-section design and structure details . 826 6.2.3.1 Design loads and armourstone size . 826 6.2.3.2 Vertical dimensions. 827 774 CIRIA C683 Contents 6.2.3.3 Horizontal dimensions . 829 1 6.2.3.4 Slope angle . 830 6.2.3.5 Armour layers . 830 6.2.3.6 Underlayers and filters. 830 6.2.3.7 Toe details and terminations . 831 6.2.3.8 Transitions and junctions . 831 2 6.2.3.9 Crest details. 831 6.2.4 Alternative materials . 832 6.2.5 Cost aspects . 833 6.2.6 Construction issues that influence design . 834 6.2.7 Maintenance issues that influence design. 835 3 6.2.8 Repair and upgrading. 835 6.3 Shoreline protection and beach control structures. 836 6.3.1 General aspects and definition of structure types . 837 6.3.1.1 Revetment . 838 4 6.3.1.2 Scour protection . 838 6.3.1.3 Groyne. 839 6.3.1.4 Detached breakwater . 840 6.3.1.5 Fishtail groyne . 841 6.3.1.6 L-shaped and T-shaped groynes . 841 5 6.3.1.7 Sill or submerged breakwater. 842 6.3.2 Plan layout . 842 6.3.2.1 General layout considerations . 842 6.3.2.2 Plan layout for different structure types . 844 6.3.3 Geometry of cross-sections . 851 6 6.3.3.1 General considerations . 851 6.3.3.2 Physical boundary conditions. 852 6.3.3.3 Overtopping . 852 6.3.3.4 Slope design . 855 6.3.3.5 Armour layer. 855 7 6.3.3.6 Underlayers and filters. 856 6.3.3.7 Layer thickness . 858 6.3.4 Structural details . 859 6.3.4.1 Toe design . 859 6.3.4.2 Crest design . 866 8 6.3.4.3 Joints and transitions . 867 6.3.4.4 Structure-specific aspects . 869 6.3.5 Cost aspects . 879 6.3.6 Construction issues that influence design . 881 6.3.7 Maintence issues that influence design. 882 9 6.3.8 Repair and upgrading. 882 6.4 Rockfill in offshore engineering . 883 6.4.1 General aspects and definitions . 883 6.4.1.1 Pipelines and cables . ..