JU, DEPARTMENT OF CIVIL ENGINEERING

Table of content

CONTENT PAGE

PART ONE: GEOMETRIC DESIGN

CHAPTER ONE:-Fundamentals of geometric design-------------------------------------

CHAPTER TWO:-Cross-section elements------------------------------------------------
CHAPTER THREE:-Horizontal Alignment-------------------------------------------------
3.1 Sight Distance----------------------------------------------------------
3.2 Design Speed ----------------------------------------------------------
3.3 Design of Horizontal curve---------------------------------------------------
3.4 Spiral curves----------------------------------------------------------------------
3.5 Super elevation-------------------------------------------------------------
3.6 Widening--------------------------------------------------------------------
CHAPTER FOUR:-Vertical Alignment-------------------------------------------------------
4.1Vertical Curves--------------------------------------------------------
4.2 Vertical Gradient ---------------------------------------------------------
CHAPTER FIVE:- Earthwork and Quantity----------------------------------------------
5.1Earthwork quantities---------------------------------------------------
5.2 Mass-haul Diagram---------------------------------------------------
PART TWO: STRUCTURAL DESIGN OF PAVEMENT
CHAPTER SIX:-Pavement design

6.1. Introduction to the Pavement Design Process--------------------

6.2. Pavement Types, Definitions, and Abbreviations---------------

INTEGRATED CIVIL ENGINEERING DESIGN II Page 1

 JU, DEPARTMENT OF CIVIL ENGINEERING

6.3. Pavement Design Terms and Definitions-----------------------------

6.4. Determination of design Period----------------------------------------

6.5. Traffic---------------------------------------------------------------------

6.6. Determination of economical pavement structure---------------------------

PART THREE: DRAINAGE DESIGN

CHAPTER: SEVEN----------------------------------------------------
PART FOUR: TRAFFIC MARKINGS
CHAPTER: EIGHT-------------------------------------------

Conclusion
Limitation
Recommendation
Appendixes
References

INTEGRATED CIVIL ENGINEERING DESIGN II Page 2

 JU, DEPARTMENT OF CIVIL ENGINEERING

PART ONE: GEOMETRIC DESIGN

CHAPTER ONE

FUNDAMENTALS OF GEOMETRIC DESIGN

Geometric design is an essential component in the design development of highway. It is

the process whereby the layout of the road through the terrain is designed to meet the needs of
the users. The principal geometric features are the road cross-section components, horizontal and
vertical alignment, sight distance, etc. Geometric aspect of the route is designed to provide a
safe, accident free and comfortable road for drivers.

Hence, the location of the road should compromise the facts that it should be short,
economical, easy and safe for construction, maintenance and operation. It is also necessary to
mention that taking the volume and composition of traffic in to account should be made in
selecting the design standard for the road.

1.1. Elements of geometric design

The most important part of highway design is geometric design to give safe and comfortable
road way to the driver and the passenger. Geometric design has the following elements

 Horizontal alignment
 Sight distance
 Vertical alignment
 Maximum gradient and length of maximum gradient
 Length of vertical curves
 Cross section
 Width of carriage way and shoulders
 Super elevation

INTEGRATED CIVIL ENGINEERING DESIGN II Page 3

 JU, DEPARTMENT OF CIVIL ENGINEERING

Design elements are influenced by the following factors:

 Road type
 Terrain
 Design speed
 Traffic volume
 Vehicle characteristics
 Economy

1.1.1 Road type

According to ERA geometric manual 2002 there are five types of roads and the
classification of them depends on the importance of the towns/city they connect.
 Class I roads(Trunk roads)-connects centers of international importance with
Addis Ababa having first year AADT>1000
 Class II roads (Link roads)-connects principal towns and urban centers each other
having first year AADT of 50-1000.
 Class III roads (Main-Access roads)-links centers of provisional importance each
other. First year AADT is between 30 and 1000.
 Class IV roads (Collector roads)-links locally important centers to each other or to
a more important center or to higher class roads. First year AADT is between 25
and 400.
 Class V roads (Feeder roads)-any road link to minor center such as markets and
local locations. First year AADT is of 0-100.

The road we are going to design connects JIMMA with BONGA and categorized under Class
III roads (Main-Access roads).

