CANAL LINING



GUIDELINES FOR LINING OF
IRRIGATION CANALS

1.0 INTRODUCTION

Irrigation canals are important infrastructure and contribute to the development of sustainable agriculture and agricultural activities.At present,there are number of major& medium irrigation projects and a good number of MIPs with vast canal networks are operational. Most of these Projects are quite old and serve for more than thirty(30) years .The canalsystems of these projectsare earthenand gets deteriorated during courseof its use. Seepage losses in these canals are prominent and they are unable to carry the design discharge. Renovation, re-sectioning & reduction in seepage loss are essential for smooth functioning of these canals. With this background,  all the new canals were designed as lined canals and existing canals may also be considered to be converted to lined canals in due course in a phased manner for prevention of seepage loss and for optimal andjudicious use of water

2.0 TYPESOF LINING

Lining is an impermeable layer provided for the bed and sides of canal to improve the life and discharge capacity of canal. 60% to 80% of water lost through seepage in an unlined canal can be saved by construction of appropriate canal lining.

• Rigid Lining : In situ Cement concrete/Cement fly ash concrete! ReinforcedCement Concrete

Semi-Rigid Lining: Pre-cast Cement Concrete Tilel Cement concreteslabl Cementfly ash concretetile/Fly ash brick or tile lining

• Flexible Lining : Geo-membrane like High density polyethylene(HDPE)1 Poly vinyl Chloride(PVC)/Lowdensity polyethylene(LDPE)

• Combination Lining: Membrane in the bed and brick/tile or concretelining on sides.

3.0 SELECTION OF TYPE OF LINING 

While selecting the type of lining, the Engineer in Charge should collectinformation on the position of water table, climatic conditions, availability of construction materials, type of subgrade, time schedule, performance of lining in the existing canals in the adjoining areas After collecting the above information, the entire canal or specific reaches of canal to be lined may be decided. Besides, for selection of particular type of lining, seepage loss, economy,structural stability, strength and durability, reparability and ease of maintenance, resistance to erosion, maximum-hydraulic efficiency etc.are required to be taken in to consideration.

Selection of Canals stretches of canals should be judicious and based on adequate justification. Project Authority hasthe final choice to decide the type of lining.

4.0 LINING OF EXISTING EARTHEN CANALS

It is seen that design section of earthen canals during course of use gets deformed/deterioratedand looses its original shape(Designed Trapezoidal section).Therefore, before taking up the lining work, proper sectioningof canals to pass the design dischargeare required to be done. The lining work in existinq earthen canals may be done in such a way that the canal hydraulic particulars such as Full supply level (FSL) and Full supply design discharge will remain unaltered after lining. After lining of earthen canal, Manning's Rugosity Coefficient (n) will be reduced and there will be increase in the velocity.The Engineer in charge should see that the FSL should not be lowered, otherwisethe outlets and off-taking canals will be affected in drawing it's full discharge due to reduction in the driving head. To take care of the above problem, the canal section is to be redesigned keeping the full supply level as per the approved LS & DS and by adjusting the full supply depth, bed width and side slope as per site requirement. using the Manning's coefficient (n) for lined canal in accordancewith the relevant IS codes.

In expansive soils such as canal in black cotton soil, suitable provision of CNS layer as per the recommendation of relevant IS codes may be made. Similarly in cutting reacheswith high ground water table, unstable side slopes etc., necessary measures as recommended in relevant IS codes, Manuals on canal lining may be adopted.

5.0 CEMENT CONCRETE LINING (IS 3873:1993)

Plain cement concrete lining will be suitable for all size of canals on firm soils. Reinforcement in canal linings is normally not required if transverse joints are provided at proper intervals(less than 6 m) to avoid cracks except in specific areas. RCC lining is justified under unusual conditions such as high back pressure, high flow velocities, swelling soils, unstable sub-grade and in reaches where the canal crosses large cross drainage works.

a. PREPARATION & COMPACTION OF SUBGRADE FOR CONCRETELINING

The subgrade should be prepared, dressed and rolled true to level and accordingto the required cross section of canal to form a firm compactedsubgrade for the lining.Forpreparation of subgrade IS 9451 : 1985 may be followed for expansive soil, IS 3873:1993 may be followed for ordinary soil, rock and sandy soiL

b. THICKNESS OF IN-SITU CONCRETE LINING

The thickness of lining should be fixed depending upon the nature of the canal requirement, namely, hydel channel or irrigation channel, full supply depth and channel capacity. Hydel channel should have a greater thickness than channels meant for irrigation because of drawdown effects and where closure for repairs may not be usual.Deeperchannels should have greater thickness than shallow depth channels. Minimum thicknessof canal lining based on canal capaciti~s is given in table below.

