draft report shalika

7/25/2019 Draft Report Shalika

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ALTERNATIVE METHODS FOR IN-SITU CONCRETE LINING

USED IN IRRIGATION CANALS IN SRI LANKA

(Draft Report)

By

Eng. EMSMK Ekanayake

PG/E/ST/2015/11

Dr. (Mrs.) C.K. Pathirana

Faculty Advisor

Faculty of Engineering

University of Peradeniya, Sri Lanka

The Thesis for partial fulfilment of the requirement of

Masters in Science of Structural Engineering


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CONTENT

Page

1.

Introduction 2

2.Literature Review 4

3.

Methodology 13

4.

Analysis 15

5.

Conclusion 19

6.

References 21


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1.0

INTRODUCTION

As Engineers we have to make our society more secure and more prosperous.

Today we are facing severe problems in our society such as Environmentaldecay, Natural disasters & Poverty in the society. We must go for solutions to

overcome these problems, through policies, that sustain and expand the

environmental resources available in our country (Ekanayake, 2013).

Irrigation in Sri Lanka had been practiced for a period of more than 2500

years. The massive irrigation systems built by our ancient kings made our

people not to depend on external sources for the purpose of feeding her people.

There are about 12,000 small tanks and anicuts in Sri Lanka and these tanks

and anicuts irrigate an extent of more than 185,000ha. This is 35% of total

irrigable area in the country. Small irrigation schemes produce 191,000

metric tons annually accounting for 20% of the national irrigated rice

production (Agricultural implementation program 1994 - 95).

The rapid increase in population will be in developing countries like Sri Lanka

and the poor people will have no alternative, but to cultivate fragile lands

needed to their own survival. With the increase of population more fragile

lands will be needed for more food production. But the land is limited and

hence the lands should be used more efficiently with a higher production

output. When maximizing the food production, the water takes a main part in

cultivation. Therefore it is necessary to have an optimum usage of water in

irrigation.

In the above almost all irrigation systems of Sri Lankas water conveying isdone using earthen canals. Though irrigation canals may be constructed in

natural or compacted earth, these suffer from certain disadvantages, such as;

Maximum velocity limited to prevent erosion

Seepage of water into the ground

Possibility of vegetation growth in banks, leading to increased friction

Possibility of bank failure, either due to erosion or activities of

burrowing animals


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Canal lining is a good solution to overcome these problems and it will play an

increasing role in conserving losses and thereby extend and improve the

irrigation facilities. Some of the broad benefits of canal lining are;

Saving of seepage water and its value

Land and produce saved as water logging in adjacent land may be

avoided

Saving in cost of, earth work, masonry structures, and cross-drainage

works

Cost of land acquisition saved due to reduction in top width in case of

lined channels

Reduced canal dimensions

Due to reduced exposed area, evaporation and transportation losses are

also reduced.

Higher velocity obviates silting problems inherent in unlined canals

Improves Canal hydraulics, equity and reliability of water distribution

Smaller channel section to pass full supplies due to lower rugosity

coefficient and higher velocities in lined sections

Lining does not permit weed growth and therefore transpiration losses

would be non-existent

Ease and saving in operation and maintenance of the canal

However in Sri Lanka in-situ concrete lining is somewhat practice. But this

may also arise some problems, such as;

Almost all canal systems located in remote areas. Therefore

transporting materials & machineries to construction sites is difficult.

Taken much time to complete the construction and finally it causes to

delay or give up a cultivation season.

Careful guidance should have to maintain side slopes, gradient of canal

and quality of construction

Therefore this research is to find a most suitable lining system to overcome

above issues in earthen canals in Sri Lankan irrigation system.


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2.0

LITERATURE REVIEW

2.1 Canal Lining & Irrigation

Irrigation is the artificial application of water to the land or soil. It is used to

assist the growing of agricultural crops, maintenance of landscapes, and re-

vegetation of disturbed soils in dry areas and during periods of inadequate

rainfall. Irrigation systems are also used for dust suppression, disposal of

sewage and in mining. Irrigation is often studied together with drainage,

which is the natural or artificial removal of surface and sub-surface water

from a given area. Lining is a resistant layer made of concrete, protecting the

canal bed and its sides in order to have a sufficient strength to resist water

pressure. The layer advantage is to save water for extension of irrigation, to

minimize filtration losses, improve duty, and minimize maintenance cost and

to prevent growth of wild plants.11

2.2 Lining of Irrigation Canals

Most of the irrigation channels in Sri Lanka are earthen channels. The major

advantage of an earth channel is its low initial cost, these suffer from certain

disadvantages, such as

1. Maximum velocity limited to prevent erosion.

2. Seepage of water into the ground.

3. Possibility of vegetation growth in banks, leading to increased friction.

4.

