Gad Loi Mini 2 . Presentation

7/30/2019 Gad Loi Mini 2 . Presentation

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PROJECT TITTLE: DESIGN OF A CULVERT.

CASE STUDY: MTONI KIJICHI ROAD(DARAJANI)

STUDENT NAME: GAD LOI

ADMISSION NUMBER: 100101P7285.


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INTRODUCTION

Mtoni kijichi road is the paved road which is in

Temeke Municipal, its 4 km and it is one of the

main entrance and exit to Kijichi and Mbagara

kuu. The road face the problem of overflowing

of water during rainy season at the place called

Darajani(150metre) which has culvert which is

not sufficient to convey water during rain seasonhence causes overflowing of water over the

road.


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PROBLEM STATEMENT

Overflowing of water across the road at

Darajani(Mtoni Kijichi paved road) during rainy

season hindering the passage of people and

traffic.


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OBJECTIVE OF THE PROJECT

To design the box culvert to convey water across

the road at Darajani(Mtoni Kijichi paved road).


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PROJECT OUT COME

To come out with the design that when

implemented will solve the problem which is

current facing the road for 20 years to come.


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METHODOLOGY

Literature review

Data collection

Data analysis Design


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LITERATURE REVIEW

Culvert is defined as a structure sized to conveysurface water runoff under a highway, railroad, orother embankment.

Whenever streams have to cross the roadway,

facility for cross drainage is to be provided. Alsooften the water from the side drain is taken acrossby these cross drain in order to divert the wateraway from the road, to a water course or valley. Thecross drainage structure commonly in use are

culverts andbridges. When a small steam crosses aroad with a linear waterway less than about 6 meter,the cross drainage structure provided is calledculvert; for higher value of linear waterway the

structure is called bridge.


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The common types of culverts in use are;

Slab culvert

Box culvert Arch culvert

Pipe culvert.

In slab culverts reinforced concrete slab is placed overabutments made of masonry and the span is generallylimited to 3metre.

Box culverts of square or rectangular shapes is made ofreinforced concrete.

Arch culverts is generally built using brick or stone

masonry, plain cement concrete may also be used.Pipe culverts of minimum diameter 75 cm and made ofsteel or prefabricated reinforced concrete is used whendischarge is low.


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Importance of culverts;

To drain off surface and subsurface water on the

road To prevent water remain stagnant along the side

of the road

To prevent the damages of the road pavement


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Location of the culvert

Should be located at moderate flow of water

Should not be placed at bend in water course

It should be at the straight reach of the watercourse i.e. passing through the opening

culvert.

Should be located where there is no possibility

of silting and scoring during functioning.


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Structure detail of a culvert design;

Barrel area is measured perpendicular to the flowand refers to the water area in the barrel.

Barrel length is the total culvert length from theentrance to the exit of the culvert. Because the heightof the barrel, barrel slope, and barrel skew influencethe actual length, an approximation of the barrellength is usually necessary to begin the designprocess.

Barrel roughness is a function of the material used tfabricate the barrel. Typical materials include

concrete, corrugated metal and plastic. Theroughness is represented by a hydraulic resistancecoefficient such as the Mannings n value.


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Barrel slope is the actual slope of the culvert barrel, and isoften the same as the natural stream slope.

Critical depth is the depth at which the specific energy of a

given flow rate is at a minimum. For a given discharge andcross section geometry there is only one critical depth.

Slope there are two classification of slope, steep and mild.

steep slope occurs where the critical depth is greater

than the normal depth,mild slope occurs where critical depth is less than

normal depth.

Headwater(HW), that depth of the water impounded

upstream of the culvert due to the influence of the culvertconstriction, friction, and configulation.

Tailwater(TW), the depth of water a the out let of theculvert.


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Part of the box culvert;


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HIGHWAY DRAINAGE

is the process of removing and controlling excess

surface and sub-soil water within the right of

way. It is divided into two;

i. Surface drainage: the removal and diversion

of surface water from the roadway and

adjoining land.

ii. Sub-surface drainage: the removal of excess

soil-water from the sub grade


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The design of surface drainage system is divided

into two parts

Hydraulic analysis

Hydrologic analysis


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Hydraulic analysis

Deal with designing facilities required toaccommodate the estimated discharge

Mannings formula is used


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V=Allowable velocity of flow in the drain m/sec

n=Mannings roughness

r=Hydraulic radius(cross section area of

flow/wetted perimeter)

S= longitudinal slope of channelQ=quantity of surface water m3/sec

A=cross sectional area of channel m2

v= average velocity m/sec


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Hydrological analysis

is used to determine the maximum quantity ofwater expected to reach the element of drainagesystem.