Table No:1 Thickness of In-Situ Concrete Lining (IS: 3873-1993)

Capacityof Canal(cumecs) Depthof Water (m) Thicknessof Lining(mm)
0-5 0-1 50-60
5-50 1- 2.5 60-75
50-200 2.5.-4.5 75-100
200-300 4.5 - 6.5 90-100
300-700 6.5-9.0 120-15

Table No:2 Tolerance in Concrete thickness, Alignment, grade (IS: 3873-1993) 

Description Allowable Limit
peparture from establishedalignment ±20 mmon straight reaches ± 50 mm on partial curvesor tangents
peparture from establishedgrade ±20 mm on small canals
Variation in concrete,liningthickness ± 10 mm provided average thickness is not lessthan specifiedthicknes

C. GRADE, MIXING, PLACING & LINING SECTION

The concrete used for lining should be design mix concrete of grade M 15 and should confirm to requirement of IS 456:2000 The concrete should be mixed by mechanicalmeans, hand mixing is not allowed. All the in-situ concrete lining are to be done strictly using paver. Manual placing of concrete for concrete lining is not allowed under any circumstancesfor any type of canal. Trapezoidal section of lining should be adopted in all canals. In vulnerable reaches, in toe of hillocks and in extra ordinary cases in view of stability of side slopes, rectangular section with vertical RCC retaining walls may be adopted under approval of the competent authority. Suitable transition in 3:1 is to be provided to negotiate to the trapezoidal section. However, the canal section up to 1.5 m bed width (widthof linedsection) may be providedwith rectangular lining sectionwith RCC cantilever walls with gradeof RGGas per the exposure conditions as recommendedin IS: 456-2000 when the trapezoidalliningusing paver is notfeasible

For water course & Field channels( CAD), rectanqular RCC section with bed width of 300 mm along with provision of 8 mm diameter reinforcement@ 200 mm clc on bothwayswith a clear cover of 30mm may be made. The reinforcement is to be provided on earthenside of both the walls and the bed. Thickness of the RCC should be 100mm.

6.0 CEMENT CONCTRE TILES (IS 10646:1991)

a. DIMENSIONS

The nominal dimension shall be 500 mm x 500 mm, 500 mm x 250 mm,400 mmx 400 mm, 300 mm x 300 mm and 250 mm x 250 mm. Each of these shall be manufacturedin the thicknesses 60, 50 and 40 mm. However, other sizes other than given above may also be manufactured if required.

b. TOLERANCE,SHAPE,FLEXURALSTRENGTH

In length and breadth shall be ± 3 mm and thickness shall be + 2.0 mm. The tile shall have "itsall sides at right angles to the faces. When tested according to the method as given IS:10646:1991, minimum breaking load per cm length of tile shall not be less than 41 kg for 60 rnm, 29 kg for 50 '*' mm and 18kg for 40 mm tiles thickness.

7.0 PARAMETERFOR DESIGN OF LINED CANALS (IS:10430:2000)

(i) INNERSIDESLOPES

Before taking up the lining work, the Engineer in charge should ensure that inner side slopes of the canal are stable. No earth pressureor any otherexternal pressure is exertedover the back of the lining. Sudden drawdown of water level in the lined canal should be avoided. Wherever, there is chance of sudden drawdown, the canal slopes should be checked for stabilityusingslip circle analysis as given in IS:7894. Besides,adequatedrainagearrangements as required should be provided before commencementof lining work. For general guidance following side slopes as mentioned below in the table are recommended. The slopes recommended below are applicable for depth of cutting/height of embankment up to six (6) meter. Fordepth / height in excess of six (6) meter,specia lstudies for the stability of slopes are recommended.

