This document provides guidance for designing coastal revetments, seawalls, and bulkheads to protect shorelines. It discusses important considerations for the functional design of these structures, including estimating design water levels and waves, determining required heights, and ensuring stability. The manual describes common materials used in armor layers and structural components. It also addresses evaluating environmental impacts and applying all applicable design guidance to avoid failures. The document aims to help engineers properly size and construct coastal protective structures.
This chapter discusses general design considerations for beach stabilization structures. It outlines the objectives to redistribute available sand while limiting adverse impacts. Shore-connected structures like groins and breakwaters are described that interrupt longshore transport, causing accumulation updrift and potential erosion downdrift. Design requires analyzing wave, current and transport conditions, and structures must be tailored to each site.
Breakwaters, jetties, and groins are coastal structures used to protect harbors and shorelines from wave energy. Breakwaters are structures that reflect and dissipate wave energy to shelter harbors. Jetties are narrow structures that project from the shore into water and provide berths for ships. Groins are structures built perpendicular to the shore to trap littoral drift and protect or build beaches. There are different types of each structure based on materials, permeability, and orientation relative to shorelines and water flow.
1. There are three main types of seawalls: vertical, curved, and mound. Vertical seawalls are the easiest to design and construct but can become undermined. Curved seawalls reduce wave reflection and turbulence but are more complex to design. Mound seawalls provide maximum wave energy dissipation but are less durable and have a shorter lifespan.
2. Several seawall systems are described: gravity walls, L-shaped walls with buttresses, and systems that use piles or diaphragm walls to provide support independently of soil weight. Pile-supported systems are less vulnerable to scour but more expensive. Diaphragm systems are flexible and independent of soil surcharge weight.
This document discusses different types of breakwaters. Breakwaters are structures built along coasts to protect areas from wave disturbance. There are three main categories: rubble mound breakwaters, vertical-wall breakwaters, and floating breakwaters. Rubble mound breakwaters are constructed from natural rubble or stone and are the most widely used in Indian ports due to their cost-effectiveness. Vertical-wall breakwaters use concrete blocks or mass concrete and reflect waves without dissipating much energy. Floating breakwaters are removable structures constructed from caissons or pontoons that can be sunk or floated as needed.
This document discusses seepage control and dewatering methods used in construction projects. It describes the need for dewatering excavation sites to allow for safe and efficient construction. The key dewatering methods discussed are seepage control linings, cutoffs, drainage systems, and pumping groundwater via wells. It also covers ground freezing as another method to temporarily stabilize soils by turning water into ice. The document provides details on factors that influence freezing like thermal conductivity and heat capacity of soils. It emphasizes the importance of properly discharging water and monitoring sites during dewatering activities.
The document discusses coastal protection techniques. It begins by explaining the importance of coasts and the need for coastal protection due to erosion from storms and rising sea levels. It then describes hard and soft engineering techniques for coastal protection. Hard techniques include breakwaters, gabions, groynes, revetments, sea walls, and use rigid structures to defend coastlines. Soft techniques like beach nourishment, dune stabilization, and mangroves are more natural and sustainable approaches. The document provides details on various hard and soft techniques, their advantages and disadvantages. It concludes by discussing physical aspects of coastal protection like wave types, wave control through reflection, refraction, and breaking.
Seismic design and construction of retaining wallAhmedEwis13
This document discusses seismic design considerations for retaining walls. It describes the common types of retaining walls, including gravity, cantilever, reinforced soil, and anchored bulkhead walls. Static lateral earth pressures are calculated using Rankine and Coulomb theories, with the Mononobe-Okabe method extending Coulomb theory to account for seismic inertial forces. Dynamic response of retaining walls is complex, with wall movement, pressures, and permanent displacements dependent on the response of the wall, backfill soil, and foundation soil to ground shaking.
The document discusses the dredging process and its effects. It provides an overview of different types of dredgers including mechanical dredgers like bucket ladder dredgers and grab dredgers, and hydraulic dredgers like suction hopper dredgers and cutter suction dredgers. It also discusses site investigation processes, soil classification, dredger selection, dumping grounds, effectiveness, impacts, and environmental effects of dredging. Dredging is necessary for activities like creating harbors and maintaining waterways, but can impact the environment through disturbed sediments and potential contamination. Careful planning is required to select the appropriate dredger and minimize negative impacts.
This chapter discusses general design considerations for beach stabilization structures. It outlines the objectives to redistribute available sand while limiting adverse impacts. Shore-connected structures like groins and breakwaters are described that interrupt longshore transport, causing accumulation updrift and potential erosion downdrift. Design requires analyzing wave, current and transport conditions, and structures must be tailored to each site.
Breakwaters, jetties, and groins are coastal structures used to protect harbors and shorelines from wave energy. Breakwaters are structures that reflect and dissipate wave energy to shelter harbors. Jetties are narrow structures that project from the shore into water and provide berths for ships. Groins are structures built perpendicular to the shore to trap littoral drift and protect or build beaches. There are different types of each structure based on materials, permeability, and orientation relative to shorelines and water flow.
1. There are three main types of seawalls: vertical, curved, and mound. Vertical seawalls are the easiest to design and construct but can become undermined. Curved seawalls reduce wave reflection and turbulence but are more complex to design. Mound seawalls provide maximum wave energy dissipation but are less durable and have a shorter lifespan.
2. Several seawall systems are described: gravity walls, L-shaped walls with buttresses, and systems that use piles or diaphragm walls to provide support independently of soil weight. Pile-supported systems are less vulnerable to scour but more expensive. Diaphragm systems are flexible and independent of soil surcharge weight.
This document discusses different types of breakwaters. Breakwaters are structures built along coasts to protect areas from wave disturbance. There are three main categories: rubble mound breakwaters, vertical-wall breakwaters, and floating breakwaters. Rubble mound breakwaters are constructed from natural rubble or stone and are the most widely used in Indian ports due to their cost-effectiveness. Vertical-wall breakwaters use concrete blocks or mass concrete and reflect waves without dissipating much energy. Floating breakwaters are removable structures constructed from caissons or pontoons that can be sunk or floated as needed.
This document discusses seepage control and dewatering methods used in construction projects. It describes the need for dewatering excavation sites to allow for safe and efficient construction. The key dewatering methods discussed are seepage control linings, cutoffs, drainage systems, and pumping groundwater via wells. It also covers ground freezing as another method to temporarily stabilize soils by turning water into ice. The document provides details on factors that influence freezing like thermal conductivity and heat capacity of soils. It emphasizes the importance of properly discharging water and monitoring sites during dewatering activities.
The document discusses coastal protection techniques. It begins by explaining the importance of coasts and the need for coastal protection due to erosion from storms and rising sea levels. It then describes hard and soft engineering techniques for coastal protection. Hard techniques include breakwaters, gabions, groynes, revetments, sea walls, and use rigid structures to defend coastlines. Soft techniques like beach nourishment, dune stabilization, and mangroves are more natural and sustainable approaches. The document provides details on various hard and soft techniques, their advantages and disadvantages. It concludes by discussing physical aspects of coastal protection like wave types, wave control through reflection, refraction, and breaking.
Seismic design and construction of retaining wallAhmedEwis13
This document discusses seismic design considerations for retaining walls. It describes the common types of retaining walls, including gravity, cantilever, reinforced soil, and anchored bulkhead walls. Static lateral earth pressures are calculated using Rankine and Coulomb theories, with the Mononobe-Okabe method extending Coulomb theory to account for seismic inertial forces. Dynamic response of retaining walls is complex, with wall movement, pressures, and permanent displacements dependent on the response of the wall, backfill soil, and foundation soil to ground shaking.
The document discusses the dredging process and its effects. It provides an overview of different types of dredgers including mechanical dredgers like bucket ladder dredgers and grab dredgers, and hydraulic dredgers like suction hopper dredgers and cutter suction dredgers. It also discusses site investigation processes, soil classification, dredger selection, dumping grounds, effectiveness, impacts, and environmental effects of dredging. Dredging is necessary for activities like creating harbors and maintaining waterways, but can impact the environment through disturbed sediments and potential contamination. Careful planning is required to select the appropriate dredger and minimize negative impacts.
The document provides an introduction to various coastal structures used for coastal protection. It describes sea dikes, sea walls, revetments, emergency protection, bulkheads, groynes, jetties, breakwaters, and detached breakwaters. Each coastal structure is defined and its applicability is discussed. The document categorizes coastal protection structures as coastal protection, shore protection, beach construction, management solutions, and sea defense. It aims to give an overview of different types of structures used to protect coasts from erosion, flooding, and damage from waves and currents.
Breakwaters are structures built along coasts to protect harbors, anchorages, and shorelines from wave damage. They work by reflecting and dissipating wave energy before it reaches the protected area. There are several types of breakwaters including detached, headland, nearshore, attached, rubble mound, vertical, and submerged. The appropriate type depends on factors like water depth, wave climate, and material availability. Successful breakwater design requires detailed surveys of seabed conditions, wave patterns, and material needs to ensure the structure is stable and effective.
This document provides information about forces acting on gravity dams. It discusses the main stabilizing and destabilizing forces, including the weight of the dam, water pressure on the upstream and downstream faces, uplift pressure, earth and silt pressures, ice pressure, and other loads. It defines key terms related to gravity dams such as structural height, base width, axis, and explains how to calculate the various forces per unit length of the dam. Uplift pressure is explained as being dependent on the permeability of the dam and foundation materials and effective drainage. Design criteria for calculating uplift forces according to Indian standards is also summarized.
The document discusses various methods for river training including constructing levees, guide banks, and spurs. Levees are embankments running parallel to rivers that are used to contain flood waters and protect areas from flooding. Guide banks are structures built to confine river flow within a reasonable waterway when constructing bridges or other works. Spurs are embankment structures built transverse to river flow to deflect currents away from banks and prevent erosion. The appropriate river training method depends on the river type, regime, and flow characteristics.
