22_1 Lining of Canal Nptel

Hydraulics Prof. B.S. Thandaveswara

Indian Institute of Technology Madras

22.1 Lining the Canals

It is always assumed that seepage losses would be reduced from the theoretical

calculations as between 3.7-1.8 cumec per million square metres (cumec/Mm2) for an

unlined canal in the sandy or clayey loams to 0.6 cumec/Mm2 for a lined canal. In 1988

a field study of the performance of lined distributaries were losing 3.5 cumec/Mm2 and

watecourses were losing 3.7 cumec / Mm2.

Why is there such a gap between assumptions at the feasibility stage and what

happens in practice?

Old earthen irrigation channels in permeable soils can lose a lot of water through

seepage. Large losses through the bed and sides of canal lead to low conveyance

efficiency; that is, (the ratio of water reaching farm turnouts to that released at the

source of supply from a river or reservoir). Earthen canals also get clogged up with

weeds which reduce the water-carrying capacity.

These two factors combine to disadvantage of the tail end farmers. Therefore Unlined

canals are inefficient, inadequate from the point of view of equitable performance.

In Punjab, the expected saving by brick lining is of the order of 20% . The brick linings

have 25 years of life.

Total losses from unlined watercourses are known to be more than those from the main

system, but they dont get the same attention during a lining programme. Lining

programmes are divided into main system lining and watercourse lining. The main

system canals (main, distributaries, and minors) are large channels supplying several

watercourses.

A typical value for the seepage rate in an unlined channel in clayey loam is 1.8 m3/s per

M m2 and through a rendered brick line water course or canal reduces to 0.1 m3/s per M

m2. However, if the impervious canal lining has few crack what would happen? The

experiments indicate it as good as that of the original unlined case when the ground

water level is high.

Inspite of the above observation, lining can significantly reduce conveyance losses.

Lined channels have a smaller surface area for a given discharge than unlined



channels. Typically a lined channel will have 40% of the unlined surface area for a given

discharge. Therefore even at the same loss rate per unit area there will be a saving in

water. When estimating the reduction in losses from a lining programme, this should be

based on the combination of a reduced cross-section and a reduced seepage rate per

unit area.

In the Indian Punjab, measurements on lined distributaries and watercourses between

four months and seven years old showed that seepage rates from the distributaries

rapidly became comparable to seepage rates from unlined canals, whilst seepage rates

from watercourses were highly variable.

Lining of the distributary canal seemed to have had a beneficial effect on the equity of

supply between watercourses. However, the effects of lining watercourses is still to be

established.

A sample of 15 out of 130 watercourses were tested on the 30,000 ha Mudki subsystem

of the Sirhind Feeder in Ferozpur district using ponding tests and inflow-outflow

methods. The mean and variability of seepage losses increased dramatically for lining

more than four years old. Some lining older than four years performed as well as new

linings, with losses as low as 0.4 m3/s per Mm2 but others has losses of up to 11.5 m3/s

per Mm2. Overall conveyance losses were significantly greater than seepage losses

alone.

The variability of conveyance losses was observed to be related to the condition of the

channels. Losses from raised watercourses with cracked or broken linings appeared as

surface leakage causing waterlogging of adjacent fields and localised crop damage.

This was due to poor quality control during construction, particularly earth compaction

behind sidewalls, and a lack of subsequent maintenance.

The design life of concrete and brick lined channels is generally assumed to be 25-50

years. Major repairs of lined channels are sometimes required within a few years of

construction. At the Kraseio Scheme in Thailand, completed in 1981, long lengths of the

concrete lined main canals have needed to be replaced each year.

In one 26-year lining test, a complete repair of the drained test channel was required

every 22 months.



There is no watertight case for or against lining.

If lining goes ahead, a high standard of construction is essential, especially of water

courses which must withstand a great deal of wear and tear. Without adequate

supervision, poor construction of channels will lead to reduce life and higher

maintenance costs.

Earthen watercourse in the Bikaner area of Rajasthan discharge an average 28.3 l/s,

but begin to seep and leak badly after little more than a year. These cracks and the slow

movement of shallow water favours developement of thick aquatic weeds, which

encourages the drying and the cracking process, and strcuturally weaken the banks.