Table No.3: Recommended Side Slopes:

Type of Soil Side Slopes (Horizontal: Vertical)
i) Very light loose sand to average sandy soil  2 : 1 to 3 : 1
ii) Sandyloam [Cutting - 1.5 : 1to 2 : 1] lEmbankment - 2: 1]
iill Sandygravel/ moorum [Cutting - 1.5 : 1] [Embankment- 1.5: 1to 2 : 1]
iv) Blackcotton [Cutting - 1.5 : 1to 2.5 : 1] [Embankment- 2 : 1to 3.5: 1]
(V)c!ayeysoilS [Cutting - 1.5 : I to 2 : 1] [Embankment- 1.5 : 1to 2.5 : 1]
vi) Rock 0.25 1to 0.5 : 1

(ii) OUTERSIDE SLOPES

The engineering properties of soil shall govern the design of outer slopes. Due consideration should be given to the stability of slopes for functional situations like moist conditions of fill etc. The need for introduction of berms will also be kept in view wherethe fill height is in excess of six (6) meter. For typical cross section of outer slopes , PI. refer Fig.IAIB,2A2B of IS: 10430 :2000.

(iii) FREE BOARD: Table No.4

Canal Discharge Minimum Free Board RemarK
Less than 0.1 cumec (Water course) 0.15 m Free boardshall be measured from FSL to top of lining
Lessthan 1 cumeC 0.30 m
1 cumeeto 3 cumec 0.50m
3 cumec to 10cume 0.60 m
Morethan 10eume 0.75 m

(iv) BERM

In deep cut reaches of canals with discharge capacity exceeding 10 cumecs, berms of 3m to 5m width should be provided in each side for stability as well as for easy maintenance . Turfing is to be done on the inner side slopes above the berms.

(v) coping

the engineer in charge should take adequate measures so that no rainwater shall be allowed to flow or percolate towards the canal slope behind lining. To check the ingress of rain water behind the lining of side slopes of the canals, horizontal cement concrete coping 100 mm
to 150 mm thick, depending upon size of canal should be provided at the top of lining. The width of coping at the top shall not be less than 225 mm for discharge up to 3 cumecs, 350 mm for discharge more than 3 cumec and 550 mm for discharge more than 10 cumec

(vi) CROSS SECTIONS & VELOCITY

Trapezoidal section is the preferred section for all types of lined canals. However, for small canals with discharge capacity up to 3 cumecs, cup shaped sections may be used. The maximum permissible velocities for different types of linings are as follows ..

Cement concrete lining - 2.7 m/s

Burnt clay tile or brick lining 1.8 m/s

Stone-pitched lining 1.5 m/s

While designing lining, critical velocity ratio should be aimed at higher than unity so that silting will not take place in the lined canal.

(vii) under drainage

embankments of relatively permeable soil do not need drainage measures behind the lining. However, drainage measures to be provided if the lined canal passes through an area where seasonal ground water level is higher than water level inside the canal, where sub-grade is sufficiently impermeable to prevent free drainage of seepage or leakage from canal, where there is built up pressure due to time lag drainage of the sub-grade following drawdown of canal.

TableNo.5 drinage details

SI.No Types of Sub-grade Position of Water Table
    below canal bed level between canal bed Level and F.S.L above canal f.s.l
1 sub grade fee draining  soil comprising sandy soil having permeability (k) greater than 10-4cm/sec] no drainage arrangment is requried drainage arrangment requried 150mm to 200 mm thick layer of well designed filter below lining should be drinage arrangment is requried 150mm thick layar of well designd filter below lining should be provied
2 Subgrade Poor Draining [Soil comprising very fine sand,  admixture of sand, silt and clay or soil having permeal5ility (K) between 10-4 cm/sec and 10-6cm/sec] Drainage arrangement required. 150mm to 200 mm thick layer of well designed filter below lining should be provided Drainage arrangement equired. 150 mm to 200 mm thick layer of well designed filter below lining should be provided Drainage arrangement is required. 200 mm to 300 mm thick layer of well designed filter below lining should be provided
3 Subgrade Practically Impervious [Soil  comprising of homogeneous clay with permeability (K) less than 10-6 cm/sec] Drainage arrangement required. The subgrade should be removed to a depth of 600 mm and replaced by sand, murrom or suitable pervious material Drainage arrangement required. The subgrade should be removed to a depth of 600 mm and replaced by sand murrom or suitable pervious material Drainage arrangement is required. The subgrade should be removed to a depth of 600 mm and replaced by sand, murrom or suitable pervious material

(viii) PRESSURE RELIEF ARRANGEMENTS

Embankments of relatively permeable soil do not need drainage measures behind the lining. However, drainage