Q=C.i.Ad

WhereQ=run-off (m3/sec )C=run-off coefficient, expressed as the ratio

of run-off to rate of rain fall,

i=intensity of rainfall (mm/sec)Ad=drainage area in 1000m

2


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Design consideration;

There are two procedures for designing culverts:

(1) the manual use of inlet and outlet controlnomographs and

(2) the use of computer system such as HY8

Culvert Analysis Microcomputer Program.


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The use of nomographs requires a trial and error

solution and Inlet and Outlet Control,

Inlet Control If the culvert is operating on a steepslope it is likely that the entrance geometry will

control the headwater and the culvert will be on

inlet control.Outlet Control If the culvert is operating on a

mild slope, the outlet characteristics will probably

control the flow and the culvert will be on outletcontrol. (Drainage manual 2000)


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HW=H+ho-LS,

ho=1/2(critical depth+D),

Q=AV,List design data:

Q = discharge

L = culvert lengthS = culvert slope

TW = tailwater depth

V = velocity for trial diameter

Ke= inlet loss coefficientD= diameter

HW=headwater


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Type of structure Design of entrance Coefficient

value ke

Box, reinforced

concrete

Wingwalls parallel(extension of side),square

edged at crown 0.7

Wingwalls at 10 to 25 degree to barrel, square

at crown

0.5

Headwall parallel to embankment(no wingwalls)

Square edged on 3 edgesRounded on 3 edges to radius of 1/12 barrel

diamension

Beveled edges on 3 sides

0.5

0.2

0.2

Wingwalls at 30 to 75 degree to barrel

Crown edge rounded to radiounof 1/12mbarreldimension

Beveled top edge

Square edge crown

0.2

0.2

0.4

Side or slope tapered inlet 0.2

Entrance loss coefficient, ke for outlet control, full or partly full


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Run-off Coefficient

Type of the surface Value of run-off coefficient

1 Bituminous and cement concrete pavement 0.8-0.9

2 Gravel and WBM pavement 0.35-0.70

3 Impervious soil 0.4-0.65

4 Soil covered with turf 0.3-0.55

5 Pervious soil 0.05-0.3

The value of run-off coefficient C depends mainly on the type of surface and its slope as

show in the table below;

When the drainage area Ad consists of several types of surfaces with run-off coefficientsc1, c2, c3, with their respective areas A1, A2, A3, the weighted value of run-off

coefficient C is determined from;

C=(A1C1A2C2A3C3..)/(A1A2A3.)


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Allowable velocity {v}

Material of the drainage Maximum limiting velocity

Cast iron pipe 3.5-4.5 m/s

Earthen channel 0.6-1.2m/s

Brick sewer pipe 1.5-2.5m/s

Stone ware sewer pipe 3.0-4.5m/s

Concrete sewer pipe 2.0-3.0m/s

The velocity of unlined channel must be high enough to prevent silting and it should notbe too high as to cause erosion. The allowable velocity of flow depends on the soil type


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Mannings roughness coefficient value n-

Type of culvert Roughness or corrugated Mannings value

Concrete culvert Smooth 0.010-0.011

Concrete box Smooth 0.012-0.015

Spiral rip metal pipe Smooth 0.012-0.013

Corrugated polyethylene smooth 0.009-0.015

Corrugated polyethylene Corrugated 0.018-0.025

Polyvinyl chloride PVC Smooth 0.009-0.011


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Data collection

The following data are required; Leveling data

Rainfall data

Catchment area


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LEVELING DATALevelling

is the process of measuring the difference in elevationbetween two or more points.

Levelling work is carried out side by side to give thecenterline profile and typical cross section. The equipmentused in leveling works are leveling staff, Dum level,wooden pags,measuring tape.

The leveling work was taken along the whole roadsegment 150m. It was commenced from the TBM locatedat small topplate of a pipe culvert along the road. The

readings were taken at interval of 20m at the centre lineof the road and on right and left hand side of the existingroad. The rise and fall method was used to compute thereduced level which is used to draw the longitudinalprofile of road.