This obviously adds significantly to the cost of maintenance.

The cracks opened in dry periods do not close fully when saturated by water flows, and

losses can be up to 25% of the water diverted into the system.

The cycle of swelling, heaving, shrinkage and settlement leads to progressive bank

deterioration. Shear strength of clays depends on cohesion between particles. In a

newly-formed compacted clay masses the interparticle cohesion is high. On first drying,

the cracks appear and close up again on wetting, but do not regain their original

interparticle cohesion. This means a reduction in shear strength after a few drying and

wetting cycles.

The reinforced concrete lining would reduce the seepage loss drastically and has lower

operation and maintenance costs.

Reference

World Water, April 1989, pp 16, 19, 21.

Appendix (i)

Table - 1 Salient Aspects of Seepage through Lined Canals [7]:

Sl.No State Adopted practice

( )2 31 200 /lQ / B D= + 1 U.P.

Practice lQ = Seepage losses in cumecs/km length B and D are bed

width and depth. 1 61 9 /

lK . Q=

lK = Seepage loss in cumecs / 106 sq.mof wetted area.

2 Punjab & Haryana

Q = Main discharge in the canal.



Lined canal (F.P.S) 0 0561 25 .lK . Q=

3 Bhakra Nangal Unlined canal (M.K.S) 0 52650 00928 .

lq . Q=

lined canal: of wetted surface 6 20 60 10lQ . cumecs / m=4 Andhra Pradesh

Unlined canal: of wetted surface and 20% extra for distributory system.

6 21 85 2 40 10lQ . to . cumecs / m=

5 CBIP Main canal - 7% of head discharge Distributory and minors - 8% of head discharge Water surface - 20% of head discharge

Table-2 Salient Aspects of Seepage through Lined Canals (After Yu. M. Kosichenko [8]):

Sl. No.

Type of lining and character of disturbance

Permeability Kl m/s seepage loss Q m3/sec/m2

Concrete-film lining i. Smooth 0.705 * 10-9 / 0.141 * 10-7 0.334 * 10-4 / 0.685 * 10-5

ii. Crack with rough walls 0.652 * 10-9 / 0.136 * 10-7 0.318 * 10-6 / 0.665 * 10-5

iii. Silted cracks 0.137 * 10-9 / 0.156 * 10-7 0.318 * 10-8 / 0.76 * 10-7

I

iv. Without cracks 0.590 * 10-11 / 0.114 * 10-9 0.228 * 10-8 / 0.556 * 10-7

Concrete lining i. Smooth 0.225 * 10-8 / 0.331 * 10-6 1.243 * 10-6 / 1.516 * 10-4

ii. Crack with rough walls 0.867 * 10-9 / 0.202 * 10-6 0.423 * 10-6 / 0.982 * 10-4

iii. Silted cracks 0.706 * 10-10 / 0.752 * 10-10 0.344 * 10-7 / 0.367 * 10-7

II

iv. Without cracks 0.694 * 10-10 0.388 * 10-7

Soil film lining i. Protective layer of

local soils 0.981 * 10-9 / 0.189 * 10-7 0.564 * 10-7 / 1.087 * 10-6

III

ii. Protective layer of compacted clay 0.221 * 10-11 / 0.425 * 10-10 0.127 * 10-9 / 0.245 * 10-8

IV Soil Membrane 1 * 10-8 0.575 * 10-6

V Unlined channel - 0.295 * 10-3

Plastics as a lining material

Introduction

Water suitable for human consumption, livestock and irrigation is limited in many parts

of the world. Since precipitation is the only source of all fresh water and since it varies

from place to place, from year to year and from season to season, water must be

collected, stored and transported, if it is to be available when and where it is required.

The loss of irrigation water in a canal system occurs during its conveyance through

canal, sub-canal, distributary, minor, water course and finally during application in the



field. In a study made by the Central Water and Power Commission (1967), the losses

during the various phases of water conveyance was found to be as shown in Table

Water use efficiency in percentage Number of System

Characteristics Canals DistributariesWater courses

Field Losses

Total Loss

Net Utilization

Entire system unlined. 15 7 22 27 71 29

Only Canal lined. 4 7 25 30 66 34

Canal and Distributary lined.