TableNo.6 Pressure relief arrangement details

SI.No Types of Sub-grade Position of Water Table
Below Canal bed
Level
Between Canal 
Bed Level and F.S.L
above canal f.s.l
1. Subgrade Free 
Draining
[Soilcomprising gravel with  sand,or sandy soil
having permeability (K)greater than 10-4cm/sec]
no pressure relif arrangment requried Bed-Longitudinal & Transversedrains with pressure relief
valves provided.
Sides- Pressure
relief valves in
pockets filled with
filter material
should be
provided
Bed-Longitudinal
& Transverse
drains with
pressure relief
valves provided.
Sides- Transverse
drain with
Pressure relief
valves should be provided
2. subgrade Poor draining soil comprising very fine sand admixture of sand slit and clay or soil having permeability (k) between 10-4 cm/sec and 10-6 cm/sec) bed-longitudinal & transverse drains with pressure relief valves provided side- pressure relief valvas in pockets filled with filter material should be provided -do- -do-
3. Subgrade Practically impervious- [Soil comprising ofhomogeneous clay with
permeability (K) lessthan l0-6cm/sec]
-do- -do- -do-

(ix) LONGITUDINAL DRAINS

The section of longitudinal drain should be trapezoidal with bottom width 500 mm, depth 525 mm and sides as steep as practicable. The drain should be carefully filled up to the bottom of the lining with graded filter with pipe as shown in Fig. and properly compacted so as to form a.vneven bedding for lining. The pipe may be asbestos cement pipe or PVC pipe. It should be perforated. Usually 150 mm diameter pipes are used. The perforations/holes should be 12 mm in diameter and should be done by drilling. On an average there should be a minimum of 100 perforations/holes per meter length of pipe and the perforations/holes in adjacent rows should be staggered. The pipe should be properly shrouded with suitable filter. The number of longitudinal drains should depend on the bed width of canal. In the bed of the canal, at least one drain for every 10m width should be provided. The drains should be placed symmetrically with reference to the centre line of canal. Care should be taken that the filter does not get clogged during lining

(X) TRANSVERSE DRAINS

Transverse drains, where necessary, should be provided in the bed and on the side slopes up to free board level. Section and all other specification of transverse drain should be same as that of longitudinal drain. Spacing of transverse drains should depend on size, location and efficiency of pressure relief valves. However, in general,transverse drain should be provided at 10m interval.

(xi) PRESSURE RELIEF VALVES

Pressure relief valves should be provided on the longitudinal trenverce drainage. If there are no transverse drains, the PRV may be provided in pockets filled with graded filter underneath the lining. Pockets may be square with sides of 600mm or cylindrical with diameter 600mm. Pockets on slopes should be excavated with their sides at right angles to the slope. The perforated PVC housing pipe for the PRV should be 750 mm bng for sides and 430 mm long for bed. It should be placed in the centre of the pocket. Graded filter as shown in Fig. 3 should then be carefully placed in the pocket and compacted to forrs an even bedding for canal lining. Perforations in the housing pipe should be as shown in Fig bEiJw.

For placing of Pressure Relief Valves (PRVs) in rows, in general,one row at every 4 m should be provided on the sides. The first row should be about 50 an above curve line and top row at 50 cm to 100 cm below full supply level. If the water depth is less than 1-5 rn, one row
should be adequate. Valves in adjacent rows should be staggered.

For spacing of Pressure Relief Valves (PRVs),in general, one pressure relief valve for every 100 Sqm should be provided in the canal bed; while on the sides, one pressure relief valve for every 40 Sqm should be provided. However, the spacing should be decided on this general consideration, keeping in view the site conditions.

8.0 LINING OF CANAL IN EXPANSIVE SOIL (lS:9451-2004)

(i) GENERAL

Expansive soils are soils that expand when water is added, and shrink when they dry out. These soils are exerting a swelling pressure ranging from SO to 300 KN/sqm when comes in contact with water. To counteract the swelling pressure and to prevent deformation of the rigid lining, a Cohesive Non-Swelling Soils (CNS) of required thickness depending on the swelling pressure·of expansive soil, is placed below the rigid lining. The CNS material usually contains 1S to 20% clay (less than 2 microns), 30 to 40% silt (0.06mm to 0.002 mm), 30 to 40% sand (2mm to 0.06 mm) & 0 to 10% gravel (greater than 2mm). The liquid limit of eNS is in between 30 to SOand Plasticity index is in between 1Sto 30. eNS material should be non-swellingwith a maximumswelling pressure of 10KN/m2.