1.1.2. Terrain

The geometric design element of a road strongly depends on the transverse terrain through which
the roads passes. Generally terrain properties are categorized in to four different classes: Flat,
rolling, mountainous, and escarpment, the terrain being flat leads to higher design speed and
mountainous leads to smaller design speed. The different classes are described as follows

INTEGRATED CIVIL ENGINEERING DESIGN II Page 4

 JU, DEPARTMENT OF CIVIL ENGINEERING

Flat – Flat or gently rolling country, which offers few obstacles to the construction of road,
having continuously suitable as well as comfortable situation for vertical and horizontal
alignment. Accordingly, the design speed is higher than the other terrains in a way that the
terrain provide safe environment to drive without threat.

The terrain transverse slope is up to 5 %

Rolling – Rolling, hilly or foothill country where generally rise and fall moderately and
occasional steep slopes are encountered, resulting in some restrictions in alignment and reduce
the design speed.

The terrain transverse slope ranges from 5% to 25%

Mountainous – includes Rugged, hilly and mountainous country and river gorges. This class of
terrain imposes definite restrictions on the standard of alignment obtainable and often involves
long steep grades and limited sight distance because of the obstruction of the topography. This
condition reduces the design speed of mountainous terrain considerably. The transverse terrain
slope varies from 25% to 50 %.

Escarpment – In addition to the terrain classes given above, a fourth class is added to catch to
those conditions where by the standards associated with each of the above types cannot be met.
We refer to escarpment situations inclusive of switchback road way sections inclusive of switch
back road way sections or side hill transverse sections where earthwork quantities are
considerable with transverse slope in excess of 50%.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 5

 JU, DEPARTMENT OF CIVIL ENGINEERING

Terrain type Transverse terrain slope (%)

Flat 0-5
Rolling 5-25
Mountainous 25-50
Escarpment >50

Table: terrain classification (source ERA manual)

In our project, we have taken elevation of points at each station from the given topographic map.
Elevation of points at the center of the road and at 5m, 10m, and 15m to the right and left of the
center are taken. Based on the transverse slope of the terrain at each station we classify the
project road as flat, rolling and mountainous as per ERA.

The detailed classification is shown by the table below.

FROM TO TERRAIN TYPE

0+00 1+00 flat
1+00 3+60 rolling
3+60 5+10 flat
5+10 8+20 rolling
8+20 8+80 mountainous
8+80 9+20 rolling
9+20 9+70 mountainous
9+70 12+20 rolling
12+20 13+80 flat

INTEGRATED CIVIL ENGINEERING DESIGN II Page 6

 JU, DEPARTMENT OF CIVIL ENGINEERING

Our road pavement passes through terrain composed of flat, rolling and mountainous.

Terrain Terrain

Chainage conditions Chainage conditions

0+20 flat 4+40 flat

0+40 flat 4+60 flat

0+60 flat 4+80 flat

0+80 flat 4+90 flat

1+00 flat 5+00 flat

1+20 rolling 5+10 flat

1+40 rolling 5+20 rolling

1+60 rolling 5+30 rolling

1+80 rolling 5+40 rolling

2+00 rolling 5+50 rolling

2+20 rolling 5+60 rolling

2+40 rolling 5+70 rolling

2+60 rolling 5+80 rolling

2+80 rolling 5+90 rolling

3+00 rolling 6+00 rolling

3+20 rolling 6+10 rolling

3+40 rolling 6+20 rolling

3+60 rolling 6+30 rolling

3+80 flat 6+40 rolling

4+00 flat 6+50 rolling

4+20 flat 6+60 rolling

INTEGRATED CIVIL ENGINEERING DESIGN II Page 7

 JU, DEPARTMENT OF CIVIL ENGINEERING

Chainage Terrain conditions Chainage Terrain condition

6+70 Rolling 9+80 rolling
6+80 Rolling 9+90 rolling
6+90 Rolling 10+00 rolling
7+00 Rolling 10+20 rolling
7+10 Rolling 10+40 rolling
7+20 Rolling 10+60 rolling
7+30 Rolling 10+80 rolling
7+40 Rolling 11+00 rolling
7+50 Rolling 11+10 rolling
7+60 Rolling 11+20 rolling
7+80 Rolling 11+30 rolling
7+90 Rolling 11+40 rolling
8+00 Rolling 11+50 rolling
8+10 Rolling 11+60 rolling
8+20 Rolling 11+70 rolling
8+30 mountainous 11+80 rolling
8+40 mountainous 12+00 rolling
8+50 mountainous 12+10 rolling
8+60 mountainous 12+20 rolling
8+70 mountainous 12+30 flat
8+80 Rolling 12+40 flat
8+90 Rolling 12+50 flat
9+00 Rolling 12+60 flat
9+10 Rolling 12+70 flat
9+20 mountainous 12+80 flat
9+30 mountainous 13+00 flat
9+40 mountainous 13+20 flat
9+50 mountainous 13+40 flat
9+60 mountainous 13+60 flat
9+70 Rolling 13+80 flat

