vidarbha irrigation development corporation, nagpur - glbc... · 2020. 6. 13. · longitudinal and...

Vidarbha Irrigation Development

Corporation, Nagpur

Tuesday, June 10, 2020

1

Learning from FailureRemedial Measures for Defective Lining of Gosikhurd Left

Bank Canal Lining

Presentation By

Pravin Zoad, Executive Engineer

(Mobile No. 7720006020)

Reconstruction of Gosikhurd Left Bank Canal Lining

Gosikhurd National Project

2

Gosikhurd Project is a

Major Irrigation project

under Vidarbha Irrigation

Development corporation

and is declared as

National Project by

Government of India in

February 2009.




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Vidarbha is a land of

extreme weather conditions

with temperature ranging

from 4°C in winter to 48°C

in summer season and

about 1400 mm rainfall.

The Gosikhurd Project comprises of two main canals i.e. Right

Bank Main Canal and Left Bank Main Canal and the focus of this

webinar will be the Reconstruction of lining of GOSIKHURD LEFT

BANK CANAL.Reconstruction of Gosikhurd Left Bank Canal Lining

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Left Bank Canal

Advantages of CC Lining


Particularly, when the command area is flat, a flatter slope to

the canal will increase the irrigable command area of the canal.

The lining also helps in minimizing the transit losses in the canal

thereby increasing utility of the available water.

The Value of “N” i.e. coefficient of rugosity is less in case of

concrete lining. This helps in reducing the canal sections thereby

reducing the cost of earthwork and structures.

It reduces the growth of vegetation in the canal which causes

obstructions to the flow.

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Left Bank Canal

Total length 22.93 KM, IP : 31577 ha, ICA : 23922 ha

After inspection in 2010, some

cracks were noticed in the lining.

The various reasons behind

development of cracks have been

identified and it was decided to

Reconstruct entire 22.93 KM Lining

at the own cost of contractor.


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Left Bank Canal

Reasons behind Development of Cracks


Poor quality of Lining Concrete resulting in low density and lower

strength of concrete.

Insufficient and improper curing.

At some locations, lining shows lesser thickness than design and

insufficient core strength of concrete.

Compaction of base material as well as CNS is not proper resulting in

settlement of subgrade and forming gap between lining and subgrade.

Thickness of CNS layer is less than minimum thickness required as per IS

: 9451 – 1994.

Longitudinal and Transverse joints with PVC strips are not placed

properly as per specifications.

Spoil Material dumped over SR and IP side, as a result increase in the

surcharge load on either side of canal section..

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Reconstruction of GLBC Lining

New Construction Methodology


Dismantling

Existing faulty lining is proposed to

be dismantled and existing CNS is

decided to be removed completely.

Construction methodology is

finalised and adopted for GLBC.

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New Construction Methodology


Dismantling

Canal section is excavated

below lining to provide murum

of sufficient thickness required

to cater swelling pressure and

discharge of canal.

Discharge in cumecs (m3/sec)Thickness of CNS layer in cm (minimum)

Swell Pressure 50-150 KN/m²Swell Pressure more than 150

KN/m²

1.4 - 2.0 ( 50 to 70 cusecs) 60 cm 75 cm

0.7 - 1.4 ( 25 to 50 cusecs) 50 cm 60 cm

0.3 - 0.7 ( 10 to 25 cusecs) 40 cm 50 cm

0.03 - 0.3 ( 1 to 10 cusecs) 30 cm 40 cm

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Swelling pressure of soil KN/m²Thickness of CNS material

(minimum)

50 to 150 75 cm

150 to 300 85 cm

300 to 500 100 cm


CNS Thickness - as mentioned in IS:9451:1994

Thickness of CNS layer in canals of carrying capacity less than 2 cumecs.

Thickness of CNS layer in canals of carrying capacity 2 cumecs and more.

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General Gradation of CNS soil

Clay ( Less than 0.002 mm ) 15 to 20%

Silt ( 0.06 - 0.002 mm ) 30 to 40%

Sand ( 2 mm - 0.06 mm ) 30 to 40%

Gravel ( Greater than 2 mm ) 0 to 10%


Specification of CNS soils

The CNS material shall be non-swelling, with a maximum swelling

pressure of 10 KN/m² when tested in accordance with IS:2720

(part-41) 1977 at optimum moisture content and minimum cohesion.

