manual for inspection of structures

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MANUAL FOR

INSPECTION OF

STRUCTURES

(SPILLWAY, HEAD REGULATOR

AND OTHER CANAL STRUCTURES)

Narmada, Water Resources, Water Supply & Kalpsar DepartmentGOVERNMENT OF GUJARAT

April 2009



Mission Statement

Harnessing the untapped waters of rivers for the survival

of millions of people and environmentally sound

sustainable development of Gujarat State by providing the

essence of life -- water and energy

Initial issue date: April 2009

Date of revision Outline of changes made



1

Preface

Like any engineering work, structures i.e. dams and canal structuresrequire continual care and maintenance, first to ensure that they remainoperational and capable of performing all intended purposes and then

to preclude endangering people and property.

The safety of all canals is of considerable concern. Given that, theprinciple purpose of this Manual is to enhance the safety of dams andcanal structures.The purpose is to ensure adherence to approvedprocedures over long periods of time and during changes in operatingpersonnel.

The Manual is prepared primarily for the use of section officers incharge of various canals and canal structures who are assigned the

responsibility for the operation and maintenance of the canal.

THIS MANUAL CONTAINS, AS A MINIMUM, ALL INFORMATIONAND INSTRUCTIONS NECESSARY FOR SECTION OFFICERS TOPERFORM THEIR DUTIES.

The instructions provided in this manual are applicable to dams &canals of all sizes and types and are useful to all. The guidanceprovided is generally applicable to all situations. However, it isrecognised that the degree to which the methods and principles are

adopted will rest with the officer in charge of the dams & canals.

Manual for inspection of earthen embankments is also required to beread and operated simultaneously.



2

C O N T E N T S

Chapter Page

1.

PART I

Inspecting the structures

(Spillway, HR & Canal structures)

PART II General Problems & Deficiencies

2. Common Material Problems

Cracks

Surface defects

Concrete deterioration

Metal problems

3. Obstructions

4. Displacement

5. Foundation and backfill problems

6. Seepage7. Poor Drainage

PART III Inspection of Structures8 Inspection of spillways/ wasteweirs/

escapes

9 Inspection of canal siphons

10 Inspection of drainage siphon

11 Inspection of HR (Outlet works) 12 Inspection of cross regulators

13 Inspection of falls

14 Inspection of aqeducts



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15.

PART IV

Schedule of Routine inspection

16.PART V

Inspection during emergency



4

PART I

INSPECTING THE STRUCTURES(SPILLWAY, HR & CANAL STRUCTURES)



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Chapter 1

INSPECTING THE STRUCTURES (SPILLWAY, HR & OTHER

CANAL STRUCTURES)

1. Purpose

The purpose of inspection is to identify deficiencies that potentially

affect the safety of the structure. A deficiency is a condition that might

affect or interfere with the safety or operational effectiveness of the

structure.

2. Reviewing data

Review any available data about the structure before you begin your

inspection.An important aspect of inspection is tracking conditions and

potential problems to determine how and to what extent they are

changing over time.Historical and design information can alert you to

conditions and features that are of special concern and that should be

checked and documented.

Types of information that may be useful to review include:

• Design criteria

• Material data

• Construction records

• Records of operation

• Records of maintenance

• Previous inspection reports

• Manual of operation



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3. General Guidelines

When an inspection is conducted several things are required to be kept

in mind:

• The purpose of an inspection is to gather facts. Person inspecting

should probe for causes till he is satisfied.

• One should look for continuities or relationships among

deficiencies.

• All features of canal as well as structure should be inspected. No

shortcuts need to be taken. Enough time should be spent for

inspection. Particular attention should be paid to areas where

data indicate that change is occurring or where past deficiencies

have been noted.

• Person inspecting should know his limits and should consult

higher officers in case of doubt.

• SMPL rule should be observed for documenting conditions:

S Sketch the deficiency and note its important characteristics

M Measure the deficiency

P Photograph the deficiency/describe its characteristics in

writing

L Locate the deficiency relative to some standard reference

point

• Good notes should be taken; thorough records should be made.

•

Findings of inspection should be reported in form of precise reportimmediately after the inspection is over. This would be very much

useful at the time of subsequent inspections and also would help

evolve plan of action.



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4. Inspection tools and equipments:

Following outlines the tools and equipments that will be needed for

conducting inspection of canals and structures:

Binocular For sighting along top of bank, crest

Camera For recording conditionsRock hammer For sounding concrete/rock

Measuring tape For measurement

Probe For measuring width of crack at a depthPocket knife For scraping rock, scraping crevices/cracks

Shovel For clearing drains, manholes, pipesBucket and timer For measuring seepage & flow rates

Torch with cells For looking into pipes, conduits, barrelsJar For taking water samples, measuring turbidity

5. Spillways/ Escapes:

Observe the spillway/ escapes from the crest of waste weir. Walk along

the concrete sill noting any cracks, leaks, heaving or erosion etc. Check

the abutment-waste weir interface for any sign of erosion. Check walls

and floors as per checklist.

6. Head Regulator/ Outlets:

Observe the condition of the HR/ outlets at the upstream headwall. (In

order to view the outlet, it will be necessary to lower the water level in

the reservoir/canal. Prior to lowering, notify downstream operators.

Once the water level is lowered, the gate should be operated through

its full range as narrated in the "Guidelines for Operation &Maintenance " and also in the Standing Operating Procedure issued if

any, however, the gate must be closed for inspection of the waste

weir.)



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7. The downstream area:

Walk along the bed of the downstream channel and observe any

unusual conditions which may affect the performance of the dam/

canal, such as debris, vegetation, seepage, wet areas or excessive

sedimentation. Observe the lining, if any, to the channel to ensure that

they are intact and in good condition.

The inspection checklist included in this Manual should be copied and

completed every time a maintenance inspection is performed.

8. Inspecting the upstream face of structure

The upstream face should be inspected from the top of the wall,

abutments, Top of Bund of canal or a boat. The number of positions

from which you inspect the face depends on the length and height. It is

desirable that the water level in the reservoir/ canal is as low as

possible when you inspect the upstream face and that is the reason

why March inspection is most likely to give better chances of

inspection.

9. Under water inspection

In some instances it may be advisable to have a divers’ team inspect

the upstream face at a specific location below the waterline. This is a

special inspection technique that is used occasionally to determine the

cause or extent of a specific problem.

10 Inspecting the downstream face of structure

If leakage is occuring or if structural distress is evident, it will

most likely be found on the downstream face. It is best to inspect

downstram face with water in the dam/ canal at the highest waterlevel



9

possible. This will increase your chances of seeing leakage on the

downstream face of the dam/ canal.

Pay particular attention to the toe of the structure where the structure

joins the foundation material as well as the junction of the structure with

the dam/ canal embankment.Look carefully for:

• Seepage along the toe

• Cracks• Alignment changes.

11. Special safety concerns when inspecting structures

The following safety issues are particularly important to the inspection

of spillway, HR & canal structures:

• Only persons who are physically fit should attempt a strenuousinspection task.

• Provide for communication between someone at the entranceand the person inspecting the inside of a structure.

• Poisonous snakes are a real threat in some parts.

• For an under water inspection, divers should be qualified in bothdiving and , if possible, diving inspection. Video may be provided

while carrying out under water inspection. Divers may be madeaware of the potential dangers near intake structures andentrance of HR,siphon barrels, such as cross currents, damage todiving equipment from sharp edges of metal or protruding bars

• When working around energy dissipators or on steep or slipperyslopes, inspecting person should be secured by ropes orharnesses.Water conveyance surfaces often have algae growththat can be particularly treacherous.

IMPORTANT INSPECTION TIP:If water is against the gates, make sure all controlequipment has been secured from operation or clearlymarked (red tagged) with warnings that personnel maybe injured if the equipment is operated. Be sure thatoperations and inspection personnel understand thesignificance of red-tag procedures.



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PART II

GENERAL PROBLEMS AND DEFICIENCIES



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CHAPTER 2

COMMON MATERIAL PROBLEMS

These include common problems observed in construction

material like concrete, metal, PVC water stops etc.

CONCRETE PROBLEMS COMMON IN STRUCTURES

1. Condition of concrete works is generally dependent on the

quality of materials used, circumstances or quality of

construction, and severity of weather exposure. Poor quality

materials and deficient composition of concrete and mortar willbe evidence by various forms of deterioration. Likewise, poor

quality construction, such as the use of too much of water in

mixes or finishing and/or permitting exposure to heat before

adequate curing and hardening of concrete or mortar, will lead

to early and accelerated concrete deterioration.

2. Expansion, contradiction, and construction joints and

pressure relief valves may be of concern when they become

"open" and permit seepage or leakage of water. Some opening or

closing of joints normally occurs with temperature changes.

3. All structures experience the entire range of possible concrete

problems, but conditions especially worthy of note are:

• Cracking

• Surface defects

• Concrete deterioration : Cavitation• Concrete deterioration : erosion

• Leaking Joints- Inadequate or damaged water stops- Other joint problems



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1. CRACKING :

4. All concrete is subject to cracking, which is usually the first

visible sign of concrete distress. You will see many cracks in thecourse of your inspections, and not all cracks are serious.

However, cracking should be monitored because cracks can

provide openings in the concrete that allow other types of

deficiencies to develop.

Characteristics of Cracks

5. Cracks in a concrete dam can be described in terms of several

characteristics: width, direction, depth, location, and trend

(change).

Length

6.Length is a self-evident concept. The length of a crack is

established by measurement.

Width

FIGURE I. DETERMINING CRACK WIDTH

(Sectional View)



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7. The width of a crack is the amount of separation between the

two concrete parts. One common mistake made by some

inspectors is that they measure the width of a crack at the

surface, where deterioration of the concrete may exaggerate thetrue dimensions of the crack. Although surface deterioration

should be noted, it should not be included in an estimate of

crack width. If possible, you should measure or estimate crack

width at a depth below the surface deterioration by inserting a

probe such as a knife blade or wire. Figure 1 illustrates how to

determine the width of a crack.

Direction

8. The direction, or orientation, of a crack can be described

using one or more of the following terms, which are illustrated

in Figure 2:

• Longitudinal: A longitudinal crack runs roughly parallelto the top of the member of the structure.

• Transverse: A transverse crack runs roughly perpendicular to the top of the member of the structure.

• Horizontal: A horizontal crack is one that lies at asingle elevation.

• Vertical: A vertical crack runs up and down.

•

Diagonal: A diagonal crack shows some inclinationbetween horizontal and vertical



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Cracking also can occur in random patterns (e.g., alligatorpattern) over the concrete surface.

FIGURE 2. ORIENTATION OF CRACKING

Depth

9. The full depth of a crack may be difficult to determine unless

the crack extends to another face or interior surface of the dam,

such as a chamber wall.

Trend

10. Trend is extremely important in monitoring cracking. The

trend of a crack is its history of change. Studying prior reports

before you begin an inspection will enable you to focus on how

cracks have changed--that is, whether they have become longer,

wider, or deeper, changed direction, or remained unchanged.Documenting any changes you observe will enable future

inspectors to do the same thing.

Location

11. Identifying the location of a given crack is vital to monitoring



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its trend in future inspections. Some of the reference

conventions are:

• Left and right facing downstream

• Block and joint numbers• Drain numbers

Other reference points are also useful:

• Stations (measured along the axis of the structure)

• Lift lines

• Elevation (on the downstream face)

• Measurements from any identifiable feature of thestructure (e.g.handrails, parapat)

Types of Cracks

12. Cracking in concrete structures generally falls into the

following four categories:

• Structural cracks

• Cracks along joints

• Shrinkage cracks

• Thermal cracking

• Pattern cracking

• D-Cracking

• Other Shallow Cracking

Structural Cracks

13. A potentially serious type of crack is the structural crack --

a crack that calls into question the structural integrity of an

element. Structural cracks are caused by the overstressing of portions of the sytucture because of extreme loading conditions,

inadequate design, poor construction techniques, or faulty

materials.

Often, structural cracks can be related to some feature of the



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structure where stress concentrations occur--for example. . .

• The corner of an opening

• Areas of large temperature gradient

• Discontinuities in the foundation caused by material or

alignment changes or by differential movement infoundation or abutments

FIGURE 3 STRUCTURAL CRACK WITH VERTICAL DISPLACEMENT (Elevation View)

14. Structural cracks are often irregular; that is, they run at an

angle to the major axes of the member (say wall or column) and

they may change direction abruptly. These cracks are usually

wide and may be associated with noticeable displacement of the

concrete adjacent to the crack. The opening may tend to

increase as a result of continuous loading and creep of the

concrete. Figure 3 shows an irregular structural crack with

vertical displacement.

Cracks Along Joints

15. Cracking may occur along joints because of structural

movement, volumetric changes, or chemical reactions. Some of

these cracks are intentional and occur by design. Other cracks

along joints are not intentional and may pose a threat to the



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integrity of the structure. Document any new or worsening

cracks along joints, unless you are certain that these cracks are

there by design.

Shrinkage Cracks

16. When concrete is subjected to cycles of wetting and drying,

it expands and contracts. Volume changes occur during this

process and develop tensile stresses within the concrete,

causing cracking. Shrinkage cracks due to drying are generally

fine and show no evidence of movement. They are usually

shallow, but they can be several feet long.

17. Shrinkage cracks often occur soon after construction, as the

cement paste cures and shrinks. These cracks usually occur

shortly after construction and usually do not penetrate deeply

enough to be a threat.