Este documento trata sobre muros de contención. Explica que los muros de contención se utilizan para retener masas de tierra u otros materiales sueltos. Luego describe la evolución de los muros de contención desde su origen en la naturaleza hasta los muros de contrafuertes romanos y los muros de hormigón armado modernos. Finalmente, explica los conceptos básicos para el diseño de muros de contención como el análisis de estabilidad frente al volcamiento y deslizamiento.
The document discusses different methods for coastal management, distinguishing between hard and soft engineering approaches. It describes various hard engineering structures like sea walls, groynes, revetments, and gabions. Soft engineering techniques mentioned include beach nourishment and cliff regrading. Students will experiment with different coastal protection methods using materials provided and write a short report evaluating the effects. They are asked to consider the most cost-effective protection for various coastal areas.
Rehabilitation and modernization of irrigation systemsNagaraj S
This document outlines a plan to improve irrigation systems through rehabilitation, modernization, and addressing maintenance issues. It discusses identifying problems in current systems, developing and implementing solutions, and achieving increased agricultural production through improved irrigation performance. Key aspects of the plan include training, research, technology transfer, organizational changes, and using tools like surveys to identify maintenance difficulties and their underlying causes.
1) Bending moment is a measure of the bending effect on a beam due to applied forces and is measured in units of Newton-meters or foot-pounds force.
2) The bending moment equation is the algebraic sum of the moments about a section of the beam from all forces acting on one side.
3) Positive bending moments cause tension in the bottom fibers and compression in the top fibers (sagging) while negative moments cause the opposite (hogging).
This document discusses several coastal protection methods:
Breakwaters reduce wave power to protect beaches from erosion. Gabions are wire cages filled with stones that absorb wave energy. Groynes are structures built perpendicular to the shore to slow longshore drift. Revetments are sloped structures that absorb wave energy and trap sediment. Sea walls are curved concrete walls that protect cliffs from wave erosion. Each method has advantages in reducing erosion but can also impact sediment movement and beaches.
This document discusses balancing depth in canal design, canal lining, and design principles for lined canals. It defines balancing depth as the depth where the amount of cut material equals the amount of fill material. It lists advantages of canal lining such as reducing seepage losses and maintenance costs. Design principles for lined canals include selecting economical cross-sectional shapes based on discharge and using side slopes of 1:1 or 1.25:1 that are stable for the soil. Input data includes discharge, roughness, slopes, and maximum velocity, and output data includes breadth and depth calculated using Manning's equation.
This document outlines the design of a canal regulator using HTML. It will involve learning about canal regulation structures like cross regulators and distributary head regulators. The team will design these structures for a specific canal scenario using HTML and AutoCAD. They will create a user-friendly interface in HTML that allows users to design canal regulators easily by varying parameters. This will help people design regulators worldwide using the online template. Team members will learn about canals and HTML before dividing tasks - some will focus on HTML designs while others use AutoCAD based on the HTML outputs. The final output will be an online tool for simple and affordable canal regulator design.
Dredging involves digging and removing material from waterways to deepen them for navigation. It maintains harbor and channel depths and creates new access points. There are two main types: mechanical dredging uses buckets to excavate material, while hydraulic dredging uses water pressure to break up and pump material through pipes. Dredging is needed to allow vessel passage, but can disturb seabeds and increase turbidity through suspended sediments. Proper planning aims to minimize environmental impacts of this necessary maintenance of waterways.
Challenges of Tunneling-- A Peep Into The Exciting World of TunnellingIEI GSC
By Shri Manoj Verman, President, Indian National Group of ISRM
President, International Commission on Hard Rock Excavation
Vice President, Indian Society of Engineering Geology
at 31st National Convention of Civil Engineering
organised by
Gujarat State Center, The Institution of Engineers (India)
at Ahmedabad
Rcc design and detailing based on revised seismic codesWij Sangeeta
The document summarizes important provisions of revised seismic codes affecting reinforced concrete (RCC) design and detailing, including:
- Revisions to building configuration definitions, load combinations, and stiffness modifiers.
- Prohibitions on certain structural systems without adequate experimentation/analysis.
- Revisions to design eccentricity, foundation isolation, column/beam sizing and reinforcement, and ductility provisions.
- Updates to standards IS:13920 regarding concrete grade, beam-column joints, lap splices, transverse reinforcement, and special confining reinforcement.
- Queries raised regarding compliance of existing/under construction buildings and clarification needed for irregular geometries.
This document provides an introduction and outline for a course on irrigation engineering. The key points are:
1. The course will cover soil-plant-water relations, irrigation water requirements, water sources and quality, irrigation planning and efficiencies, and design of irrigation systems and structures.
2. The objectives are for students to understand soil-plant-water parameters, estimate crop water needs, plan and design irrigation structures, and design irrigation channels and other structures.
3. The syllabus covers topics like irrigation methods, water requirements, canal systems, design of channels, diversion structures, outlets, seepage theories, dams, and environmental impacts of irrigation projects.
This document provides an overview of coastal engineering processes and applications. It begins with an introduction to coastal processes, including terminology, typical coastal zones, and examples of engineering projects. It then covers topics like sediment characteristics, long-term processes like sea level rise, hydrodynamics including tides, storms, and water waves. Methods for measuring and modeling coastal responses are discussed, along with techniques for modifying shorelines like beach nourishment and hard structures. The document uses diagrams and photographs of international case studies to illustrate key concepts in coastal engineering.
This document presents a summary of a presentation on analyzing and designing an RCC box culvert using ETABS. The presentation covers the objectives of determining loads, structurally designing the culvert, designing reinforcement, and analyzing the design in ETABS. It describes the culvert's design parameters from its hydraulic design and dimensions. It also details the typical reinforcement in the slab and walls. The conclusion recommends reinforcement sizes and validates the hand calculations with ETABS analysis results.
Coastal erosion is the wearing away of land and removal of beach sediments by waves, currents, and drainage. Natural forces like wind, waves and currents shape coastal regions by moving land materials. Coastal erosion is the landward displacement of the shoreline caused by these forces. Factors influencing erosion include waves, currents, tides, wind, sand sources and sinks, sea level changes, coastal geomorphology, and human activities like construction and dredging. Coastal erosion can cause loss of land and property damage from landslides. Rates of erosion vary in different locations based on slope, wave intensity, wind, and shoreline characteristics.
This document provides guidance for selecting concrete materials for civil works structures. It establishes standard practices for investigating and selecting cementitious materials like Portland cement, blended cements, pozzolans, and slag. It also provides guidance for selecting aggregates, mixing water, chemical admixtures, and investigating available material sources. The document contains policies, requirements, and considerations for choosing appropriate materials based on the type of structure and project requirements. It seeks to ensure high quality, durable concrete is used in civil works projects.
This document provides an introduction and manual for the design of hollow core slabs. It discusses the manufacturing of hollow core slabs and the materials used. It then covers advantages of hollow core slabs and common framing concepts. The bulk of the document focuses on guidelines for designing hollow core slabs, including flexural and shear design, camber and deflection, composite design, and strand development. It also covers special design considerations like load distribution, effects of openings, continuity, and cantilevers. Finally, it discusses using hollow core slabs as diaphragms to resist lateral loads. The manual is intended to provide design guidance and reference material for engineers and producers working with hollow core slab systems.
The document provides an introduction to various coastal structures used for coastal protection. It describes sea dikes, sea walls, revetments, emergency protection, bulkheads, groynes, jetties, breakwaters, and detached breakwaters. Each coastal structure is defined and its applicability is discussed. The document categorizes coastal protection structures as coastal protection, shore protection, beach construction, management solutions, and sea defense. It aims to give an overview of different types of structures used to protect coasts from erosion, flooding, and damage from waves and currents.
Breakwaters are structures built along coasts to protect harbors, anchorages, and shorelines from wave damage. They work by reflecting and dissipating wave energy before it reaches the protected area. There are several types of breakwaters including detached, headland, nearshore, attached, rubble mound, vertical, and submerged. The appropriate type depends on factors like water depth, wave climate, and material availability. Successful breakwater design requires detailed surveys of seabed conditions, wave patterns, and material needs to ensure the structure is stable and effective.
This document provides information about forces acting on gravity dams. It discusses the main stabilizing and destabilizing forces, including the weight of the dam, water pressure on the upstream and downstream faces, uplift pressure, earth and silt pressures, ice pressure, and other loads. It defines key terms related to gravity dams such as structural height, base width, axis, and explains how to calculate the various forces per unit length of the dam. Uplift pressure is explained as being dependent on the permeability of the dam and foundation materials and effective drainage. Design criteria for calculating uplift forces according to Indian standards is also summarized.
The document discusses various methods for river training including constructing levees, guide banks, and spurs. Levees are embankments running parallel to rivers that are used to contain flood waters and protect areas from flooding. Guide banks are structures built to confine river flow within a reasonable waterway when constructing bridges or other works. Spurs are embankment structures built transverse to river flow to deflect currents away from banks and prevent erosion. The appropriate river training method depends on the river type, regime, and flow characteristics.
Este documento trata sobre muros de contención. Explica que los muros de contención se utilizan para retener masas de tierra u otros materiales sueltos. Luego describe la evolución de los muros de contención desde su origen en la naturaleza hasta los muros de contrafuertes romanos y los muros de hormigón armado modernos. Finalmente, explica los conceptos básicos para el diseño de muros de contención como el análisis de estabilidad frente al volcamiento y deslizamiento.
The document discusses different methods for coastal management, distinguishing between hard and soft engineering approaches. It describes various hard engineering structures like sea walls, groynes, revetments, and gabions. Soft engineering techniques mentioned include beach nourishment and cliff regrading. Students will experiment with different coastal protection methods using materials provided and write a short report evaluating the effects. They are asked to consider the most cost-effective protection for various coastal areas.