Possibility of bank failure, due to erosion.

5. More maintenance requirement.

All these reasons lead to adoption of lining of canals, though the cost may be

excessive. Hence, it is also necessary to evaluate the cost versus the savings

due to reduction in water loss through seepage, i.e. cost-benefit ratio is to be

estimated.


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2.3 Types of Canal Lining

Types of lining are generally classified according to the materials used for their

construction. Concrete, rock masonry, brick masonry, bentonite-earthmixtures, natural clays of low permeability, and different mixtures of rubble,

plastic, and asphaltic materials are the commonly used materials for canal

lining. However the suitability of the lining material is decided by:

1. Economy

2. Structural stability

3. Resistance to erosion

4.

Durability5. Hydraulic efficiency

2.3.1 Concrete Lining

Concrete lining is probably the best type of lining. Cement concrete lining

made from selected aggregate gives very satisfactory service. Despite the fact

that they are frequently high in their initial cost, their long life and minimum

maintenance make them economical. Cement concrete lining are best suited

for main canals which carry a huge flow at high velocities. However, a firm

foundation is necessary for avoiding any possibility of cracking due to

foundation settlement. The smooth surface of the concrete lining increases

the conveyance of the channel.

Reinforcement in concrete linings usually varies from (0.1 to 0.4%) of the area

in the longitudinal direction and (0.1 to 0.2%) of the area in the transverse

direction.The reinforcement in concrete linings prevents serious cracking of

concrete to reduce seepage, and ties adjacent.

Sections of the lining together to provide increased strength against

settlement damage due to unstable sub-grade soils or other factors. The

reinforcement in concrete linings does not prevent the development of small

shrinkage which tend to close when canals are operated. The damage due to

shrinkage and temperature changes is avoided or reduced by the use of

special construction joints. (Z. Sen 2005)


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Expansive clay soils should be avoided and proper moisture and density

control of the sub grade soil should be maintained while lining. In areas where

the ground water table is likely to rise above the invert level of the lining and

cause excessive uplift pressure, drains are located below the lining to releasethe water and relieve the pressure, generally, a thickness of about ( 5 to 12

cm ) is generally adopted for C15 concrete and (7.5 cm to 15 cm) for C10

concrete. Figure (1) shows cement-concrete lining type.

Figure (1): Concrete lining for different canal sections

2.3.2 Precast concrete lining

Precast concrete slabs, laid properly on carefully prepared sub grades and

with the joints effectively grouted, form a practical type of lining. The precast

slabs are about 5 to 8 cm thick with suitable width and length to suit channel

dimensions and to result in weights which can be easily handled. Such slabs

may or may not be reinforced (Tarig EI Gamri 2009).This type of lining is best

suited for repair work as it can be placed rapidly without long breaks in canal

operation. Figure (2) shows this type of canal lining.


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Figure (2): Precast slabs lining

2.3.3 Shotcrete Lining

Shotcrete, that is, cement mortar in the ratio of 1 cement to 4 sand

proportions is through a pump-pipe-nozzle system on the surface of the

channel. Wire mesh reinforcement is generally, though not necessarily, is

clamped to the channel surface (as for a rocky excavation) before applying

shotcrete. They are suitable for lining small sections, for repair of old linings,

and for placing linings around curves or structures. Shotcrete linings are

generally laid in a thickness of about 2.5 - 6.5 cm as per requirement.

Figure (3): Shotcrete lining


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2.3.4 Bricks, Tiles and Stone lining

Bricks are installed in layers of two with about 1.25 cm of 1: 3 cement mortar

sandwiched in between. Good quality bricks should be used. Brick tiles can

be plastered to increase the carrying capacity of canal with same section andhelp in increasing the life span of the lining as shown in figure (4). Sometimes

a layer of tiles is laid over a layer of brick masonry. The top layer is generally

laid in 1 : 3cement mortar over 15 mm thick layer of plaster in 1 : 3 cement

plaster. The size of tiles is generally restricted to 30 mm150mm53 m. This

type of lining is stable even if there is settlement of foundation, since the

mortar joint between bricks or tiles provides for various cracks so fine that

seepage is insignificant. This type of lining is suitable when concrete isexpensive and skilled labour is not available.

