construction and refurbishment of earthen irrigation channel banks

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10.2.3.3 Irregular compaction – bridging of layerIrregular compaction is where adjacent layers are compacted to significantlydifferent densities. Figure 10.14 shows the case where the lower layers arecompacted to a normal density, eg 95%. The upper layer is over-compacted, eg105%. This means that the swelling and shrinkage characteristics of each layerdiffer. Over time the over-compacted layer, because it has a greater density andstrength, may begin bridging when changing from a wetted state to a drier statewhile the lower layers remain in a similar position to when they were constructed.Therefore a gap will result between the layers which will cause a piping failure.Over-compacted layerNormally compacted layerFigure 10.14Piping failure due to irregular compactionThis failure mode can be prevented by ensuring compaction density atconstruction remains within construction tolerances.10.2.3.4 Lamination of the layersLamination of layers is caused by two smooth layers being in contact with eachother but not bonded. With wetting up and drying of the bank each layer willmove independently of the other. Therefore over time, a piping pathway betweenthe layers may form. This is prevented by good construction practice duringcompaction where the surface of each layer is tined or roughened before the nextlayer of material is placed on top for compaction.Unbonded laminated layerFigure 10.15 Piping failure caused by lamination of layers10.2.3.5 Case Study - PipingPiping failure occurred on the CG Channel 5/6 during 1995/96 season. A largeleak was discovered and the channel was drained to inspect the bank. A largepipe was discovered in the base of the bank.Piping failurePhoto 10-19 Entrance to pipe near bed of channelpipePhoto 10-20 View through pipe after channel was drainedConstruction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 10-23
10.2.4 TunnellingAn investigation found that the section which failed was constructed during wetweather. It is assumed that bank material was placed in a condition aboveoptimum moisture content. This wet material shrank on drying and thus provideda passage for the water. This section of bank was re-constructed.Tunnelling failure can begin with the formation of a pothole and/or wheel ruttingon top of the bank which will eventually catch water from rainfall and formgradually larger holes. A sinkhole is formed as rainwater in the pothole creates atunnel downward through the dispersive soil. Along with cracking of the bank,serious structural failure will eventually occur.Figure 10.16 Tunnelling FailureTunnelling occurs as a combination of dispersive soil, potholes on crest filling withrainwater and animal burrows in the bank. When the burrows and tunnels meetinside batter protection will be washed out and expose the inside batter to erosion.This can also happen towards the back of bank. The result will be a weakened bankwhich may slump and erode rapidly.Photos\deterioration\pothole4.jpgPhoto 10-21 Pothole on crest of bank caused by wheel ruts and rainfall on dispersivesoilPhotos\deterioration\pothole1.jpgPhoto 10-22 Detail of pothole on crestConstruction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 10-24
Page 3 and 4:
Your comments on the format and con
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During the course of this project,
Page 7 and 8: AcknowledgmentsThese Guidelines rep
Page 9 and 10: FundingFunding of this project was
Page 11 and 12: Table of ContentsBook 1SubjectPage
Page 13 and 14: 1. Introduction1.1 GeneralGood asse
Page 15 and 16: (iv) provide proven practice approa
Page 17 and 18: 3. Research Procedure3.1 Terms of R
Page 19 and 20: 4. How to use these Guidelines4.1 W
Page 21 and 22: 6. Units of MeasurementQuantity Uni
Page 23 and 24: 8. Earthen Irrigation Channels8.1 D
Page 25 and 26: 8.3 ReferencesAustralian National C
Page 27 and 28: 9.1 IntroductionA key input to adva
Page 29 and 30: Data from Goulburn-Murray Water’s
Page 31 and 32: General 1 2 3 4 5 6DescriptionRisk
Page 33 and 34: Channel BankSequential Deterioratio
Page 35 and 36: 9.2 ReferencesGutteridge Haskins &
Page 37 and 38: 10.2.3.1 Dispersive layer of materi
Page 39 and 40: Causes ofSpecific factorDeteriorati
Page 41 and 42: 10.1.2.5 BendsA bend in the channel
Page 43 and 44: 10.1.4.1 Construction techniqueIrri
Page 45 and 46: 10.1.5.4 Overtopping of banksIn ade
Page 47 and 48: In the past maintenance techniques
Page 49 and 50: Maintenance is a continuing require
Page 51 and 52: 10.1.7.4 Yabbies/fresh water crayfi
Page 54 and 55: Direct removal ofmaterial by entrai
Page 56 and 57: Figure 10.10 shows longitudinal cra
Page 60 and 61: 10.3 ReferencesEmerson W (1996), pe
Page 62 and 63: 11.1 GeneralThe Investigation and P
Page 64 and 65: iv) Available fill materials and, w
Page 66 and 67: 12.15 Radius of Bends .............