LEVELING DATA


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LEVELING DATACHAINAGE BS IS FS RISE FALL RL REMARKS

TBM 1.485 100

0+000 1.720 0.235 99.765 RIGHT

1.740 0.020 99.745 CENTRE

1.700 0.040 99.785 LEFT

0+020 1.820 0.120 99.665 RIGHT

1.760 0.060 99.725 CENTRE

1.800 0.040 99.685 LEFT

0+040 1.610 0.190 99.875 RIGHT

1.700 0.090 99.785 CENTRE

1.820 0.120 99.665 LEFT

0+060 1.750 0.065 99.730 RIGHT

1.770 0.020 99.710 CENTRE

1.780 0.010 99.700 LEFT

0+080 1.501 0.28 99.980 RIGHT


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CHAINAGE BS IS FS RISE FALL RL REMARKS

2.420 1.530 0.030 99.950 CENTRE

1.601 0.820 100.770 LEFT

0+100 2.170 0.570 100.200 RIGHT

2.100 0.070 100.270 CENTRE

2.089 0.011 100.281 LEFT

0+120 1.380 0.709 100.990 RIGHT

1.540 0.140 100.850 CENTRE

1.600 0.060 100.790 LEFT

0+140 1.010 0.590 100.380 RIGHT

0.390 0.620 102.000 CENTRE

0.210 0.810 102.810 LEFT

0+160 1.540 1.330 101.480 RIGHT

1.890 0.350 101.130 CENTRE

1.960 0.070 101.060 LEFT

Longitudinal profile


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000 0+020 0+040 0+060 0+080 0+100 0+120 0+140

Longitudinal profileFigure; Longitudinal profile


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Rain fall intensity i, dataRain fall intensity

The design value of the rain fall intensity (i) is to be determined for the expected

duration of storm water to flow the remotest point in drainage area to the drain inletwhich is estimated using the Time flow inlet chart. The time for water to flow throughthe drain between inlet and outlet points is determined based on the allowable velocityof flow in the drain, generally ranging from 0.3-1.5m/sec, depending on the soil type.The time of concentration or the duration of storm for design may be taken as the suminlet time and time of flow through the drain. The frequency of occurrence of the stormor the return period may taken as 5; 10; 25; or 50 years.

Consider the following equation for the determination of the rain fall intensity;T2= L/V (in sec)

T= T1+T2T = time of concentration or design value of rain fall duration

T1= Inlet time

T2= time of flow

L= length of the drainV= Allowable Velocity of flow.

With known value of coefficient of run off C and the Drainage area Ad, from the graph ofrain fall intensity duration frequency curve, the rain fall intensity (i) is found in mm/seccorresponding to duration T and frequency of return period.


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DAR PORT MONTHLY RAIINFALLYear Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2001 105.7 192.4 170.9 237.4 254.8 10.9 6 15.3 12.5 3.7 16.1 87.32002 98.2 61.7 49.2 595.9 42.6 2.6 44.2 79.9 27 47.5 43.6 125.32003 56.1 49.7 68 70.3 133.9 73.1 12.1 10 3.8 22.8 39.5 40.92004 52.7 135.1 53.4 143.4 36.1 41.7 3.3 3.5 66.1 127.7 45.5 172.32005

93.3

2.1

71

138.7

408.5

8.3

9.2

25.6

10.3

13.1

45

10

2006 9.4 28.1 269.4 243.1 109.4 189.3 9 21.3 13.4 52.9 151.9 214.52007 10.2 20.9 140.2 190.8 219.9 28.5 11.2 42.3 2.3 5.9 73.8 18.92008 45.5 52.2 112.5 227.6 169.5 30.4 2.1 18.7 35.4 67 137.3 7.72009 65.4 49.6 51.7 197 16.7 16.9 2.9 2.5 0.5 17.6 7.4 32.82010 52.3 54.1 77.7 353.4 74.1 21.8 5.8 15.9 20.7 0 45.6 88.12011 9.5 34.4 40.6 205.1 72.2 13.2 3.7 19.9 38.3 22.7 77 235.12012 3.6 31.1 84.1 210.4 97.5 7.8m 8.1m m m m


