Scour Depth Calculation

Job No.

PECS2016001

Project Title

including Pumping Machineries with all related Accessories, Raw Water Transmission Main for drawing 35 MGD Raw Water from The River Hooghly

Owner

Owner's Consultant Executing Agency

Consultanct to EA Name of Unit Drawing Ref. Designed by:

Reference

Doc No. PECS/201601/APPROACH JETTY/007

Survey, Design, Construction, Supply, Erection & Commissioning of Raw Water Intake Structure (Fixed type), Pump House on Intake structure and Delivering to Water Treatment Plant on EPC Turnkey Basis

Superintending Engineer, Eastern Circle, Public Health Engineering Dte., Govt. of WB WAPCOS LIMITED (A Govt. of India Undertaking) Simplex Infrastructures Limited

Structural Analysis & Design of Approach Jetty (Calculation of Scour Depth) Checked by:

G Chakraborty

0

Design of Approach Jetty for Intake Pump House (Habra Gaighata Intake Project)

Projectscape Engineering Consultancy Services Private Limited Shubhajit Barik

Rev. No.

Approved by:

CALCULATIONS

G Chakraborty

Date:

9/6/2016

CALCULATION OF MAXIMUM SCOUR DEPTH VIS-A-VIS SCOUR DEPTH CALCULATED BY KoPT FOR HABRA-GAIGHATA INTAKE PROJECT : CALCULATION OF SILT FACTOR ( Ksf ) :

Ksf = 1.76√dm

( As per clause No. 703.2.2 of IRC:78-2014)

dm = weighted mean diameter of bed material in millimetre

(The recommendation of KoPT as per letter no: Hyd/ 12029/Jubilee bridge/PHED/862 on Dated: 02.08.2016 the value of dm along the region has been considered as 0.119 mm for the purpose of scour depth calculation.) dm = 0.119 mm

So, Ksf = 0.607

CALCULATION OF SCOUR DEPTH 40.0M FROM HIGH BANK LINE W.R.T.HHWL (for 1000Ø Pile) (Refer Sketch No. PECS/SIL/1601/003/SK-01

(Recommendation of KoPT as per Letter No.

Maxm Discharge Velocity, V = 1.50 m/sec

High Bank line has been considered

as wetted line where HHWL merges with the River Bed profile near bank

Hyd/ 12029/Jubilee bridge/PHED/862)

Discharge per M width of

waterway (Db) =(A x V) = 3.76 cumecs Depth of Water considered for unit discharge from HHWL = 2.508 m (at centre of farthest pile nearly 40.0 m away from High Bank Line, 4.67m - 2.162m) So, Design Discharge per M Increase of 30% over Design Discharge, as per width of waterway = 4.89 cumecs clause No. 703.1.1 of IRC:78-2014, Catchment area less than 3000 km2 MEAN SCOUR DEPTH (dsm): As per IRC: 78-2014 the mean scour Depth below Hight Flood Level (HHWL) can be calculated theoritically from the following equation:

dsm = 1.34 (Db /Ksf)

dsm= Mean depth of Scour

1/3

Db = The design discharge for foundation per metre width of effective Waterway

Ksf = Silt factor for a representative sample of bed material obtained uptothe level of anticipated deepest scour.

Here, Mean Scour Depth, dsm=

1.a)

1.b)

2.686 m

(From HHWL)

Maxm Deoth of Scour from HHWL (2dsm) =

5.372 m

Max Scour Depth From river Bed Level =

2.180 m

m

Maxm Scour Depth From HHWL =

Calculated Maxm Scour Depth From HHWL (2.18+2.508) =

5.372 m 4.688 m

So, for Design purpose we would consider the Maximum Value =

Page 1 of 2

( As per clause No. 703.3.1.1 of IRC:78-2014)

(As calculated above) (The recommendation of KoPT as per Letter No.

Hyd/ 12029/Jubilee bridge/PHED/862 on Dated: 02.08.2016

5.372 m

from HHWL

Job No.

PECS2016001

Project Title

including Pumping Machineries with all related Accessories, Raw Water Transmission Main for drawing 35 MGD Raw Water from The River Hooghly

Owner

Owner's Consultant Executing Agency

Consultanct to EA Name of Unit Drawing Ref. Designed by:

Reference

Doc No. PECS/201601/APPROACH JETTY/007

Survey, Design, Construction, Supply, Erection & Commissioning of Raw Water Intake Structure (Fixed type), Pump House on Intake structure and Delivering to Water Treatment Plant on EPC Turnkey Basis

Superintending Engineer, Eastern Circle, Public Health Engineering Dte., Govt. of WB WAPCOS LIMITED (A Govt. of India Undertaking) Simplex Infrastructures Limited

Structural Analysis & Design of Approach Jetty (Calculation of Scour Depth) Checked by:

G Chakraborty

Design of Approach Jetty for Intake Pump House (Habra Gaighata Intake

Approved by:

CALCULATIONS

G Chakraborty

CALCULATION OF SCOUR DEPTH BEYOND 40.0M HIGH BANK LINE W.R.T.HHWL (for1200Ø Pile) (Refer Sketch No. PECS/SIL/1601/003/SK-01

Max Discharge Velocity, V = 3.00 m/sec

( Recommendation of KoPT as per Letter No.

m

Date:

9/6/2016

High Bank line has been considered

as wetted line where HHWL merges with the River Bed profile near bank

Hyd/ 12029/Jubilee bridge/PHED/1597)

Discharge per M width of

waterway (Db) =(A x V) = 15.41 cumecs Depth of Water considered for unit discharge from HHWL = 5.138 m (at centre of farthest pile nearly 40.0 m away from High Bank Line, 4.67m + 0.468m) So, Design Discharge per M width of waterway = 20.04 cumecs

Increase of 30% over Design Discharge, as per clause No. 703.1.1 of IRC:78-2014, Catchment area less than 3000 km2

MEAN SCOUR DEPTH (dsm):

As per IRC: 78-2014 the mean scour Depth below Hight Flood Level (HHWL) can be calculated theoritically from the following equation:

dsm = 1.34 (Db /Ksf)

dsm= Mean depth of Scour

1/3

Db = The design discharge for foundation per metre width of effective Waterway

Ksf = Silt factor for a representative sample of bed material obtained uptothe level of anticipated deepest scour.

Here, Mean Scour Depth, dsm=

2.a)

2.b)

4.298 m

(From HHWL)

Maxm Deoth of Scour from HHWL (2dsm)=

8.597 m

( As per clause No. 703.3.1.1 of IRC:78-2014)

Maxm Scour Depth From HHWL=

8.597 m

(As calculated above)

Max Scour Depth From river Bed Level= m

Calculated Maxm Scour Depth From HHWL (8.400+5.138)=

0

Project)

Projectscape Engineering Consultancy Services Private Limited Shubhajit Barik

Rev. No.

8.400 m

13.538 m

So, for Design purpose we would consider the Maximum Value =

Page 2 of 2

(The recommendation of KoPT as per Letter No.

Hyd/ 12029/Jubilee bridge/PHED/1597 on Dated: 11.12.2015

13.538 m

from HHWL