Rehabilitation and modernization of irrigation systemsNagaraj S
This document outlines a plan to improve irrigation systems through rehabilitation, modernization, and addressing maintenance issues. It discusses identifying problems in current systems, developing and implementing solutions, and achieving increased agricultural production through improved irrigation performance. Key aspects of the plan include training, research, technology transfer, organizational changes, and using tools like surveys to identify maintenance difficulties and their underlying causes.
1) Bending moment is a measure of the bending effect on a beam due to applied forces and is measured in units of Newton-meters or foot-pounds force.
2) The bending moment equation is the algebraic sum of the moments about a section of the beam from all forces acting on one side.
3) Positive bending moments cause tension in the bottom fibers and compression in the top fibers (sagging) while negative moments cause the opposite (hogging).
This document discusses several coastal protection methods:
Breakwaters reduce wave power to protect beaches from erosion. Gabions are wire cages filled with stones that absorb wave energy. Groynes are structures built perpendicular to the shore to slow longshore drift. Revetments are sloped structures that absorb wave energy and trap sediment. Sea walls are curved concrete walls that protect cliffs from wave erosion. Each method has advantages in reducing erosion but can also impact sediment movement and beaches.
This document discusses balancing depth in canal design, canal lining, and design principles for lined canals. It defines balancing depth as the depth where the amount of cut material equals the amount of fill material. It lists advantages of canal lining such as reducing seepage losses and maintenance costs. Design principles for lined canals include selecting economical cross-sectional shapes based on discharge and using side slopes of 1:1 or 1.25:1 that are stable for the soil. Input data includes discharge, roughness, slopes, and maximum velocity, and output data includes breadth and depth calculated using Manning's equation.
This document outlines the design of a canal regulator using HTML. It will involve learning about canal regulation structures like cross regulators and distributary head regulators. The team will design these structures for a specific canal scenario using HTML and AutoCAD. They will create a user-friendly interface in HTML that allows users to design canal regulators easily by varying parameters. This will help people design regulators worldwide using the online template. Team members will learn about canals and HTML before dividing tasks - some will focus on HTML designs while others use AutoCAD based on the HTML outputs. The final output will be an online tool for simple and affordable canal regulator design.
Dredging involves digging and removing material from waterways to deepen them for navigation. It maintains harbor and channel depths and creates new access points. There are two main types: mechanical dredging uses buckets to excavate material, while hydraulic dredging uses water pressure to break up and pump material through pipes. Dredging is needed to allow vessel passage, but can disturb seabeds and increase turbidity through suspended sediments. Proper planning aims to minimize environmental impacts of this necessary maintenance of waterways.
Challenges of Tunneling-- A Peep Into The Exciting World of TunnellingIEI GSC
By Shri Manoj Verman, President, Indian National Group of ISRM
President, International Commission on Hard Rock Excavation
Vice President, Indian Society of Engineering Geology
at 31st National Convention of Civil Engineering
organised by
Gujarat State Center, The Institution of Engineers (India)
at Ahmedabad
Rcc design and detailing based on revised seismic codesWij Sangeeta
The document summarizes important provisions of revised seismic codes affecting reinforced concrete (RCC) design and detailing, including:
- Revisions to building configuration definitions, load combinations, and stiffness modifiers.
- Prohibitions on certain structural systems without adequate experimentation/analysis.
- Revisions to design eccentricity, foundation isolation, column/beam sizing and reinforcement, and ductility provisions.
- Updates to standards IS:13920 regarding concrete grade, beam-column joints, lap splices, transverse reinforcement, and special confining reinforcement.
- Queries raised regarding compliance of existing/under construction buildings and clarification needed for irregular geometries.
This document provides an introduction and outline for a course on irrigation engineering. The key points are:
1. The course will cover soil-plant-water relations, irrigation water requirements, water sources and quality, irrigation planning and efficiencies, and design of irrigation systems and structures.
2. The objectives are for students to understand soil-plant-water parameters, estimate crop water needs, plan and design irrigation structures, and design irrigation channels and other structures.
3. The syllabus covers topics like irrigation methods, water requirements, canal systems, design of channels, diversion structures, outlets, seepage theories, dams, and environmental impacts of irrigation projects.
This document provides an overview of coastal engineering processes and applications. It begins with an introduction to coastal processes, including terminology, typical coastal zones, and examples of engineering projects. It then covers topics like sediment characteristics, long-term processes like sea level rise, hydrodynamics including tides, storms, and water waves. Methods for measuring and modeling coastal responses are discussed, along with techniques for modifying shorelines like beach nourishment and hard structures. The document uses diagrams and photographs of international case studies to illustrate key concepts in coastal engineering.
This document presents a summary of a presentation on analyzing and designing an RCC box culvert using ETABS. The presentation covers the objectives of determining loads, structurally designing the culvert, designing reinforcement, and analyzing the design in ETABS. It describes the culvert's design parameters from its hydraulic design and dimensions. It also details the typical reinforcement in the slab and walls. The conclusion recommends reinforcement sizes and validates the hand calculations with ETABS analysis results.
Coastal erosion is the wearing away of land and removal of beach sediments by waves, currents, and drainage. Natural forces like wind, waves and currents shape coastal regions by moving land materials. Coastal erosion is the landward displacement of the shoreline caused by these forces. Factors influencing erosion include waves, currents, tides, wind, sand sources and sinks, sea level changes, coastal geomorphology, and human activities like construction and dredging. Coastal erosion can cause loss of land and property damage from landslides. Rates of erosion vary in different locations based on slope, wave intensity, wind, and shoreline characteristics.
This document provides guidance for selecting concrete materials for civil works structures. It establishes standard practices for investigating and selecting cementitious materials like Portland cement, blended cements, pozzolans, and slag. It also provides guidance for selecting aggregates, mixing water, chemical admixtures, and investigating available material sources. The document contains policies, requirements, and considerations for choosing appropriate materials based on the type of structure and project requirements. It seeks to ensure high quality, durable concrete is used in civil works projects.
This document provides an introduction and manual for the design of hollow core slabs. It discusses the manufacturing of hollow core slabs and the materials used. It then covers advantages of hollow core slabs and common framing concepts. The bulk of the document focuses on guidelines for designing hollow core slabs, including flexural and shear design, camber and deflection, composite design, and strand development. It also covers special design considerations like load distribution, effects of openings, continuity, and cantilevers. Finally, it discusses using hollow core slabs as diaphragms to resist lateral loads. The manual is intended to provide design guidance and reference material for engineers and producers working with hollow core slab systems.
AK: Anchorage: Low Impact Development Design Guidance ManualSotirakou964
This document provides guidance for designing low impact development (LID) elements like rain gardens, infiltration trenches, soak-away pits, and filter strips. It discusses evaluating sites for these elements based on soil infiltration rates, groundwater depth, and other factors. Design approaches are presented for each LID element, covering preliminary site evaluation and design considerations, pretreatment where needed, and final design details. Construction and maintenance guidelines are also provided. The overall aim is to help plan and implement LID techniques that reduce stormwater runoff impacts.
This document provides a profile of the iron mining industry and a site visit report for LTV Steel. The profile describes the economic and environmental aspects of iron mining. Iron ore deposits are formed through sedimentary, igneous, and weathering processes. Extraction methods include open pit and underground mining. Beneficiation involves milling, magnetic separation, flotation, gravity concentration, thickening, filtering, and agglomeration to produce iron ore concentrates. Wastes include waste rock, tailings, and mine water. Management includes waste rock piles, tailings impoundments, and mine reclamation. The profile also discusses environmental effects and applicable regulations. The site visit report provides background on LTV Steel and describes its
This document provides guidance on the design of lock gates and operating equipment at navigation projects. It covers various types of gates including miter gates, sector gates, vertical-lift gates, and submergible tainter gates. For each gate type, it discusses design considerations and applications. It also addresses general topics such as materials selection, load calculations, and corrosion control. The manual aims to aid engineers in the structural, mechanical, and electrical design of lock gates and associated machinery.
This document is a draft environmental impact report (EIR) prepared for the proposed E & B Oil Drilling & Production Project in the City of Hermosa Beach. The draft EIR evaluates potential environmental impacts from the proposed oil drilling and production project and associated city maintenance yard project. It includes a project description, discussion of the environmental setting and impacts in resource areas such as aesthetics, air quality, biology, cultural resources, energy, fire protection, and geology. It also describes the regulatory framework and significance criteria for each issue area.
The document discusses Eaton's molded case circuit breakers, including their Series G and Series C products. It provides an overview of the circuit breakers and their applications in equipment such as panelboards, switchgear, motor control centers, enclosures, and busbar trunking tap-offs. The document also outlines Eaton's definite purpose, specialty, and mining circuit breakers.
This document presents a major project report on the design and analysis of a vibrating screen with a vibromotor to eliminate bearings. It begins with declarations and certificates of original work. It then provides an abstract, which summarizes that the frequent bearing failures in existing vibrating screens motivated redesigning the screen to eliminate bearings by introducing a vibromotor. Various design iterations were performed to match the vibromotor and screen natural frequencies. Finite element analysis validated that the redesign's stresses and deformations were within permissible limits. Fatigue analysis also showed acceptable frequency, displacement and stresses.
This document provides a 3-page design example calculation for fatigue analysis of an aluminum alloy structural component based on the European Standard ENV 1999-2 (Eurocode 9). It summarizes the steps taken, which include: (1) describing the structural detail and loading conditions, (2) developing the stress spectrum from measurements, (3) classifying the structural detail and selecting the appropriate S-N curve, (4) computing the fatigue damage using Miner's rule summation. The calculation shows that the fatigue damage DL is 0.659, indicating a safety margin against the failure criterion of DL = 1.0.
