This document provides an overview of diversion headworks for supplying water to irrigation canals. It discusses the key components of diversion headworks including weirs/barrages, undersluices, divide walls, fish ladders, canal head regulators, and river training works. It also examines site selection factors and design considerations to prevent failures from subsurface piping or uplift and surface scouring. Khosla's theory improved earlier theories by accounting for complex seepage patterns below hydraulic structures.
This document provides an overview of hydraulic structures and their components. It defines a hydraulic structure as anything partially or fully submerged in water that disrupts natural flow. Weirs raise water levels while barrages can adjust levels using gates. Dams form deep reservoirs. Diversion structures include temporary barriers and permanent weirs/barrages. Key components are the weir/barrage, divide wall, fish ladder, approach channel, sluices, silt prevention, head regulator, and river training works like guide banks and spurs. The document describes the purpose and design of each component.
Diversion headworks are structures constructed at the head of a canal to divert river water into the canal. They include weirs or barrages that raise the water level, as well as other components like canal head regulators, divide walls, fish ladders, and scouring sluices. The objectives of diversion headworks are to raise water levels, form water storage, control silt entry, and regulate water levels during different seasons. Key considerations for siting diversion headworks include river characteristics, elevation, foundation stability, and access for construction materials.
Types- selection of the suitable site for the diversion headwork components
of diversion headwork- Causes of failure of structure on pervious foundation- Khosla’s theory- Design of concrete sloping
glacis weir.
This document discusses the components and purpose of diversion headworks. It describes how weirs or barrages are constructed across perennial rivers to divert water into canals for irrigation and other uses. The key components include the weir/barrage, undersluices, divide wall, fish ladder, canal head regulator, and silt excluders. Together these components raise the river level, regulate water flow into canals, control silt entry, and allow for fish passage, while river training works guide the river flow safely around the diversion structure.
This document provides an overview of hydraulic structures and their components. It defines a hydraulic structure as anything partially or fully submerged in water that disrupts natural flow. Weirs raise water levels while barrages can adjust levels using gates. Dams form deep reservoirs. Diversion structures include temporary barriers and permanent weirs/barrages. Key components are the weir/barrage, divide wall, fish ladder, approach channel, sluices, silt prevention, head regulator, and river training works like guide banks and spurs. The document describes the purpose and design of each component.
Diversion headworks are structures constructed at the head of a canal to divert river water into the canal. They include weirs or barrages that raise the water level, as well as other components like canal head regulators, divide walls, fish ladders, and scouring sluices. The objectives of diversion headworks are to raise water levels, form water storage, control silt entry, and regulate water levels during different seasons. Key considerations for siting diversion headworks include river characteristics, elevation, foundation stability, and access for construction materials.
Types- selection of the suitable site for the diversion headwork components
of diversion headwork- Causes of failure of structure on pervious foundation- Khosla’s theory- Design of concrete sloping
glacis weir.
This document discusses the components and purpose of diversion headworks. It describes how weirs or barrages are constructed across perennial rivers to divert water into canals for irrigation and other uses. The key components include the weir/barrage, undersluices, divide wall, fish ladder, canal head regulator, and silt excluders. Together these components raise the river level, regulate water flow into canals, control silt entry, and allow for fish passage, while river training works guide the river flow safely around the diversion structure.
Topics:
1. Types of Diversion Head Works
2. Weirs and Barrages
3. Layout Diversion Head Works
4. Causes of Failures of Weirs and Barrages on Permeable Foundations
5. Silt Ejectors and Silt Excluders
Canal headworks are hydraulic structures constructed across rivers to divert water into canals. They raise the river water level and regulate flows. There are two main types - diversion and storage headworks. Diversion headworks like weirs and barrages divert water without storage, while dams form storage reservoirs. Key components include weirs/barrages, divide walls, fish ladders, under sluices, silt excluders, and head regulators. Location depends on river characteristics, and sites must be accessible with suitable foundations. Failure can occur through subsurface piping/uplift or surface scouring during floods. Precautions include reducing exit gradients, providing sheet piles, ensuring floor thickness, using filters and energy
Diversion headworks, also known as canal headworks, are structures built across rivers to raise the water level and divert water into canals. They serve several purposes, including increasing the area that can be irrigated, regulating water supply to canals, controlling silt entry, and reducing water level fluctuations. There are two types - temporary structures built after floods, and permanent concrete or masonry structures like weirs and barrages. The location depends on the river's characteristics, with the trough or alluvial stage generally preferred. Key components include the weir/barrage, under sluices, divide wall, and head regulators.
This document provides information about hydraulic structures and diversion head works. It discusses that a hydraulic structure disrupts natural water flow and examples include dams and weirs. It then describes the key components of diversion head works, including weirs, barrages, under-sluices, divide walls, river training works, fish ladders, and canal head regulators. The purpose and functions of each component are explained. Design considerations for weirs and barrages such as their cost, control of flow, and ability to incorporate transportation are compared.
This document provides information on diversion head works for canals. It defines diversion head works as structures constructed at the head of a canal to divert river water into the canal. The objectives are to raise the water level and regulate supply. Common structures include weirs and barrages. Weirs raise water level using a raised crest, while barrages use gates to pond water. Other components are under-sluices, divide walls, river training works, and canal head regulators which control water flow into the canal. Careful site selection considers factors like river characteristics, land use, and material availability.
Canal headworks are hydraulic structures constructed across rivers to supply water to off-taking canals. There are two main types: diversion headworks and storage headworks. Diversion headworks, like weirs or barrages, are built across perennial rivers to raise water levels and divert the required quantity of water. Storage headworks, like dams, are constructed across river valleys to form storage reservoirs and divert water. The purposes of canal headworks include raising water levels, regulating water supply, controlling silt entry, and providing short-term storage.
The document provides information on diversion headworks for water resources engineering projects. It discusses the different types of diversion headworks including storage and temporary diversion structures. Key components of diversion headworks are described such as weirs, barrages, divide walls, fish ladders, and canal head regulators. Factors for selecting sites for diversion structures are outlined. Causes of failures for weirs built on permeable foundations and remedies are summarized.
This document provides information about dams and spillways. It discusses different types of dams including gravity dams, earthen dams, rock and fill dams, arch dams, and buttress dams. For gravity dams specifically, it describes the key components, forces acting on them, theoretical and elementary profiles, galleries, and construction joints. Earthen dams are also briefly introduced.
The document outlines the key steps and considerations for planning, designing, constructing, and operating a barrage, including:
1) Conducting site investigations and data collection, such as topographical surveys, hydrological studies, and assessing construction material availability.
2) Carefully selecting the location and alignment of the barrage based on factors like suitable diversion of water for irrigation canals, hydraulic conditions, and river characteristics.
3) Planning the layout of the barrage and its structures, including determining the design flood, afflux, freeboard, pond level, waterway, river training works, and crest levels of spillways.
River training structures are used to guide and direct river flow, regulate the river bed, and increase water depth. The objectives are to provide safe passage for floods, prevent river bank erosion, improve channel alignment, and efficiently transport sediment. Common structures include embankments, guide banks, groynes, cutoffs, pitched islands, and bandalling. Groynes can be impermeable or permeable, classified based on their height, functions like attracting or repelling flow, and some have special designs like T-heads or hockey shapes.
