Concrete Check dam

Earthen Check Dam

Nalla BundCement Plug

DESIGN AND ESTIMATES OF

CHECK DAMTYPES OF CHECK DAMS

EARTHEN CHECKDAMS:(EMBANKMENTS)� MADE OF EARTH & CLAY

� SUITABLE FOR SHALLOW STREAMS WITH MINIMAL FLOW & LOW GREDIENT

� UNABLE TO WITHSTAND OVERFLOW CONDITION

STONE /R.C.C. CHECK DAMS� LARGER STREAM FLOW

� ALLOWING OVER FLOW

"Check-dams" are small barriers built across the

direction of water flow on shallow rivers and

streams for the purpose of water harvesting.

FACTORS TO BE CONSIDERED IN SITE

SELECTION

� Stream size and estimated streamflow

� Maximum flood levels during the monsoon

� Presence of rocks or other natural barriers which can be incorporated into the design

� Presence of suitable bed material to promote infiltration

� Distance of fields to stream to prevent flooding

� Local need and demand for irrigation water

� Surplusing arrangement should be made

� 10 year rainfall recurrence interval is to be estimated for the design of check dams

Guidelines for selection of sites

for percolation tanks

� Site should be upper reaches of streams preferably through wasteland

� Saucer shaped

� There should be existing wells 2 wells per sq.km

� Area should be there for irrigation and a soil cover of 25 cm

� Aquifer should be weathered and fractured

Design criteria

� Dependability of rainfall

� < 300 mm 40%

� 380- 760 50 %

� 760 And above 65 %

� Absence of gauged values, adopt strange tables

� Only 20 % available yield should be considered for design

Hydro geological studies

– Detailed mapping delineating different

aquifers and rock types

– Inventory of wells

– Estimate aquifer parameters

– Estimate ground water recharge

� Advantages� Check dams not only prevent gully erosion from occurring

before vegetation is established, but also cause a high proportion of the sediment load in runoff to settle out.

� In some cases, if carefully located and designed, these check dams can remain as permanent installations with very minor repairs.

�Disadvantages/Problems� Because of their temporary nature, many of these measures

have to be repaired regularly. � Temporary check dams are only suitable for a limited

drainage area and benefits are limited.� Removal may be a significant cost depending on the type of

check dam installed.

Stability of analysis of weirsConditions for stability of

weirs� There must be no tension

in the masonry or in the contact plane between the weir and the foundation

� There must be no overturning

� There must be no tendency to slide on the joint with foundation or any horizontal plane above the base

� The maximum toe and heel pressures on foundations should not exceed the prescribed safe limits.

Safety of dam

at FSL-Sliding

Safety of

dam at

FSL-

Crushing

Safe Safe

Safety of

damat

AHFL-

Crushing

Safety of

damat

AHFL-

Sliding

Check

AHFL RL

Safe Safe AHFL RL

is OK

Safety of dam at

AHFL-over turning

Stable

MAINTENANCE

� Check dams should be checked for sediment accumulation after each significant rainfall.

� Sediment should be removed when it reaches one half of the original height or before.

� Regular inspections should be made to insure that the center of the dam is lower than the edges.

� Erosion caused by high flows around the edges of the dam should be corrected immediately.

Design and construction of check dams

Abutment

Body

wall

Side Wall

Toe

Apron

Approach

Key

wall

Salient points for design and

construction of check dams

• Need and site location

• Design

– Map of the area

– Estimation of catchment area

– Rainfall analysis

– Plan and cross section

– Yield at the site

– High flood Estimation

• Estimates

– Detailed quantities

– Men and material

• Construction

• Project proposal

• economics

1 Take a graph paper

2. Trace the water shed on the grapg

paper

3. If the scale of the map is 1:50000

ie 1cm = 50000 cm

= 500 m

ie sq.cm = 500*500=250000 sq.m

=25 ha

1.Measure full squares

2. Measure ½ squares

3. Measure ¼ squares

4. Total all squares and estimate the

area of watershed

• RF-ST R.FALL(mm) AREA POLY PRODUCT

• R1 130 0.05 6.5

• R2 100 9.05 905

• R3 160 0.3 48

• R4 150 0.15 22.5

• R5 190 11.2 2128

• R6 70 0.15 10.5

• R7 90 3.9 351

• AVERAGE RAINFALL (mm)

