06-SYPHON AQUEDUCTS



 SYPHON AQUEDUCTS

1.SITE SURVEY:

Site Survey to  be furnished as per check slip for CM & CD works  with the following details.(Check Slip enclosed.)

i ) Report accompanying the Site survey ii ) HPs of canal & drain / river.

Site plan  with flow direction of canal & drain  with net levels @ 10 mts interval & contours. LS of drain / river.( IS ; 7784 (Part I) : 1993)

i) Covering 500 metres on U/S & D/S.

ii) The LS with levels @ 10m to 20m interval with Cross sections of drain on U/S, D/S @ centre line, 10 m, 25m, 50m,100m, & @ 100m interval beyond for a length of 500m.

iii) The Cross section  levels shall be @ 3m to 5m interval in the gorge portion and 10m intervals  in the flanks extended upto MFL touching the ground.

The catchment area shall be marked on the Topo Sheet for all the C.As more than 2.5 Sq. Km. If the C.A. is less than 2.5 Sq.km., the

C.A.is to be traversed on ground and to be furnished.

2.M.F.D.CALCULATIONS:

The MFD may be computed as per the following formula.

1.IN UPLAND AREAS:

Dicken's Formula, Q = CM 3/4

where Q =  Discharge in Cusecs.

M = Catchment area in sq.mile

C = Coefficient depending on Catchment area. CA upto 1 Sq.mile.      

CA upto 1 Sq.mile C=1400

CA from 1 Sq.mile to 30 Sq.milesC=1200

CA more than 30 Sq.miles C=1060

(2) IN DELTAIC AREAS :

Ryve's Formula Q = CM2/3(Mitra Committee Report)

C = 1000 for Q  more than 500 cusec

 C = 750 for Q  less than 500 cusecs

iii) For deltaic catchment areas of Krishna & Godavari, the formula shall be Ryve's formula adopting 'c' value as per Mitra Committee Report for Upland & Deltaic Catchments.

Observed MFD may be computed from the observed MFL and shown on the LS & CSs.

Bore hole data / TPs upto Hard strata or for min. depth of 2m for shallow foundations & upto 1/3rd embedment depth below maximum scour depth, along the Centre Line @ suitable intervals depending upon the importance of the structure with minimmum 5 Nos. of TPs  covering both the Drain & Canal @ centre, U/S & D/S sides. (Table I & II of APERL for test results of foundation soils, IRC 78:2000)

3.DESIGN :

Note on Principles of Design, the assumptions made & the general features of the structure.

HYDRAULIC DESIGN :

1. MFL computations adopting Step by Step method.

2. (a) Design of ventway for the Drain / river in Aqueduct  limiting allowable velocity with minimum 1200 mm height of vent in case of barrel.(IS ; 7784 (Part II / section5) :1995,   IS : 7784 (part I) - 1993)

(b) For small discharge of Drain, Pipes can be proposed limiting the velocity with minimum 900 mm dia.(IS 458 -1988, IS :783 - 1985)

3. Design of Tail channel & Approach channel keeping in view the Lacey's Formula for Wetted perimeter & velocity limits depending on stratification.(IS : 7784 (part - I) - 1993)

4.Lift Wall on D/S side of the structure may be avoided.

5.Transition lengths on U/S & D/S of drain.(IS ; 7784 (part 2/sec5) : 1995 )

6.TEL calculations for the Drain  considering eddy loss coefficients as per IS code along with flow diagram with dimensions and levels. (IS : 7784 (part - I) - 1993)

7.Scour depth calculations  of drain.(IS : 7784 (part - I) - 1993)

R= 1.34 (q2/f)1/3 with relevant factor of safety.

8. Uplift calculations for the floor of the barrel and U/S & D/S side (IS : 7784 (part - 2 / sec 5) - 2000)
9. Exit gradient calculations(IS : 7784 (part - I) - 1993)

G E = (H/d)x [1/(π√λ)] ; Where λ = [1+ √(1+α2)]/2 ; α = b/d

10.Proposal Sketch

STRUCTURAL DESIGN :

i) SUPER STRUCTURE

a) Design of Slab under canal trough & under earth bank /RCC Box for critical load combinations. (IS : 3370 - 1965 part I & part II, IS : 7784 (Part 2 / sec 5) : 1995 )

b) Design of Head wall on U/S & D/S by adopting TVA procedure / Coulomb's Theory / Rankine's Theory with a top width of 500mm

c) In case the structure is clubbed with Single lane / Double lane bridge refer guidelines for Bridges

ii) SUB STRUCTURE I

a) CONVENTIONAL TYPE  :- 

1. Design of Pier  under canal trough & earth bank: Minimum thickness of pier shall be 1 M.(TVA Hand Book, IS - 7784 (part 2 / sec-5): 1995. )

2. Design of Abutment under canal trough and earth bank.(TVA Hand Book, IS - 7784 (part 2 / sec- 5): 1995. )

3. Abutment and Pier foundations shall be Isolated Footing / RCC raft as the case may be.(1) IRC - 78- 2000 2) SP - 16 ;3) SP 34 )

I  b) RCC BOX :RCC box under canal trough, earth bank and Head wall.(IS : 7784 (Part 2 / sec5) : 1995 )

I  c) PIPE:Pipe details(IS 458 : 1988 , IS 783 - 1985)

II  Design of Wing walls & Return walls both on U/S & D/S of drain - The walls adopting TVA procedure / Coulomb's Theory / Rankine's Theory with a top width of  500mm.(TVA Hand book)

III  Tabulation of stress table :- A consolidated stress table has to be furnished indicating the stress in concrete & stress on soil for the  Head wall, Abutment, Piers, Wings & Returns

IV  Unless otherwise mentioned, minimum Grade of concrete for PCC- M10  and for RCC- M20(IS - 456 : 2000)

MISCELLANEOUS ITEMS :-

a) Water stops(IS : 7784 (part I) :1993)

b) Weep holes in the Retaining walls(IS : 7784 (part I) :1993)

c) Bearings(IS : 7784 (part I) :1993 )

d) Expansion , Contraction & Construction Joints(IS : 3370 (part I) - 1965)

e) Bell Mouth on U/S side

f) Cut & Ease waters(IS : 7784 (Part 2 / sec5) : 1995 )

DRAWINGS

a) General Layout on net level plan duly showing contours.(Scale : 1:50, 1:100 (or) 1:200)

b) General Plan, Sectional Elevation & End View - Plan indicating Half plan @Top & Half plan @ bottom &  Sectional elevation along the LS of the drain & End view  along the cross section of  the drain.(i)Scale : 1:50 (or) 1:100 for sections)

c)  Wall Sections,  RCC Details & Details of miscellaneous items.(ii)Scale : 1:25 (or) 1:20/1:10 for RCC details.)

The Drawings shall contain assumptions made, TPs, Specifications, HPs of canals, Hydrology  of the drain,Bar bending schedule, Stress table etc.

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