4 2 26 32 64 32

Whole system lined. 4 2 6 42 54 46

It may be observed that, in a completely unlined canal irrigation system the loss of

irrigation water is as much as 71%. This loss is attributed to both evaporation and

seepage losses; evaporation losses are a function of temperature, humidity and wind

velocity. It is not practicable to prevent evaporation loss (in some reservoirs this loss

has been prevented by floating a thin PE film on the water surface) in running water.

However, seepage losses could be effectively minimised by the use of an impervious

medium between the porous soil and the water flowing in the system.

Conventional materials like clay, tiles, cement-concrete, have been used for prevention

of seepage losses. Most of the conventional methods are either too expensive or not

very effective.

Table 2 shows the state wise break-up of irrigation resources and the length of major

irrigation canals operating in each state.

Irrigation and Power Research Institute at Amristar has particularly conducted intensive

research in this field and a suitable lining technique has been evolved for existing

earthen canals and channels.

This technique is known as "Combination Lining" and in this, a low cost Polyethylene

film is laid at the bed of the canal or distributary whereas the sides are lined with pre

cast brick-tile blocks. This method can be conveniently adopted for lining distributaries

during short closures. This technique has many advantages over the other methods of

lining such as laying new lined parallel channels which involve construction of new



bridges, regulators, falls and outlets. Moreover, in case of combination lining, the

existing section, regime and stability of the channel are not changed. Irrigation supplies

are also not interrupted as lining is done during short closures.

Table 2 Statewise distribution of Irrigation area under major irrigation canals.

Percentage of net area irrigated in 1970-71 by various sources

Name of State/ Union Territory

Average rainfall in cm

Net irrigated area '000 hectares 1970-71

Canals Tanks Wells Others

Length of major canals in km

Andhra 900 3313 48 34 15 3 1,242.8 Assam 240 572 63 - - 37 137.2 Meghalaya 241 37 - - - 100 - Nagaland 193 12 - - - 100 - Manipur 193 65 - - - 100 - Sikkim 355 NA NA NA NA NA NA Tripura 193 22 - - - 100 NA Bihar 132 2160 38 8 25 29 906.2 Gujarat 81 1209 17 2 80 1 2,437.2 Haryana 76 1532 62 - 38 - 1,098.3 H.P. 184 91 - - 1 99 - J & K 102 279 98 - - 2 32.0 Karnataka 104 1137 37 32 23 8 2,924.6 Kerala 267 431 49 17 1 33 491.9 M. P. 123 1480 48 9 38 5 238.4 Maharashtra 106 1427 22 16 57 5 2,546.1 Orissa 153 1149 23 51 4 22 613.7 Punjab 64 2888 45 - 55 - 501.2 Rajasthan 46 2132 35 13 51 1 869.4 Tamil Nadu 97 2592 34 35 30 1 561.4 U. P. 117 7190 48 34 15 3 1,683.5 W. B. 174 1489 65 20 1 14 1,666.0 All India 161 31207 40 14 38 8 17,949.9

NA- Not Available (a) Includes Harayana. (b) Included in Punjab. * Source : Irrigation

Commission (1972).

Nearly 30 to 80 percent cost saving could be achieved by using combination type of

lining as compared to double tile lining. The behaviour of this lining laid in different

channels in Punjab has been studied and it has been found that this low cost lining is

durable, efficient and quite suitable for lining the existing distributaries.

Gujarat State Irrigation Department is also using Combination Lining. To render the

canals seepage proof, a 400 gauge (100 microns) thick black LDPE film is used to line



the bed of the canal which is then covered with single layer brick masonry. For further

reduction of cost, soil cover varying from 60 cm to 90 cm could be tried.

A similar trial was also carried out in Azamgarh District of Uttar Pradesh by the UP State

Irrigation Department. In this trial, 600 gauge (150 microns) PE film was used in the

canal bed overlaid with 45 cm soil cover.

The advantages of Polyethylene (PE) film lining are:

(a) Cost factor is very much in favor of PE lining in comparison with conventional lining

methods.