Thermal Cracking

18. When concrete is placed in large sections, high tensile

stresses can result from the heat generated by the hydration of

cement, followed by differential cooling. When tensile stresses

exceed the tensile strength of the concrete, the concrete will

crack. Cracking due to thermal stresses is usually orthogonal

(rectangular) or blocky. Thermally induced cracks are generally

much deeper than shrinkage cracks.

19. Cracks also can be caused by temperature variations not

associated with construction. During cold weather, upper

portions of the darn may become colder than the lower portions



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that are in contact with the reservoir water. This temperature

difference can cause cracks to form, extending from the top

down each face of the strucyural member.

Pattern Cracking

20 Pattern cracking is indicated by fine openings on concrete

surfaces in the form of a pattern. Pattern cracking results from

a decrease in volume of the material near the surface, or

increase in volume of the material below the surface, or both.

Figure 4 illustrates pattern cracking.

FIGURE 4 PATTERN CRACKING

21. Pattern cracks usually indicate a problem, such as freeze-

thaw action or some type of undesirable chemical reaction

occurring in the concrete. Chemical reactions will be discussed

in greater detail under concrete deterioration.

22. Freeze-thaw action occurs when water enters the pores,

cracks, or joints in the concrete. When the water freezes, it

expands and causes the concrete to crack. Water then can enter



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the new cracks and, when it freezes, cause the cracks to widen,

or spall at the surface.

D-Cracking

23. Sometimes D-cracking along joints is an early sign that

freeze-thaw action has occurred. (D-cracking is the progressive

formation of a series of fine cracks at close intervals, often in

random D-shaped patterns along a joint.) Figure 5 illustrates D-

cracking. As the cycle continues, the cracks extend farther away

from the joint and become more severe. This process may lead

to further disintegration of the concrete.

FIGURE 5 D-CRACKING

24. Virtually all mass concrete placed in recent years has

included entrained air to reduce freeze-thaw deterioration.

Other Shallow Cracking

25. Other types of shallow cracking you may notice in concrete

surfaces are checking and hairline cracking. Checking refers to

the developmeJ1t of shallow cracks at closely spaced but

irregular intervals on the surface of mortar or concrete. Hairline

cracking refers to small cracks of random pattern in an exposed



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CRACK SURVEYS

27. A crack survey is an examination of a concrete structure for

the purpose of locating, recording, and identifying cracks and of noting the relationship of the cracks with other destructive

phenomena. Since cracking is often the first noticeable symptom

of concrete distress, a survey is a significant part of evaluating

the future serviceability of the structure. Some cracks may

occur early and not progress, while others may occur later and

increase in extent. Some may occur after an unusual event. A

design drawing or inspection drawing is often used to record the

location and extent of cracks in this type of survey.

28. A crack survey should identify-

• Characteristics of the cracks (length, width, direction,depth, and location)

• Descriptions of types

• Descriptions of other conditions or deficiencies thatmay be associated with cracking

Whenever feasible, external cracks should be correlated with

internal cracks. Where repairs have been made to the concrete,

crack surveys are difficult to perform and may be unreliable

because cracks beneath the repairs may indicate deficiencies at

greater depths. It is significant, however, to note whether newcracks have developed in the repair concrete. Such cracks may

indicate continued structural problems.



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INSPECTION TIP: If you are at all unsure about the severity of cracking consult Design Office so the situation can be evaluated.

Figure 6 next page shows a Crack Map.



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Figure 6 Crack Map



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2. SURFACE DEFECTS

29. Surface defects are concrete deficiencies that are not

progressive in nature; that is they do not necessarily become

more extensive with time. They may include -

• Shallow deficiencies in the surface of the concrete.

• Textural defects resulting from improper constructiontechniques.

• Localized damage to the concrete surface.

If you observe surface defects in the concrete, you should-

• Record their nature and location.

• Note the need for prompt repair of defects that might leadto more extensive deterioration (e.g., by allowing water toenter the concrete mass).

Among the most common types of surface defects are

honeycombs, stratification, evidence of from slippage, stains and

impact drainage.

Honeycomb: (Figure 7)

30. Honeycomb is a void that is left in the concrete when the



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mortar fails to fill the spaces between the coarse aggregate

particles effectively. Honeycomb is caused by poor construction

practices, such as inadequate concrete mixing, segregation due

to improper placement practices, or inadequate vibration afterplacement in the forms.

Stratification: (Figure8 )

31. Stratification is the separation of overly wet or over vibrated

concrete into horizontal layers, with increasingly smaller

FIGURE 8 : STRATIFICATION

material concentrated towards the top. Stratification can result

in concrete of non-uniform strength, weak areas and disbonding

of lift lines.

Form Slippage:

32.Form slippage occurs when construction forms lack

sufficient strength to withstand the pressure resulting from

placement and vibration of the concrete. When the forms slip



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during construction, they can produce slightly off set blocks and

uneven joints and surfaces. Sometimes form slippage is

mistaken for misalignment of the concrete, which usually occurs

well after construction.

Stains:

33. Although discoloration and staining sometimes are

associated with deterioration of concrete, most stains on

concrete surfaces cause only an unpleasant appearance rather

than damage. Stains may have natural causes, such as deposits

from runoff water of deposits from corrosion of exterior steel. They may also result from construction or maintenance

accidents (e.g. oil, grease, paint, creosote or asphalt).

Imapct Damage:

34. For example, the impact of a truck, boat, or crane, or rock

thrown into chutes can mar or chip away a portion of the

concrete surface. While such damage is localized, it can lead toother damage, such as freeze thaw action, by permitting

moisture to enter the concrete.

SURFACE DEFECTS : INSPECTION ACTIONS.

35. Unlike cracks, which may penetrate well into the concrete,

surface defects usually are shallow and do not usually present

an immediate threat to the structure. However, by erecting an

opening to weather and other forces, they can lead to other more

significant deterioration.

If you observe surface defects in the concrete, you should …..



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• Record their nature and location (remember SMPL)

• Note the need for prompt repair of defects that might lead

to more extensive deterioration (e.g., by allowing water to

enter the concrete mass).



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3. CONCRETE DETERIORATION

36. Deterioration is any adverse change on the surface or in the

body of the concrete that is caused by separation of components

of the concrete.

Types of Deterioration

37. There are numerous observable conditions that can indicate

concrete deterioration. Cracks, which we have discussed at

some length, can be considered a specific type of deterioration,

and they are often associated with other types of deterioration.

The following are the most common types of concrete

deterioration that you are likely to encounter.

Disintegration

38. Disintegration is deterioration of concrete into small

particles, or crumbling, due to any cause.

Spalling

39. Spalling is the loss of chunks of concrete from a surface,

usually because of compression, impact, or abrasion. Spalling

often occurs at the edges of concrete (e.g., along cracks, joints,

and corners or next to embedded objects). Figure 1, presented

earlier in this unit, showed a spall along a crack. Spalling may

have various causes:

• A blow to the concrete

• Action of weather

• Internal pressure (e.g., from a corroded rebar near thesurface)

• Expansion within the concrete mass



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Although spalls themselves are confined to the surface of the

concrete and thus may not be a serious problem, spalling can

lead to secondary problems. For example, spalling may expose

reinforcement, create a seepage path around an embeddedwaterstop at a joint, create an offset along the flow surface, or

develop into a point of structural weakness.

Efflorescence

40.Efflorescence is a deposit of salts from within the concrete

that forms on the surface. Efflorescence is caused by water

leaking through joints and cracks, leaching calcium hydroxideor carbonate from the cement, and carrying it to the exposed

surface. As the water evaporates, a hard, white calcium deposit

forms on the surface.

As calcium is leached from the concrete around the joint, the

opening may widen. This in turn leads to increased leakage and

faster deterioration. It should be noted, however, that leachingalso can be a self-healing process. In some cases the calcium

may be deposited in such a way around the joint that it seals

the opening against additional leakage.

Drummy Concrete

41.Drummy concrete is concrete that has a void, separation, or

other weakness within the concrete--usually a thin surface layer

separated from the mass. You can check for drummy concrete

by striking a hammer or "bonker" against the surface and

listening for a hollow sound. Figure 9 illustrates drummy

concrete.



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FIGURE 9. DRUMMY CONCRETE

(Elevation View)

Popouts

42. A popout is a small portion of the concrete surface that

breaks away, due to internal pressure, leaving a shallow, conical

depression. Figure 10 illustrates popouts.

FIGURE 10. POPOUTS (Elevation View)



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Pitting

43. Pitting is the development of relatively small cavities in the

concrete surface. Pitting is caused by localized disintegration.

Figure 11 illustrates pitting.

FIGURE 11. PITTING (Elevation View)Scaling

44. Scaling is the flaking or peeling away of the surface of the

concrete or mortar. Figure 12 illustrates scaling.

FIGURE 12. SCALING(Elevation View)

Causes of Concrete Deterioration

45. In most cases cracking is both an initial cause and an effect

of concrete deterioration. That is, by exposing internal surfaces



32

of the concrete to weathering, seepage, chemicals, or other

elements, cracks lead to further deterioration. At the same time,

cracking is often an indication that concrete deterioration is

occurring.INSPECTION TIP: Whenever you observe cracking, you should be alert to the possibility of other types of concrete deterioration.

46. We have already discussed drying shrinkage, thermal stress,

and freeze-thaw action as causes of concrete deterioration.

Other common causes of concrete deterioration are the

following:

• Faulty concrete mixes

• Chemical attack

• Metal corrosion

• Erosion

• Cavitation

47. Faulty Concrete Mixes Ingredients used to make mass

concrete must be carefully proportioned to produce concrete of

adequate strength and durability. When concrete mixes contain

improperly graded aggregates or improper cement or water

content, the concrete may lack strength and be subject to

disintegration.

48. Chemical Attack There are three common types of chemically

induced deterioration in concrete: attack, acid attack, and

alkali-aggregate reaction.

49. Sulfate Attack: Sulfate attack is a chemical and/or

physical reaction between sulfates in soil or ground water and

concrete. The reaction causes expansion, or growth, in the



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concrete, which leads to disintegration. Concrete attacked by

sulfate is usually light in color and falls apart easily when

struck with a hammer. Other typical symptoms of sulfate i1 t

tack include. . .• Cracking

• Spalling

• Scaling

• Stains

50. Acid Attack: Acid attack is usually the result of bacterial

action on the calcium hydroxide found in hydrated Portland

cement, limestone, or dolomitic aggregates. In most cases, the

reaction results in leaching away of water-soluble compounds.

Symptoms of acid attack may include. . .

• Efflorescence

• Cracking

• Spalling

• Color change

Acidic water created by this reaction can also hasten corrosion

of embedded steel reinforcement. As the steel corrodes, internal

pressures develop, which may crack or spall adjacent concrete.

51. Alkali-Aggregate Reaction: An alkali-aggregate reaction is

an undesirable chemical reaction between cement and aggregate

that causes abnormal expansion and cracking. There are two

main kinds of alkali-aggregate reaction: alkali-carbonate

reaction and alkali-silica reaction. Early indicators include. . .

• Pattern cracking, usually concentrated in areas thatare exposed to moisture in a wet-dry cycle (e.g., piers,parapets, and the top of the structural member)

• Efflorescence

• Incrustation



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• White rings around aggregate particles

• A gel-like substance at pores, cracks, or openings inthe concrete (only for alkali-silica reactions)

Extreme alkali-aggregate reactions are characterized by closing

of expansion joints, hence the term growth of concrete is

sometimes used. Continued reaction can result in . . .

• Debonding of blocks at lift lines

• Binding of gates, valves, and metalwork

• Severe cracking

• Loss of strength and ultimate failure of the structureby sliding or overturning

Metal Corrosion

52. Embedded reinforcing steel normally is protected by the

concrete. When the concrete deteriorates, however, water can

reach the steel and cause it to corrode. The oxide produced

during corrosion results in an increase in volume, which causes

the overlying concrete to crack and spall. The most well-known

form of corrosion is rust. Indicators of rust corrosion in

reinforcing steel include-• Cracks running in straight, parallel lines at uniform

intervals corresponding to the reinforcement spacing

• Rust stains on the surface

• Spalling

• Exposed reinforcementFIGURE-13. CONCRETE DETERIORATION DUE TO METAL CORROSION



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Figure 13 shows concrete deterioration due to metal corrosion.

53. Other types of corrosion to steel reinforcement bars include:

•

Galvanic Corrosion, which occurs at metal-to-metalconnections and contact points and may appear as

corrosion in one of the metals but not the other.

• Pitting Corrosion, which appears as small cavities or

craters on the metal and may be indicated by changes in

surface texture of the metal.

• Stress Corrosion, which is a result of the combined action

of environmental corrosion and the application of stress to

the metal. This type of corrosion cannot be detected by

observation alone and can result in rapid, brittle failure of

the metal without warning.

CONCRETE DETERIORATION: CAVITATION

54. Concrete deterioration is any adverse change on the surface

or in the body of the concrete that is caused by separation of

components in the concrete.

Cavitation occurs when a critical combination of the flow

velocity, the flow pressure, and the vapour pressure in the water

in the water is reached. An offset or irregularity on a flow

surface exposed to high velocities produces turbulence. Thisturbulence creates negative pressures that cause water to

vaporize and form bubbles, or cavities, in the water. Bubbles

collapse when subjected to higher pressures downstream from

the formation site.



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Bubble collapse dynamics then create shock waves that can

damage the flow surface. Popping and cracking noises

(Crepitation) accompany the collapse of the cavities. The impact

of the shock waves can produce pressure up to 100,000 pounds

per square inch. Repetition of these high-energy blows

eventually forms the pits or holes known as cavitation damage.