Stone lining of canals, if economically feasible, is useful for preventing erosion

and where the ground water level is above the bed of the canal and there is a

possibility of occurrence of damaging back pressures. The stones used for

boulder linings should be hard, durable, and capable of sustaining weathering

and water action. Rounded or sub angular stones or blasted rock pieces with

sufficient base area are recommended types of stones or boulder lining.

Figure (4): Brick Lining


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2.3.5 Asphaltic Lining

The material used for asphaltic lining is asphalt-based mixture of cement and

sand mixed in hot condition. The most commonly used asphaltic linings are:

Asphaltic concrete

Buried asphaltic membrane

Asphaltic linings are relatively flexible, and can be rapidly laid in any time of

year. Asphaltic concrete is a mixture of asphalt cement, sand, and gravel

mixed at a temperature of about 110C to 200 C and is placed either

manually or with laying equipment. The lining is compacted with heavy iron

plates while it is hot. A properly constructed asphaltic concrete lining is the

best of all asphaltic linings, it is smooth, flexible, and erosion-resistant. Sinceasphaltic concrete lining becomes distorted at higher temperatures, it is

unsuitable for warmer climatic regions.

2.3.6 Earth Linings

The different types of earth linings that are used in canals include the

following:

Stabilized Earth Linings

Sub-grade is stabilized using either clay for granular subgrade or by adding

chemicals that compact the soil.

Loose Earth Blankets

Fine grained soil is laid on the sub grade and evenly spread. However, this

type of lining is subject to erosion, and requires a flatter side slopes of canal.

Compacted Earth Linings

The graded soil containing about 15 percent clay is spread over the subgrade

and compacted.

Buried Bentonite Membranes

Bentonite is a special type of clay soil, found naturally, which swell

considerably when wetted. Buried bentonite linings for canals are constructed


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by spreading soil-bentonite mixtures over the sub grade and covering it with

gravel or compacted earth.

Soil-cement Linings

These linings are constructed using cement (15 to 20 per cent by volume) and

sandy soil (not containing more than about 35 per cent of silt and clay

particles). Cement and sandy soil can be mixed in place and compacted at the

optimum moisture content. This method of construction is termed the dry-

mixed soil-cement method. Alternatively, soil cement lining can be constructed

by machine mixing the cement and soil with water and placing it on the

subgrade in a suitable manner. This method is called the plastic soil-cement

method and is preferable. In both these methods, the lining should be kept

moist for about seven days to permit adequate curing. The construction cost

of soil-cement linings is relatively high. But these resist weed growth and

erosion and also permit velocities slightly higher than those permitted by

unlined earth channels. The use of soil-cement linings for irrigation canals is

restricted to small irrigation canals with capacities of up to 10 m3/sec, and in

which the velocity of water does not exceed 1 m/s. Figure (5) shows earth

lining type for trapezoidal canal section.

Figure(5): Compacted clay or soilcement lining


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2.4 Failure of Canal Lining

The main causes of failure of lining are the water pressure that developed

behind the lining material due to high water table, saturation of the

embankment by canal water, sudden lowering of water levels in the channel,and saturation of the embankment sustained by continuous rainfall. When

the water level in canal was raised and lowered the banks suffering from

instability due to erosion and seepage through the banks may be occurs. In

order to minimize the seepage, a secondary berms were constructed along the

length of bank at various locations.

The embankment of a relatively pervious soil does not need drainage

measures behind the lining. In all situations requiring drainage measures toreduce pore pressure behind the lining, a series of longitudinal and transverse

drains satisfying filter criteria are provided. A typical arrangement of

longitudinal filter drain is as shown in figure(6).

Figure(6): Longitudinal filter drainage in lining layer


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Figures (7 & 8) shows failure of canal linings.

Figure(7)

Figure(8)


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3.0

METHODOLOGY

3.1 Data Collection & Analysis

Almost all Sri Lankan major & medium irrigation systems are managed

by Irrigation Department & Mahaweli Authority of Sri Lanka (MASL)

and minor schemes are managed by the Local authorities such as

Provincial Irrigation Departments, Agrarian Department etc. However

for this research Data is collected from major & medium schemes only

as it has a higher canal network system where much water losses is

excess.

Then analyzed the data to identify the most critical part of Main

canals/branch canal, Distributary canal or Field canal to be optimized

from water losses.

Also analyzed by reviewing the current lining practices from other

countries what the best type of lining to be practiced for Sri Lankan

irrigation system is.