(b) The PE film lining has the advantage of being a superior moisture barrier than any

other construction material including cement-concrete, tiles, tar-felt, etc. Irrigation and

Power Research Institute (IPRI), at Amristar and Central Building Research Institute at

Roorkee have conducted extensive trials on this type of lining. Permeability tests on this

type of lining. Permeability tests by IPRI showed that a 400 gauge PE film subjected to

a hydraulic head of 3.65 meter has stayed water tight for about 15 years.

(c) Another advantage of this type of lining is the speed with which it can be laid at site.

By using this type of lining, the total time involved in lining work can be substantially

reduced, thus facilitating wider coverage during short closure of canals.

The Anand Irrigation Division, Gujarat, have found that with double tile lining, the work

progress is around 30 m of canal length a day (15 m canal width) whereas for the

combination type of lining using PE film with a cover of single tile masonry, the progress

is as much as 90 m. This could be still further increased by using LDPE film lining with

60 cm to 90 cm soil cover.

Distributaries:

A Canal Irrigation system comprises of a network of Canals, Sub-Canals, Distributaries,

Minors, with water courses forming the last link. In Government Canals, the jurisdiction

of the Irrigation Department is generally up to the minors. The water courses fall under

the jurisdiction of the individual cultivators.



Use of Plastics for Lining of Canals

Introduction

Canal lining with LDPE film was undertaken in the country in 1959, as a measure to

reduce seepage losses. Punjab and Gujarat States were first to use this type of lining

during 1959 to 1962 followed by other states subsequently.

The Low Density Polyethylene (LDPE), Polyvinyl Chloride (PVC), High Molecular High

Density Polyethylene (HDPE), Linear Low Density Polyethylene etc., are the plastics

used for canal lining. In India, mostly LDPE film has been used for canal lining.

The characteristics of the plastic film are:

Light in weight, impermeable to liquids and gases, chemically inert, flexibility, resistance

to microbiological attacks, ease of transportation and installation etc.

Black LDPE film lining over laid with soil cover or protective hard cover had been widely

used during the last three decades. IPCL's Petro-Chemical Industry in Maharashtra, will

be able to provide the adequate supply of this plastic film for lining of canals.

The LDPE films presently available are too smooth and glossy to hold mortar below

blocks, tile or brick lining indicating the necessity of developing rough or serrated films.

The purpose of the canal lining which helps in reduction in seepage to save water for

additional irrigation, and to increase the velocity for reduction in canal sectional area

due to smooth lined surface. Lining with bricks tiles etc., is fraught with the problem of

seepage through the joints, cracks etc. This naturally leads us to the use of

impermeable plastic film to use as a cut-off. The LDPE film is used with soil cover/ C.C.

Cover/ P.C.C. Cover. C.C. in-situ is less costly and suitable for bed but not for sides.

P.C.C. ensures quality control in case of canal lining on large scale. It is costly but

suitable for both bed and sides. In using P.C.C. pointing needs special attention. LDPE

film is susceptible for puncturing by uneven soil surface, impact of feet, weed growth

etc. A layer of sand would help as a leveling course. Sand with a little silt content or

sand wetted would stand well on slopes. If the surface of the film is rough, it would keep

the mortar in position. The hard cover over the film is meant to be the load over the film

to keep it in position and also to be smooth surface for better flow conditions.



Vandalism with regard to LDPE film is due to lack of awareness of the farmers as to the

value of water. Burrowing by rodents is a menace. The easy and practicable solution is

a sand layer. A burrow does not stand in sand, and the hole gets closed.

Lined canal costs 20 - 25% more relative to cost of unlined canal. If LDPE film is used,

the cost of lining would be 25 - 30% (an increase of 5% due to film cost). This additional

cost due to canal lining using LDPE film is rather a wise investment as the benefits of

water saved, additional irrigation and food production, and reduced canal section would

more than offset that additional cost.

Therefore canal lining is obligatory and the use of LDPE film is bound to spread once its

efficacy commensurate with economy is realized.

Films of different thickness varying from 100 to 250 micron are used in bed or on sides.

Cement concrete cover over LDPE has been used on canals as steep as 1.3:1 on Ravi

Canal (J&K), and 1:1 on Malaprabha canal.