(ii) CRITERIA FOR FIXING MINIMUMTHICKNESSOF CNS LAYER

Table No-7Canal discharge less than 2 cumecs

Discharge in Cumecs Thickness of CNS Layer in cm (Minimum)
  Swell pressureSO- 1S0KN/m2 Swell pressuremore
than 150KN1m2
1.4 - 2.0 60.0 75.0
0.7-1.4 50.0 60.0
0.3-0.7 40.0 50.0
0.03-0.3 30.0 40.0

Canal discharge more than 2 cumecs

Swell pressure in KN ImE. Thickness of CNS Layer in cm
(Minimum)
50-150 75.0
150-300 85.0
300-500 100.0

(iii) CONSTRUCTION PROCEDURE:

A. Canals in cutting zone:

1) Proper moisture to be added to CNS material. CNS material should be compacted in layers by appropriate equipment to ensure proper density. It is advisableto provideeNS right up to ground level.

2)In deep cuts, It is advisable to provide eNS right up to ground level.TheeNS abovecanal nprism may be of lesser thickness say 150-200mm.However full designthicknessbehind the lining should be continued at least 1000mmabove the top level of lining.

B. Canals in Embankment:

1)Proper moistureshould be addedto eNS materialand expansivesoil surface.

2)Expansive soil and eNS Soil above GL should be compacted simultaneously in layers with appropriateequipment to ensure proper density.The compaction may be done either with sheep foot rollers or 8 to 10ton ordinaryroller.

3)rock toe with inverted filters may be providedat either end of canal bank.

4)A thickness of 150-200mmeNS layer on rear slopes may be provided simultaneouslywith

5)expansivesoil and proper turfing is to be providedto protect slope. eNS layer below sand blanket at rock toe portion shall be provided.

C. Pride:

1)The problem of effectively compacting the subgrade for side lining on slopes is veryimportant in case of black cotton expansive soil zone in cutting or embankments,where backfill of eNS' material is required to be placed for the sides and bed, in addition to deSignthickness. Twenty (20) cm or so ( perpendicularto side slope) of extra pride may
be prQvidedand compacted in horizontal layers to the required density. This pride should be removed only just prior to the placement of lining, thus making a fresh and well compa,ctedsurface available for bedding.

D. Use of Polythene Sheet below Concrete Lining:

1)The use of polyethylene sheet below concrete lining could be either for achieving better ultimate impervious ness of the lining as a whole or it may be used only for limited purpose as an assistance, during construction, for avoiding the cement slurry from concrete escaping in the subgrade below. Use of LOPE sheets 200, gauge ( 50 micron) is to
achieve only the latter' limited purpose. If overall imperviousness is proposed to be achieved, it would be necessary to use HOPE-HM sheet of sufficient thickness,strength, toughness and durability.

(iv) UNDERDRAINAGE ARRANGEMENTS AND JOINTS IN LINING:

1)The drainage properties of eNS material itself need to be given due considerationas water locked up in this saturated layer is likely to cause pore pressure on the liningduring canal draw down conditions. To release the same if holes are provided for drainage in concrete lining, care will have to be taken to provide inverted filters at the back of the holes so as to avoid the eNS material being washed away by fluctuating water levels in the canal. Such drainage holes are, however. not advocated for general adoption,

2)It is recommended to provide regular drainage arrangements using porous concrete sleepers, 7·7 cm x 20 cm with 50 mm perforated G.I pipes at 3m centre to centre coming out through the sides of the lining. Two porous concrete sleepers on either side of the bed, below the side may be provided. 'A 50 to 75 mm thick sand mat belowthe bedand side cast in-situ lining ( below the polyethylene sheet) should be provided.Wherethe sand mat is not economically feasible additional porous concrete sleepers may instead be provided at right angles to the longitudinal rails ( along the cross section of the canal)at 3 m centre to centre. The porous concrete sleep

a. ANTI-SALT TREATMENT:

Soil in all reaches should be tested for salt content before the lining is started.Where the salt content is over 1·00 percent or sodium sulphate is over 0·36 percent, the sub grade should be first covered with about 2 mm thick layer of bitumen obtained by evenly sprayingbitumenat a rate of about 2·35 kg/m2. To get a good bond between bitumen and soil, crude oil at a rate O·5 litlm2 should be sprayed over it in advance of spraying bitumen. In case such a situation is encountered only insmall packets the replacement of subgrade up to a suitable depth by suitable earth from adjoining reaches should be considered, if economical.

b. CURING:

Curing is of utmost importance for any concrete. Curing by ponding water in the canal upto minimum 14 days is to be done in case of availability of water otherwise curing compound shall be used for curing of in-situ-concrete lining.

c. QUALITY CONTROL:

Utmost care is to be taken for stringent quality control to get proper strength and durability and to maintain the thickness of lining I CNS layer if any as well as to achieve the properly compacted base before lining.

d. TESTS FOR LINING(non - destructive rebound hammer test):

To test the effectiveness of vibration, permeability, strength of concrete cores at suitable places from the sides of canal and from the bed canal concrete shall be taken.