127.14

• WEIGHTED AVEG.RAINFALL (mm)

139.98

Rainfall analysis of Bhavnagar

-800.00

-600.00

-400.00

-200.00

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1969

1970

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

year

Rainfa

ll (mm

)

Rainfall

average

Excess / less

Cummulative mass curve

Year 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978

Rainfall 215.90 722.38 671.58 119.89 512.06 510.03 202.18 511.05 533.40 215.39

Year 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988

Rainfall 795.78 534.42 911.86 565.91 1061.97 604.52 194.31 214.88 139.95 240.03

Year 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

Rainfall 679.20 533.40 264.16 560.07 325.12 675.64 351.03 303.02 668.78 545.85

S.NO YEAR Rainfall

(mm)

1 1988 1016.00

2 1994 1015.00

3 1979 983.00

4 1975 801.00

5 1997 765.00 50%

6 1996 755.00

7 1976 724.00

8 1977 715.00

9 1992 681.00

10 1980 615.00

ESTIMATION OF RAINFALL BY USING STRANGE TABLES

STRANGE TABLE

CATCHMENT(GOOD/AVERAGE/BAD) good

RAINFALL(MM) 377.95

RUNOFF(%) 9.4

RAINFALL

(mm) GOOD AVERAGE BAD

300 6.2 4.6 3.1

325 7.2 5.4 3.6

350 8.3 6.2 4.1

375 9.4 7 4.7

400 10.5 7.8 5.2

425 11.6 8.7 5.8

450 12.8 9.6 6.4

475 13.9 10.4 6.9 good 9.4

500 15 11.25 7.5 average 7

525 16.1 12 8 bad 4.7

Yield of the catchment� Yield of the catchment (cum)=

� Area of the catchment (Sq.M)* Runoff (in fraction) * Dependable Rainfall (m)

Capacity Table

Sr.NO RL Length

across

WW

(m)

Leng

th

acro

ss

Rive

r (m)

Differenc

e in RL

Capacity

(cum)

Cumulative

Capacity

(cum)

Remarks

1.00 98.52 0.00 0.00 0.00 0. 0. River bed

2.00 99.0 25.00 150. 0.48 1800. 1800.

3.00 99.5 55.00 330. 0.50 9075. 10875.

4.00 100.0 90.00 460. 0.50 20700. 31575. Top of spill way

=9.55*0.128*0.454

=0.55 mcm

5.74% of total flow will be held

Cross section

95

96

97

98

99

100

101

102

0 10 20 30 40 50 60 70 80 90 100 110 115 125 135

Chainage (m)

RL(m

)

Av.GL(m)

HFL (m)

FSL (m)

AHFL (m)

RL of top of foundatiion (m)

Discharge Discharge (cum) Cummulative disc (cum)

QFSL 124.84 124.84

QHFL 224.92 349.76

QAHFL 83.90 433.66

Cross sectional ares from Ground level to FSL

Sr.No Chainage (m) Av.GL(m) FSL (m) Depth

Height

(m)

Mean

depth /

Height(m

)

Distance between

two chainages

(Length) (m)(P)

Area ( sq.m)

-A

WP (m)

