CANAL ALIGNMENTS AND CANAL NETWORKS:

PROJECTONCOMPARATIVE STUDY OF CROSSINGS OF DRAINAGES BY THE IRRIGATION CHANNELSWITH SPECIAL REFERENCE TODESIGN OF A PROTOTYPE C.D. WORK: AQUEDUCTIntroduction

Cross drainage works are structural elements which are constructed at the crossing of a canal and a natural drain, so as to dispose of drainage water without interrupting the continuous canal supplies.

NECESSITY OF CROSS DRAINAGE WORK:The water shed canals do not cross natural drainages. But in actual orientation of the canal network, this ideal condition may not be available and the obstacles like natural drainages may be present across the canal. So, the cross drainage works must be provided for running the irrigation system.

At the crossing point, the water of the canal and the drainage get intermixed. So, for the smooth running of the canal with its design discharge the cross drainage works are required.If the site condition of the crossing point may be such that without any suitable structure the water of the canal and drainage cannot be diverted to their natural directions, cross drainage works must be provided to maintain their natural direction of flow.

TYPES OF CROSS DRAINAGE WORKS AND THEIR SALIENT FEATURES:

A: By passing the canal over the drain. They are of three types: 1. Aqueduct 2.Syphon aqueduct 3.Drainage syphonAQUEDUCT & SYPHON AQUEDUCT

B: By passing the canal below the drainage. They are of two types: 1.Super-passage 2.Canal syphon

SUPERPASSAGE AND CANAL SYPHON

C: By passing the canal through the drain. They are of two types:1. Level crossing2.Inlets And Outlets

LEVEL CROSSING & INLET AND OUTLET

SELECTION CRITERIA: A)-FSL of Canal in relation to HFL of Drainage ChannelB)-Suitable Canal alignmentC)-Topography of Terrain:D)-Regime of Drainage ChannelE)-Foundation StrataF)-Dewatering RequirementsG)-Ratio of Design Flood in Drainage Channel to the Discharge in CanalH) - Envisaged Head Loss

REQUIREMENT OF DATA:

A) Topographical / physical/contour data:B) Hydraulic Data:C) Cross sectionD) Longitudinal section

FLUMING

Reduction of width of waterway of canal CD works become economicalPossibility of hydraulic jumpTo avoid this we have to control velocity of water.

TRANSITIONProvides smooth changeAvoid sudden transition and formation of eddiesAt U/S section splay of 2:1 and at D/S splay of 3:1

Three methods for design of transition:- 1.Mitras transition method2.Chaturvedis method3.Hinds methods

MITRAS TRANSITION METHOD

Bn=Bed width of the normal channel section Bf=Bed width of the flumed channel section Bx=Bed width at any distance x from the flumed section Lf= Length of transitionCHATURVEDIS TRANSITION METHOD

Bn=Bed width of the normal channel section Bf=Bed width of the flumed channel section Bx=Bed width at any distance x from the flumed section Lf= Length of transitionCUTOFF WALL

Built under the floor of hydraulic structureReduces uplift pressureReduces seepage of waterDepth of cut-off is decided from the scour depth

From laceys Normal regime scour Depth*= R =0.473(Q/f)1/3

From Laceys Normal Scour depth*= R=1.35(q/f)1/3 Where Q= Discharge w.r.t drainage f= slit factor , normally taken as 1 q= intensity=max. velocity*max. depthAt U/S cut-off 1.5 R and D/S cut-off 2R

FLOOD ESTIMATION:

The various methods for estimation of design flood are broadly classified as under:Maximum Probable flood/Application of suitable factor of safetyReturn periodRational methodEmpirical flood formulae

DESIGN CONSIDERATION

I) SELECTION OF TYPE OF C.D WORKII) HYDRAULIC DESIGNEstimation of flood.Design of drainage Section.Estimation of HFL.Design of drainage waterway.Design of canal waterway.ScouringHead loss and bed level at different levels.Design of transitions

ContIII) STRUCTURAL DESIGNDesign of Trough .Design of Pier.Design of Abutment.Design of Retaining wall.COMPARATIVE STUDY OF DIFFERENT CROSS DRAINAGE WORK

DESIGN OF THE GIVEN CROSS DRAINAGE PROBLEMHYDRAULIC PARTICULARS OF THE CANAL AND DRAINCANAL DATA U/S D/SDesign discharge 4.905cumecs 4.905cumecsBed width 5.30m 5.30mBed level 285.596m 285.382mFull supply level 286.846m 286.632mFree board 0.50m 0.50mLeft bank top level 287.346m 287.132mRight bank top level 287.346 287.132mLeft bank width 5.00m 5.00mRight bank width 1.50m 1.50mVelocity 0.662m/sec 0.662m/secSide slope 1 in 1.50 1 in 1.50Water surface slope 1 in 4000 1 in 4000

DRAIN DATA

Catchment area 28.67km2Observed high flood level 282.930mDeepest bed level 280.500mAverage bed level 281.600mLeft bank level 286.46mRight bank level 283.74m Angle of crossing 90degreeDirection of flow Right to leftType of soil/Foundation Hard soil/DI/Rock FoundationSafe bearing capacity 35t/ m2DRILL HOLE AT RD 1075M FROM THE CROSSING

C/S OF DRAIN AT VARIOUS RDS

L/S OF THE DRAIN

C/S OF THE CANAL

I) SELECTION OF TYPE OF C.D WORKTerms Canal Drain Discharge 4.905m3/s 198.23m3/s F.S.L 286.846m --H.F.L _ 284.3m Bed level 285.596m 281.75m Velocity 0.662m/s 1.5m/s On the basis of above discussion, it can be concluded that the best and most economical structure that can be built is AQUEDUCT.