This document describes the design of the Waterspout, a compact rotorcraft intended to support special operations forces. A student design team from Penn State University and Technion - Israel Institute of Technology collaborated on the project. The Waterspout is designed to be launched from a submarine and complete missions including transporting small teams or payloads. It can carry out tasks autonomously or under operator control from the submarine. The document outlines the vehicle's aerodynamic, structural, mechanical and interface designs, including considerations for stability on water, launch and retrieval from the submarine, and operation in various weather conditions.
This document is the ASME B30.2-2001 safety standard for overhead and gantry cranes. It provides definitions, requirements, and guidelines related to the construction, installation, inspection, testing, maintenance, and operation of overhead and gantry cranes. The standard addresses topics such as crane markings, clearances, construction requirements, electrical systems, hoisting equipment, inspections, qualifications for operators, load handling procedures, and lockout/tagout procedures. The document establishes mandatory safety rules and advisory guidelines to help ensure the safe design, operation and maintenance of overhead and gantry cranes.
This document presents the preliminary design of a floating offshore wind turbine (FOWT) structure. It includes calculations for buoyancy, statics, and damage stability in intact and damage conditions. Structural members such as cylinders, stringers, decks, bulkheads, and crossbeams are designed and sized. Mooring line and ballasting systems are also analyzed. The design aims to develop a stable FOWT structure that meets classification society rules for safety in various operating conditions.
The document provides instructions and standards for designing concrete gravity dams. It serves as a guide for engineers and provides specialized technical information to assist in dam design. The manual covers all aspects of gravity dam design, from initial site investigations and layout, to stress analysis methods like the gravity and trial-load methods, to considerations for dynamic loading, construction, and the environment. It aims to support safe and adequate dam design while not relieving users of their design responsibilities.
This document presents the American Society of Mechanical Engineers (ASME) B30.2-2011 safety standard for overhead and gantry cranes. It covers the scope, definitions, references, general construction and installation requirements, inspection and testing procedures, operator training and operation guidelines, and maintenance training and maintenance practices for overhead and gantry cranes. The standard provides safety requirements for cranes with top running bridges, single or multiple girders, and top running trolley hoists. It was revised in 2011 and establishes the minimum performance and design criteria to help ensure cranes are safe to operate.
This document provides a technical manual on electric power plant design. It discusses site selection considerations, typical steam turbine power plant cycles and components, auxiliary systems, fuel and ash handling systems. The manual provides guidance on civil facilities, steam generators, turbines, condensers, feedwater systems, cooling water systems, and water conditioning. It aims to aid in the design of efficient and economical electric power plants.
This document provides a technical manual on electric power plant design. It discusses site selection considerations, typical steam turbine power plant cycles and components, auxiliary systems, fuel and ash handling systems. The manual provides guidance on civil facilities, steam generators, turbines, condensers, feedwater systems, cooling water systems, and water conditioning. It aims to aid in the design of efficient and economical electric power plants.
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Similar to Em 1110-2-1614 design of coastal revetments,seawalls, and bulkheads (20)
Em 1110-2-1614 design of coastal revetments,seawalls, and bulkheads
1. CECW-EH-D Department of the Army EM 1110-2-1614
U.S. Army Corps of Engineers
Engineer Washington, DC 20314-1000 30 June 1995
Manual
1110-2-1614
Engineering and Design
DESIGN OF COASTAL REVETMENTS,
SEAWALLS, AND BULKHEADS
Distribution Restriction Statement
Approved for public release; distribution is
unlimited.
2. EM 1110-2-1614
30 June 1995
US Army Corps
of Engineers
ENGINEERING AND DESIGN
Design of Coastal Revetments,
Seawalls, and Bulkheads
ENGINEER MANUAL
3. DEPARTMENT OF THE ARMY EM 1110-2-1614
U.S. Army Corps of Engineers
CECW-EH-D Washington, DC 20314-1000
Manual
No. 1110-2-1614 30 June 1995
Engineering and Design
DESIGN OF COASTAL REVETMENTS, SEAWALLS, AND BULKHEADS
1. Purpose. This manual provides guidance for the design of coastal revetment, seawalls, and
bulkheads.
2. Applicability. This manual applies to HQUSACE elements, major subordinate commands (MSC),
districts, laboratories, and field operating activities (FOA) having civil works responsibilities.
3. Discussion. In areas subject to wind-driven waves and surge, structures such as revetments,
seawalls, and bulkheads are commonly employed either to combat erosion or to maintain development
at an advanced position from the natural shoreline. Proper performance of such structures is pre-
dicated on close adherence to established design guidance. This manual presents important design
considerations and describes commonly available materials and structural components. All applicable
design guidance must be applied to avoid poor performance or failure. Study of all available structural
materials can lead, under some conditions, to innovative designs at significant cost savings for civil
works projects.
FOR THE COMMANDER:
This manual supersedes EM 1110-2-1614, dated 30 April 1985.
8. EM 1110-2-1614
30 Jun 95
List of Tables
Table Page Table Page
2-1 Relationships Among Tp, Ts, and Tz . . . . 2-4 E-4 Site Preparation Costs for
2-2 Rough Slope Runup Revetment Alternative . . . . . . . . . . . E-9
Correction Factors . . . . . . . . . . . . . . . 2-7 E-5 Material Costs for Armor
2-3 Suggested Values for Use in Stone Revetment Alternative . . . . . . . E-9
Determining Armor Weight E-6 Material Costs for Concrete
(Breaking Wave Conditions) . . . . . . . 2-9 Block Revetment Alternative . . . . . . . E-10
2-4 Layer Coefficients and Porosity E-7 Material Costs for Gabion
for Various Armor Units . . . . . . . . . . 2-11 Revetment Option . . . . . . . . . . . . . . E-10
2-5 H/HD=0 for Cover Layer Damage E-8 Material Costs for Soil-
Levels for Various Armor Types . . . . . 2-11 Cement Revetment Option . . . . . . . . E-10
2-6 Galvanic Series in Seawater . . . . . . . . . 2-17 E-9 Summary of Initial Costs
6-1 Environmental Design Considerations for the Revetment Options . . . . . . . . E-10
for Revetments, Seawalls, E-10 Material Costs for Steel
and Bulkheads . . . . . . . . . . . . . . . . . 6-3 Sheetpile Bulkhead Option . . . . . . . . E-11
B-1 Shiplap Block Weights . . . . . . . . . . . . B-15 E-11 Material Costs for Railroad Ties
E-1 Predicted Runup and Required and Steel H-Pile Bulkhead Option . . . E-11
Crest Elevations for Sample E-12 Material Costs for Gabion
Revetments Options . . . . . . . . . . . . . E-5 Bulkhead Option . . . . . . . . . . . . . . . E-12
E-2 Estimated Toe Scour Depths for E-13 Summary of Initial Costs for
Sample Revetment Options . . . . . . . . E-5 the Bulkhead Options . . . . . . . . . . . . E-12
E-3 Summary of Revetment E-14 Summary of Annual Costs for
Design Options . . . . . . . . . . . . . . . . . E-7 Revetment and Bulkhead Options . . . E-12
v
9. EM 1110-2-1614
30 Jun 95
Chapter 1 b. Bulkheads and seawalls. The terms bulkhead
Introduction and seawall are often used interchangeably. However, a
bulkhead is primarily intended to retain or prevent sliding
of the land, while protecting the upland area against wave
1-1. Purpose
action is of secondary importance. Seawalls, on the other
hand, are more massive structures whose primary purpose
This manual provides guidance for the design of coastal
is interception of waves. Bulkheads may be either can-
revetments, seawalls, and bulkheads.
tilevered or anchored (like sheetpiling) or gravity struc-
tures (such as rock-filled timber cribs). Their use is
1-2. Applicability
limited to those areas where wave action can be resisted
by such materials. In areas of intense wave action, mas-
This manual applies to HQUSACE elements, major
sive concrete seawalls are generally required. These may
subordinate commands, districts, laboratories, and field
have either vertical, concave, or stepped seaward faces.
operating activities having civil works responsibilities.
c. Disadvantages. Revetments, bulkheads, and
1-3. References
seawalls mainly protect only the upland area behind them.
All share the disadvantage of being potential wave reflec-
Required and related publications are listed in Appen-
tors that can erode a beach fronting the structure. This
dix A. Bibliographic items are cited in the text by author
problem is most prevalent for vertical structures that are
and year of publication, with full references listed in
nearly perfect wave reflectors and is progressively less
Appendix A. If any reference item contains information
prevalent for curved, stepped, and rough inclined struc-
conflicting with this manual, provisions of this manual
tures that absorb or dissipate increasing amounts of wave
govern.
energy.
1-4. Background
1-5. Discussion
Structures are often needed along either bluff or beach
The designer is responsible for developing a suitable solu-
shorelines to provide protection from wave action or to
tion which is economical and achieves the project’s
retain in situ soil or fill. Vertical structures are classified
purpose (see EM 1110-2-3300). Caution should be exer-
as either seawalls or bulkheads, according to their func-
cised, however, when using this manual for anything
tion, while protective materials laid on slopes are called
beyond preliminary design in which the primary goal is
revetments.
cost estimating and screening of alternatives. Final design
of large projects usually requires verification by hydraulic
a. Revetments. Revetments are generally constructed
model studies. The construction costs of large projects
of durable stone or other materials that will provide suf-
offer considerable opportunities for refinements and pos-
ficient armoring for protected slopes. They consist of an
sible cost savings as a result of model studies. Model
armor layer, filter layer(s), and toe protection. The armor
studies should be conducted for all but small projects
layer may be a random mass of stone or concrete rubble
where limited budgets control and the consequences of
or a well-ordered array of structural elements that inter-
failure are not serious.
lock to form a geometric pattern. The filter assures drain-
age and retention of the underlying soil. Toe protection is
needed to provide stability against undermining at the
bottom of the structure.