1 0 101.5 100.00 0.00 0.00 0.00 0.00 0.00

2 10 100.03 100.00 0.00 0.00 0.00 0.00 0.00

3 20 98.86 100.00 1.14 0.57 10.00 5.70 10.02

4 30 98.68 100.00 1.32 1.23 10.00 12.30 10.08

5 40 98.69 100.00 1.31 1.32 10.00 13.15 10.09

6 50 98.89 100.00 1.11 1.21 10.00 12.10 10.07

7 60 98.94 100.00 1.06 1.09 10.00 10.85 10.06

8 70 98.81 100.00 1.19 1.13 10.00 11.25 10.06

9 80 98.52 100.00 1.48 1.34 10.00 13.35 10.09

10 90 98.79 100.00 1.21 1.35 10.00 13.45 10.09

11 100 99.01 100.00 0.99 1.10 10.00 11.00 10.06

12 110 99.85 100.00 0.15 0.57 10.00 5.70 10.02

13 115 100.42 100.00 0.00 0.08 0.00 0.00 0.08

14 125 100.45 100.00 0.00 0.00 0.00 0.00 0.00

15 135 100.85 100.00 0.00 0.00 0.00 0.00 0.00

average GL 98.77 100.00 108.85 100.70

Min 98.52 101.50 Q=A*V

(cumec)

124.84 R=A/P 1.08

Approach Velocities at different levels� Approach velocities at FSL,HFL and AHFL are

required.� The velocity is calculated as under:

� V= 1/N* R ^(2/3)*S^(1/2)

� Where Velocity (m/sec)

� N= Roughness coefficient (0.25 to 0.3)

� R= Hydraulic Mean depth ( A/P)� Where A= Area of Cross Section (sq.m)

� P= Wetted perimeter)

� S= River bed slope in fraction

Approach discharges at different levels

Q= A* V

Flood Discharge Estimation� Dicken’s formula

� Q=C*M^3/4

� C= 11.4 for North India

� C= 13.9 to 19.5 for Central India

� C= 22.5 to 25 for Western India

� Government of Gujarat Qspf= 0.8*C*A^b

� C=29.0402� b=0.9232

� Ryve’s formula

Q = CM ^(2/3)

� Where C = varies from 6.8 to 15 kms

� C = 6.75 if area is less than 24 kms from coast

� C = 8.45 if area is 24 - 16 kms

� C = 10.1 for hills

� Q = Discharge in cumecs

� M = Area in Sq. kms

� Ali Nawaj Jung Bahadur’s formula

� (0.993 - 1/14 Log A)

� Q = CA

� Value of C taken from 48 to 60

� This is applicable mainly in Deccan plains

� A = Area of catchment in sq. km

Englis gave the following formulae

derived from data collected from 37

catchments in Bombay Presidency

For Ghat areas

R = 0.85 P - 30.5

Where R is run off in cms

P = Precipitation cm

For non Ghat areas

R = {P - 17.8} x P/254

Khoslas’ formula

R = P - (T - 32)/3.74

Where T = mean temp F

R & P are in cms.

Ingle’s formula

Q=123*A/SQRT(A+10.4)

A= Area(sq.km)

Barlow’ and Lacey have also given empirical formula as under

R = KP

Where R = Run off

P = Precipitation

K = Run off coefficient for different class of catchments like,

A = Flat cultivated soil

B = Flat partly cultivated

C = Average

D = Hills & plains with cultivation

E = Very hilly areasBarlow has added another coefficient based on light rain, average

rainfall with intermittent rains and continuous down pour etc.

Lacey has given a formula as

R = P

------------------

1 + (304.8 F/PS)

Where S = Catchment factor

F = reservoir duration factor which is based on different classes

as defined by Barlow’s equation.