The document discusses different types of canals including contour canals, ridge canals, and side slope canals. It describes how canals are classified based on alignment and position. The key parts of a canal system are described including main canals, branch canals, distributaries, and water courses. Methods for fixing canal alignment and designing canal cross-sections are outlined. Different types of canal lining materials and their purposes are also summarized.
Engr. Amir Adnan's document discusses spillways and fish ladders. A spillway is part of a dam designed to allow water to flow safely over the dam during floods to prevent overtopping. Spillways provide a safe release of flood waters from the dam downstream, usually to the river the dam was built on. Spillways draw water from the top of the reservoir to avoid situations where flood waters would cause the reservoir level to rise and potentially overtop the dam. Controlled spillways have gates that can be raised or lowered, providing advantages over uncontrolled spillways. Fish ladders are structures that allow fish to pass through dams to access spawning habitats.
The document discusses various components of water conveyance systems for hydropower projects. It begins by defining an open channel as a conduit that transports water with a free surface. It then describes different types of open channels based on shape, natural vs artificial classification, changes in cross-section and slope, and boundary characteristics. The document also discusses intake structures, including their components, functions, types and locations. It concludes by briefly describing forebays, tunnel linings, and the purpose of surge tanks in dissipating pressure fluctuations within penstocks.
This chapter discusses irrigation structures at the head of canals, known as diversion head works. The objectives of diversion head works are to raise water levels, form storage areas, control silt and water level fluctuations. The key components discussed are weirs, barrages, under-sluices, divide walls, river training works like guide banks and spurs/groynes, fish ladders, and silt regulation works. Weirs are distinguished from barrages based on how ponding is achieved. Typical layouts of head works and structures like concrete, masonry and rock-fill weirs are presented.
Dams are constructed across rivers to store water in reservoirs. There are several types of dams classified based on their use, hydraulic design, materials used, and mode of stability. The key types include storage dams, diversion dams, detention dams, gravity dams, buttress dams, arch dams, earth dams, and rockfill dams. Dams require site selection studies involving foundation conditions, material availability, and reservoir capacity. Investigation of dam sites includes surveys and testing. Reservoirs have storage zones and evaporation losses need to be estimated. Spillways like chute spillways, shaft spillways, and tunnel spillways are constructed for surplus discharge. Earth dams are economical but require suitable foundations and can fail due to seep
Chapter 1: Introduction to River Hydraulicsgemedo gelgelu
This document provides an overview of river hydraulics and morphology. It discusses how rivers adjust over time based on natural forces and human activities. Key points include:
- Rivers can be classified based on factors like flow patterns, location, and channel shape. Meandering and braided rivers are described.
- Sediment transport involves erosion, deposition, and different load types being suspended, rolling along the bed, or in traction.
- River channels and morphology vary based on location in a watershed and sediment characteristics. Meandering develops through erosion on concave banks and deposition on convex banks.
This document provides an overview of the hydraulic design considerations for barrages. It discusses key aspects of barrage design including sub-surface flow calculations to determine seepage pressure, force, and exit gradients. It also covers surface flow hydraulics to determine the waterway length. Critical design elements like cut-offs, scour depth, block protections are explained. Emphasis is given to ensuring safety against piping failure and sand boilling. The document concludes that model studies are necessary before prototype construction due to uncertainties in soil properties.
This document discusses different types and classifications of canals used for irrigation. Canals are classified in several ways, including by their source of water (permanent, non-perennial, inundation), function (feeder, carrier, distribution, hydel, navigation), size and importance in a network (main, branch, major/minor distributors, water courses), alignment (ridge, contour, side slope), financial role (protective, productive), soil type traversed (alluvial, non-alluvial), and whether they have lining or not (lined, unlined). The key purpose of canals is to transport water from its source to irrigate agricultural lands.
SAQIB IMRAN 0341-7549889 11
1. The document is notes written by Saqib Imran, a civil engineering student in Pakistan, to provide knowledge on hydraulic structures to other students and engineers.
2. It defines hydraulic structures as anything used to divert, restrict, or manage natural water flow, such as dams, weirs, and spillways. It also discusses factors that affect the design of canals, barrages, and culverts.
3. The notes provide definitions for various technical terms related to hydraulic structures like khadir, weir axis, river axis, and retrogression. It also describes river training works including guide banks and marginal bund
A water distribution system is a part of water supply network with components that carry potable water from a centralized treatment plant or wells to consumers to satisfy residential.
1. Diversion headworks divert river water into canals to supply irrigation water. They include weirs or barrages to raise water levels, under sluices to remove silt, and canal head regulators to control water flow into canals.
2. Key components are weirs/barrages, under sluices, divide walls, fish ladders, and canal head regulators. Weirs/barrages raise water levels while under sluices and silt excluders/ejectors remove silt from the water. Canal head regulators control water entering the canals.
3. Site selection considers factors like river characteristics, canal economics, construction feasibility, land and material costs,
Topics:
1. Types of Diversion Head Works
2. Weirs and Barrages
3. Layout Diversion Head Works
4. Causes of Failures of Weirs and Barrages on Permeable Foundations
5. Silt Ejectors and Silt Excluders
Canal headworks are hydraulic structures constructed across rivers to divert water into canals. They raise the river water level and regulate flows. There are two main types - diversion and storage headworks. Diversion headworks like weirs and barrages divert water without storage, while dams form storage reservoirs. Key components include weirs/barrages, divide walls, fish ladders, under sluices, silt excluders, and head regulators. Location depends on river characteristics, and sites must be accessible with suitable foundations. Failure can occur through subsurface piping/uplift or surface scouring during floods. Precautions include reducing exit gradients, providing sheet piles, ensuring floor thickness, using filters and energy
Diversion headworks, also known as canal headworks, are structures built across rivers to raise the water level and divert water into canals. They serve several purposes, including increasing the area that can be irrigated, regulating water supply to canals, controlling silt entry, and reducing water level fluctuations. There are two types - temporary structures built after floods, and permanent concrete or masonry structures like weirs and barrages. The location depends on the river's characteristics, with the trough or alluvial stage generally preferred. Key components include the weir/barrage, under sluices, divide wall, and head regulators.
This document provides information about hydraulic structures and diversion head works. It discusses that a hydraulic structure disrupts natural water flow and examples include dams and weirs. It then describes the key components of diversion head works, including weirs, barrages, under-sluices, divide walls, river training works, fish ladders, and canal head regulators. The purpose and functions of each component are explained. Design considerations for weirs and barrages such as their cost, control of flow, and ability to incorporate transportation are compared.
This document provides information on diversion head works for canals. It defines diversion head works as structures constructed at the head of a canal to divert river water into the canal. The objectives are to raise the water level and regulate supply. Common structures include weirs and barrages. Weirs raise water level using a raised crest, while barrages use gates to pond water. Other components are under-sluices, divide walls, river training works, and canal head regulators which control water flow into the canal. Careful site selection considers factors like river characteristics, land use, and material availability.
Canal headworks are hydraulic structures constructed across rivers to supply water to off-taking canals. There are two main types: diversion headworks and storage headworks. Diversion headworks, like weirs or barrages, are built across perennial rivers to raise water levels and divert the required quantity of water. Storage headworks, like dams, are constructed across river valleys to form storage reservoirs and divert water. The purposes of canal headworks include raising water levels, regulating water supply, controlling silt entry, and providing short-term storage.
