03-AQUEDUCTS / VIADUCTS



AQUEDUCTS / VIADUCTS

I.SITE SURVEY:

Site Survey to  be furnished as per check slip for CM &   CD works  with the following details.

i) Report accompanying the Site survey

ii ) HPs of canal & drain / river.

iii) Covering 500 metres on U/S & D/S.ITEM / COMPONENT

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

LS of drain / river:

i).IN UPLAND AREAS: Dicken's Formula, Q = CM 3/4 Q =  Discharge in Cusecs. M = Catchment area in sq.miles C = Coefficient depending on Catchment area.

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(C.A.) shall be marked on the Topo Sheet for all the C.A.s 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. 

iv)The catchment area(C.A.) shall be marked on the Topo Sheet for all the C.A.s 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

M.F.D.CALCULATIONS:

C=1400, C=1200, C=1060,C = 750 for Q  less than 500 cusecs

C.A. upto 1 Sq.mile. CA from 1 Sq.mile to 30 Sq.miles CA more than 30 Sq.miles.

IN DELTAIC AREAS :  Ryve's Formula Q = CM2/3 C = 1000 for Q  more than 500 cusecs

The MFD may be computed as per the following formula:

i).IN UPLAND AREAS: Dicken's Formula, Q = CM 3/4 Q =  Discharge in Cusecs. M = Catchment area in sq.miles C = Coefficient depending on Catchment area.

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 minimum 5 Nos. of TPs  covering both the Drain & Canal @ centre, U/S & D/ (Table I & II of APERL for test results of foundation soils enclosed. IRC 78:2000.)

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. Design of Small Dams by USBR.
2. (a) Design of ventway for the Drain / river in Aqueduct limiting allowable velocity with minimum 1200 mm vent height in case ofbarrel (IS ; 7784 (Part II / section1) :1995, IS : 7784 (part I) - 1993)

(b) For small discharge of Drain, Pipes can be proposed limitin g the velocity with minimum 900 mm dia. (c) In case of viaduct irrespective of drain ventway- number of vents for the viaduct have to be finalised keeping the limiting velocity in view(IS ; 7784 (Part II / section1) :1995,   IS : 7784 (part I) - 1993)

3. Design of Tail channel & Approach channel keeping in view the Lacey's Formula for Wetted perimeter & velocity limits depending on stratification.(IS 458 -1988, IS :783 - 1985)

4.Lift Wall on D/S side of the structure may be avoided.(IS : 7784 (part - I) - 1993)

5. Transition lengths on U/S & D/S of drain(IS ; 7784 (part 2/sec1) : 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)

8. Uplift calculations for the floor of the barrel and U/S & D/S side apron

9. Exit gradient calculations(IS : 7784 (part - 2 / sec 2) - 2000)

G E = (H/d)x [1/(π√λ)] ; Where λ = [1+ √(1+α2)]/2 ; α = b/d;(IS : 7784 (part - I) - 1993)

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 I) : 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(TVA Hand Book)

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 TVA Hand Book, (IS - 7784 (part 2 / sec- I): 1995.)

2. Design of Abutment under canal trough and earth bank. TVA Hand Book,       

3. Abutment and Pier foundations shall be Isolated Footing / RCC raft as the case may be.(IS - 7784 (part 2 / sec- I): 1995. 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 / sec I) : 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

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, IS : 7784 (part 2/Section 3) :1996 )

e) Bell Mouth on U/S side

f) Cut & Ease waters (IS : 7784 (part 2/Section 3) :1996 )

IV DRAWINGS

a) General Layout on net level plan duly showing contours.

The Drawings shall contain assumptions made, TPs, Specifications, HPs of canals, Hydrology  of the drain,Bar bending schedule, Stress table etc.(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 sectionsii) Scale : 1:25 (or) 1:20/1:10 for RCC details.)

c)  Wall Sections,  RCC Details & Details of miscellaneous items

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