BARLOW'S TABLE

CLASS

DESCRIPTION OF

CATCHMENT

RUNOFF

PERCENTAGE

A

Flat , cultivated and black

cotton soils 10

B flat partly cultivated stiff soils 15

C Average catchment 20

D

Hills and plains with little

cultivation 35

E

Very hilly and steep with little

or no cultivation 45

NATURE OF

SEASON A B C D E

Light rain, no heavy

down pour 0.7 0.8 0.8 0.8 0.8

Average or no

continuous rain 1 1 1 1 1

continuous

downpour 1.5 1.5 1.6 1.7 1.8

Rational Method:

In this method the basic equation which correlates runoff

and rainfall is as followsQ = C * I * A

Where Q = Runoff (Cubic meters per hour)

C = Runoff Coefficient

I = Intensity of rainfall in meters per hour

A = Area of the drainage basin (Sq. Meters)

Intensity of Rainfall(m/hr)(I)

=P/Tr ((Tr+1)/Tc+1)

P Precipitation meters

Tr Storm period hrs

Tc Time of Concentration hrs

if Tc is not known, then

I = P/Tr

Time of Concentration(Tc) is the time in hours taken by rain water that falls at the

farthest point to reach the outlet of a catchment

The value of runoff coefficient C depends on the characteristics

of the drainage basin such as soil type, vegetation, geological

features etc. For different types of drainage basins the values of

C are given below in table

Table Value of C for different types of drainage basins

Types of drainage basin Value of C

Rocky and impermeable 0.8-1.0

Slightly permeable, bare 0.6-0.8

Cultivated or covered with

vegetation

0.4-0.6

Cultivated absorbent soil 0.3-0.4

Sandy soil 0.2-0.3

Heavy forest 0.1- 0.2

Unit Hydrograph

0.00

1.00

2.00

3.00

4.00

5.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

No of hours

Discharge (cumec)

(unit hydrograph method)• Date hour Disch base rdinate ordinate

• cumec flow dir -rf unit hyd

• 12 aug 6 6 6 0 0

• 12 16 5 11 0.46

• 18 60 3.5 56.5 2.39

• 24 100 2.5 97.5 4.12

• 13 aug 06 68 3 65 2.75

• 12 35 4 31 1.31

• 18 11 4.5 6.5 0.27

• 24 7 5.5 1.5 0.06

• 14 aug 06 6 6 0 0

Unit hydrograph method

� A unit hydrograph is hydrograph representing 1 cm of run off from a rainfall of some unit duration and specific aerial distribution. A unit hydrograph is derived from an observed hydrograph. Data regarding duration of rainfall, amount of rainfall and the resulting run off data as observed by gauging from the observed hydrograph is used for the construction of unit hydrograph. The basic assumptions in constructing unit hydrograph are� All the combined characteristics of the basin are reflected in the

hydrograph.

� Identical rainfall with the same characteristics produce identical hydrograph

� The vertical ordinates of the hydrograph are proportional to thevolume of run off on the same catchment.

� Rainfall as a hypothetical storm covering the whole catchment over duration of time equal to time of concentration I.e.. Travel time of water from the last point of water shed to the gauging point.

Construction of Unit hydrograph

Follow the steps for constructing a unit hydrograph as given

below

1. From the past records select some unit period of intense

rainfall duration corresponding to an isolated storm uniformly

distributed over the area.

2. From past records plot the storm hydrograph for some

days before and after the period of rainfall of that unit

duration.

3. Separate the ground water base flow.

4. Subtracting the ordinates of base flow from the total

ordinates find the ordinate of direct runoff.

5. Calculate the volume of direct run off using the

following formula

Direct run off = 0.36 E (O) * t

--------------

A

Where E(O) = Sum of discharge ordinate (direct run off)

t = Time interval between successive ordinate in hours

A = Area of drainage in sq.km.

The input data required for estimating unit hydrograph and the

actual results are given in Annexure V.

The Unit hydrograph can be used to construct flood

hydrograph resulting from rainfall of the same unit duration

for which the unit hydrograph has been calculated. The results

of unit hydrograph are given in Annexure V.

ESTIMATION OF FLOOD DISCHARGE BY UNIT HYDROGRAPH

CATCHMENT TIME INTER RAINFALL

DATE HOUR TOTAL Q BASE FLOW ORDINATE ORDINATE AREA(SQ.KM) VAL(HRS) (CM)

OF DIRECT OF UNIT 25 2 9.00

RUNOFF HYDRO Estimtion of Total discharge based on Unit Hydrograph.