The document provides information on diversion headworks for water resources engineering projects. It discusses the different types of diversion headworks including storage and temporary diversion structures. Key components of diversion headworks are described such as weirs, barrages, divide walls, fish ladders, and canal head regulators. Factors for selecting sites for diversion structures are outlined. Causes of failures for weirs built on permeable foundations and remedies are summarized.
This document provides information about dams and spillways. It discusses different types of dams including gravity dams, earthen dams, rock and fill dams, arch dams, and buttress dams. For gravity dams specifically, it describes the key components, forces acting on them, theoretical and elementary profiles, galleries, and construction joints. Earthen dams are also briefly introduced.
The document outlines the key steps and considerations for planning, designing, constructing, and operating a barrage, including:
1) Conducting site investigations and data collection, such as topographical surveys, hydrological studies, and assessing construction material availability.
2) Carefully selecting the location and alignment of the barrage based on factors like suitable diversion of water for irrigation canals, hydraulic conditions, and river characteristics.
3) Planning the layout of the barrage and its structures, including determining the design flood, afflux, freeboard, pond level, waterway, river training works, and crest levels of spillways.
River training structures are used to guide and direct river flow, regulate the river bed, and increase water depth. The objectives are to provide safe passage for floods, prevent river bank erosion, improve channel alignment, and efficiently transport sediment. Common structures include embankments, guide banks, groynes, cutoffs, pitched islands, and bandalling. Groynes can be impermeable or permeable, classified based on their height, functions like attracting or repelling flow, and some have special designs like T-heads or hockey shapes.
The document discusses different types of canals including contour canals, ridge canals, and side slope canals. It describes how canals are classified based on alignment and position. The key parts of a canal system are described including main canals, branch canals, distributaries, and water courses. Methods for fixing canal alignment and designing canal cross-sections are outlined. Different types of canal lining materials and their purposes are also summarized.
Engr. Amir Adnan's document discusses spillways and fish ladders. A spillway is part of a dam designed to allow water to flow safely over the dam during floods to prevent overtopping. Spillways provide a safe release of flood waters from the dam downstream, usually to the river the dam was built on. Spillways draw water from the top of the reservoir to avoid situations where flood waters would cause the reservoir level to rise and potentially overtop the dam. Controlled spillways have gates that can be raised or lowered, providing advantages over uncontrolled spillways. Fish ladders are structures that allow fish to pass through dams to access spawning habitats.
The document discusses various components of water conveyance systems for hydropower projects. It begins by defining an open channel as a conduit that transports water with a free surface. It then describes different types of open channels based on shape, natural vs artificial classification, changes in cross-section and slope, and boundary characteristics. The document also discusses intake structures, including their components, functions, types and locations. It concludes by briefly describing forebays, tunnel linings, and the purpose of surge tanks in dissipating pressure fluctuations within penstocks.
This chapter discusses irrigation structures at the head of canals, known as diversion head works. The objectives of diversion head works are to raise water levels, form storage areas, control silt and water level fluctuations. The key components discussed are weirs, barrages, under-sluices, divide walls, river training works like guide banks and spurs/groynes, fish ladders, and silt regulation works. Weirs are distinguished from barrages based on how ponding is achieved. Typical layouts of head works and structures like concrete, masonry and rock-fill weirs are presented.
Dams are constructed across rivers to store water in reservoirs. There are several types of dams classified based on their use, hydraulic design, materials used, and mode of stability. The key types include storage dams, diversion dams, detention dams, gravity dams, buttress dams, arch dams, earth dams, and rockfill dams. Dams require site selection studies involving foundation conditions, material availability, and reservoir capacity. Investigation of dam sites includes surveys and testing. Reservoirs have storage zones and evaporation losses need to be estimated. Spillways like chute spillways, shaft spillways, and tunnel spillways are constructed for surplus discharge. Earth dams are economical but require suitable foundations and can fail due to seep
Chapter 1: Introduction to River Hydraulicsgemedo gelgelu
This document provides an overview of river hydraulics and morphology. It discusses how rivers adjust over time based on natural forces and human activities. Key points include:
- Rivers can be classified based on factors like flow patterns, location, and channel shape. Meandering and braided rivers are described.
- Sediment transport involves erosion, deposition, and different load types being suspended, rolling along the bed, or in traction.
- River channels and morphology vary based on location in a watershed and sediment characteristics. Meandering develops through erosion on concave banks and deposition on convex banks.
This document provides an overview of the hydraulic design considerations for barrages. It discusses key aspects of barrage design including sub-surface flow calculations to determine seepage pressure, force, and exit gradients. It also covers surface flow hydraulics to determine the waterway length. Critical design elements like cut-offs, scour depth, block protections are explained. Emphasis is given to ensuring safety against piping failure and sand boilling. The document concludes that model studies are necessary before prototype construction due to uncertainties in soil properties.
This document discusses different types and classifications of canals used for irrigation. Canals are classified in several ways, including by their source of water (permanent, non-perennial, inundation), function (feeder, carrier, distribution, hydel, navigation), size and importance in a network (main, branch, major/minor distributors, water courses), alignment (ridge, contour, side slope), financial role (protective, productive), soil type traversed (alluvial, non-alluvial), and whether they have lining or not (lined, unlined). The key purpose of canals is to transport water from its source to irrigate agricultural lands.
SAQIB IMRAN 0341-7549889 11
1. The document is notes written by Saqib Imran, a civil engineering student in Pakistan, to provide knowledge on hydraulic structures to other students and engineers.
2. It defines hydraulic structures as anything used to divert, restrict, or manage natural water flow, such as dams, weirs, and spillways. It also discusses factors that affect the design of canals, barrages, and culverts.
3. The notes provide definitions for various technical terms related to hydraulic structures like khadir, weir axis, river axis, and retrogression. It also describes river training works including guide banks and marginal bund
A water distribution system is a part of water supply network with components that carry potable water from a centralized treatment plant or wells to consumers to satisfy residential.
1. Diversion headworks divert river water into canals to supply irrigation water. They include weirs or barrages to raise water levels, under sluices to remove silt, and canal head regulators to control water flow into canals.
2. Key components are weirs/barrages, under sluices, divide walls, fish ladders, and canal head regulators. Weirs/barrages raise water levels while under sluices and silt excluders/ejectors remove silt from the water. Canal head regulators control water entering the canals.
3. Site selection considers factors like river characteristics, canal economics, construction feasibility, land and material costs,
Presenation on Diversion Headworks irrigation.pptxqureshixahoor
1. A diversion headwork is a weir or barrage constructed across a river to divert water into a canal. It regulates water flow into the canal through a head regulator.
2. A barrage differs from a weir in that it uses large gates that can be opened and closed to directly control water levels, whereas a weir uses fixed crest heights.
3. The main purpose of a barrage is to stabilize river water levels for uses like irrigation while still allowing easy control over flow, unlike a dam which relies on water levels behind the full wall height.
chapter-3.pptx: CHANNEL HEADWORKS AND CANALSmulugeta48
Purposes:
Raises water level in the river
Regulates supply of water into the canal
Controls the entry of silt into the canal
Provides some storage for a short period
Reduces the fluctuations in the level of supply in river
Temporary diversion head works
Consists of a bund constructed across river to raise the water level in the river and will be damaged by floods.
