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الرحيم الرحمن الله بسم

An Najah National UniversityFaculty of Engineering

Civil Engineering Department

Prepared by : 1. Bashar abu hajji 2. Ahmad abu asbih 3. Adham sulimanSupervisor : Dr. Hafez Q. Shaheen

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Study and conceptual design of Al-Malaqi

bridge dam

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Study area :

Jeser Al Malaqi is located 3.5 km from the main intersection of

Al-Badan village with Al-Faria and linking with the Jordan Valley

(Al Ghor) and Jericho City.

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The selected location of the dam is approximately 500m downstream from Jesser Al-Malaqi at the confluence Wadi Al-Faria and wadi Al-Badan.

Wadi Al BadanWadi Al Faria

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Wastewater and springs flow :

The wastewater comes from Nablus city and the amount of

wastewater flow about (6000m³/day – 8000m³/day), only

Small portion of it reaches the dam. the spring flow is natural

Storage in al faria catchment, the number of spring is 13

springs distributed as groups (Al-faria, Al-badan, Nablus).

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the four sub- catchments for the upper part of Wadi Al-Faria and Wadi Al-Badan.

The area of the watersheds is :

A1 = 14.35 km2

A2 = 20.04km2

A3 = 21.55 km2.

B1 = 82.88 km2

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SCS is used to construct the unit hydrograph (example)

Tc= ( L / V ) / 60

Tctr 6.02

TP =

PT

A08.2qP=

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Description of

water course

Slope in percent

0 – 3 4 – 7 8 – 12 Larger than 12

Unconcentrated

Woodland 0 - 1.5 1.5 - 2.5 2.5 - 3.25 Larger than 3.25

Pastures 0 - 2.5 2.5 -3.5 3.5 – 4.25 Larger than 4.25

Cultivated 0 – 3 3 – 4.5 4.5 – 5.5 Larger than 5.5

Pavement 0 -8.5 8.5 – 13.5 13.5 – 17 Larger than 17

Concentrated

Outlet channel-determine velocity by manning formula

Natural channel

not well defined

0 -2 2 – 4 4 – 7 Larger than 7

approximate average velocities in ft/s runoff flow for calculating time of concentration

(chow, 1989)

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t / Tp q / qp t(hr) q=(m3/s.cm)

0.000 0.000 0.000 0.000

0.500 0.400 1.18 5.01

1.000 1.000 2.36 12.54

1.500 0.660 3.54 8.27

2.000 0.320 4.72 4.01

2.500 0.100 5.9 1.25

3.000 0.050 7.08 0.62

3.500 0.015 8.26 0.19

4.000 0.025 9.44 0.31

this table shows the coordinates to construct the 1 cm-unit hydrograph of area (A3).

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Unit hydrograph for area 1

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Flow Routing

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S= K {XI + (1 - X) O}

K: is a constant, approximates travel time of the flood wave through the reach.

X: is a factor that weighs the relative influence of inflow and outflow upon the

storage for most river channels, X lies between 0.1 and 0.3, indicating both

attenuation and translation. The modal value is about 0.2.

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The routed unit hydrograph is shown below.

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CIA method (peack value) :

Runoff volume = C * I * A

Where:

C: runoff coefficient. I: intensity of rainfall (mm).A: area of the catchment (m2).

Runoff coefficient = 0.2

(example) For I = 2.5 mm/day

Q = C * I * A = 0.2 * 0.0025 (m / day) * 138 * 106 m2 = 0.069 MCM/day

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Dam design

Dam height(m) Dam face

Soil conditions

>50% gravel

>15% clay

>50% sand

>15% clay

>55%clay

3

Upstream 2.5:1 2.5:1 3:1

Downstream 2:1 2:1 2.5:1

3.1-6

Upstream 2.5:1 2.5:1 3:1

Downstream 2.5:1 2.5:1 3:1

6.1-15

Upstream 3:1 3:1 3.5:1

Downstream 2.5:1 3:1 3:1

Nelson (1985)

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Storage volumeThe calculation of storage volume done by using the following equation (prismoidal formula):

V = L/3 (A1 + An + 2 ( A3+A5+ …… + An-2) +4(A2+A4+……+An-1)

For n = 3:V = L/3 * (A1 + 4A2 + A3)

Height of dam (m)

Depth of water(m) Area of

surface (m²)Cumulative volume (m³)

05

5108 8514

55

24403 73778

105

54303 180362

155

99087 517355

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Evaporation volume :

Month pan Evaporation rate(mm/month)January 49.6February 67.2March 99.2April 149.1May 202.7June 225.9July 237.9August 218.2September 177.6October 131.1November 74.4December 48.6Summation 1681Average for winter seasons 67.8

Evaporation Volume=Evaporation rate*area

Evaporation Volume= (67.8/ (1000*30))* 45725.25=103.33 m3/day (average daily )

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Infiltration volume

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From the above figure we get the infiltration rate:Infiltration rate = 10 mm/hrInfiltration volume = infiltration rate * area = (10/1000)*45,725.25 *24 = 10,974 m3/day

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Seepage volume

For k : the value depend on the type of the soil .

Hydraulic conductivity (K)

Soil type Cm/sec Ft/min

Clean gravel 100-1.0 200-2.0

Coarse sand 1.0-0.01 2.0-0.02

Fine sand 0.01-0.001 0.02-0.002

Silty clay 0.001-0.00001 0.002-0.00002

Clay <0.000001 <0.000002

The type of soil is silty clay K = 0.0005

(L.Casagrande’s method 1932)q = k Lsinϴ² in (m²/s)L = (√ (d²+H²) –√ (d²- H²cotϴ²)) in (m)

From Principles of geotechnical engineering

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H=15 m , D=69.55m , ϴ=21⁰ , K=0.0005

L= √5062.2-√3310.24 = 13.61m

q = (0.0005) *(13.61) (sin21)2 = 8.73*10^-4 (m²/s)

Take length of the dam = 85m Q= 8.73*10^-4 (m²/s)* 85 (m) = 0.0007429 m3/s

Q= 0.0745*60*60*24=64.2 m3/d

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Design of spillway

I = 8 mm/hrQ = C *I *A = 0.2 * 0.008 (m/hr) * 138 * 10 6 m2 / 3600s = 61.33 m3/s

The time of concentration = 2.5hr = 150 min

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For three pipes :

Q = 20.44 m3/s

Assume velocity = 5 m/s

A = Q / V = 20.44 / 5 = 12.26 m2

D = 2.28 m

We will use 3 pipes with diameter 2.5 m each.

(this is for emergency outflow to avoid damage of dam).

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Requirements

1. Change the road connect Nablus to Jordan valley such as the new road become over the reservoir level.

2. Badan sub-catchment wastewater flowing from Nablus East should be treated and stored with the runoff water and to recharge into the aquifer and used for agricultural activities.

3. Studies are needed to investigate the infiltrated water quality at the site of the dam.

4. Evaluate the required infiltration rate (hydraulic conductivity) and treat the soil of the dam accordingly.

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Happy to answer your question