GRRAPH DATE HOUR BASEFLOW DIR.RUNOFF TOT.DISCH

(Cumec) (Cumec) (Cumec) (Cm) (Cumec) (Cumec) (Cumec)

12 AUG 6 6.00 6.00 0.00 0.00 AUG 24 6 4 0.00 4

8 8.00 6.00 2.00 0.08 8 3.5 0.00 3.50

10 10.00 5.50 4.50 0.19 10 3 0.00 3.00

12 16.00 5.00 11.00 0.46 12 2.5 0.00 2.50

14 28.00 4.50 23.50 0.99 14 2 0.00 2.00

16 42.00 4.00 38.00 1.61 16 1.5 0.00 1.50

18 60.00 3.50 56.50 2.39 18 1.8 0.00 1.80

20 80.00 3.00 77.00 3.25 20 2.1 0.00 2.10

22 110.00 2.50 107.50 4.54 22 2.4 0.00 2.40

13 AUG 24 100.00 2.50 97.50 4.12 24 2.7 0.00 2.70

2 90.00 2.50 87.50 3.70 2 3 0.00 3.00

4 80.00 3.00 77.00 3.25 4 3.3 0.00 3.30

6 68.00 3.00 65.00 2.75 6 3.6 0.00 3.60

8 56.00 3.50 52.50 2.22 8 3.8 0.00 3.80

10 45.00 3.50 41.50 1.75 10 4 0.00 4.00

12 35.00 4.00 31.00 1.31 12 4 0.00 4.00

14 26.00 4.00 22.00 0.93 14 4 0.00 4.00

16 18.00 4.50 13.50 0.57 16 4 0.00 4.00

18 11.00 4.50 6.50 0.27 18 4 0.00 4.00

20 9.00 5.50 3.50 0.15 20 4 0.00 4.00

22 8.00 5.50 2.50 0.11 22 4 0.00 4.00

14 AUG 24 7.00 5.50 1.50 0.06 24 4 0.00 4.00

2 6.00 6.00 0.00 0.00 2 4 0.00 4.00

TOTAL 308 919.00 97.50 821.50

DIRECT

RUNOFF= 23.6592

Maximum flood with different formula

MFD (Area velocity

method)cum/sec (Q=A* V)HFL

349.76

MFD at the site (Dicken)cum/sec 135.81

Ingle's formula 262.99

MFD (Rainfall intensity method

(C*I*A))- rational method cum / sec

124.35

MFD at the site (GOG)-Standard

Project flood method) cum/sec

233.21

Average MFLD 221.22

Length of Check Dam

L=(1.5*Q)/(C*H*SQRT(2*9.81*H))

Design Flood(cum) 163.24

Flood lift (H)-(FSL to HFL) 1.00

Calculated Length of Weir(m) 88.45

Length of check dam actually

proposed due to site

conditions

100.00

Crest width and base width of CD

height of weir above GL(H) from foundation to FSL 2.70

Height above crest (Free board / (h= 0.00

Crest widh(m

=0.55*(SQRT(H))

H=Ht of weir above GL up to FSL

including Free board if any

0.90

Actual provided 0.75

Base width

calculated

=H*S

S= Slope of body wall to the height

of the dam

2.16

Actually provided 2.75

Score depth

Height of check dam from River

bottom to HFL(m)

2.48

Design Discharge(cum) 163.24

q= discharge per m lenth of spill

way

1.63

Fround No(F)=V/sqrt(g*d1) 4.14

Scoure Depth(SC)=0.473*(Q/F)^1/3 1.61

Max SC 2.41

RL of bottom SC from AHFL 98.82

Foundation RL= AHFL-1.5SD 97.30

MAX RL of SC as per site conditions 98.82

Height of Check dam from foundation

to FSL (Z)

2.70

height of check dam fromFSL to HFL 1.00

Height of Check dam from GL

toHFL(H)