2. Permanent diversion head works
Consists of a permanent structure such as a weir or barrage constructed across river to raise water level in the river.River section at the site should be narrow and well-defined.
Should have a large commanded area.
Site should be such that the weir (or barrage) can be aligned at right angles to the direction of flow in the river.
Good foundation should be available at the site.
Site should be easily accessible by road or rail.
Overall cost of the project should be a minimum
The document discusses the components and objectives of diversion headworks. The key components include weirs or barrages, canal head regulators, divide walls, fish ladders, scouring sluices, silt excluders, and guide banks. The objectives are to raise water levels, control silt entry and deposition, and regulate water flow levels throughout the year. Site selection considerations and causes of failure on permeable foundations are also summarized.
The document discusses the types, location, and components of diversion head works. There are two types of diversion head works - temporary and permanent. Permanent diversion head works consist of structures like weirs or barrages built across rivers to raise water levels and divert water into canals. Key components include the weir/barrage, undersluices, divide wall, fish ladder, canal head regulator, and river training works. The site selection considers factors such as river characteristics, cost, accessibility, and potential impacts.
This document discusses different types of water resources including surface water and groundwater. It provides details on reservoirs, including definitions, classifications, and factors to consider when selecting sites. Reservoirs can be used for storage, flood control, or multiple purposes. The document also describes components of water diversion structures like barrages and weirs, as well as methods for extracting groundwater like dug wells, tube wells, and bore wells.
Diversion headworks are structures constructed at the head of a canal to divert river water into the canal. They include components like weirs, barrages, canal head regulators, divide walls, fish ladders, and guide banks. The objectives are to raise water levels, control silt entry, regulate water flow, and allow fish passage. Proper site selection and design are needed to prevent failures from subsurface water flow, uplift pressure, hydraulic jumps, or scouring during floods. Remedies include increasing seepage lengths, adding sheet piles, and using thicker impervious floors.
Diversion headworks are structures constructed at the head of a canal to divert river water into the canal. Their objectives are to raise the water level, form water storage, control silt entry and deposition, and regulate water level fluctuations. Key components include a weir or barrage, canal head regulator, divide wall, fish ladder, scouring sluices, silt excluder, silt ejector, and marginal embankments. Together, these structures divert and regulate river flow into the canal while attempting to minimize silt accumulation and allow fish passage.
Diversion headworks are structures constructed across rivers to raise water levels and divert water into canals. They have several purposes, including increasing the commanded area, regulating water supply to canals, and controlling silt entry. There are two types - temporary and permanent. Key components include weirs/barrages, under sluices, divide walls, fish ladders, and head regulators. The optimal location depends on the river's characteristics, balancing factors like water availability, construction costs, and proximity to agricultural land.
This presentation covered Diversion head work topic. Details topics selection of the suitable site for the
diversion headwork- different parts of
diversion headwork- Causes of failure of
structure on pervious foundation- Khosla’s
theory- Design of concrete sloping glacis weir covered.
Canal fall- necessity and location- types of falls- Cross regulator and
distributory head regulator- their functions, Silt control devices, Canal
escapes- types of escapes.
Dams, weirs, barrages, and check dams are common hydraulic structures used to store or divert water. Dams are constructed across rivers to impound water and form reservoirs. The main types of dams include gravity dams, earth dams, rockfill dams, arch dams, and buttress dams. Weirs are barriers that alter river flows and can be used to divert water into canals. Barrages are low-head dams that consist of gates to control water levels for irrigation. Check dams are small temporary or permanent dams built across drainage ditches to settle sediments, pollutants, and recharge groundwater.
Diversion head works divert river water into canals and include components like weirs, barrages, undersluices, divide walls, fish ladders, head regulators, and silt prevention devices. Weirs and barrages raise the river's water level to divert it into canals. Undersluices and divide walls help control silt and water flow. Fish ladders allow fish to pass through. Head regulators control water entering canals while silt prevention devices like silt excluders and ejectors remove silt from the water and canal bed. Guide banks and marginal embankments also help direct water flow and prevent flooding.
The document describes the components and purposes of weirs and barrages. Weirs and barrages are solid structures built across rivers to raise water levels and divert water into canals. The main differences are that barrages use gates to regulate flow, while weirs use crest height. Barrages are more expensive than weirs. The structures are used to control water levels and flows, prevent flooding, divert water, and train rivers to reduce impacts on canal headworks. Key components include the main body, divide wall, under sluices, fish ladder, sheet piles, apron, and river training works.
Intakes are structures used to admit water from surface sources like rivers or lakes into treatment plants. They are generally constructed of masonry or concrete to provide relatively clean water free from pollution. Their main purpose is to provide calm conditions for collecting purer water. There are several types of intakes - submerged, exposed, wet, and dry. Factors considered when selecting intake sites include providing purer water, avoiding heavy currents, sufficient water availability, accessibility, and foundation conditions. Intakes are designed to withstand forces on the structure and prevent the entry of large floating objects. Water is conveyed from intakes to treatment plants and customers through various means such as open channels, aqueducts, tunnels or pipes made of materials
The document discusses various aspects of selecting a site for a diversion headworks and its components. It provides criteria for selecting an optimal site, such as the river being straight and narrow, having a higher elevation than the irrigation area, and having stable banks. It also discusses types of weirs, barrages, and other structures used at diversion headworks, such as under sluices, fish ladders, canal head regulators, and silt control works. Key considerations for site selection aim to minimize construction costs and water losses while safely diverting water for irrigation.
This document discusses various hydraulic structures used for river engineering, including headworks, diversion structures, weirs, and flow control structures. It describes the functions and types of structures such as storage versus diversion headworks, vertical drop versus sloping weirs, and bendway weirs versus engineered log jams. Modes of failure for weirs and methods to control flow and grade using structures like vanes, drop structures, and logjams are also summarized.
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The document outlines the key terms of a lease agreement between John Doe as the landlord and Jane Smith as the tenant. It specifies the monthly rent amount and due date, the security deposit required, allows for pets but prohibits smoking, and describes the process for repairs, entry by the landlord, and early termination of the lease. The landlord and tenant must both sign the agreement prior to the tenant moving into the rental property.
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This document discusses tension members in structural engineering. It defines tension members as linear members that experience axial forces that elongate or stretch the member. Examples given include ropes, ties in trusses, suspenders in bridges. The document discusses the types of cross-sections used for tension members like angles, channels, rods. It also discusses the calculation of net effective sectional area and provides examples. Other topics covered include types of failures in tension members, design strength calculations, limiting slenderness ratios, tension splices, and lug angles.
This document contains a question bank for the subject of Design of Steel Structures. It includes multiple choice and numerical questions covering various topics in steel design such as bolted and welded connections, tension members, riveted joints, and limit state design approach. Some sample 16-mark design questions are provided related to designing tension members using angles, plates, and bolted/riveted connections to gusset plates to transmit axial forces. The document is intended as a study guide for students in the third year of a Civil Engineering program.