1-1
10. EM 1110-2-1614
30 Jun 95
Chapter 2 2-4. Design Conditions for Protective Measures
Functional Design
Structures must withstand the greatest conditions for
which damage prevention is claimed in the project plan.
All elements must perform satisfactorily (no damage
2-1. Shoreline Use exceeding ordinary maintenance) up to this condition, or it
must be shown that an appropriate allowance has been
Some structures are better suited than others for particular made for deterioration (damage prevention adjusted accor-
shoreline uses. Revetments of randomly placed stone dingly and rehabilitation costs amortized if indicated). As
may hinder access to a beach, while smooth revetments a minimum, the design must successfully withstand con-
built with concrete blocks generally present little difficulty ditions which have a 50 percent probability of being
for walkers. Seawalls and bulkheads can also create an exceeded during the project’s economic life. In addition,
access problem that may require the building of stairs. failure of the project during probable maximum conditions
Bulkheads are required, however, where some depth of should not result in a catastrophe (i.e., loss of life or inor-
water is needed directly at the shore, such as for use by dinate loss of money).
boaters.
2-5. Design Water Levels
2-2. Shoreline Form and Composition
The maximum water level is needed to estimate the maxi-
a. Bluff shorelines. Bluff shorelines that are com- mum breaking wave height at the structure, the amount of
posed of cohesive or granular materials may fail because runup to be expected, and the required crest elevation of
of scour at the toe or because of slope instabilities aggra- the structure. Minimum expected water levels play an
vated by poor drainage conditions, infiltration, and important role in anticipating the amount of toe scour that
reduction of effective stresses due to seepage forces. may occur and the depth to which the armor layer should
Cantilevered or anchored bulkheads can protect against extend.
toe scour and, being embedded, can be used under some
conditions to prevent sliding along subsurface critical a. Astronomical tides. Changes in water level are
failure planes. The most obvious limiting factor is the caused by astronomical tides with an additional possible
height of the bluff, which determines the magnitude of the component due to meteorological factors (wind setup and
earth pressures that must be resisted, and, to some extent, pressure effects). Predicted tide levels are published
the depth of the critical failure surface. Care must be annually by the National Oceanic and Atmospheric
taken in design to ascertain the relative importance of toe Administration (NOAA). The statistical characteristics of
scour and other factors leading to slope instability. Grav- astronomical tides at various U.S. ports were analyzed in
ity bulkheads and seawalls can provide toe protection for Harris (1981) with probability density functions of water
bluffs but have limited applicability where other slope sta- levels summarized in a series of graphs and tables. Simi-
bility problems are present. Exceptions occur in cases lar tables are available for the Atlantic Coast in Ebersole
where full height retention is provided for low bluffs and (1982) which also includes estimates of storm surge
where the retained soil behind a bulkhead at the toe of a values.
higher bluff can provide sufficient weight to help counter-
balance the active thrust of the bluff materials. b. Storm surge. Storm surge can be estimated by
statistical analysis of historical records, by methods
b. Beach shorelines. Revetments, seawalls, and described in Chapter 3 of the Shore Protection Manual
bulkheads can all be used to protect backshore develop- (SPM), or through the use of numerical models. The
ments along beach shorelines. As described in paragraph numerical models are usually justified only for large proj-
1-4c, an important consideration is whether wave reflec- ects. Some models can be applied to open coast studies,
tions may erode the fronting beach. while others can be used for bays and estuaries where the
effects of inundation must be considered.
2-3. Seasonal Variations of Shoreline Profiles
c. Lake levels. Water levels on the Great Lakes
Beach recession in winter and growth in summer can be are subject to both periodic and nonperiodic changes.
estimated by periodic site inspections and by computed Records dating from 1836 reveal seasonal and annual
variations in seasonal beach profiles. The extent of win- changes due to variations in precipitation. Lake levels
ter beach profile lowering will be a contributing factor in (particularly Ontario and Superior) are also partially
determining the type and extent of needed toe protection.
2-1
11. EM 1110-2-1614
30 Jun 95
controlled by regulatory works operated jointly by Cana-
dian and U.S. authorities. These tend to minimize water Hs d C1
(2-3)
exp C0
level variations in those lakes. Six-month forecasts of Hmo gT 2
lake levels are published monthly by the Detroit District p
(Figure 2-1).
where
2-6. Design Wave Estimation
C0, C1 = regression coefficients given as 0.00089 and
Wave heights and periods should be chosen to produce 0.834, respectively
the most critical combination of forces on a structure with
due consideration of the economic life, structural integrity, d = water depth at point in question (i.e., toe of
and hazard for events that may exceed the design con- structure)
ditions (see paragraph 2-4). Wave characteristics may be
based on an analysis of wave gauge records, visual obser- g = acceleration of gravity
vations of wave action, published wave hindcasts, wave
forecasts, or the maximum breaking wave at the site. Tp = period of peak energy density of the wave
Wave characteristics derived from such methods may be spectrum
for deepwater locations and must be transformed to the
structure site using refraction and diffraction techniques as A conservative value of Hs may be obtained by using
described in the SPM. Wave analyses may have to be
0.00136 for C0, which gives a reasonable upper envelope
performed for extreme high and low design water levels
for the data in Hughes and Borgman. Equation 2-3
and for one or more intermediate levels to determine the
should not be used for
critical design conditions.
2-7. Wave Height and Period Variability and d
< 0.0005 (2-4)
2
Significant Waves g Tp
a. Wave height.
or where there is substantial wave breaking.
(1) A given wave train contains individual waves of
varying height and period. The significant wave height, (3) In shallow water, Hs is estimated from deepwater
Hs, is defined as the average height of the highest conditions using the irregular wave shoaling and breaking
one-third of all the waves in a wave train. Other wave model of Goda (1975, 1985) which is available as part of
heights such as H10 and H1 can also be designated, where the Automated Coastal Engineering System (ACES) pack-
H10 is the average of the highest 10 percent of all waves, age (Leenknecht et al. 1989). Goda (1985) recommends
and H1 is the average of the highest 1 percent of all for the design of rubble structures that if the depth is less
waves. By assuming a Rayleigh distribution, it can be than one-half the deepwater significant wave height, then
stated that design should be based on the significant wave height at a
depth equal to one-half the significant deepwater wave
H10 ≈ 1.27 Hs (2-1) height.
b. Wave period. Wave period for spectral wave
and conditions is typically given as period of the peak energy
density of the spectrum, Tp. However, it is not uncom-
H1 ≈ 1.67 Hs (2-2)
mon to find references and design formulae based on the
average wave period (Tz) or the significant wave period
(2) Available wave information is frequently given as (Ts , average period of the one-third highest waves).
the energy-based height of the zeroth moment, Hmo. In Rough guidance on the relationship among these wave
deep water, Hs and Hmo are about equal; however, they periods is given in Table 2.1.
may be significantly different in shallow water due to
shoaling (Thompson and Vincent 1985). The following c. Stability considerations. The wave height to be
equation may be used to equate Hs from energy-based used for stability considerations depends on whether the
wave parameters (Hughes and Borgman 1987):
2-2
12. EM 1110-2-1614
30 Jun 95
Figure 2-1. Monthly lake level forecast
structure is rigid, semirigid, or flexible. Rigid structures 2-8. Wave Gauges and Visual Observations
that could fail catastrophically if overstressed may warrant
design based on H1. Semirigid structures may warrant a Available wave data for use by designers is often sparse
design wave between H1 and H10. Flexible structures are and limited to specific sites. In addition, existing gauge
usually designed for Hs or H10. Stability coefficients are data are sometimes analog records which have not been
coupled with these wave heights to develop various analyzed and that are difficult to process. Project funding
degrees of damage, including no damage.
2-3
13. EM 1110-2-1614
30 Jun 95
Table 2-1
Relationships among Tp, Ts, and Tz
Tz /Tp Ts /Tp Comments γ
1
0.67 0.80 Severe surf zone conditions NA
0.74 0.88 Pierson-Moskowitz spectrum2 1.0
0.80 0.93 Typical JONSWAP spectrum2 3.3
2
0.87 0.96 Swell from distant storms 10.0
1
Developed from data in Ahrens (1987).
2
Developed from Goda (1987).
and time constraints may prohibit the establishment of a 2-11. Breaking Waves
viable gauging program that would provide sufficient
digital data for reliable study. Visual observations from a. Wave heights derived from a hindcast should be
shoreline points are convenient and inexpensive, but they checked against the maximum breaking wave that can be
have questionable accuracy, are often skewed by the supported at the site given the available depth at the
omission of extreme events, and are sometimes difficult to design still-water level and the nearshore bottom slope.
extrapolate to other sites along the coast. A visual wave Figure 2-2 (Weggel 1972) gives the maximum breaker
observation program is described in Schneider (1981). height, Hb, as a function of the depth at the structure, ds ,
Problems with shipboard observations are similar to shore nearshore bottom slope, m, and wave period, T. Design
observations. wave heights, therefore, will be the smaller of the maxi-
mum breaker height or the hindcast wave height.
2-9. Wave Hindcasts
b. For the severe conditions commonly used for
Designers should use the simple hindcasting methods in design, Hmo may be limited by breaking wave conditions.
ACES (Leenknecht et al. 1989) and hindcasts developed A reasonable upper bound for Hmo is given by
by the U.S. Army Engineer Waterways Experiment Sta-
tion (WES) (Resio and Vincent 1976-1978; Corson et al.
1981) for U.S. coastal waters using numerical models.