3.2 Select a Most Economical Section

Using a typical irrigation system in Sri Lanka it is suggest to check a

most economical canal section according to the analyzed outcome in

3.1 by applying irrigation theories.

3.3 Design

According to the selected lining type, it is to be designed a canal section

using theory of Structural Analysis & British Standards code of

practice.


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3.4 Jointing System & Construction Technique

According to the designed lining a proper jointing system and the

construction technique is to be introduced.

3.5 Cost Benefit Analysis

The cost of the selected lining is to be weighed against the obtainable

benefits. The Benefit Cost Ratio (BCR) must be greater than one, if

lining is to be feasible at all. Costs and benefits should be assessed as

present values over the life cycle of the individual canal, water savings,

benefits and eventual replacement costs of the liners and the other

specific factors inherent in a given project.


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4.0

ANALYSIS

Here are some reservoirs canal data collected from Irrigation Department and

Mahaweli Authority of Sri Lanka.

Kaudulla Tank

Capacity : 104,000 Acft

Command area : 13,500 Acrs

Main canal length : 18,762 m

Branch canal length : 17,234 m

Distributary canal length : 63,682 m

Field canal length : 287,411 m

All are earthen canals.

Kantale Reservoir




Branch canal length : 6,450 mDistributary canal length : 26,500 m



Vendrasan Tank




Branch canal length : -




Wanela Tank

Capacity : 2,160 AcftCommand area : 1,620 Acrs


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Branch canal length : -



Only 0.4% of Field canals is concrete lined

Peramaduwa Tank


Command area : 600 Acrs






Kalawewa



Main canal length : 106 km

Branch canal length : 91 km

Distributary canal length : 511 km

Field canal length : 1,521 km

2% of Main canals, 0.5% of Branch canals, 2% of Distributary canals and 1%

of Feeder canals are concrete lined.

Huruluwewa









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Kandalama Tank



Main canal length : 41,028 mBranch canal length : 2,600 m



0.5% of of Distributary canals and 0.2% of Feeder canals are concrete lined.

4.1 Water loss calculation

Irrigation Duty for Yala season = 5 Acr.ft/Acr.

Crop water requirement for paddy = 1.5 Acr.ft/Acr

Water loss = 3.5 Acr.ft /Acr

Specimen Calculation

For Kantale Irrigation Scheme

Total Water loss for a Season = 18,560Acr x 3.5 Acr.ft/Acr = 64,960 Acr.ft

These conveying losses are due to seepage, evaporation, deep peculation and

due to bank failures etc. However the water losses are proportional to the

permeability of the soil where canal excavated and the wetted perimeter of the

canal. In most irrigation systems in Sri Lanka most lengthy canals are Feeder

canals having lesser wetted perimeter. According to the canal lengths, the

conveyance efficiencies are as follows.

Canal lengthEarthen canals

Lined canalsSand Loam Clay

Long (> 2000m) 60% 70% 80% 95%

Medium (200-2000m) 70% 75% 85% 95%

Short (< 200m) 80% 85% 90% 95%

All canals in Kantale scheme are lengthy than 2000m Hence by assuming

Conveyance efficiency for Lined canals is 95%,


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Water loss during conveying is 3,248 Acr.ft and saving is 61,712 Acr.ft

Also all these water is conveying through Main canals, Branch canals,

Distributary canals & Field canals. Therefore total saving water is factored to

the canal length vise.

Type of canalWater loss in Acft/Acr

Earthen Lined

Main Canals 9448 472

Branch Canals 1800 90

DistributaryCanals

7394 370

Feeder Canals 46318 2316Total 64960 3248

Saving of water;

From Main canals : 61,712 x 0.15 = 8,975 Acr.ft

From Branch canals : 61,712 x 0.03 = 1,710 Acr.ft

From Distributary canals : 61,712 x 0.11 = 7,025 Acr.ft

From Field canals : 61,712 x 0.71 = 44,003 Acr.ft

The saving water from FCC is enough for additional cultivation of almost

29,000 Acrs ie. The command area can be increased by 158%

0

5000

10000

15000

20000

2500030000

35000

40000

45000

50000

Main Canals Branch Canals Distributary Canals Feeder Canals

Water Losses from Kantale Irrigation Scheme

Earthen Lined


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5.0

DISCUSSION

Water is an essential resource for all life on the planet. Water resource

management planning has to take account of all the competing demands of

water by mankind (sanitation, drinking, manufacturing, leisure and

agriculture etc.) and seeks to allocate water on an equitable basis to satisfy

all uses and demands. Against this background this research was done to

optimize the water usage in Irrigation practices in Sri Lanka.