111

1

LDPE Film

F.S

LDPE Film

Free board

Single tile liningin Cement Mortar

LDPE Film

LDPE Film

Lining of Canal with LDPE film Reference "Proceeding of the workshop on Use of Plastics for Lining of Canals", Central Board of

Irrigation and Power, New Delhi, Vadodara, 7-8, May 1987

Venkatasubramanian K.N, Kamal Nanavaty, Prasanta Misra - Role of plastics in water

management published by Indian Petro chemicals Corporation Limited, Government of

India undertaking, august 1968.



Table 3 - Performance of different Canal Linings

The details regarding the design, specifications and performance of various types of

linings as provided in the case of the following projects.

S.No. Canal Type of lining 1 Nangal Hydel Channel (Punjab) Concrete and Tile Lining.

2 Sundernagar Hydel Channel, Beas Project (Punjab) Cement Concrete.

3 Yamuna Power Channel (U.P) Concrete, Brick and Concrete Tile.

4 Gandak Canal (U.P) Brick Tile Lining. 5 Lower Ganga Canal-Link Canal (U.P) Sandwiched Brick Lining.

6 Kosi Feeder Channel (U.P) Cement Concrete Tile Lining.

7 Rajasthan Feeder Channel (Rajasthan) Tiles Lining with plasting, Single tile lining in bed and double tile lining in the side.

8 Banaskantha Left Bank Main Canal of Dantiwada Project (Gujarat) Cement Concrete Lining.

9 Banaskantha Left Bank Main Canal of Dantiwada Project (Gujarat) Brick Lining.

10 Mahi Right Bank Canal (Gujarat) Sandwiched Brick Tile Lining.

11 Shetrunji Canal Project (Gujarat) Masonry Lining. 12 Shetrunji Canal Project (Gujarat) Lime Concrete Lining. 13 Karad Project Canal (Gujarat) Precast Blocks.

14 Tungabhadra Project (A.P) Cement Concrete and Rubble Masonry.

15 Krishanarajasagar Canal (Karnataka) Cement Concrete Lining.

16 Krishnarajasagar, Right Bank Low Level Canal (Karnataka) Soil Cement Lining.

17 Krishnarajasagar Right Bank Low Level Canal (Karnataka)

Lime Surkhi Concrete Lining.

18 Manniaru Canal (Tamil Nadu) In situ Cement Concrete Lining.

19 Pattanamkal Main Canal ( Tamil Nadu) Cement Concrete and Metal.

20 Rethapuram Channel (Tamil Nadu) Cement Concrete and Metal.

21 Left Bank Main Canal, Pamba Irrigation Project (Kerala)

Random Rubble Masonry and Cement Concrete Lining.

22 Left Bank Canal, Kuttiady Irrigation (Kerala) Precast Cement Concrete Slabs.

23 Right Bank Main Canal, Peechi Irrigation Scheme (kerala)

Rubble Masonry in Cement Mortar.

24 Left Bank Canal (Kerala) Precast Slabs and Blocks. 25 Kuthanur Branch (Kerala) Bitumen and Cement.



KERS, Krishnarajasagar had tried HMHDPE film (Tuflene) covered with 1:4:8 or 1:5: 10

Cement Concrete in a length of 140 m on 38.4 km distributory of Visveswaraya Canal

and reported about 90% reduction in seepage losses when compared with unlined

reaches. Likewise Fibre glass Reinforced Plastic Tissue Asphaltic Canal Liner had been

experimented.

Backing Material for Swelling Soil

I.I.T, Bombay after conducting field studies with various types of backing materials in

swelling soil (especially black cotton soil) area in Karnataka has suggested that a 1 m

thick cohesive non-swelling (CNS) layer covered with P.C.C. slabs would suffice the

need for lining in swelling soil. The minimum specification suggested for backing

material is

Gravel - Less than 10 percent, Sand - 30 - 40 percent Silt - 45 - 50 percent Clay - 20 - 25 percent Compaction - 96 percent of standard proctor density, in layers not exceeding 20 cm. Moisture content - OMC ± 1.5 percent. Shear Parameters - 0.2 kg/cm2 25° to 0.5 kg/cm2 for 2 to 15°

KERS, Krishnarajasagar had conducted experiments with different lining materials, viz.,

(1) Size stone pitching over 22.5 thick layer of murrum backing, (2) Rough stone

pitching over 15 cm thick layer of murrum backing, and (3) 15 cm, 22.5 cm and 30 cm

murrum lining without any protective cover for small channels only.