55. Common sites for cavitation are:

• Downstream of gates and valves

• In steep spillway chutes, tunnels or conduits

Cavitation may occur on the floor of a chute, or on the walls or

sides of a structure.

Cavitation damage resembles erosion damage, but cavitation is

potentially a much more serious problem, once the process

begins, deterioration can occur quickly. A tiny offset or

carbonate deposit may induce cavitation, leading to serious

damage or failure of the concrete in a structure during heavy

flows.

56. A pitted surface and/or rough holes with aggregate plucked

out suggest cavitation damage. Damage upstream and

progresses downstream in a “leapfrog” pattern: each cavitation

site triggers the deterioration of a new site downstream.

57. If cavitation is detected, try to determine what event caused

the damage and to evaluate the potential for further damage.

Consider the frequency of operation. Examine air vents to flow

passages visually or by pouring water into them to ensure that

they are not obstructed.



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58. Cavitation effects can sometimes be mitigated by repairing

the area stronger material such as steel polymer concrete.

Installing aeration slots in tunnels/ conduits eliminates negative

pressures by providing additional air to the affected areas.

Concrete Deterioration: Erosion:

59. Erosion in concrete usually begins with wearing away of the

matrix material around the aggregate, and appears as relatively

uniform damage over a large surface. In a spillway, fall or

escape, erosion is usually due to the movement of abrasive

materials being carried by the flowing water. Aprons and stillingbasins (also known as hydraulic jump basins or simply jump

basins) are especially susceptible. Erosion often occurs after

initially cavitation damage, and serves to increase and extend

the damage.

60.Points of abrupt change in the flow channel or corners

subjected to abrasive action are likely to show pronounced

effects. Examples are:

Bends leading from tunnels,Conduits, and chutes.

Energy dissipators in stilling basins.

61. Ballmilling is a specific form of concrete erosion. Repeated

rotation of debris (usually rocks) by discharging water grinds the

surface, usually in a circular pattern. Stilling/hydraulic jump

basins are prone to ball milling damage.

If the flows continue for long time periods and if abrasive

material is carried at relatively high velocities, extensive erosion

damage to concrete structures results. Erosion in a



38

stilling/hydraulic jump basin floor can excavate enough

material to make the structure unstable.

Leaking Joints

62. Joints may leak because of damage to waterstops or other

joints problems.

Innadequate Or Damaged Waterstops:

Figure 14 : Waterstop

63. Concrete channels and conduits & masonry spillways often

include waterstops, which are continuous strips of waterproof

material, usually metal, PVC, or rubber. During concrete

placement, waterstops are embedded in joints between sections

to prevent moisture from penetrating the joints by providing a

restricted route for seepage water.

If damaged waterstops no longer provide a continuous seal,extensive seepage through the joint could erode foundation

material or promote freeze thaw damage to the joints. Figure 14

shows a typical waterstop.



39

Other Joint Problem:

Figure 15: Open joints in a channel

64. Joints should be inspected while dry if possible. Conduits

also can be inspected just after dewatering, since water shoots

back through the leaking joints, and the worst leaks can be

identified. (Some leakage after dewatering is normal). Sometimes

construction joint drawings and joint survey information exist,

and provide useful reference when joint problems are suspected. The following points apply to inspection of joints.

• Soil fines oozing through a joint are evidence of seepage.

• Joints in concrete sections are often sealed with joint

sealant, or plastic or rubber compression seals. When the

sealant or seal is missing or hardened, the joint is exposed

to damage. Vegetation in joints indicates damaged or

missing joint sealant.

INSPECTION TIP: - If the joint is located in a conduit running through the dam or canal embankment (as in case of HR at damsite, missing or defective joint sealant is cause for concern.



40

Surface Mapping

65. Surface mapping involves documenting concrete defects in a

systematic manner. All types of deterioration should beincluded. Surface mapping can be accomplished using detailed

drawings, photographs, or videotape. When photographs are

used, a ruler or familiar object should be included to indicate

scale. A grid is sometimes used to overlay a section of a drawing

so the location of cracks and other defects can be shown easily.

Figure 16 shows an example of surface mapping of concrete

deterioration.

CONCRETE DETERIORATION : INSPECTION ACTIONS

66. Common sense and your organization’s procedures must

guide you in responding to concrete deterioration. If you observe

cracking or other deterioration of concrete, you should ….

• Use the SMPL rule to document the deteriorationSketch, measure, photograph and locate indicatingdirection (longitudinal, transverse, horizontal, vertical

FIGURE-16. SURFACE MAPPING



41

or diagonal), size, length, width, depth of deterioration.

.

• If surface maps exist, or if deterioration has beendocumented before, compare your observations with

recorded date and document your findings.

• Be alert to other types of deterioration in the concretethat may be related to an overall problem.

• Use a hammer or “bonker” to sound the concretesurface for drummy concrete.

INSPECTION TIP : Immediately notify Executive Engineerof any deterioration that is extensive, has changedsignificantly since the previous inspection or appears toaffect the integrity of the structure.

Carry out IMMEDIATE repairs if deterioration in concretereaches embedded reinforcement steel.



42

4. METAL PROBLEMS COMMON IN STRUCTURES

Corrosion (Rust, Galvanic Action)

67. Corrosion is progressive deterioration resulting from

exposure to moisture acid and other corrosive agents, or

electrolysis, and usually is marked by scaling or flaking, pitting,

and color changes. Loss of paint or other protective coatings can

leave a metal surface subject to corrosion,

ESPECIALLY IF THE SURFACE is cycled between wet and dry.

Unchecked corrosion eventually leads to failure of a metal

structure.

Fatigue:

68.Fatigue is loss of metal strength from repetitive loading such

as being bent back and forth. Protrusions on metal components

or components with moving parts are most likely to suffer

fatigue. Distortions or cracked point may indicate sites where a

metal structure suffers from fatigue. The process continues untilthe affected area cracks and/or breaks.

Erosion :

69. Flow surface and areas around rivets and splice plates may

be scoured by abrasive debris.

Tearing and Rupture :

70. Tearing and rupture may result from impact, such as a log

slamming into a steel lining. On structures, metal components

are most likely to tear and rupture during storms or other

occasions when flows are heavy. Tears and ruptures can cause a



43

metal structure to fail completely, or expose the structure to

corrosion, cavitation, fatigue or other damage.

Cavitation:

71. Cavitation of metal surfaces, such as metal conduits, can

occur when high flow velocities exist on a flow surface with

offsets and irregularities. The bubble collapse dynamics of

cavitation cause pitting of the surface which results in

progressive deterioration to the point of failure. As in concrete,

the site of initial cavitation damage triggers the formation of

another site downstream, so the process develops in a leapfrogpattern. Areas just downstream of gates and valves are

susceptible.

Cracking:

72. Cracking is usually induced by vibrations.

Deformation:

73. Stress may deform metal shapes. (“Egg-shaped” pipe is an

example.)



44

Chapter 2

OBSTRUCTIONS

1. An obstruction is an unauthorized or unplanned addition to a

structure that reduces flow capacity.

Significance of Obstructions:

2. An obstructed spillway,escape or outlet works cannot perform

its function properly. During a flood, if reduced flow capacity

prevents the spillway or escapes from diverting enough water

from the reservoir/canal or the outlet works from lowering thewater level in reservoir/canal, the dam/canal embankment may

be overtopped, and put in danger of failure.

3. Causes of Obstructions:

Figure 17 : Obstructions

• OVERGROWN VEGETATION, Grass is the ideal cover foran earth-lined surface, shrubs, tall weeds, and treesreduce flow capacity.

• AQUATIC VEGETATION, Submerged aquatic plants suchas water hyacinths can obstruct a submerged entrancechannels to an outlet works. Algae is a problem at outlets.



45

• Adjacent Slope Failure, Causes for slope failure includeoverly steep channel and bank slopes, drawn down of areservoir/ canal bank in saturated bank material, and flowundercutting banks slopes due to:

• - Unprotected soil- High flow velocities- Loose or deteriorated bottom and slope material- Failed protective surface

Figure 18: Other Obstructions

• DEBRIS, Dead trees, slide material, and other debris canform obstruction Sediment accumulation, vandalism, andbeaver activity are also sources of debris. The approachchannel, trash racks, and gates of an outlet works areliable to be obstructed by debris.

• BEAVER DAMS,: Beaver dams can obstruct channels,submerged structures, riser pipes, and box inlets.

• Manmade structures, Fences or boat docks sometimes arebuilt on earth-lined spillways. Also, unauthorized

flashboards sometimes are added to the control section forheading up water level. Watch for earth or concretediles orsills or wooden logs added to the crest near CR/HR toraise storage capacity.

Chapter 3



46

DISPLACEMENT

1. Displacement occurs when a structure or component moves

from its originally constructed position. Movements do occur as

a result of seasonal temperature change or other causes. Such

movements are taken into account in the design of a concrete

structure.

2. Movement resulting in displacement can be caused by such

factors as …..

• Abutment or foundation settlement or displacement.

• Chemical reactions in the concrete.

• Structural behavior of the dam.• Other applied loadings of exceptional magnitude (e.g.,

uplift pressure, Earth-quake, extreme temperaturevariations).

FIGURE-19. MISALIGNMENT AND DIFFERENTIAL MOVEMENT

3. There are two main types of displacement in a concrete dam :

misalignment and differential movement.

Misalignment.



47

4. Misalignment is any variation from the original structural

configuration.

Differential Movement.

5. Differential movement occurs when one part of the structuremoves with respect to adjacent parts of the structure. Figure 19

presents examples of misalignment and differential movement.

Detecting Displacement

6.You are most likely to detect displacement by using sighting

techniques at the top of the structural member. Differential

movement most often appears as deflection at joints between

adjacent blocks. Other indicators of displacement include……

• Volume change in the concrete.

• Closing or opening of joints.

• Loss of joint filler.

• Cracking.

• Debonding of lifts.

• Tilting, shearing, or shifting of hardware or machinery.

• Binding of gates.

DISPLACEMENT : INSPECTION ACTIONS.

7. Movement in and of itself is not bad. Small movements are of

little concern and usually are considered in the design of the

structure. Movement becomes significant when it has an

adverse impact on the entire structure or on one or more of its

parts.

INSPECTION TIP : Significant changes – either in

magnitude or in directions should be evaluated immediately

consult Design Circle.

When you prepare for an inspection, you should-



48

• Study data from previous inspection reports or derivedfrom surveys, if available.

• Focus on areas of the structure where evidence of movement has been noted.

When you inspect for displacement, you should …

• Use sighting techniques along the top of thestructural member to look for misalignment anddifferential movement.

• Inspect joints, hardware, and equipment for evidenceof differential movement.

• Watch for structural cracking.

• Be alert for any changes in or new occurrences of displacement.

• For all displacement observed, record :o Location.o Extent.o Direction of displacement.o Any other evidence of movement.o Observations on date, time, and temperature.

INSPECTION TIP : Make sure to record the relative water

levels in the canal both upstream and downstream of the

structure.

Graphics or computer plots can be developed that allow you to

distinguish between seasonal movement cycles and potential

problems.

SMALL SCALE MISALIGNMENT:

Defining Small-Scale Misalignment

8. One type of small-scale misalignment, called differential

movement, is localized movement of one section of a lining, wall

ogee monolith, or other escape component relative to adjacent

sections, Causes of differential movement include:



49

• Loss of foundation or backfill

• Expensive clay shale foundation

• Poor drainage resulting in pressure behind the structure

9. Small-Scale misalignment may also result from misplacement

during construction. Figure 20 shows an offset between

sections of a chute. Pressures (possibly from poor drainage)

have moved the sidewalls inward in the upper section of the

chute).

Significance of Small-Scale Misalignment:

10.Small-Scale misalignment is a significant problems because -

• Offsets on flow surfaces can cause erosion and, in some

cases, cavitation. Both can eventually cause the structure to

fail.

• Gaps between joints allow water to penetrate and undermine

foundation material, creating excessive uplift pressure,

and/or allowing earth or rock material to escape.

• Compression across joint surfaces can result in concrete

spalling metal deformation, or ruptured water stops

Large-Scale Misalignment:

Defining Large Scale Misalignment :

11. Large Scale Misalignment is the dislocation of entire

structures from their design locations.

Causes of Large-Scale Misalignment:



50

12. One example of large-scale misalignment is a conduit that

sags below its design horizontal centerline. Deformations of

failures responsible for large-scale misalignment include:

• Over compacted backfill, excessive earth pressure, orhydrostatic pushing the structure out of position.

• Loss of backfill or foundation materials.

• Base spreading.

• Shear failure in foundation.

• Settlement of foundation.

• Seismic activity causing foundation collapse.

13. Large-Scale misalignment may cause a structure to fail.

Landmarks, boundaries, and sighting techniques can be used to

check for this problem.

Chapter 5

FOUNDATION AND BACKFILL PROBLEMS:



52

SEEPAGE

1. Seepage is the slow percolation of water through the

embankment and its foundation.

What are Leakage and Seepage?

2. Some use the terms leakage and seepage interchangeably. For

the purposes of this module:

• Leakage is the flow of water through joints, cracks, andopenings in hydraulic structures.

• Seepage is the flow of water through the abutments or

foundation of the dam.

Significance of Seepage

3. Both the velocity and quality of seepage must be controlled or

piping will occur. Piping is a term that describes internal erosion

that begins at the downstream side of the embankment and

continues at a progressive rate towards the reservoir until an

internal pipe or direct conduit to the reservoir/canal has been

formed. Rapid failure of the dam/ canal embankment results.

Figure 21 shows one way a piping failure can occur from

seepage through an outlet works.