This document contains a question bank for a steel structures design course. It includes 20 questions in Part A testing basic knowledge of steel structures terminology and concepts. Part B contains 14 design problems testing application and evaluation skills. Topics covered include riveted and bolted connections, tension members, compression members, beams, plate girders, roof trusses, and crane girders. Students are asked to calculate strengths, suitable dimensions, and designs meeting loading criteria. Design factors like load magnitudes, member lengths, connection materials, and support conditions are provided.
The document contains 43 pages of lecture notes from Srividya College of Engineering and Technology on the design of steel structures. The notes cover various topics related to the design of tension members, compression members, and beams under the bending, shear, and axial forces. Design examples are included for the analysis and design of different steel structural elements.
1. The document discusses best practices for analyzing risks related to dam and levee spillway gates.
2. It describes different types of spillway gates and their vulnerabilities, including issues that led to the 1995 failure of Gate 3 at Folsom Dam in California due to trunnion pin friction.
3. Key factors that influence spillway gate risk are discussed, such as reservoir water level, seismic hazard, gate size, maintenance practices, and the potential for multiple gate failures. Event tree and fragility curve methods are presented for evaluating failure probabilities under different loading conditions.
This document discusses the analysis of safety and stability for concrete gravity dams. It begins with an outline of the topics to be covered in Lecture 5, including a summary of loading cases, design of concrete gravity dams, safety analysis, and stability analysis. The document then provides detailed descriptions and diagrams for each of the 8 loading cases to be considered in the safety and stability analysis. It discusses the design of gravity dams and the procedures for analysis. Key aspects of the safety and stability analysis are described, including checking for overturning, sliding, shear stresses, and overstressing of the concrete. Diagrams are provided to illustrate the concepts of checking for overturning, sliding, and factors of safety.
Spillways are designed to safely pass excess water from a reservoir to prevent overtopping of a dam. They come in many forms depending on site conditions but commonly include an overflow structure like an ogee crest to control reservoir levels. Proper spillway capacity is essential for dam safety as inadequate capacity contributes to 40% of dam failures. Spillway design considers hydrologic factors, hydraulic performance including discharge coefficients, and structural aspects like cost-effectiveness. Gates may be added to overflows to allow flexible reservoir operation while preventing overtopping during floods.
1) Canals are artificial channels constructed to carry water from a source like a river or reservoir to agricultural fields.
2) Canals are classified based on their water source (permanent or inundation), function (irrigation, navigation, power), alignment (watershed, contour, side slope), discharge (main, branch, distributary), and whether they have lining.
3) The cross-section of a canal includes components like side slopes, berms, freeboard, banks, and may involve partial cutting and filling to achieve a balancing depth.
Canal lining involves adding an impermeable layer to canal beds and banks to reduce water seepage losses. Common lining materials include compacted earth, concrete, and plastic membranes. Lining can conserve up to 50% of irrigation water by preventing seepage and allowing canals to maintain higher water velocities using smaller cross-sections. It also stabilizes canal banks, prevents erosion, and increases the command area by allowing flatter canal slopes. Hard linings include cast concrete while earth linings use compacted soil or soil-bentonite mixes. Buried plastic membranes are another option but are susceptible to damage.
Spillways are structures constructed near dams to safely discharge surplus water from reservoirs. There are several types of spillways classified by their utility and prominent features. Main spillways are designed to pass the entire design flood volume, while auxiliary spillways supplement the main spillway. Emergency spillways activate only during emergencies. Common spillway types include overflow, which guides water smoothly over a curved crest; side channel, which diverts flow through a parallel channel; and tunnel, which conveys flow through a closed channel around the dam. Shaft spillways similarly direct water vertically then horizontally through a tunnel.
A gravity dam resists external forces through its own weight. It is a solid, durable structure constructed of masonry or concrete. Forces acting on a gravity dam include water pressure, the weight of the dam, uplift pressure, silt pressure, wave pressure, ice pressure, and pressure from earthquake forces. Water pressure is the major external force and varies with depth, while the weight of the dam is the main resisting force.
This document discusses different types of earth and rockfill dams. It describes rolled fill dams which are constructed by compacting soil in thin layers. Homogeneous dams consist of a single material throughout while zoned dams have distinct core, shell, and filter zones. Diaphragm dams contain an impervious core like a thin wall. Key elements of earth dam design include the top width, freeboard, slopes, central core, and downstream drainage system.
This document discusses different types of subsurface irrigation methods, including natural and artificial subsurface irrigation. Natural subsurface irrigation involves using the natural water table to irrigate crops through capillary action, while artificial subsurface irrigation uses buried perforated pipes to maintain the water table below the soil surface. The document also discusses sprinkler irrigation systems, how they work, their advantages of uniform water distribution and adaptability, and disadvantages like high costs and interference from wind. Finally, it defines and discusses drip irrigation, how it efficiently applies water directly to plant roots, and its advantages like water and fertilizer efficiency as well as disadvantages like sensitivity to clogging.
The document discusses different types of spillways used in dam construction including:
- Main and emergency spillways which provide controlled water release from dams.
- Straight (free overfall) spillways where water freely drops over the crest edge.
- Ogee spillways with an S-shaped crest profile that are commonly used in rigid dams.
- Side channel spillways which divert water away from the main dam through an adjacent channel.
- Chute spillways which lower water levels through steeply inclined channels.
- Tunnel spillways which pass water through underground tunnels.
- Siphon spillways which use siphonic action through enclosed conduits to discharge water downstream.
Spillways are structures used to release water from reservoirs to prevent overflow of dams. There are two main types of spillways: controlled and uncontrolled. Controlled spillways have gates to regulate water flow, while uncontrolled spillways release water once the reservoir level rises above the spillway crest. Spillways can also be classified based on their shape, such as ogee, side channel, labyrinth, chute, conduit, and baffled chute spillways. Each type has distinct hydraulic characteristics that make it suitable for different dam designs and site conditions.
This presentation discusses different types of spillways used in dam structures. Spillways are needed to safely discharge water from the reservoir during floods to prevent overtopping of the dam. The main types discussed are chute, shaft, saddle, and side channel spillways. Chute spillways convey water down an excavated open channel with a steep slope. Shaft spillways allow water to pass through a vertical shaft and horizontal conduit below the dam. Saddle spillways use natural depressions as spillway routes. Side channel spillways route flood water parallel to the dam.
This document discusses the design principles for retaining walls. It describes:
1) Different categories of retaining structures based on height, including curbs under 0.6m, short walls up to 3m using reinforcement, and taller walls requiring bracing.
2) Design considerations for stability of soils, the wall itself, structural strength, and effects on adjacent structures.
3) Basic loading factors including earth pressures, water pressures, and surcharges from loads or traffic.
4) Considerations for soil properties, selection of backfill material, and effects of groundwater.
ENVIRONMENT~ Renewable Energy Sources and their future prospects.tiwarimanvi3129
This presentation is for us to know that how our Environment need Attention for protection of our natural resources which are depleted day by day that's why we need to take time and shift our attention to renewable energy sources instead of non-renewable sources which are better and Eco-friendly for our environment. these renewable energy sources are so helpful for our planet and for every living organism which depends on environment.