1. Specification of Materials

The detailed specification of the materials to be used may not be described in detail. Rather relevant IS Codes I Manuals/ CBIP Publications may be specified to refer for this purpose. Any specific materials not covered under above records of reference may be described in detail.

2. Specification of Works

Normal specification of works which are described in relevant IS codes need not be mentioned rather relevant IS Codes IManualsl CBIP Publications may be specified to refer for this purpose.Any specific work not covered under above records of referencemay be described in detail.

Some of the relevant I.S. Codes/Manuals/CBIP Publications are listed below for ready reference

SI.No. Name Code
Number/Publisher
1 Criteria for design of lined canals and guidance for
selection of type of lining.
IS:10430
2 Laying cement concrete/stone slab lining on canals- code of practice IS:3873
3 Canal linings - cement concrete tiles - specification IS:10646
4 Guidelines for lining of canals in expansive soils. IS:9451
5 Code of practice for under drainage of lined canals. IS:4558
6 Lining of canals with polyethylene film- Code of practice. IS:9698
7 Code of practice for Plain and reinforced concrete IS:456
8 Manual on canal lining INCID
9 Classification and identification of soils for general purpose IS:1498
10 Sealing Expansion joints in Concrete lining of Canals IS:5256
11 Code of practice for lining water courses and field channels. IS:12379
12 Guide lines for seepage losses for canals by analytical  method. IS:9447
13 Methods of sampling and analysis of concrete IS:1199

14

Methods of test for soils (Relevant parts) IS-2720
15 Workshop on Canal Lining CBIP
16 Stability analysis of slopes IS: 7894
17 A manual on LOPE film for water conservation Indian
Petrochemicals
Corporation Limited

JOINTS

Joints shall be spaced and located as shown in the approved drawing or as directed by the Engineer-in-charge. The grooves at the joints shall be of size and shape as shown on the drawing and filled with hot applied sealing compound. Filling of the joint with hot applied sealing compound should be taken up after completion of all other canal work. In the mean time the  grooves shall be filled with clean coarse sand.

Expansion Joints:

Expansion joint shall not be provided except where structure intersect the canal. At intersecting structures an expansion joint of 25 mm width filled with sealing compound bconforming to IS : 5256-1968 or with P.v.C. water stops shall be provided.

Construction Joint:

Construction joints is placed at any location where it is suited as an exigency to construction (interruption of work.). The construction joints are provided in the canal lining, wherever there is discontinuity of concrete work for a period of time leading to creation of cold joint. Generally, bed lining is executed in advance of the laying side lining. As such construction joints are required on either side of canal bed at the junction of bed and side lining. Normally longitudinal construction joints are provided at about 500 to 1000 mm from the tangent point of the curve at the junction of canal bed and the side slope on either side of the bed. In the case of small channels, where bed and side lining are laid simultaneously, longitudinal construction joints are not provided. Transverse construction joints should be provided, where discontinuity of work for considerable time is expected. 200 mm x 150 mm size CC M15grade sleepers are provided under the construction joints. The joint should be filled with hot pour sealing compound as per specifications in IS: 5256 - 1992.

SPECIFICATIONS OF SEALING COMPOUND FOR FILLING LONGITUDINAL AND TRANSVERSE CONTRACTION JOINT GROOVES: The sealant is prepared fro~the materials as under:

(i) Bitumen 85/25........ 55%

(ii) Sand (ftineness modulus 1.0 to 1.5)..... 43%

(iii) Asbestos powder .......2%

Contraction joints :Contraction joints should be provided in canal lining at interval of not more than 36 times the thickness of lining, in both longitudinal and 38 transverse directions. The following spacing is adopted for different thicknesses of lining.

SI No. Thickness of lining in MM Spacing of contraction joint in MM
1 60 2000
2 75 2500
3 100 3500
4 125 4000

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