53

4. A hole in the conduit allowed water to seep outside the

conduit and move along the pipe to the toe of the dam/ canal.

As the seepage water emerged from the embankment, it carried

some of the embankment material with it, As the hole enlarged,seepage increased. The embankment was progressively eroded

back toward the hole, forming a “pipe” through the embankment

material. The piping failure was completed when sloughing of

the embankment caused the dam/ canal to be breached.

Figure 21 EXAMPLE OF PIPING FAILURE

Characteristics of Leakage.

5. Leakage normally occurs through joints or cracks in the

concrete. The main causes of leakage are the following :• Cracks.

• Open joints.

• Broken seals.

• Leaking pipes or conduits.

• Deteriorated or defective concrete.



54

Evidence of leakage can vary from a moist or wet surface to a

concentrated flow of water. The most common indicators of

leakage in a concrete structure are:

•

Wetness on the downstream face of the structure.• Staining or buildup of sediments along joints and cracks.

• Water spurting or running out of joints or cracks on thedownstream face.

• Significant flows in the drainage system, and formeddrains, tail channels, river .

6. Leakage can result in an increased rate of deterioration of

concrete, leaching of concrete, loss of mass, and reduced

structural strength. Leakage can also cause excessive

hydrostatics pressure within the structure, leading to

overturning or sliding of blocks of the structure.

Characteristics of Seepage :

7. Seepage through the foundation and abutments can be

caused by the following conditions :

• Foundation deterioration.• Inadequate grout curtain.

• Joints or seems in the foundation or abutment material.

Evidence of seepage may include:-

• Wet areas on the abutments or foundation downstream of the structure.

• Lush vegetative growth in an area downstream of thestructure.

• Instability of the slopes (e.g., slumps and slides)downstream of the structure.

• Indications in instrument readings of undesirablehydrostatic pressure buildup.

8. The potential consequences of seepage include increased

uplift pressure and differential movement in the structure.



55

Seepage also has the potential for solutioning soluble rock

materials or instability (sliding) of the abutment or foundation

and thus weakening the foundation, with potential failure as a

consequence in some cases. In very basic terms, excessiveleakage and seepage can lead to loss of usable water.

Monitoring Leakage and Seepage.

9. All concrete structures leak and seep. The amount of leakage

and seepage usually correlates with the water level in the

reservoir/ canal. Generally, as the water level in the reservoir/

canal rises, the seepage flow rate increases. Temperatures alsoaffect the amount of leakage during cold weather, concrete

contracts and joints or cracks open, increasing leakage.

10. As part of your inspection, you should monitor the rate and

trends of leakage and seepage. You will need to check previous

records of leakage and seepage for comparable water surface

elevations in the reservoir/canal so that you can compare your

findings. You are looking for:

• Significant new leakage or seepage.

• Major changes in leakage / seepage pattern or flow.

• Turbidity in seepage.

Turbidity.

11. Turbid water is cloudy, and is an indication that the

foundation material may be eroding.INSPECTION TIP : Turbidity is cause for concern.

Each time seepage is measured, clarity should be evaluated.



56

Taking Measurements

12. Measure the amount of seepage and leakage and record in

the Operating Log (LogBook). If previous records are not

available for comparison, a program to collect flow data may need to be initiated. Don’t forget to include the water level in the

reservoi/ canal each time flows are measured. This will help

determine the cause of a change in the amount of flow. Clarity of

seepage i.e. whether clear or carrying sediment and any staining

or discoloration of concrete is to be noted in the LogBook.

There are various ways to take flow readings. The most common

are:

• The use of weirs (refer to the module on instrumentation).

• The use of a bucket and stopwatch.

Blocked Drains.

13. In monitoring leakage, increased flows are not the only

cause for concern. A noticeable decrease in seepage can indicate

that a drain is becoming blocked. Blocked drains can lead to

deterioration of the concrete/ masonry, increased

uplift/hydrostatic pressures, and potential stability problems.

LEAKAGE AND SEEPAGE : INSPECTION ACTIONS.

14. If you observe leakage or seepage, you should ….

Monitor the flow and record the following :

• Location and quantity or flow rate of all leakage andseepage at exit points.

• Occurrence of recent precipitation that may affect theappearance and quantity of seepage.

• Water level in the canal at the time of the observation.

• Check seepage for turbidity.



57

• Document any suspected drain blockages. Arecommendation that the drains be cleaned may bewarranted.

INSPECTION TIP : Consult Executive Engineer if you

observe significant new leakage or seepage, major changes

in leakage / seepage pattern or flow, or turbidity in seepage.



58

Chapter 7.

POOR DRAINAGE

Weepholes and Drains

1. Structures commonly have weepholes or other means of

drainage to prevent excess water pressure from developing

behind a structure. When no weepholes or drainage systems

exist, or when drains are plugged, excess water will accumulate.

This is a problem for the following reasons:

• A saturated foundation has lower bearing capacity.

• Uplift pressure from seepage water may cause damage to a

chute.

• Structure are designed for certain waterloads. If these

hydrostatic pressures are exceeded because of defective

drainage, then instability or distress can result.

2. Weepholes can become plugged by debris, infiltration of fines,

iron incrustation, and carbonate deposits. An inspection sight

includes probing weepholes to check for obstructions and

recording depth measurements on the crack maps.

Signs of poor drainage include:

• Ponding of water behind walls.

• Dampness on concrete surface, especially at cracks and

joints.

• Moistures seeping through cracks or joints.

• Tilted walls or heaved slabs



59

Faulty Drainage: Inspection Actions.

3. You should-

• Observe the drain opening. Lock for deposits blocking the

opening.• Probe or sound drains to detect blockages.

• Check flow records for changes in flow rates that may indicate faulty drainage.

• Walk the gallery system and note the condition of gutters.Report gutter blockages and recommend prompt cleaning.

• Check pressure gauges.



60

PART III

INSPECTION OF STRUCTURES



61

Chapter 8

INSPECTION OF SPILLWAYS, WASTEWEIRS & ESCAPES

1. Spillways, Wsateweirs and Escapes are constructed to release

water in excess of the storage space in a dam/ canal. These are

important to the safety of dams/ canals, and maintenance to

allow proper functioning is essential. These usually are located

to discharge away from the embankment in order to preclude

erosion of the embankment when spilling. Regulated spillways/

escapes employ gates of various types to control the rate of flow

through the structure. Structural instability is evidenced by

deep cracks in slabs or walls, slab removal, foundation piping,

tilting of walls, and misalignment of walls. Obstructions

including debris, trash, trees, brush, and sediment diminish the

flow capacities of escape structures, stilling basins, and inflow

and outlet channels and may also produce undesirable erosion-

producing currents. Weep holes and drainage openings are

usually installed in the walls and floors of escape structures,

and these often become clogged with sediment and may be

occupied by animals or birds.

INSPECTION ACTION:

Inspect Annually the escape structure and channel for

instability, deterioration, obstructions, and erosion. Evidence of structural instability should be reportedimmediately, through Superintending Engineer in charge of the work to Design Circle who can assess significance andsuggest appropriate action to be taken.



62

Structural deterioration that is progressive andendangering the structural integrity of the canal should berepaired.

Obstructions including debris, trash, dead and live trees,

and brush and sediment deposits should be removed.(Debris, trash, trees, and brush should be disposed of inaccordance with forest and environmental regulations)

2. General inspection required as outlined vide Part II shall

apply for all the components of spillways/wasteweirs/escapes.

Following gives further details for inspection to be carried out.

Checklist for inspection of spillways/wasteweirs/escapes is

provided at the end of this chapter.

Control Section:

3. The control section is a particularly critical portion of a

spillway/wasteweir/ escape, as it receives flow of water from the

reservoir/canal and passes on to river/ tail channel via energy

dissipation system. It may also be in the form of a weir with

crest (or sill level) raised above ground/canal bed level. The

spillway/wasteweir/escape must begin releasing water as

intended by design, whether the flow is triggered, when canal

water level reaches a predetermined level or through the

operation of gates or the removal/failure of stoplogs. The most

serious danger posed by the inability of the control section to

operate properly is that the water level in reservoir/canal may

rise and overtop the banks.

Problems typical to the escape control section include:

• Deterioration of surface materials:Check the following

points for deterioration in the control section:



63

Look at surfaces in areas of concentrated and highvelocity flows, such as near gates, for erosion.

Check areas near large gates for cracking in concrete,and tearing, rupture, and fatigue in metal.

Examine the upstream edges of weirs for damage frombattering by debris. A boat may be used to inspect theupstream side of a weir immediately adjacent to thewater level.

INSPECTION TIP : High velocity flow over a concrete surface containing abnormalities can initiate cavitation damage. Check surfaces carefully for offsets, small holes and calcium carbonate deposits. The bearing surfaces

where gates rest and areas immediately downstream of gate slots, liner plates and air vents should be examined with special care.

• Obstructions:

4. Besides general types of obstructions already discussed,

check for the following obstructions to control sections:

Check for unauthorized equipment added to the controlsection.

• Backfill and Foundation Deficiencies:

5. Points to remember when inspecting the control section

for backfill and foundation deficiencies are:

Foundation in the control section often must bear thestress of heavy equipment. Check carefully fordisplacements that may indicate settling foundationshifts, or undermining. Check for voids under concretechannel walls and floors.

It is critical that gaps in joints do not expose foundationor backfill material where escape extends through the



64

embankment section, and that water stops, sealantsand compressive joint fillers are intact and in goodcondition.

Check for clogged weep holes and foundation drains if present and watch for seepage and other signs of problems with the drainage system.

• Operating Bridge And Pier Problems:

6. Deficiencies in the operating bridge, piers, decks, or

other access structures on the spillway/wasteweir/escape

could make gates and other controls unworkable in an

emergency, and collapse of the supporting structure couldobstruct the spillway/wasteweir /escape.

7. Check for the following deficiencies.

On concrete bridges, check joints and water runoff points for exposed metal and corrosion of reinforcementsteel.

Check for peeling or missing paint

On steel flashing over joints inspect for break down of welds or mechanical connectors, couplings, and flanges.

Look for loose or insecurely anchored guardrails.

Check the condition of previously repaired areas.

Check & clear bridge drains every quarter

8. Check bridge support as follows.

On concrete bridge supports look for stress cracking.

Check the bearing supports at the abutments forcondition and evidence of movement.

Look for misalignment or damage at sliding joints.



65

• Problems With Gates, Stoplogs:

9. When inspecting the control section of a

spillway/wasteweir/escape, your primary concern is to

ensure that the operation of gates and otherreservoir/canal evacuation equipment is not impaired by

adjacent and supporting structures.

10. When inspecting, stoplogs and structures adjacent to

and supporting gates check the following points.

Look for displacement of structural elements or

concrete deterioration that may be jamming ormisalignment gates. Have the equipment operated if possible, to detect jamming, or gates not seatedproperly on the crest. During operations, look fordeterioration of material on the underside of thegates. Note excessive leakage.

Watch for misalignment of gate stems and othersigns of strain from holding water or from debris or

over tightening.

Mechanical Equipment

11. All accessible parts of mechanical and associated

electrical equipment should be inspected visually every year

for damaged, deteriorated, corroded, cavitated, loose, worn,

or broken parts.

12. Mechanical and electrical equipment should be lubricated at

periodic intervals. The service and maintenance procedures

prescribed by the manufacturer should be followed for pumps,

motors, and other commercial components, where available.



67

Inspection of Gates and valves (annual).

(1) Visual inspection. –

When water conditions permit, inspect the downstreamsurfaces of the guard gate leaves and bodies, theupstream and downstream surfaces of regulating gateleaves and bodies, and outlet pipes.

Particular attention should be given to signs of cavitations damage to waterway surfaces downstreamfrom gate or valve leaves and flanged joints.

Inspect neoprene or rubber gate seals for deterioration,cracking, wear, foreign material deposits, and leakage.

Inspect valve and gates metal seats or seals for wear,scratches, foreign material deposits, and leakage.

Repairs should be made as necessary to keep theequipment in a safe and reliable operating condition.

(2) Exercising –

After lubrication, operate each valve and gate through afull cycle while under actual operating conditions, if

possible.

During operation, listen for unusual noises and checkfor binding or vibration.

Inspection of Hydraulic and manual operators and controlsystems for gates and valves (annual)

(1) Visual inspection -

Check hydraulic oil in the tank for proper fluid level(take into account displacement of the gate stem), water,and foreign materia1.

Check all pipe joints, cylinder flanges, packing, andhydraulic equipment for leaks.



68

Check oil filters and strainers and change or clean if required.

Check hydraulic hoist piston stem for rusting andforeign deposits. Remove deposits and rough areas on

stems to prevent damage to packing or seals.

(2)Exercising

Operate hydraulic control and manual operator systemsand check for unusual noises or vibrations.

Check motors and hydraulic fluids for overheating, andcheck pressure switches, pressure gages, and limitswitches for proper operation according to operatinginstructions.

Clean manual operators of dirt and foreign material andlubricate as appropriate.

16. Physical security - The physical security should be

inspected for adequacy and repairs and improvements made, as

necessary, to avoid unauthorized operation and ensure the

safety of the equipment.

Inspection of Traveling crane, hoist, and tracks (annual)

(1) Visual inspection

Examine hoist, crane, and tracks for broken, bent,misaligned, worn, or loose parts and corrosion anddeterioration of protective coatings.

(2)Exercising

After lubrication, operate crane and hoist throughoutall functions and check for unusual noises, binding,and vibration during operation.