Page 68 and 69: There are several ways a channel ca
Page 70 and 71: • Land acquisition extent and typ
Page 72 and 73: The investigation should generally
Page 74 and 75: • Backfill: 10% compaction factor
Page 76 and 77: 1. Flow Area, A, is the cross-secti
Page 78 and 79: after ageing and weed growth. If an
Page 80 and 81: elationships may be the controlling
Page 82 and 83: These maximum velocities should be
Page 84 and 85: Thus channels are usually designed
Page 86 and 87: Some of the design issues that shou
Page 88 and 89: 12.12.1.3 Best PracticeEither of th
Page 90 and 91: 12.13.2 Channel MaintenanceIncrease
Page 92 and 93: along a channel. The depth of the w
Page 94 and 95: 12.13.4.7 Change of AlignmentThe in
Page 96 and 97: 12.15 Radius of Bends12.15.1 Flow A
Page 98 and 99: 12.16 Channel Cross SectionThe cros
Page 100 and 101: Some irrigation authorities use one
Page 102 and 103: 12.16.2 BanksChannel cross sections
Page 104 and 105: Unless the bank is very high, the s
Page 106 and 107: The stability of channel batters ca
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drop bars become difficult and time
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Both the height above the bed and t
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• enable maintenance of the chann
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- Access agreementsA description of
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13/08/02 19:2012.20 Channel Tenure
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13/08/02 19:20As with the damage to
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13/08/02 19:20Advantages of Protect
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- gates provide a better deterrent
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13/08/02 19:20When considering expo
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13/08/02 19:20A typical design draw
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13/08/02 19:20Sinclair Knight Merz
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13.1 IntroductionIn many irrigation
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For example, the initial constructi
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13.2.6 When to use Life Cycle Analy
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The timing of the life-cycle costin
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• assess cost of collecting missi
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Microsoft Excel has quite a good pr
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The costs used in these methods sho
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Life CyclePhaseInvestigationDesignC
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Life CyclePhaseMaintenanceRehabilit
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ReplacementProject managementInvest
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Residual valueLegal feesInsuranceAd
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13.4.6.2 Recurring CostsChannel con
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$1.00.80Percent ofValue of$1.00.60.
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13.4.11 Evaluate ResultsThe results
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13.6 Tipsthe way open to incur sign
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14. Risk AnalysisTable of ContentsS
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Consequences for irrigation authori
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15. Material Selection and TestingT
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c) Shrinkage - will the bank crack
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depth. For this reason, the soils o
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Natural moisture content should als
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The study identified some confusion
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15.4.2 Determination of the plastic
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1. Preparation of PatTake approxima
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EmersonClass No.Degree ofDispersion
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15.7.1 Coarse grained soilsIn this
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sufficient gravel for erosion resis
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GroupSymbolsSuitability for Earthen
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The uniform application and thoroug
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essential that the chemical is thor
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Where laboratory testing facilities
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Clays are the plastic fines. They c
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etween the soil sample and the wate
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16. Compaction ControlTable of Cont
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16.1 PurposeDuring this research pr
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All compaction equipment utilises s
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The soil density required for a cha
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In the past, a method specification
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Low permeability and high stability
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16.10.1.1 Tamping Foot RollerTampin
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16.10.1.5 Non-Circular Impact Rolle
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16.10.3 Compactor OperationsAfter t
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16.11.4 Moisture Content ControlBef
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16.12 Density Control Tests and Pro
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Correlation with local materials an
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The main advantages of the Nuclear
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Figure 16.4Hilf Density Ratio Repor
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The location and test results for e
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16.14.3 Reporting and RecordsTest r
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16.16 Tests for small projectsThe s
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The advantages of the Drop Test are
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AS1289.6.3.2-1997AS1289.6.3.3-1997A
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17. Protective CoverTable of Conten
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The bank dries and cracks from the
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17.5 Specifications17.5.1 GravelPar
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17.6 Establish Vegetation CoverTops
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Species Growing Conditions Establis
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17.7.2 Rope Wick ApplicationMuch of
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There are a number of fibre mats or
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17.10 Australian StandardsAS1289.3.