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RAINFALL INTENSITY IN mm/hr

15 MIN 30 MIN 1 HR 2 HRS 3 HRS 6 HRS 12 HRS

2 YRS 92.08 65.04 42.78 23.66 16.62 9.50 4.99

5 YRS 117.48 84.18 57.02 31.61 21.92 12.77 7.49

10 YRS 134.32 96.84 66.44 36.87 25.42 14.93 7.91

25 YRS 155.60 112.84 78.35 43.52 29.85 17.67 9.37

50 YRS 171.40 124.72 87.19 48.45 33.13 19.70 10.46

100 YRS 187.08 136.50 95.96 53.34 36.39 21.71 11.54


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Catchment Area(Ad)Drainage area(the area which drains rainfall into drainage)consists of;

1 pavement area

2 area of the adjoining land

3 area of land on the other side of drain, with therecorresponding value of run-off coefficient C.

From Chainage 0+00 to 0+150

Length of road(the length of the stretch of land parallel tothe road from where water is expected to flow to theculvert)=150m

Therefore drainage area consists of:-A half width of Carriageway 3.4m, C=0.8

Width shoulder 1.35m, C=0.8

Drainage Area (Ad)=


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CATCHMENT AREA (Ad)

Drainage area (the area which drains rainfall into drainage)consists of;

1 pavement area


3 area of land on the other side of drain, with theircorresponding value of run-off coefficient C.

From Chainage 0+00 to 0+150

By using Simpsons rule the Drainage Area (Ad) = h/3(ho +hn4*even+ 2*odd+)

= 20/3 (50.8+32.4) +4(79.8+15.2+21.8+32.4) +2(17.7+101.3)Drainage Area (Ad) =5746.7m

2

DATA ANALYSIS


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DATA ANALYSIS THE LENGTH, WIDTH AND THE HEIGHT OF THE EXISTING CULVERT.

The culvert which is current not sufficient with the quantity of water flowing through its

Length = 8.5m,

Width = 3m,

Height = 3m

RUN OFF COEFFICIENT

The value of run off coefficient C

This determined by the type of material to be used to construct the culvert, which isconcrete material ranging from 0.3 - 0.55

Therefore run off coefficient C = 0.4

CATCHMENT AREA (Ad)

Drainage area (the area which drains rainfall into drainage) consists of;

1 pavement area


3 area of land on the other side of drain, with their corresponding value of run-offcoefficient C.

From Chainage 0+00 to 0+150By using Simpsons rule the Drainage Area (Ad) = h/3(ho hn4*even+ 2*odd+)

= 20/3 (50.8+32.4) +4(79.8+15.2+21.8+32.4)+2(17.7+101.3)

Drainage Area (Ad) =2593788.7m2

HYDROLOGIC ANALYSIS


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HYDROLOGIC ANALYSIS This involves determining three parameters which are used in calculating quantity

of water (Q) to be drain according to the following equation:

Q=C*I*A

Determination of Rainfall intensity (I)

T1 = 27 min, the drain inlet is estimated using the Time flow inlet chart.

T2= L/v =8.5/2*60

=0.071min

The time of concentration or the duration of storm for design may be taken as thesum inlet time and time of flow through the drain

Tc = 27+0.071= 27 min

Quantity of run off

From the rationale formula

Q= C i Ad

C=0.4

I =161mm/hrAd=2593789m

2

Q= (0.4 x 161 x 2593789 x 10-3)/3600

=34.8m3/sec

=35m3/sec

CROSS SECTIONAL AREA OF THE


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CROSS SECTIONAL AREA OF THE

CULVERT

Q =A V

A = Q/V

V= 2m/sec

Q =35m3/sec

A =35/2

=17.5

Cross sectional area of the culvert =18m2

The designed width and height of the culvert which will the

sufficient to convey water across the Kijichi road;Width = 6m

Height = 3m and the length of 8.5m.


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Designing of the culvert


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REFERENCE

Drainage Manual. (2000).

Craig, F. R. (2004). Soil Mechanic,3rd Edition.

KHANNA, S. K. (1991). Highway Engineering. 7th

Edition: Nem Chand & Bros, Civil lines.

Schofield, W. (n.d.). Engineering Survey 5th Edition.

Tanzania Work Ministry (1999). Tanzania Pavement

and Material design.

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Gad Loi Mini 2 . Presentation