69

ENERGY DISSIPATION SECTION:17. Use these general guidelines during your inspection of the

energy dissipation section of a spillway/wasteweir/escape or

HR/outlet works:

First and foremost, know how the structures are supposedto function.

Make close observations of the structures when in use.Note unusual water currents, eddies and swirls, especially return currents that would carry rock and debris into thestructure from downstream.

Look for “Sand boils” which result from the upward flow of

seepage under pressure and are characterized by a boilingaction of the surface seepage. A sand boil is oftenaccompanied by a cone of material around the boil whichdevelops from the deposition of foundation or embankmentmaterial varied by the seepage.

If possible, dewater the pool to inspect surfaces fordamage.

To inspect a large pool that cannot be dewatered, plan a

boat inspection and record soundings made A plumb bob/surveying equipment may be needed to determine thelocation of subsurface damage.

Underwater inspections by divers are recommended if problems are suspected. As with any underwaterinspection, a detailed inspection, a plan and a goodcommunication system are important considerations forlogging damaged areas.

Typical Problems With Energy Dissipation Section:

18. Damage can occur to all elements of an energy dissipation

section because these structures reduce the velocity and

dissipate the energy of a flow. If the energy dissipation structure



71

terminal structures are alwaysreinforced.

Inspect the submerged portions of plunge pools and stilling / hydraulic

jump basins while dewatered, if possible or use divers. (An underwatercamera or a remotely operated vehicle(ROV) might be used before divers.)

Riprap/Pitching Make sure that riprap/pitching is notdisplaced or lost and that foundationmaterial is protected. Look for pipingor voids beneath riprap/pitching.

Geotextiles Check riprap or gabion plunge poolsand downstream channels for exposedgeotextiles, which typically should notbe exposed to direct flow or sunlight.

20. Obstructions: Check energy dissipation sections for the

following obstruction:

Debris clogging baffles

Plunge pools, stilling / hydraulic jump basins, andareas down stream of flip buckets filling with debris(often rocks and other objects thrown by people)

Return currents bringing downstream materials intothe structure

Heavy vegetative growth (such as thick grasses) inplunge pools.

If you see material blocking flow note the type of material

dimensions and depth, and location relative to a side or an end.

A boat can be used to perform a hydrographic survey of a large

pool bottom to check for obstructions or damage.



72

21. Damaged Or Missing Baffles: Baffles may be cracked

severely eroded loose or missing.

22. Misalignment Of Walls Or Baffles: The force of flows may

deflect the portion of terminal structures.

Check for vertically, and sight along the top of a sill foralignment deviation.

Check instrumentation data to measure deflections.

Offsets may occur as a result of misalignment, and cavitation

can developed downstream of such offsets.

23. Malfunctioning Drains: Check for clogged drains in the

energy dissipation area. Determine whether water flowing from

drains is clear or contains sediment or fine materials.

24. Backfill And Foundation Deficiencies: Check the following

points when inspecting the energy dissipation section for

backfill and foundation deficiencies:

Inspect plunge pools, hydraulic jump basins, and riprap-lined dissipators carefully for foundation and crack fillproblems. Look for settlement and cracks in backfill.Measure the size and distance of problem areas measuresettlement depth and probe for voids and erosion channels.

Watch especially for erosion of backfill behind the

downstream portion of a stilling / hydraulic jump basinscutoff walls and reinforcement should not be visible.

Settlement or improper elevation or length may change the jump location is stilling / hydraulic jump basins. Checkthat jump within the structure occurs at design locations(If the spillway/wasteweir/escape or HR/outlet works is



73

not operating, water stains on the walls will indicate wherethe jump is actually occurring).

Look for misaligned dry walls, cracks in the basin, andcracked backfill for evidence that a jump basin is settling.

Check a riprap plunge pool for undermining by loss of underlying soil or lack of filter action.

If a plunge pool lining is sand or gravel, check for piping.TAIL CHANNEL

25. The tail channel discharges the flow from

spillway/wasteweir/escape into nearby river or nalla or even

drain. If it fails, excess discharge is likely to erode the lower

portion of the spillway/wasteweir/escape control section or

energy dissipation system, the groin and toe areas of

embankment or areas downstream of the spillway/wasteweir/

escape.

Tail channel is subject to the same general problems with

structure and material as Approach channel of the drainagesiphon, with additional concerns described below:

Erosion: Discharge entering the tail channel is generally at a higher velocity than flows through the approachchannel.The tail channel is very susceptible to erosion if not properly sized, aligned and protected from excessvelocity.Look for erosion gullies that may indicate impropercompaction, overtopping because of downstream

obstructions or poor vegetative cover.

Inadequate Length: The tail channel should extend farenough downstream to ensure that flows will notdamage the embankment groin and toe areas. If damageis occuring, it is extremely important to note thedeficiency.



74

CHECKLIST FOR EXAMINATION OF SILLWAY/WASTEWEIR/ESCAPE

______________________ dam/ canal

Chainage _______________

Date of Examination Signature Completed

_________________ _________________________

Operational Status at Time of Examination

Water Surface-Elevation __________ M

Releases:

Escape __________ m3 /s

Outlet Works for irrigation __________ m3 /s

Water supply __________ m3 /s

Examination Participants

Name Affiliation

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

GLACIS OF WASTE WEIR/SPILLWAY

Debris ______________________

Crest

Surface condition(Cracks / Honey comb / stratification /

Form slippage / Stains / Bar Projection) _________________

General condition of concrete( Disintegration / Spalling /

Drummy Concrete / Pop out / Pitting / Sealing) __________________

Cracks or areas of distress ______________________

Sign of movement ______________________

Training Walls

Surface condition(Observe Cracks / Honey comb / stratification /



75

Form slippage / Stains / Bar Projection) ____________________

General condition of concrete (Observe Disintegration / Spalling /

Drummy Concrete / Pop out / Pitting / Sealing) ________________

Signs of Movement (offsets/Misalignment/Differential movement ) ________________

Joints( If washed out /crack/differential movement /vegetation growth) ______________

Cracks or areas of distress( Measure location/extent ) ______________________

Condition of backfill (watch for seepage/erosion/settlement) _____________________

Functioning of weep holes(Whether clean/choked) ______________________

Seepage( Record stains at joints/ turbidity) ______________________

Debris( If present at at joints/lift joints) ______________________

Floor/apron/cistern

Surface condition (Cracks / Honey comb / stratification /

Form slippage / Stains / Bar Projection) ______________________






Amount of flow ______________________

Location of seeping drains ______________________

Endsill alignment(Watch for Damage/ distortion) ______________________

Backfill beyond endsill (Watch for erosion/Reinforcement visibility) _______________

TAIL CHANNEL

Slope protection ______________________

Stability of side slopes ______________________

Vegetation or other obstructions ______________________

Any other deficiency (Scour, Retrogression) ______________________

GATES

Description ______________________

General Condition(watch for corrosion/fatigue/rupture/cavitations

of metal &position of welds) ______________________

Protective coating ______________________



76

Leakage (In closed condition at seal/through concrete) ______________________

Condition of rubber seals ______________________

Alignment of gate stem ______________________

Exercising frequency ______________________

Operation during inspection ( Raise & lower fully

if loss of water is not a problem) ___________________

CONTROLS FOR GATES

Mechanical

Hoists(watch for wear of brakeshoe lining / key-bolts are

tightened/ handcranks in locked position ) ______________________

Wire ropes( watch for rusting/ breakage/reduction indiameter/ condition of socket--clamps) ______________________

Protective coatings(watch if peeling/missing) ______________________

Condition of hoist platform (Watch for rusting/ loss of weld/bending/

misalignment/movement) ______________________

Guard rails(Watch for damage/ loss of

sleeves/coupling /check anchors) ______________________

Change of oil (Gear box) ______________________

Condition of Gear teeth (Check for damage/wear/cracks) ______________________

Lubrication ( Of ropes/bearing points/Pinions/Hinges/

Spin gear/Chains) ______________________

Electrical

Power supply ______________________

Standby power ______________________

Operation instructions ______________________

STOPLOGS

General condition ______________________

Protective coating(watch if peeling/missing) ______________________

Seals ______________________

BRIDGE

Condition of piers ( Leaks / Staining / Projection) ______________________



78

Chapter 9

INSPECTION OF CANAL SIPHON

1. Canal siphons consist of gated or ungated conduits (RCC

barrels or pipes ) with upstream and downstream transitions.

General inspection required as outlined vide Part II shall apply

for all the components of canal siphon. Following gives further

details for inspection to be carried out. Checklist for inspection

of canal siphon is provided at the end of this chapter.

Barrels / Pipes (Conduits)

2. A conduit is a pipe or box structure constructed by joining

sections.All outlets, HRs, canal siphons and drainage siphons

can generally be termed as conduits.

External Inspection Procedures for Conduits:

3. Evidence of potential conduit problems may BE found by

examining external features of the conduit (if it is exposed) or

the embankment.

If the material is reaching its life expectancy, it may bepossible to dig down to expose all sides of the conduit at apoint where the surrounding soil is still damp. Examinethe outside of the conduit for signs of deterioration. Thecondition of the outside of the conduit could besignificantly different from the interior. In some cases thesoil protects the exterior from oxygen-induced corrosion.

On the other hand local site conditions may haveaccelerated the deterioration of the exterior. Consider theoutside of the conduit to be just one indicator.

** Look for signs of infiltration of soil into the conduit:



79

Sinkholes and piping cavities that exit the surface. Holestaken over by animals may not be easily recognized assinkholes or piping cavities.

Holes that appear to be in a line. These may be anindication that piping or settlement is occurring.

Fines in the discharged water.

** Look for seepage or indications that seepage is sometimespresent. (This is best done while the conduit is full).Indications of seepage are: Wet spots

Increased vegetation or the presence of plants that

thrive in wet ground.

** Watch for water flow when all intakes are closed. If any isobserved, double-check to see if intakes are leaking. If notdocument where water is entering the waterway, and examinethe water for fines.

** Look for piping related erosion around the conduit near thedownstream end. Check for seepage adjacent to the structure. The situation may be especially serious if the seepage is

carrying sediment.

** With exposed conduit, check the support for settlement of movement of the joints.

Internal Inspection Procedures for Conduits:

4. To attempting to inspect conduit interiors, you may

experience the following difficulties:

** Dewatering difficulties: You cannot inspect a conduitcomprehensively unless it has been dewatered. However,dewatering may be impractical or impossible for one ormore of the following reasons.

- The need to limit maximum drawdown



80

- The need to maintain water flows.

- Structural inadequacy of the conduit to withstand

hydrostatic pressure in a dewatering condition.

To assess the probable condition of the conduit interior, itmay be necessary to rely on results of the exterior

inspection.

** Inaccessibility of conduit interior- The conduit may be

too dangerous for internal inspection by a person. One

possibility is to use remotely operated video equipment. If

that is not feasible, the inspection must be based on:

- The condition of the exposed portion of the conduit orthe embankment above it.

- The internal inspection of accessible portions of theconduit. (some details can be observed from thedownstream end of the conduit with the aid of astrong light and possibly a mirror).

INSPECTION TIP : One indication of settlement related problems that may be observed from the downstream end of a conduit is the pending of water in certain reaches of pipe.

5. A deficiency commonly encountered in the internal inspection

of conduit is cracking. Be aware of previously reported cracks

and note any new cracks, using a crack map or similar reporting

method. Figure --- shows one page of a crack map prepared by

an inspection team. Cracks should be documented as fully aspossible, with measurements and/or sketches drawn to scale

showing the length and position of each crack. The crack map in

figure includes measurements of the depth of weep holes, which

were probed during the inspection.



81

6. To get some indication of whether cracks are continuous

through a concrete structure, use a geologists' pick or other

hammer to tap the concrete. More comprehensive studies of the

concrete using dye tests and sonic methods may be necessary if

there are indications that the crack extends any distance into

the structure.

7. When inspecting the interior of a conduit, document the

following:

** Cavitation damage downstream, from gates and at sharpbends, joints or other discontinuities.

** Corrosion of metal conduit or liner.

** Cracking: Use crack maps, Describe position, length andorientation (Transverse, longitudinal, or diagonal) Estimatethe depth of the crack.

** Damaged coating or lining materials. (Cracking or buckling

is a sign of structural stress Missing chunks can causecavitation).

** Debris impact.

** Deformation of the conduit shape.

** Efflorescent or gel on the concrete. (Indicates possiblechemical deterioration of the concrete).

** Erosion, especially in areas of high-velocity flow.

** Joint separation, compression, or deterioration. Mentionany unsound welds, rivets, or flanges.

** Leakage from the conduit, or seepage entering the conduit.

** Misalignment of sections of the conduit.



82

** Plugged drain holes.

** Voids behind the conduit near any observed cracks,misalignments or other areas of possible seepage.

8. Problems with conduits occur most often at joints, andspecial attention should be given to them during inspection.

Open joints can permit erosion of envelope material or cause

leakage of water into the embankment during pressure flow.

Joints in conduits should be inspected in dry conditions, if

possible. Inspection just after a conduit is dewatered may reveal

the locations of leaks, because water sometimes spurts through

affected joints.

9. Typically, conduit joints pull apart under the lowest part of

siphon and are under compression at the end. When inspecting

conduit joints be sure to:

** Examine joints for leaks

** Examine the joints between adjacent sections of conduitfor leaks and for ruptured water stops.

** Look for compression spalling of concrete.

** Check for misalignment of sections due to differentialsettlement.



83

Figure shows a conduit joint which has opened along the bottomdue to localized settlement along the conduit.