3.70

height of check dam from HFL to

AFHL

0.23

height of check dam from FSL to

AFHL(H)

1.23

Apron length (y) 4/3*sqrt(Z)*H 2.69

As the ground conditions are good ,

appron width can be kept at

5.00

Toe Height above GL =Top of toe RL/

approach bottom- River bottom RL at the

site(m)

0.13

d1=q/v1 0.25

Hydraulic jump(d2)=-

(d1/2)+(d1^2/4+2*va^2*d1)/

g))^0.5

1.35

Length of appron

(calculated)

5.50

Top of appron RL= 98.35

Thickness of appron (t )=

(d2-d1)/2*(W1/(W1-W))

0.39

Proposed (t)as it is hard

rock

0.60

Bottom RL of Appron 97.75

Top width (

Thickness)

of end sill

0.54 Height

of end

sill

0.27

Provide 0.45 provid

e

0.45

Apron calculationsEffective head(h)= AHFL-Appron RL+d1

effective velocity (m/sec) v1=0.9*sqrt(2*g*h)

Assumed d1= 0.22

h= 2.66

v1= 6.50

Estimation of AHFL Level

Discharge passing Between HFL and AHFL

AA= Area between AHFL nd HFL,

AB= Area between HFL FSL

CA,CB= Consts,

H= Flood lift, h= Velocity Head

QA= AA*CA*(2/3)*sqrt(2*g)*((H+ha)^3/2-

(ha)^3/2)/H

61.22

QB= AB*CB)*sqrt(2*g)*sqrt((H+ha)) 380.26

Discharge passing Between FSL and HFL

QA+QB= 441.48

Designed discharge 163.24

AHFL RL AHFL RL is OK

Check for crushing.

Eccentriciy(e) e= z-b/2 -0.70

Pmax (kg/m^2) W/b(1+6*e/b)*1/10 -0.20

Pmin ( kg/m^2) W/b(1-6*e/b)*1/10 0.63

Safe

The crushing strength is far less than 30

kg/cm^2 as such it is in order

Check for over turningH= Height of the dam from

foundation

Net moment considering 100

% uplift pressure

1.77

B= Dam width Net weight considering

100% uplift(w)

4.64

D2= thickness of foundation

concrete

Resultant (z) sigma M/sigma W= 0.38

Stable

C.Sp.gravity of concrete The resultant momentum passes through between 1/3 to 2/3 rd base , the

structre is safe

T= Width of the dam Net moment considering50%

% uplift pressure

D1= thickness of concrete on

top of dam

Net moment considering

50% uplift pressure

5.74

M=Sp.gravity of dam material Net weight considering 50%

uplift(w)

8.31

W= sp.gravity of water Resultant (z) sigma M/sigma W= 0.69

Stable

The resultant momentum passes through between 1/3 to 2/3 rd base , the structure is safe

Check for slidingCoeffient of friction sigma H/net weight 0.30 Safe

Less than 2/3rs (0.67 )as such it is safe against sliding.Force details vertical horizont

al

lever moment

W0 ht of water above dam (h*T*1)W 1.11 0.45 T/2 0.50

W1 concrete on the dam (T(D1)*1*C 0.20 0.45 T/2 0.09

W2 Dam weight on the rect.side(

H*T*1*M

5.21 0.45 T/2 2.35

W3 Dam weight on the angle.side( 0.5

(B-T)H*1*M

3.62 0.60 T+(B-T)/3 2.18

W4 Foundation concrete(B*d2*1*C) 1.45 1.08 B/2 1.57

W5 weight of water on the dam( 0.5 (B-

T)H*1*W

1.51 0.60 T+(B-T)/3 0.91

P1 2.17 1.20 H/2 2.60

11.99 2.17 9.70

VI Uplift (100%) 7.34 1.08 B/2 7.93

VI uplit(50%) 3.67 1.08 B/2 3.97

V2 Uplift (100%) 1.33 0.72 B/3 0.96

V2 uplit(50%) 0.66 0.72 B/3 0.48

Stability Analysis at FSLSp.gravity of water (ton/meter)w 1.00 Top width 0.90

sp.gravity concrete (ton/meter)w1 2.40 Base= 2.16

sp.gravity ofdam material 2.24 1/3 base 0.72

ahfl 101.23 2/3 base 1.44

fsl 100.00Check for crushing.