It is clear from the analysis most losses of water from Field canals. This is due

to those canals are more lengthy than others. Even though the seepages from

a canal is a loss, in a way it is more favorable as it is environmentally feasible

due to recharging the ground water table.

However, if concern the field canals area, it is not necessary to improve the

water table because whole area is used only for cultivation. But Main/branch

or distributary canals are mostly going through villages, hence improving

ground water table is much important in that area too. Also losses from above

canals is minimum than FCC according to the analysis therefore Lining is not

suggest for Main/branch or Distributary canals.

By considering the above reasons it is more adequate to propose a suitable

lining method for field canals.

Sri Lanka most currently practicing method is just earthen canals with fever

in-situ or pre-cast concrete linings. Concrete lining is also adopt only

concerning the difficulty of construction of earthen canals. But with the

concern of water management it is clear that much water is lost during

conveying. Hence to optimize the conveyance losses this research is followed

to introduce lining for irrigation canals in Sri Lanka.

The literature review clears that there are so many lining methods. But no

one particular type of lining can be considered the best or most economical

for use in all locations. Each type of lining has its own specific technical and

economic merits and limitations depending on such factors as specific site

and soil conditions, location, experience of installation crews and weather


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conditions during installations. A particular type of lining may be unsuitable

for use at another location.

Therefore by considering the factors such as purpose of lining, soil

characteristics, ground water levels, land use, operation and maintenance,

Canal dimensions, acceptable seepage rate, service life, availability of

construction materials, availability of labor and equipment, in irrigation

canals in Sri Lanka it is more suitable method is concrete linings. But it could

be in type of in-situ or pre-cast. In-situ concerting is also somewhat difficult

as have to wait for off-season to execute the works and also any how complete

within that time too. Also materials to be transported to the sites and

technical attention is also needed to maintain the canal slope & quality of

construction works. This difficulties could be overcome by using Pre-cast.

Therefore it is suggest Pre-cast concrete lining alternative for in-situ

concreting as it is easy handling, installing & making in a yard to an optimum

quality.


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6.0 REFERENCES

1. Construction and Refurbishment of Earthen Channel Banks,(2002),Australia

2. Ekanayake EMSMK, (2013). Designing to find the Head WorksParameters for the Breached Divulkele Tank & Introducing a WaterManagement Plan. IESL Part III(C) Thesis, Institution of Engineers, SriLanka.

3. IS 10430:2000,(2000). Criteria for Design of Lined Canals andGuidance for Selection of Type of Lining.Bureau of Indian Standards,New Delhi, India

4. M.Riaz, Z. Sen(2005). Aspects of Design and Benefits of AlternativeLining Systems, European Water 11/12:17-27, 2005 2005 E.W.Publications

5. Syed Hasan, GunvantVaghela, James Yip, Ben Chung. ShotcreteDesign for Irrigation Canal Lining, GHD Pty Ltd, Sydney.

6. SK Garg(1996).Irrigation Engineering and Hydraulic Structures,Khanna Publishers ,New Delhi, India

7.Tahir MA, Tarig EI Gamri(2009). Use of Pre-cast Concrete Slabs and

Bricks for Lining Irrigation Canals, J.Sc. Vol. 10(2) 2009, DesertificationResearch Institute, Sudan.

8. http://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=en, 2015 July

9. http://www.srilankaheritages.com/ecosystem.html, 2015 July

10.http://www.fao.org/docrep/t7202e/t7202e08.htm#TopOfPage,2015 July

11.

http://www.fiorigroup.com/products/applications/canal-lining, 2015 July
http://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=enhttp://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=enhttp://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=enhttp://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=enhttp://www.srilankaheritages.com/ecosystem.htmlhttp://www.fao.org/docrep/t7202e/t7202e08.htm#TopOfPagehttp://www.fao.org/docrep/t7202e/t7202e08.htm#TopOfPagehttp://www.fiorigroup.com/products/applications/canal-lininghttp://www.fiorigroup.com/products/applications/canal-lininghttp://www.fao.org/docrep/t7202e/t7202e08.htm#TopOfPagehttp://www.srilankaheritages.com/ecosystem.htmlhttp://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=enhttp://www.irrigation.gov.lk/index.php?option=com_content&view=article&id=301&Itemid=161&lang=en

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