Operating Bridge And Pier Problems:

10. Deficiencies in the operating bridge, piers, decks, or other

access structures on the siphon could make gates and other

controls unworkable in an emergency, and collapse of the

supporting structure could obstruct the escape.

11.Check for the following deficiencies.










Problems With Gates, Stoplogs:

13. When inspecting the control section of a siphon, your

primary concern is to ensure that the operation of gates and

other canal evacuation equipment is not impaired by adjacent

and supporting structures.



84

When inspecting, stoplogs and structures adjacent to and

supporting gates check the following points.

Look for displacement of structural elements or

concrete deterioration that may be jamming ormisalignment gates. Have the equipment operated if possible, to detect jamming, or gates not seatedproperly on the crest. During operations, look fordeterioration of material on the underside of thegates. Note excessive leakage.

Watch for misalignment of gate stems and other

signs of strain from holding water or from debris or

over tightening.



When water conditions permit, inspect the downstreamsurfaces of the guard gate leaves and bodies, theupstream and downstream surfaces of regulating gateleaves and bodies, and outlet pipes.

Particular attention should be given to signs of cavitations damage to waterway surfaces downstreamfrom gate or valve leaves and flanged joints.

Inspect neoprene or rubber gate seals for deterioration,cracking, wear, foreign material deposits, and leakage.



(4) Exercising –

After lubrication, operate each valve and gate through afull cycle while under actual operating conditions, if possible.



86



Examine hoist, crane, and tracks for broken, bent,misaligned, worn, or loose parts and corrosion anddeterioration of protective coatings.

(2)Exercising

After lubrication, operate crane and hoist throughoutall functions and check for unusual noises, binding,and vibration during operation.

Energy Dissipation Section:

15. Use these general guidelines during the your inspection of

the energy dissipation section of a canal siphon:


Make close observations of the structures when in use.Note unusual water currents, eddies and swirls, especially

return currents that would carry rock and debris into thestructure from downstream.

Look for “Sand boils” which result from the upward flow of seepage under pressure and are characterized by a boilingaction of the surface seepage. A sand boil is oftenaccompanied by a cone of material around the boil whichdevelops from the deposition of foundation or embankmentmaterial varied by the seepage.


Underwater inspections by divers are recommended if problems are suspected. As with any underwaterinspection, a detailed inspection, a plan and a good



88

See if ball milling has ground circularpatterns in the floor or apron of stilling / hydraulic jump basins.

Check joints for spells or settlement

on one side. See if joint sealant orcompressive joint filler is crackedmissing, moved, or deteriorated. Lookfor broken waterstops.

Watch for corroded and damagedreinforcement resulting from erosionand cavitation damage. Concreteterminal structures are alwaysreinforced.

Inspect the submerged portions of plunge pools and stilling / hydraulic jump basins while dewatered, if possible or use divers. (An underwatercamera or a remotely operated vehicle(ROV) might be used before divers.)

Riprap/Pitching Make sure that riprap/pitching is notdisplaced or lost and that foundation

material is protected. Look for pipingor voids beneath riprap/pitching.

Geotextiles Check riprap or gabion plunge poolsand downstream channels for exposedgeotextiles, which typically should notbe exposed to direct flow or sunlight.

19. Obstructions: Check energy dissipation sections for the

following obstruction:

Debris clogging baffles

Plunge pools, stilling / hydraulic jump basins, andareas down stream of flip buckets filling with debris(often rocks and other objects thrown by people)



89

Return currents bringing downstream materials intothe structure

Heavy vegetative growth (such as thick grasses) in

plunge pools.





















90


Watch especially for erosion of backfill behind thedownstream portion of a stilling / hydraulic jump basinscutoff walls and reinforcement should not be visible.

Settlement or improper elevation or length may change the jump location is stilling / hydraulic jump basins. Checkthat jump within the structure occurs at design locations(If the escape or outlet works is not operating, water stains

on the walls will indicate where the jump is actually occurring).

Look for misaligned dry walls, cracks in the basin, andcracked backfill for evidence that a jump basis is settling.


If a plunge pool lining is sand or gravel, check for piping.



91

CHECKLIST FOR EXAMINATION OF CANAL SIPHON

_____________________Canal offtaking from ______________________ canal

Chainage _______________ to _________________


_________________ _________________________


Canal Water Surface-Elevation __________ M

Releases:

Escape __________ m3 /s




Name Affiliation

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

APPROACH CHANNEL

General condition (Siltation/Debris) ______________________

Vegetation (trees, willows etc.) ______________________

Slides above channel (Deep / Shallow) ______________________

Channel side slope stability ______________________

Slope protection(Adequacy / Degradation / Displacement) ______________________

BARREL

Entrance transition

Debris (Watch if coming out from joints) ______________________




92

Form slippage/ Stains/Bar Projection) ______________________

General condition ( Disintegration / Spalling / Drummy Concrete

/Pop out / Pitting / Sealing) ______________________

Settlement ______________________

Joints( If washed out/crack/differential movement

/vegetation growth) ______________________

Cracks/Area of distress ( Measure location/extent ) ______________________

Seepage( Record stains a tjoints / turbidity ) ______________________

Walls





Signs of Movement (offsets/Misalignment/Differential movement ) _________________






Floor






Joints( If washed out /crack/differential movement /vegetation growth) _____________


Amount of flow ______________________




BRIDGE

Condition of piers ( Leaks / Staining / Projection) ______________________



93

Surface of roadway slab ______________________

Water Spouts (whether choked) ______________________

Condition of parapet/Guard rails (watch for misalignment/

differential settlement) ______________________

Structural condition of slab and beams (watch for Deflection / Cracks) _____________________

Bridge bearings ______________________

Overall condition ______________________

TAIL CHANNEL





GATES

Description ______________________

General Condition(watch for corrosion/fatigue/rupture/cavitations

of metal &position of welds) ______________________







if loss of water is not a problem) ____________________

CONTROLS FOR GATES

Mechanical



Wire ropes( watch for rusting/ breakage/reduction in

diameter/ condition of socket--clamps) ______________________





94

misalignment/movement) ______________________

Guard rails(Watch for damage/ loss of





Spin gear/Chains) ______________________

Electrical

Power supply ______________________

Standby power ______________________


STOPLOGS


Protective coating (watch if peeling/missing) ______________________

Seals ______________________

TRASH RACKS ______________________

OTHER

______________________ ______________________

______________________ ______________________



95

Chapter 10.

INSPECTION OF DRAINAGE SIPHON

1. Drainage siphons consist of conduits (RCC barrels or pipes )

with upstream and downstream transitions, approach and tail

channel. General inspection required as outlined vide Part II

shall apply for all the components of drainage siphon. Following

gives further details for inspection to be carried out. Checklist

for inspection of drainage siphon is provided at the end of this

chapter.

Approach Channel :

Typical Problems

2. Failure of the approach channel may block flow to the

drainage siphon entirely, greatly reduce the flow capacity, or

cause flow irregularities that imprnage upon or overtop channel

walls. As a result, the water surface in the drain may be raised

above safe levels, and the canal bank may even be overtopped.

3. Approach channels may be affected by:

• Deterioration of Materials. Slope and wall failure may

result when surface materials deteriorate. To inspect for

deterioration of surface materials perform the actions listed

in Table : 2 Inspecting approach channel Materials.



96

TABLE 2 INSPECTING APPROACH CHANNEL MATERIALS

MATERIAL INSPECTION POINT

Concrete • Check concrete linings for cracks,displacement, and erosion

• Sight along the walls to make surethat they have not moved.

RCC, Shotcrete • Check for cracks and erosionAaphaltic Concrete • Check for cracks, erosion, and

disintegrationEarth • Note any severe erosion gulliesRock • Look for excessive deterioration of

rock in natural rock channels

• Check riprap for weathering

deterioration of stone, and slidesin sides walls.GABIONS • Note signs of gabion settling or

rock deterioration.

• Check baskets for rusted, broken,cut, or deform wires.

NOTE :- Gabions are wire “cages” filled with rocks that can bepiled up for slope stabilization.

4. OBSTRUCTIONS. Approach channels may be obstructed by:

- Vegetation- Debris- Sediment- Fallen rocks- Trees- Manmade structures

To inspect for obstructions in the approach channel, take these

actions:

• Check the channels for debris.

• Record the type, location and extent of any obstruction.



97

5. Slope And Wall Failure. While inspecting the approach

channel for slope and wall failure, do the following:

• Examine the side slopes or walls for slides, movement,

cracked or wet spots. Check for foundation undermining by flow from springs.

• Look at the topography above the channel for signs of instability, such as sinkholes or slumps behind the walls. If you see soil loss with seepage, look for an exit points.

• Check for indications of poor drainage, such as seepage andclogged weepholes or drains.

6. Poor Floor Condition or Stability. Check these points when

examining the entrance channel floor.

• If the channel is unlined:o Look at the toe of the channel slope for wet areas.o Check for erosion sinkholes and lack of vegetation.

• Check foundation foe signs of undermining by clow from

springs.

• Look for signs of poor drainage, such as seepage andclogged weepholes or drains,

• Inspect for voids under a concrete floor, using a bunker ora hammer. (Another device that may be used is a “Chaindrag” which is a series of chains fastened to a bar.Concrete is sounded by dragging the chains over a surface. This device is used to test large areas).

7. Concrete Deteriaration From Wetting/Drying. Concrete

deteriorates from wetting and drying as the water level rises and

falls. The waterline of the approach channel needs to be checked

for cracking, scaling and crumbing of the concrete surface.



98

8. Wave Erosion. Check side slopes or pitching for beaching

from wave erosion. The overly-steep channel slope above the

beach may fail.

9. Insufficient Capacity. If you see evidence of overtopping and

a flow restriction does nor appear to be contributing factor,

recommended that a hydrologic study be conducted to see

whether the approach channel can satisfy operational

requirements.

Tail Channel

10 The tail channel discharges the flow from the conduit(s) of

drainage siphon into nearby river or nalla or even drain. If it

fails, excess discharge is likely to erode the downstream portion

of the drainage siphon or energy dissipation system, the groin

and toe areas of canal emabankment or areas further

downstream of the drainage siphon.

Tail channel is subject to the same general problrms with

structure and material as Approach channel of the drainage

siphon, with additional concerns described below:

Erosion: Discharge entering the tail channel is generally at a higher velocity than flows through the approachchannel.The tail channel is very susceptible to erosion if not properly sized, aligned and protected from excessvelocity.

Look for erosion gullies that may indicate impropercompaction, overtopping because of downstreamobstructions or poor vegetative cover.

Inadequate Length: The tail channel should extend farenough downstream to ensure that flows will notdamage the embankment groin and toe areas. If damage



99

is occuring, it is extremely important to note thedeficiency.

Barrels (Conduits)


sections.All outlets, HRs, canal siphons and drainage siphons

can generally be termed as conduits.


12. Evidence of potential conduit problems may be found by


the embankment.




Depression of the embankment along the centerline of theconduit.


Holes that appear to be in a line. These may be anindication that piping or settlement is occurring.



100


** Look for seepage or indications that seepage is sometimespresent. (This is best done while the conduit is full).

Indications of seepage are: Wet spots Increased vegetation or the presence of plants that


** Watch for water flow when there is no flow in the conduit. If any is observed, document from where water is entering thewaterway, and examine the water for fines.

** Look for piping related erosion around the conduit near the

downstream end. Check the embankment slope above theconduit outfall carefully for voids or erosion that may indicatepiping. Check for seepage adjacent to the structure. Thesituation may be especially serious if the seepage is carryingsediment.





** Dewatering difficulties: You cannot inspect a conduitcomprehensively unless it has been dewatered. However,dewatering may be impractical or impossible due tostructural inadequacy of the conduit to withstandhydrostatic pressure in a dewatering condition.

To assess the probable condition of the conduit interior, it

may be necessary to rely on results of the exterior

inspection.



101


too small or too dangerous for internal inspection by a

person. One possibility is to use remotely operated video

equipment. If that is not feasible, the inspection must bebased on:



INSPECTION TIP : One indication of settlement related problems that may be be observed from the downstream end of a conduit is the ponding of water in certain reaches of pipe.

14. A deficiency commonly encountered in the internal

inspection of conduit is cracking. Be aware of previously

reported cracks and note any new cracks, using a crack map or

similar reporting method. Figure -6- shows one page of a crack

map prepared by an inspection team. Cracks should be

documented as fully as possible, with measurements and/or

sketches drawn to scale showing the length and position of each

crack. The crack map in figure includes measurements of the

depth of weep holes, which were probed during the inspection.







102


the structure.

16. When inspecting the interior of a conduit, document the

following:

** Cavitation damage downstream, at sharp bends, joints orother discontinuities.

** Corrosion of metal conduit or liner.

** Cracking: Use crack maps, Describe position, length andorientation (Transverse, longitudinal, or diagonal) Estimate

the depth of the crack.

** Damaged coating or lining materials. (Cracking or bucklingis a sign of structural stress Missing chunks can causecavitation).

** Debris impact.


** Efflorescent or gel on the concrete. (Indicates possible

chemical deterioration of the concrete).






** Voids behind the conduit near any observed cracks,

misalignments or other areas of possible seepage.



103

17. Problems with conduits occur most often at joints, and

special attention should be given to them during inspection.


leakage of water into the embankment during pressure flow. Joints in conduits should be inspected in dry conditions, if



affected joints.

18. Typically, conduit joints pull apart under the highest part of

an embankment and are under compression at the end of thewaterway. When inspecting conduit joints be sure to:



** Look for compassion spelling of concrete.

** Check for misalignment of sections due to differential

settlement.