Index propertiesLiquid limit Greater than 30, but less than 50%

Plasticity Index Greater than 15, but less than 30%

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Serration / steps / benches shall

be provided in the slopes of canal

in cutting to provide a good bond

between the CNS layers and

expansive soil and to also prevent

contact slides between CNS

materials and expansive soil.

CNS material shall be laid in

layers and compacted to at least

95 percent proctor Density,

preferably by Power Rollers viz.

mechanized compaction.


During construction, it shall be ensured that

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CNS Filling


On slope, Murum compacted in

layers with rolling/ compactors/

mechanical tampers where sufficient

slant length is available.

Proper moisture shall be added to

CNS material and expansive soil.

The final sub grade is made

thoroughly moist with fine spray

nozzles to a depth of about 15 cm,

before placement of concrete to

prevent it from absorbing water

from the freshly laid concrete.

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CNS Filling


Whereas, flat horizontal rolling

with vibratory roller is proposed

for smaller sections by providing

35 cm thick extra murum filling on

slope.

In small section channels, it may be

appropriate to fill in the entire

section with CNS material.

Thereafter scoop this section to the

designed section for placement of

lining.

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CNS Filling


For consolidation, one complete

Monsoon season is allowed to pass

after the work of murum filling is

completed.

In addition to the designed thickness

of CNS, 15 cm or more of extra

thickness (called pride) is provided to

take care of damages due to rainfall

and weathering action.

This pride is removed just prior to the

placement of lining (shall not exceed

3 days).

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Seepage drains - Transverse


Sufficient drainage arrangement

below new lining is provided.

Transverse Seepage drains

provided at 15 m c/c in canal

slope

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Seepage drains - Longitudinal


Longitudinal Seepage drains are provided in 1 to 3 rows in bed

depending on bed width.

Also, PVC perforated pipe are provided at central portion for

collection and disposal of water.

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Porous Plugs with Filter Block


Replacement of pressure relief valve (PRV)/non return valve (NRV)

In original work, PRVs have been provided in sloping portion of canal

at 1/3 and 2/3 of FSD vertically and 15 m c/c longitudinally

staggered and NRV was provided in bed portion of canal 15 m c/c

in two rows.

As per IS 4558:1995 specification

one PRV with pocket filter per 40

Sqm area in canal slope is required.

But these NRVs and PRVs have

either stolen or become non

functional, resulting in creating

problems of under drainage.

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Instead of PRV/ NRV, porous plug

in 1:4 proportion of cement and

coarse aggregate with filter block

are proposed at 5 m c/c

staggered.

Porous plugs with filter block

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Contraction Joints instead of PVC Strip Joint


In original work, transverse PVC strip was

provided at 15m c/c and longitudinal PVC strips

was provided at 1/3rd and 2/3rd of FSD each

on SR, IP Slope .

But due to paver rolling, PVC strip has been

dislocated from desired position and due to this

cracks have been developed above PVC strip in

Zigzag manner.

22


LDPE sheet


In original work, LDPE sheet was

provided above the longitudinal

drain only in bed lining.

Now as per Clause 6.5 of IS

9451:1994 Low Density Polythene

Sheet (LDPE) sheet is proposed

below lining to improve quality of

new concrete work.

LDPE sheets prevents the

absorption of water and cement

slurry from the freshly laid

concrete to CNS layer.

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M15 CC Lining


Concreting is produced using a

batching plant and transported by

transit mixers and Lining is carried

out with mechanical paver and with

28 days curing.

Concrete transported by transit mixers shall be delivered to the

hopper of the side discharge conveyers of concrete paver.

With the use of LDPE sheets, a slump range of about 30 mm - 35 mm

is found to be adequate at the placement site from considerations of

proper discharge of concrete from the transit mixer, ease of

placement and attaining a well consolidated lining with a good finish.

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M15 CC Lining


Contraction joints have been cut with

groove cutters attached to the paver.

Each canal lining at an average

advancement rate of not less than

about 8 m/hr so that cutting of

contraction joints is achieved smoothly

and efficiently when the concrete is still

in a good plastic state.

Concrete Porous plugs of 100 mm dia

and 300 mm length have been

provided in bed and side slopes

underlain by graded filter.

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Curing


The concrete lining of the canal bed

shall be cured in conventional

manner with water by making small

earth bunds of, say 20 cm to 30 cm

height and ponding water.