2πd
These later results are presented in a series of tables for Hmo 0.10 Lp tanh
L
(2-5)
max
each of the U.S. coasts. They give wave heights and p
periods as a function of season, direction of wave
approach, and return period; wave height as a function of
return period and seasons combined; and wave period as a where Lp is wavelength calculated using Tp and d.
function of wave height and approach angle. Several
other models exist for either shallow or deep water. Spe- 2-12. Height of Protection
cific applications depend on available wind data as well
as bathymetry and topography. Engineers should stay When selecting the height of protection, one must consid-
abreast of developments and choose the best method for a er the maximum water level, any anticipated structure
given analysis. Contact the Coastal Engineering Research settlement, freeboard, and wave runup and overtopping.
Center (CERC) at WES for guidance in special cases.
2-13. Wave Runup
2-10. Wave Forecasts
Runup is the vertical height above the still-water level
Wave forecasts can be performed using the same method- (swl) to which the uprush from a wave will rise on a
ologies as those for the wave hindcasts. Normally, the structure. Note that it is not the distance measured along
Corps hindcasts waves for project design, and the Navy the inclined surface.
forecasts waves to plan naval operations.
2-4
14. EM 1110-2-1614
30 Jun 95
Figure 2-2. Design breaker height
a. Rough slope runup. a, b = regression coefficients determined as 1.022
and 0.247, respectively
(1) Maximum runup by irregular waves on riprap-
covered revetments may be estimated by (Ahrens and ξ= surf parameter defined by
Heimbaugh 1988)
tan θ
ξ
Rmax aξ (2-6) 2 π Hmo 1/2 (2-7)
Hmo 1 bξ
gT 2
p
where
where θ is the angle of the revetment slope with the hori-
Rmax = maximum vertical height of the runup above zontal. Recalling that the deepwater wavelength may be
the swl determined by
2-5
15. EM 1110-2-1614
30 Jun 95
2
g Tp Rmax in Equation 2-6 by the correction factor listed in
Lo (2-8) Table 2-2, and divide by the correction factor for quarry-
2π stone. For example, to estimate Rmax for a stepped 1:1.5
slope with vertical risers, determine Rmax by Equation 2-6
and multiply by (correction factor for stepped
the surf parameter is seen to be the ratio of revetment slope/correction factor for quarrystone) (0.75/0.60) = 1.25.
slope to square root of wave steepness. The surf param- Rmax for the stepped slope is seen to be 25 percent greater
eter is useful in defining the type of breaking wave con- than for a riprap slope.
ditions expected on the structure, as shown in Figure 2-3.
b. Smooth slope runup. Runup values for smooth
slopes may be found in design curves in the SPM. How-
ever, the smooth slope runup curves in the SPM were
based on monochromatic wave tests rather than more
realistic irregular wave conditions. Using Hs for wave
height with the design curves will yield runup estimates
that may be exceeded by as much as 50 percent by waves
in the wave train with heights greater than Hs. Maximum
runup may be estimated by using Equation 2-6 and con-
verting the estimate to smooth slope by dividing the result
by the quarrystone rough slope correction factor in
Table 2-2.
c. Runup on walls. Runup determinations for ver-
tical and curved-face walls should be made using the
guidance given in the SPM.
2-14. Wave Overtopping
a. It is generally preferable to design shore protec-
tion structures to be high enough to preclude overtopping.
In some cases, however, prohibitive costs or other con-
siderations may dictate lower structures than ideally
needed. In those cases it may be necessary to estimate
the volume of water per unit time that may overtop the
structure.
b. Wave overtopping of riprap revetments may be
estimated from the dimensionless equation (Ward 1992)
Figure 2-3. Surf parameter and breaking wave types
(2) A more conservative value for Rmax is obtained by Q′ C0 e
C1 F′
e
C2 m (2-9)
using 1.286 for a in Equation 2-6. Maximum runups
determined using this more conservative value for a pro-
vide a reasonable upper limit to the data from which the where Q′ is dimensionless overtopping defined as
equation was developed.
Q
(3) Runup estimates for revetments covered with Q′ (2-10)
3 1/2
materials other than riprap may be obtained with the g Hmo
rough slope correction factors in Table 2-2. Table 2-2
was developed for earlier estimates of runup based on
monochromatic wave data and smooth slopes. To use the where Q is dimensional overtopping in consistent units,
correction factors in Table 2-2 with the irregular wave such as cfs/ft. F′ in Equation 2-9 is dimensionless free-
rough slope runup estimates of Equation 2-6, multiply board defined as
2-6
16. EM 1110-2-1614
30 Jun 95
Table 2-2
Rough Slope Runup Correction Factors (Carstea et al. 1975b)
Relative Size Correction Factor
Armor Type Slope (cot θ)
H / Kra,b r
Quarrystone 1.5 3 to 4 0.60
Quarrystone 2.5 3 to 4 0.63
Quarrystone 3.5 3 to 4 0.60
Quarrystone 5 3 0.60
Quarrystone 5 4 0.68
Quarrystone 5 5 0.72
Concrete Blocksc Any 6b 0.93
Stepped slope with vertical risers 1.5 1 ≤ Ho’/K r
d
0.75
Stepped slope with vertical risers 2.0 1 ≤ Ho’/Krd 0.75
Stepped slope with vertical risers 3.0 1 ≤ Ho’/K r
d
0.70
Stepped slope with rounded edges 3.0 1 ≤ Ho’/K r
d
0.86
Concrete Armor Units
Tetrapods random two layers 1.3 to 3.0 - 0.45
Tetrapods uniform two layers 1.3 to 3.0 - 0.51
Tribars random two layers 1.3 to 3.0 - 0.45
Tribars uniform one layer 1.3 to 3.0 - 0.50
a
Kr is the characteristic height of the armor unit perpendicular to the slope. For quarrystone, it is the nominal diameter; for armor units,
the height above the slope.
b
Use Ho’ for ds/Ho’ > 3; and the local wave height, Hs for ds/Ho’ ≤ 3.
c
Perforated surfaces of Gobi Blocks, Monoslaps, and concrete masonry units placed hollows up.
d
Kr is the riser height.
F variety of fronting berms, revetments, and steps. Infor-
F′ (2-11) mation on overtopping rates for a range of configurations
2 1/3
H Lo
mo is available in Ward and Ahrens (1992). For bulkheads
and simple vertical seawalls with no fronting revetment
where F is dimensional freeboard (vertical distance of and a small parapet at the crest, the overtopping rate may
crest above swl). The remaining terms in Equation 2-9 be calculated from
are m (cotangent of revetment slope) and the regression
coefficients C0, C1, and C2 defined as
C0 exp C1 F′ C2
F (2-13)
Q′ d
C0 0.4578 s
C1 29.45 (2-12) where Q′ is defined in Equation 2-10, F′ is defined in
C2 0.8464 Equation 2-11, ds is depth at structure toe, and the regres-
sion coefficients are defined by
C0 0.338
The coefficients listed above were determined for dimen-
C1 7.385 (2-14)
sionless freeboards in the range 0.25 < F′ < 0.43, and
revetment slopes of 1:2 and 1:3.5. C2 2.178
c. Overtopping rates for seawalls are complicated by
the numerous shapes found on the seawall face plus the
2-7
17. EM 1110-2-1614
30 Jun 95
For other configurations of seawalls, Ward and Ahrens θ = is structure slope (from the horizontal)
(1992) should be consulted, or physical model tests should
be performed. Stones within the cover layer can range from 0.75 to
1.25 W as long as 50 percent weigh at least W and the
2-15. Stability and Flexibility gradation is uniform across the structure’s surface. Equa-
tion 2-15 can be used for preliminary and final design
Structures can be built by using large monolithic masses when H is less than 5 ft and there is no major overtop-
that resist wave forces or by using aggregations of smaller ping of the structure. For larger wave heights, model
units that are placed either in a random or in a tests are preferable to develop the optimum design.
well-ordered array. Examples of these are large rein- Armor weights determined with Equation 2-15 for mono-
forced concrete seawalls, quarrystone or riprap revet- chromatic waves should be verified during model tests
ments, and geometric concrete block revetments. The using spectral wave conditions.
massive monoliths and interlocking blocks often exhibit
superior initial strength but, lacking flexibility, may not b. Equation 2-15 is frequently presented as a stabi-
accommodate small amounts of differential settlement or lity formula with Ns as a stability number. Rewriting
toe scour that may lead to premature failure. Randomly Equation 2-15 as
placed rock or concrete armor units, on the other hand,
experience settlement and readjustment under wave attack, H
and, up to a point, have reserve strength over design Ns
1/3
γ (2-16)
conditions. They typically do not fail catastrophically if W r 1
minor damages are inflicted. The equations in this γ γ
r w
chapter are suitable for preliminary design for major
structures. However, final design will usually require
verification of stability and performance by hydraulic it is readily seen that
model studies. The design guidance herein may be used
for final design for small structures where the conse- Ns KD cot θ 1/3 (2-17)
quences of failure are minor. For those cases, project
funds are usually too limited to permit model studies.
By equating Equations 2-16 and 2-17, W is readily
2-16. Armor Unit Stability obtained.
c. For irregular wave conditions on revetments of
a. The most widely used measure of armor unit
dumped riprap, the recommended stability number is
stability is that developed by Hudson (1961) which is
given in Equation 2-15:
Nsz 1.14 cot1/6 θ (2-18)
γr H 3
W where Nsz is the zero-damage stability number, and the
γ 3 (2-15) value 1.14 is obtained from Ahrens (1981b), which rec-
KD r
γ 1 cot θ
ommended a value of 1.45 and using Hs with Equation 2-
w 16, then modified based on Broderick (1983), which
found using H10 (10 percent wave height, or average of
where highest 10-percent of the waves) in Equation 2-16 pro-
vided a better fit to the data. Assuming a Rayleigh wave
W = required individual armor unit weight, lb (or W50 height distribution, H10 ≈ 1.27 Hs. Because Hs is more
for graded riprap) readily available than H10, the stability number in Equa-
tion 2-17 was adjusted (1.45/1.27 = 1.14) to allow Hs to
γr = specific weight of the armor unit, lb/ft3 be used in the stability equation while providing the more
conservative effect of using H10 for the design.