INTEGRATED CIVIL ENGINEERING DESIGN II Page 8

 JU, DEPARTMENT OF CIVIL ENGINEERING

1.1.3. Design speed

Design speed is the maximum safe speed that can be maintained over a specified section of
highway when conditions are so favourable that the design features govern. It is the most
important factor controlling the geometric design element of a highway.

The choice of design speed is governed primarily by topography, traffic volume, function and
class of highway, etc. For each terrain characteristics, type of road and traffic volume ERA
recommends a list of maximum design speed.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 9

 JU, DEPARTMENT OF CIVIL ENGINEERING

1.1.4. Traffic volume and characteristics

The development of design standard of the road in particular the design speed is influenced by
volume and composition of traffic. Traffic indicates the need for improvement and directly
affects features of design such as width and number of lanes, alignments and gradients. It is not
only the volume of traffic that affects the design speed. ERA classifies vehicles into five groups.

1.1.5. Economy

Economy is also the other factor that controls of the design of highway. The alignment and
gradient of the road preferred to be economical.

Based on the above facts the design of this project is proceeds by using DS4 and different types
of terrain condition which varies with the location of the points.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 10

 JU, DEPARTMENT OF CIVIL ENGINEERING

CHAPTER TWO

CROSS-SECTION ELEMENTS

Features which define the space available for effective vehicle movement are known as Cross-
section elements. The choice of these parameters is related to traffic flow, traffic composition,
pedestrian and non-motorized traffic needs.

The cross sectional elements of the highway include the travelled way, shoulders, curbs,
medians, side slopes and back slopes, clear zone, pedestrian facilities, bicycle facilities.

Lane

Lane width refers to the paved width of the road, which can carry the design vehicle traffic. The
design depends upon number of important factors which are; design traffic, lane capacity,
maximum overall width of vehicle, clearance between the edges of the road way and the body of
the vehicle and clearance between two vehicles placed in the transverse direction. Based on ERA
manual 2002, the recommended lane width for this project is 7m.

Shoulder

INTEGRATED CIVIL ENGINEERING DESIGN II Page 11

 JU, DEPARTMENT OF CIVIL ENGINEERING

Shoulder is a portion of highway which lies between outer edges of the travel lane and side
slope. Some important advantages of shoulder are:-

1. Provide a space for emergency stopping (temporary parking) of vehicle

2. Maintenance operation and design
3. Improving sight distance and highway capacity
4. Provide structural support for the pavement

As per ERA design manual 2002, the shoulder width for our project is 1.5m

Formation width

The formation width is the total width of the pavement and shoulders. The formation width in
our project is:-

7m+2*1.5m=10m

Side and back slopes

On fill the side and back slopes are used to provide stability and safety for the road way.

ERA design manual 2002 recommends the side slopes for use in the design based on the height
of the fill and cut and soil type.

(1) HINGE POINT

CARRIAGEWAY (2) SIDESLOPE

(5) BACKSLOPE

(4) DITCH BOTTOM

SHOULDER

(3) TOE OF SLOPE

INTEGRATED CIVIL ENGINEERING DESIGN II Page 12

 JU, DEPARTMENT OF CIVIL ENGINEERING

The table below indicates the side slope ratios recommended for use in the design according to the height
of fill and cut, and the material.
Material Height of Slope Side Slope Back Slope Zone Description

Cut Fill
Earth or Soil 0.0 - 1.0m 1:4 1:4 1:3 Recoverable
1.0 - 2.0m 1:3 1:3 1:2 Non-recoverable
Over 2.0m 1:2 1:2 1:1.5 Critical
Rock Any height See Standard Details Critical
Black Cotton Soil* 0.0 - 2.0m - 1:6 - Recoverable
Over 2.0m 1:4

Cross slope

For highway with two lanes or more, the road way usually is sloped from the middle of the road
way downward towards the opposing edges. Opposing cross slopes have the advantage of being
able to drain the roadway quickly during a heavy storm which requires installation of drainage
facilities on both sides of the roadway. The design of cross slope is based on the necessity of
adequate drainage and driven safety. A cross slope that is too flat will not drain properly and one
that is too steep can course vehicle to drift toward the edge of the pavement.