105





fails to operate properly the main structure can be eroded at the

down stream end, causing a loss of foundation support.

21. Problems typical to the energy dissipation section include

the following:

Deteriaration of Materials:22. Follow the actions described in Table--4 Inspection of

Energy Dissipation materials to check for deterioration of

materials.

TABLE – 4 INSPECTION OF ENERGY DISSIPATIONMATERIALS

Concrete Check for signs of cavitation. Thesides of chute blocks baffles. Anddentates are exposed to considerableturbulence, and any offsets orirregularities can trigger cavitation.

Look for erosion damage fromabrasion of wasteweir aprons, the topsurfaces and undersides of buckets,and the floors, walls chute blocks and

dentates of stilling basins.




107

Heavy vegetative growth (such as thick grasses) inplunge pools.



















Inspect plunge pools, hydraulic jump basins, and riprap-lined dissipators carefully for foundation and crack fillproblems. Look for settlement and cracks in backfill.



108

Measure the size and distance of problem areas measuresettlement depth and probe for voids and erosion channels.

Watch especially for erosion of backfill behind thedownstream portion of a stilling / hydraulic jump basins

cutoff walls and reinforcement should not be visible.

Settlement or improper elevation or length may change the jump location is stilling / hydraulic jump basins. Checkthat jump within the structure occurs at design locations(If the escape or outlet works is not operating, water stainson the walls will indicate where the jump is actually occurring).






109

CHECKLIST FOR EXAMINATION OF DRAINAGE SIPHON


Chainage _______________ to _________________


_________________ _________________________



Releases:

Escape __________ m3 /s




Name Affiliation

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

APPROACH CHANNEL

General condition (Siltation/Debris) ______________________

Vegetation (trees, willows etc.) ______________________

Slides above channel (Deep / Shallow) ______________________

Channel side slope stability ______________________

Slope protection (Adequacy / Degradation / Displacement) ______________________

BARREL

Walls







110








Floor




Drummy Concrete / Pop out / Pitting / Sealing) _________________




Amount of flow ______________________




TAIL CHANNEL





OTHER

______________________ ______________________

______________________ ______________________



111

Chapter 11

INSPECTION OF OUTLET WORKS (HEAD REGULATOR)

1. Outlet works are conduits through or around an

embankment used for releasing water. Regulated outlets use

gates or valves for controlling the rate of flow. At unregulated

conduits, the rate of flow is controlled by the size of the conduit

and the height of the water in the canal above the invert, or

floor, of the conduit. Conduits at embankments usually have

regulating gates or valves within the upstream portion of the

conduit so that flows can be shut off to prevent water from

eroding the embankment in the event of failure or leakage

through the conduit. Outlet works gates are susceptible to

plugging with debris and sediment deposition. Thus, it is

important that any trash racks in front of the gates be cleaned

whenever possible and that the gates be opened periodically to

flush debris and sediment.

INSPECTION ACTION:

Semiannual1y inspect the end of each outlet. Inspectthe outlet end of the conduit for breaks in the conduit,erosion of the downstream toe of the embankment orundercutting of the outlet end of the conduit.

Operate each gate sufficiently to ensure that it is fully

operable and debris and sediment are flushed out.

Inspect gate stems to the waterline, and correct any misalignment that interferes with operation.

Inspect downstream cistern of the outlets and get removeddebris/vegetation.



113

Misalignment of an intake structure - Misalignment may indicate movement of the abutments or other seriousstructure problem affecting the integrity of the canal.

4. In the paragraphs that follow, descriptions of the elements of

an intake structure are accompanied by specific points to check

during your inspection and recommendations to make in your

report.

Shaped Entrances:

5. Entrance in to or within intake structures are usually

rounded or otherwise specially shaped to streamline the flow of

water and minimize hydraulic. Even so, localized zones of

negative pressure resulting from rapid change in direction or

discontinuities can cause vibration and/or cavitation damage.

• Look for damaged concrete and exposed reinforcing steel.

Barrels, Outlet Pipes (Conduits)


sections.All outlets, HRs, canal siphons and drainage siphonscan generally be termed as conduits.


7. Evidence of potential conduit problems may be found by


the embankment.




114



Depression of the embankment along the centerline of theconduit.


Holes that appear to be in a line. These may be an

indication that piping or settlement is occurring.


** Look for seepage or indications that seepage is sometimespresent. (This is best done while the conduit is full).Indications of seepage are: Wet spots

Increased vegetation or the presence of plants that


** Watch for water flow when all intakes are closed. If any isobserved, double-check to see if intakes are leaking. If notdocument where water is entering the waterway, and examinethe water for fines.

** Look for piping related erosion around the conduit near thedownstream end. Check the embankment slope above theconduit outfall carefully for voids or erosion that may indicate

piping. Check for seepage adjacent to the structure. Thesituation may be especially serious if the seepage is carryingsediment.




115

** Check the concrete anchors of exposed steel conduit forcracking, weathering, and/or chemical deterioration.




** Dewatering difficulties: You cannot inspect a conduitcomprehensively unless it has been dewatered. However,dewatering may be impractical or impossible for one ormore of the following reasons.

- Lack of a bulkhead or other closure device.- The need to limit maximum drawdown

- The need to maintain water flows.- Structural inadequacy of the conduit to withstand

hydrostatic pressure in a dewatering condition.

To assess the probable condition of the conduit interior, it


inspection.

** Inaccessibility of conduit interior- The conduit may

betoo small or too dangerous for internal inspection by a

person. One possibility is to use remotely operated video

equipment. If that is not feasible, the inspection must be

based on:



INSPECTION TIP : One indication of settlement related problems that may be observed from the downstream end if a conduit is the ponding of water in certain reaches of pipe.



116


of conduit is cracking. Be aware of previously reported cracks

and note any new cracks, using a crack map or similar reporting

method. Figure 6 shows one page of a crack map prepared by an inspection team. Cracks should be documented as fully as

possible, with measurements and/or sketches drawn to scale

showing the length and position of each crack. The crack map in



10. To get some indication of whether cracks are continuousthrough a concrete structure, use a geologists' pick or other




the structure.

11. When inspecting the interior of a conduit, document thefollowing:

** Cavitation damage downstream, from gates and valves andat sharp bends, joints or other discontinuities.

** Corrosion of metal conduit or liner.** Cracking: Use crack maps, Describe position, length and

orientation (Transverse, longitudinal, or diagonal) Estimate

the depth of the crack.

** Damaged coating or lining materials. (Cracking or bucklingis a sign of structural stress Missing ### can causecavitation).

** Debris impact.



117



** Erosion, especially in areas of high-velocity flow.** Joint separation, compression, or deterioration. Mention

any unsound welds, rivets, or flanges.




** Voids behind the conduit near any observed cracks,

misalignments or other areas of possible seepage.

12. Problems with conduits occur most often at joints, and

special attention should be given to them during inspection.


leakage of water into the embankment during pressure flow.

Joints in conduits should be inspected in dry conditions, if



affected joints.

13. Typically, conduit joints pull apart under the highest part of

an embankment and are under compression at the end of the

waterway. When inspecting conduit joints be sure to:



** Look for compassion spelling of concrete.



118

** Check for misalignment of sections due to differentialsettlement.

Figure shown a conduit joint which has opened along the

bottom due to localized settlement along the conduit.


14. Deficiencies in the operating bridge, piers, decks, or otheraccess structures on the Head Regulator could make gates and

other controls unworkable in an emergency, and collapse of the

supporting structure could obstruct the Head Regulator.


On concrete bridges, check joints and water runoff points for exposed metal and corrosion of reinforcement

steel.






119







17. When inspecting the control section of a Head Regulator/

Outlet, your primary concern is to ensure that the operation of

gates and other canal evacuation equipment is not impaired by

adjacent and supporting structures.

18. When inspecting, stoplogs and structures adjacent to and


Look for displacement of structural elements orconcrete deterioration that may be jamming or

misalignment gates. Have the equipment operated if possible, to detect jamming, or gates not seatedproperly on the crest. During operations, look fordeterioration of material on the underside of thegates.

Note excessive leakage.

Watch for misalignment of gate stems and other signsof strain from holding water or from debris or overtightening.



When water conditions permit, inspect the downstreamsurfaces of the guard gate leaves and bodies, the



120

upstream and downstream surfaces of regulating gateleaves and bodies, and outlet pipes.

Particular attention should be given to signs of cavitations damage to waterway surfaces downstream

from gate or valve leaves and flanged joints. Inspect neoprene or rubber gate seals for deterioration,

cracking, wear, foreign material deposits, and leakage.



(2) Exercising –



Inspection of Hydraulic and manual operators and control

systems for gates and valves (annual)


Check hydraulic oil in the tank for proper fluid level(take into account displacement of the gate stem), water,and foreign materia1.



Check hydraulic hoist piston stem for rusting andforeign deposits. Remove deposits and rough areas onstems to prevent damage to packing or seals.



121

(2)Exercising










a. Examine hoist, crane, and tracks for broken, bent,misaligned, worn, or loose parts and corrosion anddeterioration of protective coatings.

(2)Exercising

b. After lubrication, operate crane and hoistthroughout all functions and check for unusual noises,binding, and vibration during operation.



122

Chapter 12

INSPECTION OF CROSS REGULATOR


apply for all the components of cross regulator. Following gives

further details for inspection to be carried out. Checklist for

inspection of cross regulator is provided at the end of this

chapter.


2. Deficiencies in the operating bridge, piers, decks, or other

access structures on the cross regulator could make gates and

other controls unworkable in an emergency, and collapse of the

supporting structure could obstruct the canal.







4.Check bridge support as follows.




123




5.When inspecting the control section of an cross regulator,

your primary concern is to ensure that the operation of gates is

not impaired by adjacent and supporting structures.



Look for displacement of structural elements orconcrete deterioration that may be jamming ormisalignment gates. Have the equipment operated if possible, to detect jamming, or gates not seatedproperly on the crest. During operations, look fordeterioration of material on the underside of thegates.


Watch for misalignment of gate stems and other signs

of strain from holding water or from debris or overtightening.


(1)Visual inspection. –

a When water conditions permit, inspect the downstreamsurfaces of the guard gate leaves and bodies, theupstream and downstream surfaces of regulating gate

leaves and bodies, and outlet pipes

b Particular attention should be given to signs of cavitations damage to waterway surfaces downstreamfrom gate or valve leaves and flanged joints.



124

c. Inspect neoprene or rubber gate seals for deterioration,cracking, wear, foreign material deposits, and leakage.

d. Inspect valve and gates metal seats or seals forwear, scratches, foreign material deposits, and leakage.

e. Repairs should be made as necessary to keep theequipment in a safe and reliable operating condition.

(2) Exercising –



Inspection of Hydraulic and manual operators and controlsystems for gates and valves (annual)


Check hydraulic oil in the tank for proper fluid level(take into account displacement of the gate stem), water,

and foreign materia1.



Check hydraulic hoist piston stem for rusting andforeign deposits. Remove deposits and rough areas on

stems to prevent damage to packing or seals.

(2)Exercising




125









a. Examine hoist, crane, and tracks for broken, bent,misaligned, worn, or loose parts and corrosion anddeterioration of protective coatings.

(2)Exercising

b. After lubrication, operate crane and hoistthroughout all functions and check for unusual noises,binding, and vibration during operation.



126

CHECKLIST FOR EXAMINATION OF OUTLET WORKS (H.R. & C.R.)


Chainage _______________ to _________________


_________________ _________________________



Releases:

Escape __________ m3 /s




Name Affiliation

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

Trashracks ______________________

Trashracks concrete structure ______________________

SERVICE CONTROL FACILITY

GATES

Description ______________________

General Condition(watch for corrosion/fatigue/rupture/cavitationsof metal &position of welds) ______________________






127




if loss of water is not a problem) ___________________

CONTROLS FOR GATES

Mechanical



Wire ropes( watch for rusting/ breakage/reduction in

diameter/ condition of socket--clamps) ______________________



misalignment/movement) ______________________Guard rails(Watch for damage/ loss of





Spin gear/Chains) ______________________

Electrical

Power supply ______________________

Standby power ______________________


STOPLOGS


Protective coating (watch if peeling/missing) ______________________

Seals ______________________

Valve(s) ( IF PROVIDED)General condition ______________________

Protective coatings ______________________

Cavitations ______________________

Leakage (closed) ______________________

Creep ______________________



128


Operation of valves at time of

examination ______________________

Control system for valves

Mechanical ______________________

Electrical ______________________

Operating instructions ______________________

GATE CIVIL WORKS (including Access Bridge)

Walls











Debris( If present at at joints/lift joints) ______________________Floor




Drummy Concrete / Pop out / Pitting / Sealing) _________________




Amount of flow ______________________






129

Chapter 13

.INSPECTION OF FALL


apply for all the components of canal fall. Following gives further

details for inspection to be carried out. Checklist for inspection

of canal fall is provided at the end of this chapter.

CONTROL SECTION:

2. The control section is a particularly critical portion of a canal

fall as it receives flow of water from upstream and passes on

further downstream via energy dissipation system. It may be in

the form of a weir with crest (or sill level) raised above canal bed

level.

3. Problems typical to the canal fall control section include:

• Deterioration of surface materials:Check the following

points for deterioration in the control section:

Look at surfaces in areas of concentrated and highvelocity flows, such as near gates,(in case of fall cumCross regulator) for erosion.

Check areas near large gates for cracking in concrete,and tearing, rupture, and fatigue in metal.

Examine the upstream edges of weirs for damage frombattering by debris.