The size stone pitching and rough stone pitching have functioned well and have

recommended size stone pitching for small channels in view of lower rugosity coefficient

and lesser maintenance cost though it is slightly costlier initially.



PCC lining withdrainage arrangement 1 m thick CNS layer

IP 2.43

2.74 FSD

3.0415 cm thickCNS layer

3.04

1.82

21__2

2.741

3.043.04

Typical section in deep cutting of Malaprabha Right Bank Canal kilometer number 35.354

2.103 m

FB 3.04

3.653.04

2.74 Full Supply Depth15 cm thickCNS layer

3.04

1 m thick CNS layer

2.74

PCC lining

Typical section in cutting at MRBC kilometer number 35.354 (a) Canal section in cutting

(a) Canal section in cutting

PCC slab lining 2:1

FSD 2.74SR 4.26

1 m thick CNSIP 2.43

30 cm thick CNS

Rock toe

30 cm thick sand blanket

Black Cotton soil

2 m and below

B__ 2y2 +2.74

1 m

30 cm thick CNS

Bed filling 2 m and below

L

PCC slab lining 2:11 m thick CNSSR 4.26 2.43

30 cm thick CNS

60 cm thick CNS

Rock toe

60 cm thick CNS

B__ 2y2 + L30 cm thick sand blanket

Bed filling 2 m and below

below 2 m bed filling 2 m and above1 m

2.74 FSD2.74

(b) Canal section in embankmentConstruction of Malaprabha Right bank Canal in expansive soil area using Cohesive Non-swelling Soil (CNS) layer of 1 m thickness as suggested by IIT-Bombay

Black Cotton soil



Geo synthetic Reinforced Canal Lining Currently, in India the lining systems adopted generally consist of three components.

The top is usually a lining cover of either concrete slabs or brick tiles. Sometimes

flagstone or soil as cover has also been used, depending on suitability. Below the cover

a LDPE lining is provided underlain by a graded sand filter normally placed to account

for planned drainage. Film of 175 micron thickness has been used in the bed lining of

Indira Gandhi Main Canal in Rajasthan. The thickness of the LDPE film depends on

whether it is the primary water barrier constituent of the lining (in that case the thickness

varies from 150-250 micron) and the rigid cover is provided to protect it against damage

and heaving. The rigid cover may also be provided as the main lining and the film is

provided as a secondary back up specification (generally 100 micron film is provided for

this purpose). Figure shows typical details of LDPE lined canal system used in India.

ABCDE

Details of Sandwitched Brick Lining Index:

A = Top layer of 50.8 mm Flat Brick (C.H.1:3)

B = A layer of (1:3) Red Cement Mortar 6.35 mm thick

C = 15.875 mm layer of (1:3) Red Cement Mortar

D = 50.8 mm thick Flat Brick layer with joints of Red Cement Mortar of proportion (1:3)

E = 9.525 mm thick Red Cement Mortar layer (1:5)



FLAGSTONE LINING

FLAGSTONE LINING 40 to 50 mm thickon a bed of cement mortar 1:6 and pointing with 1:3 cement mortar

100 MICRON LDPE FILM AND GAUGE

20 mm THICK BEDDINGIN CEMENT MORTAR 1:6

TRANSVERSE SLEEPERS.30 m centre to centre incement concrete 1:3:6with 10 mm metal rod

Brick lining 76.2 mm thick in cement mortar 1:3

LDPE 600/800/1000 Gauge

Dressed sub grade

Brick Lining



Geotextile filter

HDPE Membrane

Graded soil slope

SECTIONAL VIEW SHOWING DETAILS OF CANAL LINING

Perforated drainage pipewrapped in Geotextile(Pressure relief drainagewith laminar drainage path)