II) HYDRAULIC DESIGN

Step1: Estimation of flood in drain:-

Dickenss Formula says, Q = CA3/4Let us assume C = 16Design Discharge, Q = 1628.673/4 =198.23cumecs

Step2: Design of Drainage selection:

Area of cross-section at crossing from graph is 24.8 m 25mVelocity of flow at crossing in the drain = 198.23/25 = 7.92m/s 8 m/sLet us restrict the flow of water up to 1.5 m/sNew area, A = 198.23/1.5 = 132.2mLaceys regime perimeter (water way) is given by, W=4.75Q =4.75198.23=66.83m Average waterway required=50.56m

Step3: Estimation of High Flood level (HFL) Stage discharge curve was plotted at crossing point for drain and will adopt HFL according to our Qp (198.2 cumecs)

Step4: Design of drainage waterwayWe have laceys regime waterway =4.75Q

Clear span between piers be 9m and thickness be 0.7 m

Using 7 bays of 9m each, clear waterway= (97) m=63 m

Using 6 piers of 0.7m each, we have got length occupied by piers =60.7 m=4.2 m

Total length of waterway=67.2 m.

Step5:- Design of canal waterway.

Providing a splay of 2:1 in contraction, the length of contraction transition =( (5.3-3)/2)x2 = 2.3

Providing a splay of 3:1 in expansion, the length of expansion transition = ( (5.3-3)/2)x3=3.45 m

Step6:- Scoura)Scour in Drain

From laceys Normal regime scour Depth*= Rr =0.473(Q/f)1/3 . From this formula we found safe scour level at RL 277.58m which is 2.92m below deepest nallah bed.

(ii) From Laceys Normal Scour depth*= R=1.35(q/f)1/3 q= maximum velocity maximum depth of flowFrom this formula we found safe scour level at RL 278.1m which is 2.4m below deepest nallah bed.

(b)Scour in canal Upstream:-Assume scour factor=1.25Safe scour depth below FSL= SFR Safe scour level=284.096mSo, the bottom R.L of upstream cut-off is fixed at 284.096

Downstream:-Assume scour factor =1.50.Downstream cut off 1m below NSL i.e. =282.882mStep7: Head loss and bed levels at different sections

Fig- Plan and Section of Canal Trough

Step9:-Design of transitions

(a) Contraction transitions:-Since the depth is kept constant, the transition can be designed on the basis of Mitras hyperbolic transition equation given asBX= (Bn .Bf. Lf)/Lf. Bn x (Bn-Bf) whereBf=3m, Bn=5.3m, Lf=2.3m

(b) Expansion transitions: - In this case, Bn=5.3, Bf=3, Lf=3.45m Using above equation, we have, calculated BX

HALF TOP AND HALF FOUNDATION PLANDESIGN OF TROUGH

DESIGN OF PIERLOADING CONSIDERATION:Length of trough=9.7mLoad on each beam=5.871t/mLoad of trough/meter run=25.871=11.742t/mTotal load on each pier=113.897tonsLoads to pier from each span =56.95tonsDl of trough =2 (17.25+9.38+3.45+1.00) =62.16 tonsDl of tie beam =0.6 tonsTotal DL =62.76 tonsWt of water and slit =2 (26.25+1.38) =55.26tonsTotal DL+ water and slit =118.02tons@0.5t/m2 live load =15 tons.ANALYSIS OF PIER1) Pressure developed at the foundation level:-2) Stress at the pier bottom, i.e., R.L.277 metrea) Stress due to live load, dead load and self weightb) Stress due to buoyancy effectc) Stress due to eccentricity of live load and dead loadd) Stress due to longitudinal force 1. Due to tractive effort or breaking force 2. Due to resistance in bearingse) Stress due to wind loadf) Stress due to water current

Factors When dryWhen floodsMax (t/m)Min (t/m)Max (t/m)Min (t/m)live load, dead load and self weight66.3366.3366.3366.33Buoyancy---7.3-7.3Eccentric loading10.62-4.6710.62-4.67Longitudinal forces1. Tractive effort39.79-39.7939.79-39.792. Bearing resistance88.87-88.8788.87-88.87Wind load9.492-9.4929.492-9.492Water current--36.253-36.253Total215.102-76.492244.055-120.045SUMMARY OF RESULTREINFORCEMENT DETAILS OF PIER

3)-STABILITY ANALYSIS OF ABUTMENT

Assumptions:1. Unit weight of soil=2.08 t/cum2. Unit Weight of wing wall=2.3 t/cum3. Unit Weight of R.C.C= 2.5t/cum4. Angle of Repose of soil=30o5. Coefficient Of Friction between concrete and concrete= 0.75 6. Coefficient of Friction between concrete and soil=0.6

Structural details of Abutment

4)-STABILITY ANALYSIS OF GRAVITY RETAINING WALL

Assumptions:Unit weight of soil=2.08t/cu mUnit weight of wing wall= 2.3t/cu mUnit weight of RCC=2.5t/cu mAngle of repose of soil() =30Coefficient of friction between concrete & concrete = 0.75Coefficient of friction between concrete & soil= 0.6

Structural details of Gravity Retaining Wall

CONCLUSION

The comparative study for the project reveals that not only the selection of type of CDs for a particular crossing plays a vital decisive discriminatory role, but also the design of the structural with various alternatives with respective to (i) suitability of foundation vis--vis various foundation strata, (ii) transitions (iii) u/s and d/d protection works (iv) post construction operation and maintenance etc. does equally challenge the hydraulic engineers exposure to the veracity of the jobs complex nature.The aqueduct which we have designed is found to be the most stable and economical structure as compared to the any other cross drainage work. Here we have not provided any inspection road but in future, if required, then we can design and provide an inspection road.