Right of way

Right of way is the entire area needed for construction, drainage and maintenance of a highway
as well as for access to and exit from the highway.

An achievement of many of the desirable design features, such as flatter slope and proper
drainage facilities is facilitated by procurement of sufficient of right of way.

In addition, acquisition of sufficient right of way allows future highway expansion to

accommodate larger traffic volumes. As a minimum, however, the size of the right of way
acquired for a highway should be at least that required for incorporation of all elements in the
design cross section and the appropriated boarder areas.

As per ERA 2002 design manual, the right of way width recommended is 50m.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 13

 JU, DEPARTMENT OF CIVIL ENGINEERING

CHAPTER THREE

HORIZONTAL ALIGNMENT

The design elements of the horizontal alignment are the tangent and curves. Curves are provided
at changes in direction to have smooth transition between tangents.

The alignment should enable consistent, safe and smooth movement of vehicle operating at a
given design speed. While doing the road alignment the safety is improved by providing enough
sight distance.

3.1. SIGHT DISTANCE

The design of a highway must be provided with adequate sight distance for a safe vehicle
operation. The distance along road surface at which a driver has visibility of objects stationary or
moving at a specified height (usually 1.04m) above the road surface is known as Sight distance. .
Sight distance is of two types.

 Stopping sight distance

 Passing sight distance

3.1.1. STOPPING SIGHT DISTANCE

Stopping sight distance is the distance required by a driver of a vehicle travelling at a given
speed to bring his vehicle to stop after an object on the road way becomes visible. It is the sum of
the braking distance and the distance traversed during the brake reaction time. The stopping sight
distance on a roadway must be sufficient long enough to enable a vehicle traveling at the design
speed to stop before reaching a stationary object in its path. The minimum requirement stopping
sight distance is given by

INTEGRATED CIVIL ENGINEERING DESIGN II Page 14

 JU, DEPARTMENT OF CIVIL ENGINEERING

2
V
d=(0 .278 )(t )(V )+
254 f

Where d=distance (meter)

t = driver reaction time, generally taken to be 2.5 seconds

V =initial speed (km/h)

f =coefficient of friction between tires and roadway

For different terrain type different design speed is given. This also corresponds to the radius
provided.

Design Speed Coefficient of FrictionStopping Sight Passing Sight

(f) Distance (m) Distance (m)
(km/h)
from formulae

20 0.42 20 160

30 0.40 30 217

40 0.38 45 285

50 0.35 55 345

60 0.33 85 407

70 0.31 110 482

85 0.30 155 573

100 0.29 205 670

120 0.28 285 792

INTEGRATED CIVIL ENGINEERING DESIGN II Page 15

 JU, DEPARTMENT OF CIVIL ENGINEERING

Table: Minimum sight distance (ERA manual)

Some calculation are given below for different design speed criteria

2
V
d=(0 .278 )(t )(V )+
254 f

For design speed of 70 km/h

t=2.5 seconds

f=0.31

d= (0.278)*2.5*70+702/254*0.31=110.8801245m

V2
d=(0 .278 )(t )(V )+
254 f

For design speed of 60 km/h

t=2.5 seconds

f=0.33

d= (0.278)*2.5*60+602/254*0.33=84.64917681m

Available sight distances at curves must be greater than the given recommendations. In our case

Available sight distance=2RsinӨ

For curve one=2(175m)(sin44.5)

=245.32m

This is greater than the minimum required stopping sight distance=110m

For curve two=2(125m)(sin45.5)

INTEGRATED CIVIL ENGINEERING DESIGN II Page 16

 JU, DEPARTMENT OF CIVIL ENGINEERING

=178.32m

This is greater than the minimum required stopping sight distance=85

For curve three=2(200m)(sin26)

=175.35m

This is greater than the minimum required stopping sight distance=110

3.1.2. PASSING SIGHT DISTANCE

Passing sight distance is the minimum sight distance on two-way two-lane roads that must be
available for the driver of one vehicle to pass another vehicle safely without interfering with the
speed of the oncoming vehicle. The passing sight distance is the length of the roadway that the
driver of the passing vehicle must be able to see initially, in order to make a passing maneuver
safely and comfortably. It is considered only on two-lane roads and the capacity of a two- lane
roadway is greatly increased if a large percentage of the roadway’s length can be used for
passing. For horizontal curves, it may be necessary to remove obstructions and widen cuttings on
the insides of curves to obtain the required sight distance.