Climate Change All over the World .pptxsairaanwer024
Climate change refers to significant and lasting changes in the average weather patterns over periods ranging from decades to millions of years. It encompasses both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. While climate change is a natural phenomenon, human activities, particularly since the Industrial Revolution, have accelerated its pace and intensity
Microbial characterisation and identification, and potability of River Kuywa ...Open Access Research Paper
Water contamination is one of the major causes of water borne diseases worldwide. In Kenya, approximately 43% of people lack access to potable water due to human contamination. River Kuywa water is currently experiencing contamination due to human activities. Its water is widely used for domestic, agricultural, industrial and recreational purposes. This study aimed at characterizing bacteria and fungi in river Kuywa water. Water samples were randomly collected from four sites of the river: site A (Matisi), site B (Ngwelo), site C (Nzoia water pump) and site D (Chalicha), during the dry season (January-March 2018) and wet season (April-July 2018) and were transported to Maseno University Microbiology and plant pathology laboratory for analysis. The characterization and identification of bacteria and fungi were carried out using standard microbiological techniques. Nine bacterial genera and three fungi were identified from Kuywa river water. Clostridium spp., Staphylococcus spp., Enterobacter spp., Streptococcus spp., E. coli, Klebsiella spp., Shigella spp., Proteus spp. and Salmonella spp. Fungi were Fusarium oxysporum, Aspergillus flavus complex and Penicillium species. Wet season recorded highest bacterial and fungal counts (6.61-7.66 and 3.83-6.75cfu/ml) respectively. The results indicated that the river Kuywa water is polluted and therefore unsafe for human consumption before treatment. It is therefore recommended that the communities to ensure that they boil water especially for drinking.
Evolving Lifecycles with High Resolution Site Characterization (HRSC) and 3-D...Joshua Orris
The incorporation of a 3DCSM and completion of HRSC provided a tool for enhanced, data-driven, decisions to support a change in remediation closure strategies. Currently, an approved pilot study has been obtained to shut-down the remediation systems (ISCO, P&T) and conduct a hydraulic study under non-pumping conditions. A separate micro-biological bench scale treatability study was competed that yielded positive results for an emerging innovative technology. As a result, a field pilot study has commenced with results expected in nine-twelve months. With the results of the hydraulic study, field pilot studies and an updated risk assessment leading site monitoring optimization cost lifecycle savings upwards of $15MM towards an alternatively evolved best available technology remediation closure strategy.
Recycling and Disposal on SWM Raymond Einyu pptxRayLetai1
Increasing urbanization, rural–urban migration, rising standards of living, and rapid development associated with population growth have resulted in increased solid waste generation by industrial, domestic and other activities in Nairobi City. It has been noted in other contexts too that increasing population, changing consumption patterns, economic development, changing income, urbanization and industrialization all contribute to the increased generation of waste.
With the increasing urban population in Kenya, which is estimated to be growing at a rate higher than that of the country’s general population, waste generation and management is already a major challenge. The industrialization and urbanization process in the country, dominated by one major city – Nairobi, which has around four times the population of the next largest urban centre (Mombasa) – has witnessed an exponential increase in the generation of solid waste. It is projected that by 2030, about 50 per cent of the Kenyan population will be urban.
Aim:
A healthy, safe, secure and sustainable solid waste management system fit for a world – class city.
Improve and protect the public health of Nairobi residents and visitors.
Ecological health, diversity and productivity and maximize resource recovery through the participatory approach.
Goals:
Build awareness and capacity for source separation as essential components of sustainable waste management.
Build new environmentally sound infrastructure and systems for safe disposal of residual waste and replacing current dumpsites which should be commissioned.
Current solid waste management situation:
The status.
Solid waste generation rate is at 2240 tones / day
collection efficiently is at about 50%.
Actors i.e. city authorities, CBO’s , private firms and self-disposal
Current SWM Situation in Nairobi City:
Solid waste generation – collection – dumping
Good Practices:
• Separation – recycling – marketing.
• Open dumpsite dandora dump site through public education on source separation of waste, of which the situation can be reversed.
• Nairobi is one of the C40 cities in this respect , various actors in the solid waste management space have adopted a variety of technologies to reduce short lived climate pollutants including source separation , recycling , marketing of the recycled products.
• Through the network, it should expect to benefit from expertise of the different actors in the network in terms of applicable technologies and practices in reducing the short-lived climate pollutants.
Good practices:
Despite the dismal collection of solid waste in Nairobi city, there are practices and activities of informal actors (CBOs, CBO-SACCOs and yard shop operators) and other formal industrial actors on solid waste collection, recycling and waste reduction.
Practices and activities of these actor groups are viewed as innovations with the potential to change the way solid waste is handled.
CHALLENGES:
• Resource Allocation.
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Epcon is One of the World's leading Manufacturing Companies.EpconLP
Epcon is One of the World's leading Manufacturing Companies. With over 4000 installations worldwide, EPCON has been pioneering new techniques since 1977 that have become industry standards now. Founded in 1977, Epcon has grown from a one-man operation to a global leader in developing and manufacturing innovative air pollution control technology and industrial heating equipment.
Presented by The Global Peatlands Assessment: Mapping, Policy, and Action at GLF Peatlands 2024 - The Global Peatlands Assessment: Mapping, Policy, and Action
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Optimizing Post Remediation Groundwater Performance with Enhanced Microbiolog...Joshua Orris
Results of geophysics and pneumatic injection pilot tests during 2003 – 2007 yielded significant positive results for injection delivery design and contaminant mass treatment, resulting in permanent shut-down of an existing groundwater Pump & Treat system.
Accessible source areas were subsequently removed (2011) by soil excavation and treated with the placement of Emulsified Vegetable Oil EVO and zero-valent iron ZVI to accelerate treatment of impacted groundwater in overburden and weathered fractured bedrock. Post pilot test and post remediation groundwater monitoring has included analyses of CVOCs, organic fatty acids, dissolved gases and QuantArray® -Chlor to quantify key microorganisms (e.g., Dehalococcoides, Dehalobacter, etc.) and functional genes (e.g., vinyl chloride reductase, methane monooxygenase, etc.) to assess potential for reductive dechlorination and aerobic cometabolism of CVOCs.
In 2022, the first commercial application of MetaArray™ was performed at the site. MetaArray™ utilizes statistical analysis, such as principal component analysis and multivariate analysis to provide evidence that reductive dechlorination is active or even that it is slowing. This creates actionable data allowing users to save money by making important site management decisions earlier.
The results of the MetaArray™ analysis’ support vector machine (SVM) identified groundwater monitoring wells with a 80% confidence that were characterized as either Limited for Reductive Decholorination or had a High Reductive Reduction Dechlorination potential. The results of MetaArray™ will be used to further optimize the site’s post remediation monitoring program for monitored natural attenuation.
2. Content…
Types- selection of the suitable site for the
diversion headwork components of diversion
headwork- Causes of failure of structure on
pervious foundation- Khosla’s theory- Design of
concrete sloping glacis weir.
3. Introduction…
Any hydraulic structure which supplies water to
the off-taking canal is called a headwork.
Headwork may be divided into two
1. Storage headwork.
2. Diversion headwork.
4. Storage head works
Dam is constructed across a river valley to
form storage reservoir, known as storage head
works.
Water is supplied to the canal from this
reservoir through canal regulator.
These serves for multipurpose function like
hydro- electric power generation, flood control,
fishery.
5. Diversion head works
Weir or barrage is constructed across a
perennial river to raise water level and to divert
the water to canal, is known as diversion head
work.