Tenax Mint 100Composite liner and Drainage

Tenax Mint 100Composite membraneas laid in profile

30 mm thick concretesize in flush point orbrick lining forcounter weight

It has been ascertained through field seepage tests that lined canals save a

considerable amount of water loss as shown in Table

State Average seepage loss m3/s/million sq.m

Percentages savings in water due to lining

compared with unlined canal

Haryana a) Unlined canal 2.25 - b) Conventional lined canal without LDPE film 0.43 81

c) Lined Canal with LDPE film 2.5 mm 0.16 93

GUJARAT a) Unlined Canal 2.50 - b) Lined Canal without LDPE film 1.00 60

c) Lined Canal with LDPE film 0.80 68



WEST BENGAL a) Unlined Canal i) in rocky strata 2.94 - ii) in lateritic strata 20.00 - b) Conventional lined Canal without LDPE film 0.30 rocky strata 90

c) Only LDPE film with soil cover 0.12 rocky strata 96

Seepage studies - Ponding method Semi field Studies - KERS

Sl. No. Type of lining material Minimum value of seepage after two years in m3 / s / M m2

1 Tuflene with brick in cement mortar cover. 0.0008 2 Tuflene with earth cover. 0.0057

3 Tuflene with concrete cover (1 : 4 : 8 proportion) 0.0008

Before reconstruction 2.34 to 6.63 m3 / s / M m2

After reconstruction 1.53 m3 / s / M m2

LDPE 400 gauge (0.1 mm)

LDPE 1000 gauge (0.25 mm)

HMHDPE 700 gauge (0.1 mm)

Fibre glass Reinforced Plastic Tissue

Reinforced asphaltic canal liner (2.5 kg / m2)

Inspite of the advantages offered by conventional lining system with and without LDPE

film lining, they have several shortcomings. For example, in case of lined canals with

PCC concrete tiles as cover complete impermeability is not ensured as construction

joints are a must between two concrete panels, where the LDPE film below serves the

lining purpose. The ill achieved compaction of side slope of a canal in most cases give

rise to local shear failure due to lining overburden, with excessive slope settlement. In

such case of slope stability failure the unreinforced concrete slab cracks, consequently,

the unreinforced weak LDPE liner also gets damaged. LDPE membranes do not

possess suffficient strength and hence under sub grade reaction, or dead load and live

load on cover or hydrostatic pressure, the membrane gets ruptured on many occasions.

Under steep slope conditions and high flow discharge in the canal stringment reinforced

cover specifications are required which often makes the construction process of the

lined canal very tedious and time consuming.



Geo synthesis for Irrigation Structures

A wide range of Geo synthetic products find application in irrigation structures. They

include geo membrane, geo textiles, geo composites, geo grids, geo drains, gabions

and mattresses. Gabions are constructed using bi-oriented geo grids.

Geo synthetic Canal Lining and Drainage

As a fabric layer this system is extremely easy to install. The lining geo composites are

found in combinations of membrane-grid-textile, membrane-grid or grid-textile

sandwiches which can be used depending on the requirement of the project.

In case of the canal lining systems Geo composites having HDPE membrane-grid-

textile combination is the most suitable. HDPE membranes composites now available in

India, eliminates the shortcomings of the LDPE lined canal systems. The grid eliminates

the requirement of graded filter for drainage resulting in considerable reduction of time

and costs, increasing canal capacity of discharge. Drainage Geo nets, a few millimetres

thick have the same capacity of drainage water as a graded sand layer a few hundred

millimetres thick. The textile layer provided in these composites prevents the fines from

interfering with the drainage path. The Geo composites are used in canal lining system

with the water proof membrane in contact with the cover (required to weigh down the

geo composite on the slope) and the geo textile is laid against the well graded slope.

Geo composites are available in light weight roll form which can be easily laid on slopes

as well as on prepared canal beds. Geo composites have strength ranging from 6.5

kN/m to 23 kN/m which can adequately resist soil pressure on slopes and distribute

concentrated forces preventing local shear failure conditions from developing. The Geo

net with its high drainage capacity prevents high pore pressure development on the

slope and provides an efficient flow line.

Saving Geo synthetic lining vs Conventional lining 19%.

Reference

Som, S. Sarkar and Ranjana Majumder, Geo synthetic Reinforced Canal Systems and

Irrigation Structures, Proceedings Water Energy 2004, International R&D Conference

1995, New Delhi, India, pp 262 to 274.

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22_1 Lining of Canal Nptel

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