H = monochromatic wave height
d. Stability equations derived from an extensive
KD= stability coefficient given in Table 2-3 series of laboratory tests in The Netherlands were pre-
sented in van der Meer and Pilarczyk (1987) and van der
γw = specific weight of water at the site (salt or fresh)
2-8
18. EM 1110-2-1614
30 Jun 95
Table 2-3
Suggested Values for Use In Determining Armor Weight (Breaking Wave Conditions)
Armor Unit n1 Placement Slope (cot θ) KD
Quarrystone
Smooth rounded 2 Random 1.5 to 3.0 1.2
Smooth rounded >3 Random 1.5 to 3.0 1.6
Rough angular 1 Random 1.5 to 3.0 Do Not Use
Rough angular 2 Random 1.5 to 3.0 2.0
Rough angular >3 Random 1.5 to 3.0 2.2
2
Rough angular 2 Special 1.5 to 3.0 7.0 to 20.0
Graded riprap3 24 Random 2.0 to 6.0 2.2
Concrete Armor Units
Tetrapod 2 Random 1.5 to 3.0 7.0
Tripod 2 Random 1.5 to 3.0 9.0
Tripod 1 Uniform 1.5 to 3.0 12.0
Dolos 2 Random 2.0 to 3.05 15.06
1
n equals the number of equivalent spherical diameters corresponding to the median stone weight that would fit within the layer thickness.
2
Special placement with long axes of stone placed perpendicular to the slope face. Model tests are described in Markle and David-
son (1979).
3
Graded riprap is not recommended where wave heights exceed 5 ft.
4
By definition, graded riprap thickness is two times the diameter of the minimum W50 size.
5
Stability of dolosse on slope steeper than 1 on 2 should be verified by model tests.
6
No damage design (3 to 5 percent of units move). If no rocking of armor (less than 2 percent) is desired, reduce KD by approximately
50 percent.
Meer (1988a, 1988b). Two stability equations were pre- slopes of 1:2 or 1:3, or S = 3 for revetment slopes of 1:4
sented. For plunging waves, to 1:6. The number of waves is difficult to estimate, but
Equations 2-19 and 2-20 are valid for N = 1,000 to N =
S 0.2 0.5 7,000, so selecting 7,000 waves should provide a conser-
Ns 6.2 P 0.18 ξz (2-19) vative estimate for stability. For structures other than
N riprap revetments, additional values of P and S are pre-
sented in van der Meer (1988a, 1988b).
and for surging or nonbreaking waves,
e. Equations 2-19 and 2-20 were developed for
S 0.2 deepwater wave conditions and do not include a wave-
Ns 1.0 P 0.13 cot θ ξz
P (2-20) height truncation due to wave breaking. van der Meer
N therefore recommends a shallow water correction given as
where 1.40 Hs
Ns (shallow water) (2-21)
H2
P = permeability coefficient
Ns (deep water)
S = damage level
where H2 is the wave height exceeded by 2 percent of the
N = number of waves waves. In deep water, H2 ≈ 1.40 Hs , and there is no
correction in Equation 2-21.
P varies from P = 0.1 for a riprap revetment over an
impermeable slope to P = 0.6 for a mound of armor stone
with no core. For the start of damage S = 2 for revetment
2-9
19. EM 1110-2-1614
30 Jun 95
2-17. Layer Thickness (2) The upper limit of the W100 stone, W100 max,
should equal the maximum size that can be economically
a. Armor units. As indicated in the SPM, the thick- obtained from the quarry but not exceed 4 times W50 min.
ness of an armor layer can be determined by
Equation 2-22: (3) The lower limit of the W100 stone, W100 min, should
not be less than twice W50 min.
1/3 (4) The upper limit of the W50 stone, W50 max, should
n k∆
W (2-22)
r w be about 1.5 times W50 min.
r
(5) The lower limit of the W15 stone, W15 min, should
where r is the layer thickness in feet, n is the number of
be about 0.4 times W50 min.
armor units that would fit within the layer thickness (typi-
cally n=2), and k∆ is the layer coefficient given in (6) The upper limit of the W15 stone, W15 max, should
Table 2-4. For estimating purposes, the number of armor be selected based on filter requirements specified in EM
units, Nr, for a given surface area in square feet, A, is 1110-2-1901. It should slightly exceed W50 min.
2
(7) The bulk volume of stone lighter than W15 min in a
P wr 3
(2-23) gradation should not exceed the volume of voids in the
Nr A n k∆ 1
100 W revetment without this lighter stone. In many cases, how-
ever, the actual quarry yield available will differ from the
where P is the average porosity of the cover layer from gradation limits specified above. In those cases the
Table 2-4. designer must exercise judgment as to the suitability of
the supplied gradation. Primary consideration should be
b. Graded riprap. The layer thickness for graded given to the W50 min size under those circumstances. For
riprap must be at least twice the nominal diameter of the instance, broader than recommended gradations may be
W50 stone, where the nominal diameter is the cube root of suitable if the supplied W50 is somewhat heavier than the
the stone volume. In addition, rmin should be at least required W50 min. Segregation becomes a major problem,
25 percent greater than the nominal diameter of the however, when the riprap is too broadly graded.
largest stone and should always be greater than a mini-
mum layer thickness of 1 ft (Ahrens 1975). Therefore, 2-18. Reserve Stability
a. General. A well-known quality of randomly
W 1/3 placed rubble structures is the ability to adjust and resettle
rmin 2.0 50 min ;
max under wave conditions that cause minor damages. This
γr (2-24) has been called reserve strength or reserve stability.
Structures built of regular or uniformly placed units such
W 1/3 as concrete blocks commonly have little or no reserve
1.25 100 ; 1 ft
γ stability and may fail rapidly if submitted to greater than
r design conditions.
where rmin is the minimum layer thickness perpendicular
b. Armor units. Values for the stability coefficient,
to the slope. Greater layer thicknesses will tend to
KD, given in paragraph 2-16 allow up to 5 percent dam-
increase the reserve strength of the revetment against
ages under design wave conditions. Table 2-5 contains
waves greater than the design. Gradation (within broad
values of wave heights producing increasing levels of
limits) appears to have little effect on stability provided
damage. The wave heights are referenced to the
the W50 size is used to characterize the layer. The fol-
zero-damage wave height (HD=0) as used in Equation 2-15.
lowing are suggested guidelines for establishing gradation
Exposure of armor sized for HD=0 to these larger wave
limits (from EM 1110-2-1601) (see also Ahrens 1981a):
heights should produce damages in the range given. If
the armor stone available at a site is lighter than the stone
(1) The lower limit of W50 stone, W50 min, should be size calculated using the wave height at the site, the zero-
selected based on stability requirements using damage wave height for the available stone can be
Equation 2-15.
2-10
20. EM 1110-2-1614
30 Jun 95
Table 2-4
Layer Coefficients and Porosity for Various Armor Units
Armor Unit n Placement K∆ P (%)
Quarrystone (smooth) 2 Random 1.00 38
Quarrystone (rough) 2 Random 1.00 37
Quarrystone (rough) ≥3 Random 1.00 40
a
Graded riprap 2 Random N/A 37
Tetrapod 2 Random 1.04 50
Tribar 2 Random 1.02 54
Tribar 1 Uniform 1.13 47
Dolos 2 Random 0.94 56
a
By definition, riprap thickness equals two cubic lengths of W50 or 1.25 W100.
Table 2-5
H/HD=0 for Cover Layer Damage Levels for Various Armor Types (H/HD=0 for Damage Level in Percent)
Unit 0 ≤ %D < 5 5 ≤ %D < 10 10 ≤ %D < 15 15 ≤ %D < 20 20 ≤ %D ≤ 30
Quarrystone (smooth) 1.00 1.08 1.14 1.20 1.29
Quarrystone (angular) 1.00 1.08 1.19 1.27 1.37
Tetrapods 1.00 1.09 1.17 1.24 1.32
Tribars 1.00 1.11 1.25 1.36 1.50
Dolos 1.00 1.10 1.14 1.17 1.20
calculated, and a ratio with the site’s wave height can be structure which prevents waves from scouring and under-
used to estimate the damage that can be expected with the cutting it. Factors that affect the severity of toe scour
available stone. All values in the table are for randomly include wave breaking (when near the toe), wave runup
placed units, n=2, and minor overtopping. The values in and backwash, wave reflection, and grain-size distribution
Table 2-5 are adapted from Table 7-8 of the SPM. The of the beach or bottom materials. The revetment toe
SPM values are for breakwater design and nonbreaking often requires special consideration because it is subjected
wave conditions and include damage levels above to both hydraulic forces and the changing profiles of the
30 percent. Due to differences in the form of damage to beach fronting the revetment. Toe stability is essential
breakwaters and revetments, revetments may fail before because failure of the toe will generally lead to failure
damages reach 30 percent. The values should be used throughout the entire structure. Specific guidance for toe
with caution for damage levels from breaking and non- design based on either prototype or model results has not
breaking waves. been developed. Some empirical suggested guidance is
contained in Eckert (1983).
c. Graded riprap. Information on riprap reserve
stability can be found in Ahrens (1981a). Reserve stabi- b. Revetments.
lity appears to be primarily related to the layer thickness
although the median stone weight and structure slope are (1) Design procedure. Toe protection for revetments
also important. is generally governed by hydraulic criteria. Scour can be
caused by waves, wave-induced currents, or tidal currents.
2-19. Toe Protection For most revetments, waves and wave-induced currents
will be most important. For submerged toe stone, weights
a. General. Toe protection is supplemental can be predicted based on Equation 2-25:
armoring of the beach or bottom surface in front of a
2-11
21. EM 1110-2-1614
30 Jun 95
γr H 3 by the moment of its own weight supported by the zone
Wmin of bearing beneath the toe of the structure. Possible toe
γ 3 (2-25) configurations are shown in Figure 2-5.