Flow of water in the canal is controlled by
canal head regulator.
6. Objective of diversion head work
It raises the water level on its upstream side.
It regulates the supply of water into canals.
It controls the entry of silt into canals
It creates a small pond (not reservoir) on its
upstream and provides some pondage.
It helps in controlling the fluctuation of water
level in river during different seasons.
7. Site selection for diversion head work
The river section at the site should be narrow
and well-defined.
The river should have high, well-defined, in
erodible and non-submersible banks so that the
cost of river training works is minimum.
The canals taking off from the diversion head
works should be quite economical and
Should have a large commanded area.
8. There should be suitable arrangement for the
diversion of river during construction.
The site should be such that the weir (or
barrage) can be aligned at right angles to the
direction of flow in the river.
There should be suitable locations for the
under sluices, head regulator and other
components of the diversion head works.
9. The diversion head works should not
submerge costly land and property on its
upstream.
Good foundation should be available at the
site.
The required materials of construction should
be available near the site.
The site should be easily accessible by road or
rail.
The overall cost of the project should be a
minimum.
10. Components of a diversion headwork
Weir or barrage
Undersluices
Divide wall
Fish ladder
Canal head regulator
Silt excluders/ Silt prevention devices
River training works (Marginal bunds and
guide banks)
11.
12. Weir
Normally the water level of any perennial river is such
that it cannot be diverted to the irrigation canal.
The bed level of the canal may be higher than the
existing water level of the river.
In such cases weir is constructed across the river to
raise the water level.
Surplus water pass over the crest of weir.
Adjustable shutters are provided on the crest to raise
the water level to some required height.
13.
14. Barrage
When the water level on the up stream side of
the weir is required to be raised to different
levels at different time, barrage is constructed.
Barrage is an arrangement of adjustable gates
or shutters at different tires over the weir.
15.
16. Barrage Weir
Low set crest High set crest
Ponding is done by means of gates Ponding is done against the raised
crest or partly against crest and partly
by shutters
Gated over entire length Shutters in part length
Gates are of greater height Shutters are of smaller height, 2 m
Perfect control on river flow No control of river in low floods
High floods can be passed with
minimum afflux
Excessive afflux in high floods
Less silting upstream due to low set
crest
Raised crest causes silting upstream
Longer construction period Shorter construction period
Silt removal is done through under
sluices
No means for silt disposal
Costly structure Relatively cheaper structure
17. Under sluices
Also known as scouring sluices.
The under sluices are the openings provided
at the base of the weir or barrage.
These openings are provided with adjustable
gates. Normally, the gates are kept closed.
The suspended silt goes on depositing in front
of the canal head regulator.
18. When the silt deposition becomes appreciable
the gates are opened and the deposited silt is
loosened with an agitator mounting on a boat.
The muddy water flows towards the
downstream through the scouring sluices.
The gates are then closed. But, at the period
of flood, the gates are kept opened.
19.
20. Divide wall
The divide wall is a long wall constructed at
right angles in the weir or barrage, it may be
constructed with stone masonry or cement
concrete.
On the upstream side, the wall is extended just
to cover the canal head regulator and on the
downstream side, it is extended up to the
launching apron.
21. The functions of the divide wall are as follows:
To form a still water pocket in front of the canal head
so that the suspended silt can be settled down which
then later be cleaned through the scouring sluices from
time to time.
It controls the eddy current or cross current in front
of the canal head.
It provides a straight approach in front of the canal
head.
It resists the overturning effect on the weir or barrage
caused by the pressure of the impounding water.
22. Fish ladder
The fish ladder is provided just by the side of the
divide wall for the free movement of fishes.
Rivers are important source of fishes.
The tendency of fish is to move from upstream to
downstream in winters and from downstream to
upstream in monsoons.
This movement is essential for their survival.
Due to construction of weir or barrage, this
movement gets obstructed, and is detrimental to
the fishes.
23. In the fish ladder, the fable walls are constructed in
a zigzag manner so that the velocity of flow within
the ladder does not exceed 3 m/sec.
The width, length and height of the fish ladder
depend on the nature of the river and the type of
the weir or barrage.
24.
25. Canal head regulator
A structure which is constructed at the head of
the canal to regulate flow of water is known as
canal head regulator.
It consists of a number of piers which divide
the total width of the canal into a number of
spans which are known as bays.
The piers consist of number tiers on which the
adjustable gates are placed.
26. The gates are operated form the top by suitable
mechanical device.
A platform is provided on the top of the piers
for the facility of operating the gates.
Again some piers are constructed on the down
stream side of the canal head to support the
roadway.
27. Functions of Canal Head Regulator
It regulates the supply of water entering the
canal
It controls the entry of silt in the canal
It prevents the river-floods from entering the
canal
28.
29. Silt regulation works
The entry of silt into a canal, which takes off
from a head works, can be reduced by
constructed certain special works, called silt
control works.
These works may be classified into the
following two types:
(a) Silt Excluders
(b) Silt Ejectors
30. Silt Excluders
Silt excluders are those works which are
constructed on the bed of the river, upstream of
the head regulator.
The clearer water enters the head regulator
and silted water enters the silt excluder.
In this type of works, the silt is, therefore,,
removed from the water before in enters the
canal.
31. Silt Ejectors
Silt ejectors, also called silt extractors, are those
devices which extract the silt from the canal
water after the silted water has travelled a
certain distance in the off-take canal.
These works are, therefore, constructed on the
bed of the canal, and little distance downstream
from the head regulator.
32. River training works
River training works are required near the weir site in
order to ensure a smooth and an axial flow of water,
and thus, to prevent the river from outflanking the
works due to a change in its course.
The river training works required on a canal headwork
are:
(a) Guide banks
(b) Marginal bunds
(c) Spurs or groynes
33. Guide Bank
When a barrage is constructed across a river which
flows through the alluvial soil, the guide banks must
be constructed on both the approaches to protect the
structure from erosion.
Guide bank serves the following purposes:
It protects the barrage from the effect of scouring and
erosion.
It provides a straight approach towards the barrage.
It controls the tendency of changing the course of the
river.
It controls the velocity of flow near the structure.
34. Marginal Bunds
The marginal bunds are earthen embankments
which are constructed parallel to the river bank
on one or
both the banks according to the condition. The
top width is generally 3 m to 4 m. The side
slope on the
river side is generally 1.5: 1 and that on the
country side is 2:1.
35. The marginal bunds serve the following
purposes:
It prevents the flood water or storage water
from entering the surrounding area which may
be submerged or may be water logged.
It retains the flood water or storage water within
a specified section.
It protects the towns and villages from
devastation during the heavy flood.
It protects valuable agricultural lands.
36. Causes of failure of structure
Irrigation structures (or hydraulic structures)
for the diversion and distribution works are
weirs, barrages, head regulators, distributary
head regulators, cross regulators, cross-drainage
works, etc.
These structures are generally founded on
alluvial soils which are highly pervious.
37. These soils are easily scoured when the high
velocity water passes over the structures.
The failures of weirs constructed on the
permeable foundation may occur due to
various causes, which may be broadly classified
into the following two categories:
1. Failure due to- subsurface flow
2. Failure due to surface flow
38. 1. Failure due to- subsurface flow
(a) Failure by Piping or undermining
water from the upstream side continuously percolates
through the bottom of the foundation and emerges at
the downstream end of the weir or barrage floor.