The side lining shall be cured with

rolls of hessian cloth.

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Contraction Joints

Contraction joints are

proposed at 3 m c/c in

transverse direction

In longitudinal direction, 1st

contraction joint is proposed at

1.8 m maximum from top.

2nd & 3rd at remaining

sloping length with maximum 3

m c/c.

At bed, contraction joints are

provided at maximum 3 m c/c.

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Sealing Compound

Filling of joints have been taken up after a minimum of 28 days

setting period of CC lining.

The grooves have been cleaned thoroughly to their full depth & width

by brush, air jet, water jet etc. and the grooves shall be thoroughly

clean and dry so as to ensure good adhesion to the sealant.

The primer shall then be applied before the application of prepared

sealing compound.

Groves of contraction joints are provided for the depth of 1/3rd

thickness of concrete with 14 mm width at top 11 mm width at bottom

and further filled with mixture of sealing compound having 55 %

bitumen (85/25 Grade), 45 % sand.

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Expansion Joints


In transverse direction,

expansion joints have been

proposed at 15 m c/c in

slope.

In Longitudinal direction,

Expansion joints have been

proposed at junction of

bed and slope.

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Field Test


For CNS work, Sand replacement tests

shall be performed on field to confirm

that subgrade is compacted to not less

than 95% of the proctor density.

Slump Test is carried out at the

placement site from considerations of

proper discharge of concrete from the

transit mixer, ease of placement and

attaining a well consolidated lining

with a good finish.

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Laboratory Test


Laboratory tests for materials like murum,

soil etc Have been be carried out to

determine the physical, textural,

engineering & chemical properties of

expansive soils and evaluate the swelling

pressures of soils in various reaches to

establish thickness of CNS layers required.

Also, cube tests and concrete core tests

have been conducted in laboratory.

Cores have been taken to evaluate the

quality of concrete lining laid in respective

reaches. Broadly, one core from bed lining

and one core each from side lining per

250 meters length have been taken.

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Results


All the core samples are satisfying the criteria specified by IS

456:2000 as per concrete core test conducted at VNIT, Nagpur.

Under reconstruction, Lining work which has been executed in 2013

is found to be in good conditions.

No settlement / hogging of lining and cracks observed after

discharging water for irrigation in Kharip from last 5 years.

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Results

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Common Deficiencies observed during execution of

Construction of Lining – Before Concreting


Provision of murum thickness without identification of swelling pressure

of soil.

Provision of extra thickness for pride not done.

Compaction of murum not carried out in layers.

Optimum Moisture content not maintained during murum compaction

by sufficient watering.

Steel Mould not used for placing material in seepage drains and

filter block.

Outer slope to Service Road and Inspection Path not maintained which

lead to rain cuts on inner side of slope.

Concreting without passing one monsoon season over the compacted

murum.

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Common Deficiencies observed during execution of

Construction of Lining – During Concreting


Porous plugs are not covered during concreting of Lining.

A Slump is more than 40 mm which means more water cement ratio

which leads to more shrinkage cracks.

Vibratory compactor of mechanical paver not in working condition

during concreting.

Groves of construction joints are not sufficiently deep.

Improper panelling arrangement.

Proper cleaning of groves using air compressor not done before

placing sealing compound in the contraction joint.

Sufficient curing arrangement not provided after concreting.

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Water Released

36


Water Released

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Indian standard IS : 873-1978 - Indian code of Practice for laying in-

situ cement concrete lining on canal (The preparation of sub grade in

different soils for laying the cement concrete lining shall conform to

clauses 4.1, 4.2, 4.3, 4.4, 4.5)

The test sections shall conform to clause 4.3.2 of IS : 3873-1993.

The thickness of CNS layer to be provided shall be governed by the

Indian Standard, IS : 9451-1994

The compaction of sub grade shall be done at optimum moisture

content to obtain a dry bulk density of 95% obtained in accordance

with IS : 2720 (Part VII) – 1965.

The model sections in the bed and sides shall be constructed in M15

cement concrete conforming to IS : 383 standard specification.

IS 3873 : Laying cement concrete lining on canals


References

LAST WORDS …

38Sliding of Retaining Walls in KM 21, 32 of Gosikhurd Right Bank Canal

38

vidarbha irrigation development corporation, nagpur - glbc... · 2020. 6. 13. · longitudinal and...

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