N r 1
3
γ
s
w (2) Seepage forces. The hydraulic gradients of
seepage flows beneath vertical walls can significantly
where Ns is the design stability number for rubble toe increase toe scour. Steep exit gradients reduce the net
protection in front of a vertical wall, as indicated in the effective weight of the soil, making sediment movement
SPM (see Figure 2-7). For toe structures exposed to under waves and currents more likely. This seepage flow
wave action, the designer must select either Equation 2-15 may originate from general groundwater conditions, water
which applies at or near the water surface or Equation 2- derived from wave overtopping of the structure, or from
25 above. It should be recognized that Equation 2-25 precipitation. A quantitative treatment of these factors is
yields a minimum weight and Equation 2-15 yields a presented in Richart and Schmertmann (1958).
median weight. Stone selection should be based on the
weight gradations developed from each of the stone (3) Toe apron width. The toe apron width will
weights. The relative importance of these factors depends depend on geotechnical and hydraulic factors. The pas-
on the location of the structure and its elevation with sive earth pressure zone must be protected for a sheet-pile
respect to low water. When the toe protection is for wall as shown in Figure 2-6. The minimum width, B,
scour caused by tidal or riverine currents alone, the from a geotechnical perspective can be derived using the
designer is referred to EM 1110-2-1601. Virtually no Rankine theory as described in Eckert (1983). In these
data exist on currents acting on toe stone when they are a cases the toe apron should be wider than the product of
product of storm waves and tidal or riverine flow. It is the effective embedment depth and the coefficient of
assumed that the scour effects are partially additive. In passive earth pressure for the soil. Using hydraulic con-
the case of a revetment toe, some conservatism is pro- siderations, the toe apron should be at least twice the
vided by using the design stability number for toe protec- incident wave height for sheet-pile walls and equal to the
tion in front of a vertical wall as suggested above. incident wave height for gravity walls. In addition, the
apron should be at least 40 percent of the depth at the
(2) Suggested toe configurations. Guidance contained structure, ds. Greatest width predicted by these geotech-
in EM 1110-2-1601 which relates to toe design con- nical and hydraulic factors should be used for design. In
figurations for flood control channels is modified for all cases, undercutting and unraveling of the edge of the
coastal revetments and presented in Figure 2-4. This is apron must be minimized.
offered solely to illustrate possible toe configurations.
Other schemes known to be satisfactory by the designer (4) Toe stone weight. Toe stone weight can be
are also acceptable. Designs I, II, IV, and V are for up to predicted based on Figure 2-7 (from Brebner and
moderate toe scour conditions and construction in the dry. Donnelly 1962)). A design wave between H1 and H10 is
Designs III and VI can be used to reduce excavation suggested. To apply the method assume a value of dt the
when the stone in the toe trench is considered sacrificial distance from the still water level to the top of the toe. If
and will be replaced after infrequent major events. A the resulting stone size and section geometry are not
thickened toe similar to that in Design III can be used for appropriate, a different dt should be tried. Using the
underwater construction except that the toe stone is placed median stone weight determined by this method, the
on the existing bottom rather than in an excavated trench. allowable gradation should be approximately 0.5 to
1.5 W.
c. Seawalls and bulkheads.
2-20. Filters
(1) General considerations. Design of toe pro-
tection for seawalls and bulkheads must consider geotech- A filter is a transitional layer of gravel, small stone, or
nical as well as hydraulic factors. Cantilevered, anchored, fabric placed between the underlying soil and the struc-
or gravity walls each depend on the soil in the toe area ture. The filter prevents the migration of the fine soil
for their support. For cantilevered and anchored walls, particles through voids in the structure, distributes the
this passive earth pressure zone must be maintained for weight of the armor units to provide more uniform set-
stability against overturning. Gravity walls resist sliding tlement, and permits relief of hydrostatic pressures within
through the frictional resistance developed between the the soils. For areas above the waterline, filters also
soil and the base of the structure. Overturning is resisted
2-12
22. EM 1110-2-1614
30 Jun 95
Figure 2-4. Revetment toe protection (Designs I through VI)
prevent surface water from causing erosion (gullies) where the left side of Equation 2-27 is intended to prevent
beneath the riprap. In general form layers have the rela- piping through the filter and the right side of Equation 2-
tion given in Equation 2-26: 27 provides for adequate permeability for structural
bedding layers. This guidance also applies between suc-
d15 upper cessive layers of multilayered structures. Such designs
< 4 (2-26) are needed where a large disparity exists between the void
d85 under
size in the armor layer and the particle sizes in the under-
lying layer.
Specific design guidance for gravel and stone filters is
contained in EM 1110-2-1901 and EM 1110-2-2300 (see b. Riprap and armor stone underlayers.
also Ahrens 1981a), and guidance for cloth filters is con- Underlayers for riprap revetments should be sized as in
tained in CW 02215. The requirements contained in these Equation 2-28,
will be briefly summarized in the following paragraphs.
a. Graded rock filters. The filter criteria can be d15 armor
<4 (2-28)
stated as: d85 filter
d15 filter d15 filter
< 4 to 5 < (2-27)
d85 soil d15 soil
2-13
23. EM 1110-2-1614
30 Jun 95
Figure 2-5. Seawall and bulkhead toe protection
where the stone diameter d can be related to the stone For armor and underlayers of uniform-sized quarrystone,
weight W through Equation 2-22 by setting n equal to 1.0. the first underlayer should be at least 2 stone diameters
This is more restrictive than Equation 2-27 and provides thick, and the individual units should weigh about
an additional margin against variations in void sizes that one-tenth the units in the armor layer. When concrete
may occur as the armor layer shifts under wave action. armor units with KD > 12 are used, the underlayer should
For large riprap sizes, each underlayer should meet the be quarrystone weighing about one-fifth of the overlying
condition specified in Equation 2-28, and the layer thick- armor units.
nesses should be at least 3 median stone diameters.
2-14
24. EM 1110-2-1614
30 Jun 95
c. Plastic filter fabric selection. Selection of filter
cloth is based on the equivalent opening size (EOS),
which is the number of the U.S. Standard Sieve having
openings closest to the filter fabric openings. Material
will first be retained on a sieve whose number is equal to
the EOS. For granular soils with less than 50 percent
fines (silts and clays) by weight (passing a No. 200
sieve), select the filter fabric by applying Equation 2-29:
Figure 2-6. Toe aprons for sheet-pile bulkheads
Figure 2-7. Value of Ns, toe protection design for vertical walls (from Brebner and Donnelly 1962)
2-15
25. EM 1110-2-1614
30 Jun 95
EOS sieve
≤ 1 (2-29)
d85 soil
For other soils, the EOS should be no larger than the
openings in a No. 70 sieve. Furthermore, no fabric
should be used whose EOS is greater than 100, and none
should be used alone when the underlying soil contains
more than 85 percent material passing a No. 200 sieve.
In those cases, an intermediate sand layer may provide the
necessary transition layer between the soil and the fabric.
Finally, the gradient ratio of the filter fabric is limited to
a maximum value of three. That is, based on a head
permeability test, the hydraulic gradient through the
fabric and the 1 in. of soil adjacent to the fabric (i1)
divided by the hydraulic gradient of the 2 in. of soil
between 1 and 3 in. above the fabric (i2) is:
i1
Gradient ratio ≤ 3 (2-30)
i2
Figure 2-8. Use of filter cloth under revetment and toe
protection stone
Studies such as those in Chen et al. (1981) suggest that
these filter cloth selection requirements may be somewhat the slope. Dropping stone can rupture some fabrics even
restrictive. with free falls of only 1 ft, although Dunham and Barrett
(1974) suggest that stones weighing up to 250 lb can
d. Filter fabric placement. Experience indicates that safely be dropped from 3 ft. Greater drop heights are
synthetic cloths can retain their strength even after long allowable under water where blocks up to 1 ton can be
periods of exposure to both salt and fresh water. To dropped through water columns of at least 5 ft.
provide good performance, however, a properly selected
cloth should be installed with due regard for the following 2-21. Flank Protection
precautions. First, heavy armor units may stretch the
cloth as they settle, eventually causing bursting of the Flank protection is needed to limit vulnerability of a
fabric in tension. A stone bedding layer beneath armor structure from the tendency for erosion to continue around
units weighing more than 1 ton for above-water work its ends. Return sections are generally needed at both
(1.5 tons for underwater construction) is suggested (Dun- ends to prevent this. Sheet-pile structures can often be
ham and Barrett 1974), and multiple underlayers may be tied well into existing low banks, but the return sections
needed under primary units weighing more than 10 tons. of other devices such as rock revetments must usually be
Filter guidance must be properly applied in these cases. progressively lengthened as erosion continues. Extension
Second, the filter cloth should not extend seaward of the of revetments past the point of active erosion should be
armor layer; rather, it should terminate a few feet land- considered but is often not feasible. In other cases, a
ward of the armor layers as shown in Figure 2-8. Third, thickened end section, similar to toe protection, can be
adequate overlaps between sheets must be provided. For used when the erosion rate is mild.
lightweight revetments this can be as little as 12 in. and
may increase to 3 ft for larger underwater structures. 2-22. Corrosion
Fourth, sufficient folds should be included to eliminate
tension and stretching under settlement. Securing pins Corrosion is a primary problem with metals in brackish
with washers is also advisable at 2-to 5-ft intervals along and salt water, particularly in the splash zone where mate-
the midpoint of the overlaps. Last, proper stone place- rials are subjected to continuous wet-dry cycles. Mild
ment requires beginning at the toe and proceeding up carbon steel, for instance, will quickly corrode in such
2-16