The force of percolating water removes the soil
particles by scouring at the point of emergence.
As the process of removal of soil particles goes on
continuously, a depression is formed which extends
backwards towards the upstream through the bottom
of the foundation.
39. A hollow pipe like formation thus develops
under the foundation due to which the weir or
barrage may fail by subsiding.
This phenomenon is known as failure by
piping or undermining.
40. (b) Failure by Direct uplift
The percolating water exerts an upward
pressure on the foundation of the weir or
barrage.
If this uplift pressure is not counterbalanced by
the self weight of the structure, it may fail by
rapture.
41. 2. Failure due to- surface flow
(a) By hydraulic jump
When the water flows with a very high velocity
over the crest of the weir or over the gates of
the barrage, then hydraulic jump develops.
This hydraulic jump causes a suction pressure
or negative pressure on the downstream side
which acts in the direction uplift pressure.
If the thickness of the impervious floor is
sufficient, then the structure fails by rapture.
42. (b) By scouring
During floods, the gates of the barrage are kept
open and the water flows with high velocity.
The water may also flow with very high velocity
over the crest of the weir.
Both the cases can result in scouring effect on
the downstream and on the upstream side of
the structure.
Due to scouring of the soil on both sides of the
structure, its stability gets endangered by
shearing.
43. Design aspects
(a)Subsurface flow
1. The structure should be designed such that the
piping failure does not occur due to subsurface
flow.
2. The downstream pile must be provided to
reduce the exit gradient and to prevent piping.
3. An impervious floor of adequate length is
provided to increase the path of percolation
and to reduce the hydraulic gradient and the
seepage force.
44. 4. The seepage path is increased by providing
piles and impervious floor to reduce the uplift
pressure.
5. The thickness of the floor should be sufficient
to resist the uplift pressure due to subsurface
flow.
6. A suitably graded inverted filter should be
provided at the downstream end of the
impervious floor to check the migration of soil
particles along with water. The filter layer is
loaded with concrete blocks.
45. (b) Surface flow
1. The piles (or cut-off walls) at the upstream and
downstream ends of the impervious floor
should be provided upto the maximum scour
level to protect the main structure against scour.
2. The launching aprons should be provided at
the upstream and downstream ends to provide
a cover to the main structure against scour.
3. A device is required at the downstream to
dissipate energy. For large drops, hydraulic
jump is used to dissipate the energy.
46. 4. Additional thickness of the impervious floor is
provided at the point where the hydraulic jump
is formed to counterbalance the suction
pressure.
5. The floor is constructed as a monolithic
structure to develop bending resistance (or
beam action) to resist the suction pressure.
47. Khosla’s theory
Many of the important hydraulic structures,
such as weirs and barrage, were designed on the
basis of
Bligh’s theory between the periods 1910 to
1925.
In 1926 – 27, the upper Chenab canal siphons,
designed on Bligh’s theory, started posing
undermining troubles.
Investigations started, which ultimately lead to
Khosla’s theory.
48. Following are some of the main points
from Khosla's Theory.
1. Outer faces of end sheet piles were much
more effective than the inner ones and the
horizontal length of the floor.
2. Intermediated piles of smaller length were
ineffective except for local redistribution of
pressure.
3. Undermining of floor started from tail end.
49. 4. It was absolutely essential to have a reasonably
deep vertical cut off at the downstream end to
prevent undermining.
5. Khosla and his associates took into account the
flow pattern below the impermeable base of
hydraulic structure to calculate uplift pressure
and exit gradient.
6. Seeping water below a hydraulic structure does
not follow the bottom profile of the impervious
floor as stated by Bligh but each particle traces
its path along a series of streamlines.
50. Method of independent variable
Most designs do not confirm to elementary
profiles (specific cases).
In actual cases we may have a number of piles
at upstream level, downstream level and
intermediate points and the floor also has some
thickness.
Khosla solved the actual problem by an
empirical method known as method of
independent variables.
51. This method consists of breaking up a complex
profile into a number of simple profiles, each of
which is independently amiable to mathematical
treatment.
Then apply corrections due to thickness of
slope of floor.
As an example the complex profile shown in fig
is broken up to the following simple profile and
the pressure at Key Points obtained.
52. Straight floor of negligible thickness with pile at
upstream ends.
Straight floor of negligible thickness with pile at
downstream end.
Straight floor of negligible thickness with pile at
intermediate points.
The pressure is obtained at the key points by
considering the simple profile.
53. For the determination of seepage below the
foundation of hydraulic structure developed the
method of independent variable.
In this method, the actual profile of a weir which is
complex, is divided into a number simple profiles,
each of which cab be solved mathematically without
much difficulty.
The most useful profile considered are:
(i) A straight horizontal floor of negligible thickness
provided with a sheet pile at the upstream end or a
sheet pile at the downstream end.
(ii) A straight horizontal floor depressed below the bed,
but without any vertical cut-off.
54.
55. Intermediate point
The mathematical solution of the flow-nets of the
above profiles have been given in the form of curves.
From the curves, percentage pressures at various key
points E, C be determined. The important points to
note are:
Junctions of pile with the floor on either side{E, C
(bottom), E1, C1 (top) }
Bottom point of the pile (D), and
Junction of the bottom corners (D, D’) in case of
depressed floor
56. The percentage pressures at the key points of a
simple forms will become valid for any complex profile,
provided the following corrections are effected:
correction for mutual interference of piles
correction for the thickness of floor
correction for slope of the floor.
57. Correction for Mutual Interference of Piles
Let b1 = distance between the two piles 1 and
2, and
D = the depth of the pile line (2), the influence
of which on the neighbouring pile (1) of depth
d must be determined
b = total length of the impervious floor
c = correction due to interference.
58. The correction is applied as a percentage of
the head
This correction is positive when the point is considered
to be at the rear of the interfering pile and negative for
points considered in the forward or flow direction with
the interfering pile.
59. Correction for Floor Thickness
Standard profiles assuming the floors as having
negligible thickness.
Hence the values of the percentage pressures
computed from the curves corresponds to the top
levels (E1*, C1*) of the floor.
However, the junction points of the floor and pile are
at the bottom of the floor (E1, C1)
60.
61. The pressures at the actual points E1 and C1
are interpolated by assuming a straight line
variation in pressures from the points E1* to
D1 and from D1 to C1.
The corrected pressures at E1 should be less
than the computed pressure t E1*. Therefore
the correction for the pressure at E1 will be
negative. And so also is for pressure at C1.
62.
63. Correction for Slope of Floor
A correction for a sloping impervious floor is
positive for the down slope in the flow direction
and negative for the up slope in the direction of
flow.
The correction factor must be multiplied by
the horizontal length of the slope and divided
by the distance between the two poles between
which the sloping floor exists.
64.
65. Exit gradient (GE)
It has been determined that for a standard
form consisting of a floor length (b) with a
vertical cut-off of depth (d), the exit gradient at
its downstream end is given by:
Values of safe exit gradient may be
taken as:
0.14 to 0.17 for fine sand
0.17 to 0.20 for coarse sand
0.20 to 0.25 for shingle