INSPECTION TIP : High velocity flow over a concrete surface containing abnormalities can initiate cavitation damage. Check surfaces carefully for offsets, small holes and calcium carbonate deposits. The bearing surfaces



130

where gates rest and areas immediately downstream of gate slots, liner plates should be examined with special care.

• Obstructions: Besides general types of obstructionsalready discussed, check for the following obstructions to

control sections:

Check for unauthorized equipment added to the controlsection.

• Operating Bridge And Pier Problems:Deficiencies in theoperating bridge, piers, decks, or other access structureson the escape could make gates and other controlsunworkable and collapse of the supporting structure couldobstruct the canal.

Check for the following deficiencies.






Check bridge support as follows.


Check the bearing supports at the abutments for

condition and evidence of movement. Look for misalignment or damage at sliding joints.

• Problems With Gates, Stoplogs:

When inspecting the control section of a fall cum Cross

regulator, your primary concern is to ensure that the



131

operation of gates is not impaired by adjacent and

supporting structures.

When inspecting, stoplogs and structures adjacent to and


Look for displacement of structural elements orconcrete deterioration that may be jamming ormisalignment gates. Have the equipment operated if possible, to detect jamming, or gates not seatedproperly on the crest. During operations, look fordeterioration of material on the underside of thegates.


Watch for misalignment of gate stems and othersigns of strain from holding water or from debris orover tightening.

• Backfill and Foundation Deficiencies:

Points to remember when inspecting the control section

for backfill and foundation deficiencies are:

Foundation in the control section often must bear thestress of heavy equipment. Check carefully fordisplacements that may indicate settling foundationshifts, or undermining. Check for voids underconcrete channel walls and floors.

It is critical that gaps in joints do not exposefoundation or backfill material where escape extendsthrough the embankment section, and that waterstops, sealants and compressive joint fillers are intactand in good condition.




132

Energy Dissipation Section:

4. Use these general guidelines during the your inspection of the

energy dissipation section of a canal fall:


Make close observations of the structures when in use.Note unusual water currents, eddies and swirls, especially return currents that would carry rock and debris into thestructure from downstream.

Look for “Sand boils” which result from the upward flow of seepage under pressure and are characterized by a boiling

action of the surface seepage. A sand boil is oftenaccompanied by a cone of material around the boil whichdevelops from the deposition of foundation or embankmentmaterial varied by the seepage.


To inspect a large pool that cannot be dewatered, plan aboat inspection and record soundings made A plumb bob/

surveying equipment may be needed to determine thelocation of subsurface damage.

Underwater inspections by divers are recommended if problems are suspected. As with any underwaterinspection, a detailed inspection, a plan and a goodcommunication system are important considerations forlogging damaged areas.







133

fails to operate properly the main structure can be eroded at the

down stream end, causing a loss of foundation support.

6. Problems typical to the energy dissipation section include the

following:

Deteriaration of Materials:

7. Follow the actions described in Table--5- Inspection of Energy

Dissipation materials to check for deterioration of materials.

TABLE – 5 INSPECTION OF ENERGY DISSIPATION

MATERIALS

Concrete Check for signs of cavitation. Thesides of chute blocks baffles. Anddentates are exposed to considerableturbulence, and any offsets orirregularities can trigger cavitation.

Look for erosion damage fromabrasion of wasteweir aprons, the top

surfaces and undersides of buckets,and the floors, walls chute blocks anddentates of stilling basins.


Check joints for spells or settlementon one side. See if joint sealant or

compressive joint filler is crackedmissing, moved, or deteriorated. Lookfor broken waterstops.

Watch for corroded and damagedreinforcement resulting from erosionand cavitation damage. Concrete



135
















Watch especially for erosion of backfill behind the

downstream portion of a stilling / hydraulic jump basinscutoff walls and reinforcement should not be visible.

Settlement or improper elevation or length may change the jump location is stilling / hydraulic jump basins. Checkthat jump within the structure occurs at design locations(If the escape or outlet works is not operating, water stains



136

on the walls will indicate where the jump is actually occurring).






137

CHECKLIST FOR EXAMINATION OF CANAL FALL STRUCTURE


Chainage _______________ to _________________


_________________ _________________________



Releases:

Escape __________ m3 /s




Name Affiliation

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

GLACIS OF WASTE WEIR/SPILLWAY

Debris ______________________

Crest

Surface condition(Cracks / Honey comb / stratification /

Form slippage / Stains / Bar Projection) ________________


Drummy Concrete / Pop out / Pitting / Sealing) __________________

Cracks or areas of distress ______________________

Sign of movement ______________________

Training Walls


Form slippage / Stains / Bar Projection) ___________________



138


Drummy Concrete / Pop out / Pitting / Sealing) _______________


Joints( If washed out /crack/differential movement /vegetation growth) _____________






Floor/apron/cistern








Amount of flow ______________________






139

Chapter 14

INSPECTION OF AQEDUCTS


apply for all the components of canal aqueduct. Following gives

further details for inspection to be carried out. Checklist for

inspection of canal aqueduct is provided at the end of this

chapter.

2. Operating Bridge And Pier Problems:Deficiencies in theoperating bridge, piers, decks, or other access structures on theescape could make gates and other controls unworkable andcollapse of the supporting structure could obstruct the canal.

Check for the following deficiencies.






Check bridge support as follows.






140


3. When inspecting the control section of a fall cum Cross

regulator, your primary concern is to ensure that the operation

of gates is not impaired by adjacent and supporting structures.



Look for displacement of structural elements orconcrete deterioration that may be jamming ormisalignment gates. Have the equipment operated if

possible, to detect jamming, or gates not seatedproperly on the crest. During operations, look fordeterioration of material on the underside of thegates. Note excessive leakage.

Watch for misalignment of gate stems and othersigns of strain from holding water or from debris orover tightening.

Backfill and Foundation Deficiencies:

5. Points to remember when inspecting the control section for

backfill and foundation deficiencies are:

Foundation in the control section often must bear thestress of heavy equipment. Check carefully fordisplacements that may indicate settling foundationshifts, or undermining. Check for voids underconcrete channel walls and floors.

It is critical that gaps in joints do not exposefoundation or backfill material where escape extendsthrough the embankment section, and that waterstops, sealants and compressive joint fillers are intactand in good condition.



141


Inspection of Aqueduct Barrels:

External Inspection Procedures:

6. Evidence of potential problems may be found by examining

external features of the barrels.

Examine the outside of the barrel for signs of deterioration. The condition of the outside of the barrel could be

significantly different from the interior e.g. local siteconditions might have accelerated the deterioration of theexterior. Consider the outside of the conduit to be just oneindicator.

** Look for seepage or indications that seepage is sometimespresent. (This is best done while the barrel is full).Indications of seepage are: Wet spots

Increased vegetation or the presence of plants thatthrive in wet ground.

** Watch for water flow when all intakes are closed. If any isobserved, double-check to see if intakes are leaking. If notdocument where water is entering the barrel, and examinethe water for fines.

** Check for seepage adjacent to the structure. The situationmay be especially serious if the seepage is carrying sediment.


** Check the concrete anchors of exposed steel conduit forcracking, weathering, and/or chemical deterioration.



142

Internal Inspection Procedures:

7. To attempting to inspect barrel interiors, you may experience

the following difficulties:

** Dewatering difficulties: You cannot inspect a barrelcomprehensively unless it has been dewatered. However,dewatering may be impractical or impossible for one ormore of the following reasons.

- The need to limit maximum drawdown

- The need to maintain water flows.

- Structural inadequacy of the barrel to withstandhydrostatic pressure in a dewatering condition.

To assess the probable condition of the barrel interior, it


inspection.


too dangerous for internal inspection by a person. One

possibility is to use remotely operated video equipment. If

that is not feasible, the inspection must be based on:

- The condition of the exposed portion of the barrel

- The internal inspection of accessible portions of thebarrel. (some details can be observed from thedownstream end of the barrel with the aid of a stronglight and possibly a mirror).

INSPECTION TIP : One indication of settlement related

problems that may be observed from the downstream end if a conduit is the ponding of water in certain reaches of barrel.


of barrel is cracking. Be aware of previously reported cracks and



143

note any new cracks, using a crack map or similar reporting

method. Figure -6 shows one page of a crack map prepared by

an inspection team. Cracks should be documented as fully as

possible, with measurements and/or sketches drawn to scaleshowing the length and position of each crack. The crack map in





hammer to tap the concrete. More comprehensive studies of theconcrete using dye tests and sonic methods may be necessary if


the structure.

10 When inspecting the interior of a barrel, document the

following:

** Cavitation damage downstream, at joints or otherdiscontinuities.

** Corrosion of metal conduit or liner.** Cracking: Use crack maps, Describe position, length and

orientation (Transverse, longitudinal, or diagonal) Estimatethe depth of the crack.

** Debris impact.

** Deformation of the barrel shape.





144


** Leakage from the barrel,

** Misalignment of sections of the barrel.

11. Problems with barrel occur most often at joints, and special

attention should be given to them during inspection. Open joints

can permit erosion of envelope material or cause leakage of

water into the embankment during pressure flow. Joints in

barrel should be inspected in dry conditions, if possible.

Inspection just after a barrel is dewatered may reveal thelocations of leaks, because water sometimes spurts through

affected joints.

12. Typically, barrel joints pull apart under the highest part of

an embankment and are under compression at the end of the

waterway. When inspecting barrel joints be sure to:


** Examine the joints between adjacent sections of barrel forleaks and for ruptured waterstops.

** Look for compression spalling of concrete.

** Check for misalignment of sections due to differential



145

settlement.Figure shows a barrel joint which has opened along the bottom

due to localized settlement along the barrel.



146

CHECKLIST FOR EXAMINATION OF AQUEDUCT


Chainage _______________ to _________________


_________________ _________________________



Releases:

Escape __________ m3 /s

Outlet Works for irrigation __________ m3

/s



Name Affiliation

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

BRIDGE ______________________


Vegetation at abutments and piers ______________________

Bridge supports

Foundations ______________________

Substructures-piers ______________________

Bridge bearings ______________________

Moving parts ______________________



147

Accumulation of birds, nests etc. ______________________

Visual examination of scour

protection ______________________


Main supporting members

Deteriorated and/or damaged

members(SLABS/BEAMS) ______________________


Bridge deck


Surface of roadway slab ______________________

Drainage ______________________

Water spouts ______________________

Expansion joints ______________________

Guardrails/Parapats ______________________

Signage ______________________

BARREL

Walls




Drummy Concrete / Pop out / Pitting / Sealing) _______________








Floor







148




Amount of flow ______________________






149

PART IV

SCHEDULE OF ROUTINE INSPECTION



150

Chapter 15

SCHEDULE OF ROUTINE INSPECTION

1. Operation of the dam/canal during normal conditions shallbe the responsibility of the section officer in charge of the canal.It shall be ensured that unauthorized encroachments do notoccur, that existing or potential conditions do not lead to publiccriticism or injury to the public and that nothing is done whichconflicts with the primary purpose of the project. Following givesschedule of duties to be performed by the Section officer:

Daily

1. Record water surface elevation in reservoir/canal2. Record discharge released into various canals/ direct outlets

offtaking from the canal within his jurisdiction3. Record releases from escapes/wasteweirs/spillways4. Check security and safety devices5. Make required changes in gate openings6. Record pertinent information in Operating Log7. Check escape tail channel for debris

Monthly

1. Check condition of :Downstream cisterns

2. Run generators for minimum one hour3. Keep batteries charged4. Replace light bulbs if required5.Check signs that warn public of hazards near falls, escapes,

Head regulators and siphons6. Check fence conditions and caution signs

Quarterly

1. Operating instructions--uptodate & legible2. Clean gate control switchboxes3. Check & clear bridge drains4. Clean inside of motor control cabinet



151

Semiannually

1. Inspect approach and tail channels of structures for trees,vegetation, shrubs, bush growth and remove deep rootedvegetation and shrubs.

2. Inspect for erosion in and around structures3. Inspect and record quality and clarity of seepage and

corresponding water level in canal.4. Lubricate gate rollers5. Lubricate hoist cables6. Replace grease in gear case of hoist7. Change oil in generator8. Check hydraulic oil lines9. Check oil reservoir level in hydraulic gate system10. Check rubber seals and seal clamps

11. Check paint on gates12. Check mechanical hoist bearings and flexible coupling

bearings13. Spur gear units and gear motors

Annually

1. Check and repaint metal works of bridge, gates, fence2. Review Standing Operating Procedure3. Exercise gates and valves

4. Check condition of exterior and interior of siphon barrels5. Examine approach and tail channels of siphons, tail

channels of escapes, apron, downstream cistern of escapes,falls & outlets

6. Check electrical pull boxes, conduits & switches7. Inspect ends of drainage pipes at or near upstream toe of

embankment and clean out debris / material that mightchoke that drain.

After Heavy Rains

1.Inpect and repair escapes/spillways and drainage structures

Every three years

1.Inspect and repair conduits/ barrels having more than 60 cmdiameter



152

2. Following officers shall carry out inspection as per thefrequency shown against their designation:

Designation Of inspecting officer

Inspection to be carried out during month of

Note

Deputy ExecutiveEngineer

March,October

Executive Engineer AprilOctober

SuperintendingEngineer

MidMay MidNovember

Vulnerablearea

Chief Engineer May lastfortnightNovember last fortnight

At Random



153

PART V

INSPECTION DURING EMERGENCY



Chapter 16

INSPECTION DURING EMERGENCY

Detailed guidelines are under preparation for inspection and operation

during emergency situations. These form part of Standing Operating

Procedures of each of the dams.

manual for inspection of structures

Documents