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18.1 IntroductionFor many earthen c
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When re-shaping the batters of exis
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LifeCrestOld bank lineBattered bank
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Photos\inside batter\CG7channel2arm
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4. To help place the rock material
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False ToeFigure 18.8Protective laye
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The confinement system would be adv
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• Able to survive during non-oper
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18.6 ReferencesHutchison D & Locke
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19.20 Guidelines on Field Quality C
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Construction and Refurbishment of E
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• Figure 19.2)3. Temporary Bench
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The capabilities and limitations of
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19.3.1 Construction EquipmentThe ba
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construction. The aim of scarifying
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Whether or not a front-end loader o
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The thickness of each layer will va
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distribution. The use of alternativ
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19.8 Construction RecordsAdequate r
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19.12 Protective Cover on Crest and
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19.21 Australian StandardsAS 1726-1
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20.1 ScopeAustralia’s earthen irr
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Bank re-construction normally requi
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•meter outlet locations and type
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In the case of channel bank refurbi
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20.4.1.1 StrippingWith outside bank
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All public roads to be used by truc
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5. Material is delivered by trucks
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Need to drain and de-waterEBM befor
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significantly and a more conservati
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Aim for crest width ofabout 2 metre
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Refer to Section 18, Inside Batter
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21.8.10 Re-alignment ..............
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Seepage is a complex hydrologic phe
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2. Seepage losses increase as the d
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Refer also to the following section
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21.4 Channel Seepage ConsequencesSe
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Channel seepage is one of the sever
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Seepage is proportional to soil per
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Methods based on vertical flow meas
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ainfallPumpingevapotranspirationIrr
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Flow NetsA flow net is a system of
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Data from indirect measurement proc
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(ii) EM SurveyElectro-magnetic (EM)
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The volume of waterloss from the dr
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21.7.3.2 Inflow-Outflow Method (Dyn
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Imperfect seal will cause the meter
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The groundwater level can then be d
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Stable IsotopesThe basis of testing
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To be most successful, there needs
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21.8.6 Surface interception drainag
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KeyWatertable before tree plantingW
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• The preparation of a best pract
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21.11 ReferencesAustralian National
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22. Channel LiningTable of Contents
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22.1 IntroductionThe conservation o
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The different types of channel lini
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Table 22-1Unlined Earthen Channels
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Lining of channels will not elimina
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To supply a given discharge, the cr
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22.4.5 Structural SafetyThe stabili
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soil pressures and under-drainage i
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Concrete linings are suitable for b
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22.5.12 Availability of Constructio
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esistance to erosion. To improve th
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Construction and Refurbishment of E
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22.7.1.2 General Design Considerati
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22.7.1.4 Lining ThicknessThe thickn
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particular problems, but in smaller
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Where the earth lining finishes abo
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control where the channel material
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sand requires about 5% cement by we
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22.7.6 Soil SealantsSoil sealants a
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22.7.7 Cost of Earth LiningsThe cap
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Although they can assist with shear
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22.8.2 Membrane Liner TypesGeomembr
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Polyethylene has also appeared in m
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FPP resistance to common chemical e
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The base coat and seal coat rates m
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A common and misleading argument is
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These thermal expansion and contrac
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Another factor is the ability to ha
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Some lining methods expand and cont
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22.8.9.1 Geomembrane ThicknessThe t
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Cover typeThickness ofEarth fill(m)
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22.8.9.5 Cover MaterialGeomembranes
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As well, velocities which are permi
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22.8.11 FencingWhen livestock, part
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22.10 ReferencesAlther GR (1987), T
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23. Measures to Reduce the Rate ofD
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Channel DesignBank MaterialDeterior
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Stock and VerminAdjacentlandholders
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To ensure that a channel bank has a
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Advantages of Draining• Allows fo
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To efficiently maintain a channel,
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Compared with other countries where
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23.4.7 LeaksTransverse cracks are t
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23.5 Reduction of Deterioration due
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Photo 23-1Channel bed showing mumbl
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Thus, control of carp by draining c
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The disadvantages of a biological c
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Carp have been blamed for erosion o
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Management Groups gives guidelines
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Organisation Contact Details Aims/A
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Chemical treatment is often recomme
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23.7 Reduction of Deterioration due
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Grey Parrot Pea - Dillaynia cineres
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Lodge G (1998), Review on Fish Barr
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cation exchange capacity (CEC) a me
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fetch the distance over which the w
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plant term used for construction eq
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supply level the supply level is a
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