bottom rl 98.52

HFL 101.00 e= z-b/2 0.09

RL of Hard rock 97.30 Pmax (kg/m^2) W/b(1+6*e

/b)*1/10

0.46

foundation rl 97.30 Pmin ( kg/m^2) W/b(1-

6*e/b)*1/10

0.27

RL of top of foundation 97.60 Safe

foundation concrete 0.30The crushing strength is far

less than 30 kg/cm^2 as such

it is in order

concrete on upper side of dam (D1) 0.10

Height above top ofFSL upto AHFL 1.23Check for sliding

Height above top of foundation and AHFL 3.63 Coeffient of friction sigma

H/net

weight

0.37 Safe

Height above top of foundation and FSL 2.40 Less than 2/3rs (0.67 )as such it is

safe against sliding.Height above foundation andHFL 3.40

For

ce

details vertical horizontal lever moment

W1 concrete on the dam (T(D1)*1*C 0.20 0.45 T/2 0.09

W2 Dam weight on the rect.side( H*T*1*M 5.21 0.45 T/2 2.35

W3 Dam weight on the angle.side( 0.5 (B-

T)H*1*M

3.62 1.32 T+(B-

T)/3

4.78

W4 Foundation concrete(B*d2*1*C) 1.45 1.08 B/2 1.57

P1 2.88 0.80 H/3 2.30

10.48 2.88 11.10

VI Uplift (100%) 2.59 0.72 B/3 1.87

VI uplit(50%) 1.30 0.72 B/3 0.93

Check for over turningH= Height of the dam from foundation Net moment considering 100 % uplift pressure 9.23

B= Dam width Net weight considering 100% uplift(w) 7.89

D2= thickness of foundation concrete Resultant (z) sigma M/sigma W= 1.17

Stable

C.Sp.gravity of concrete The resultant momentum passes through between 1/3 to 2/3 rd base , the structre

is safe

T= Width of the dam Net moment considering50% % uplift pressure

D1= thickness of concrete on top of

dam

Net moment considering 50% uplift pressure 10.17

M=Sp.gravity of dam material Net weight considering 50% uplift(w) 9.18

W= sp.gravity of water Resultant (z) sigma M/sigma W= 1.11

The resultant momentum passes through between 1/3 to 2/3 rd base , the structre is

safe

Summary of estimates

Qty Unit Item Rate per Amount (

Rs)

Item1:Excavation in all sorts of soils

614.32 cum soil 29.00 cum 17815.26

429.16 cum soft rock 70.00 cum 30041.17

143.05 cum hard rock 125.00 cum 17881.65

Item 2: PCC

93.38 cum PCC 1:3:6 1208.00 cum 112798.88

99.32 cum PCC 1:5 870.00 cum 86406.51

501.54cum

PCC 1:2:4 1509.00cum 756823.33

Item 3:Drilling of bores 50mm dia 1 m length

303.00 no No of holes 60.00 no 18180.00

Item 4: Providing and fixisng in position mild steel

7.36 qtls Providing and

fixisng in position

mild steel

2070.00 qtls 15241.20

Item 5: Back filling

172.50 cum Back filling 15.00 cum 2587.50

Total 1057775.50

3 % for contingencies and work

charge estt. & tools

31733.26

Grand total 1089508.76

Economics of the project

Total cost of the project 1089509.00

Height above Crest(FSL

upto AFHL (H)) flood lift (actual)

1.23

Total net incremental benefit( Rs)

350000.00

Benefit cost ratio 1.61

IRR (%) 45.73