The passing sight distance is generally determined by a formula with four components, as
follows:

d1 = initial maneuver distance, including a time for perception and reaction

d2 = distance during which passing vehicle is in the opposing lane

d3 = clearance distance between vehicles at the end of the maneuver

d4 = distance traversed by the opposing vehicle

d1 = 0.278 t1 (v – m + a t1/2)

INTEGRATED CIVIL ENGINEERING DESIGN II Page 17

 JU, DEPARTMENT OF CIVIL ENGINEERING

Where

t1 = time of initial maneuver, take 4 sec

a = average acceleration, take 2.4km/h/s

v = average speed of passing vehicle, km/h

m = difference in speed of passed vehicle and passing vehicle, take 15km/h

d2 = 0.278 vt2

Where

t2 = time passing vehicle occupies left lane, s

v = average speed of passing vehicle, km/h

d 3 = safe clearance distance between vehicles at the end of the maneuver, is

dependent on ambient speeds as per Table below.

Speed Group 50-65 66-80 81-100 101-120

(km/h)

d3 (m) 30 55 80 100

Speed group and d3

d4 = distance traversed by the opposing vehicle, which is approximately equal to d 2 less

the portion of d2 whereby the passing vehicle is entering the left lane, estimated at:

d4 = 2d2/3

The minimum Passing Sight Distance (PSD) for design is therefore:

PSD = d1 + d2 + d3 + d4

For different value of design speed different value of PSD calculated as follows.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 18

 JU, DEPARTMENT OF CIVIL ENGINEERING

For design speed of 70 km/h

d1 = 0.278 t1 (v – m + a t1/2)

Take t1 =4 second

a =2.4 km/h/s

m =15 km/h

d1 = 0.278*4(70 – 15 + 2.4*4/2)=66.4976m

d2 = 0.278 vt2

Take t2=10s

v=70km/h=70*.278=19.46m/s

d2=.278*19.46*10=54.1m

d3=80 [from table]

d4=2d2/3

=2*54.1/3=36.1

d=d1+d2+d3+d4 =66.4976+54.1+80+36.1=236.67m

For design speed of 60 km/h

d1 = 0.278 t1 (v – m + a t1/2)

Take t1 =4 second

a =2.4 km/h/s

INTEGRATED CIVIL ENGINEERING DESIGN II Page 19

 JU, DEPARTMENT OF CIVIL ENGINEERING

m =15 km/h

d1 = 0.278*4(60 – 15 + 2.4*4/2)=55.3776m

d2 = 0.278 vt2

Take t2=10sec

v=60km/h*0.278=16.68

d2=0.278*16.68*10=46.36m

d3=55 m [from table]

d4=2d2/3

=2*46.36/3=30.91m

d=d1+d2+d3+d4 =55.38+46.36+55+30.91=187.65m

Available sight distance for the first curve is 245.32m (calculated above) this is greater than the
required passing sight distance (236.67m).

Available sight distance for the second and third curves is less than the required passing sight
distance. Hence provide markings (traffic signs) to aware the driver not to pass over.

Alignment of tangents and curves

The horizontal alignment consists of straight road way sections (tangents) connected by
horizontal curves, which have normally circular curves with or without transition (spiral) curves.
The basic feature of horizontal alignment includes minimum radius, transition curves, super
elevation and sight distance.

In this sub topic tangents, minimum radius, design speed, horizontal curves and super elevation
which are considered while designing the horizontal alignment will be presented.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 20

 JU, DEPARTMENT OF CIVIL ENGINEERING

Tangents

According to its geometric definition a tangent (straight) section is the shortest distance between
two points. Straight section is advantageous because it has no centrifugal force on
implementation of steering movement are needed and it is also economical

Even though straight sections have the above mentioned advantages, long tangent sections
increases the danger from head height glare and usually land to excessive speeding. According to
ERA Geometric design manual, the length of a tangent section should not exceed 4.0 Kilometers.
But due to the land features of the project road, tangent with length greater than 4 Kilometers is
not encountered.

3.2. DESIGN SPEED

The design speed is used as an index which links road function, traffic flow and terrain to
the design parameters of sight distance and curvature to ensure that a driver is presented with a
reasonably consistent speed environment.

Design elements such as lane and shoulder widths, horizontal radius, super elevation, sight
distance and gradient are directly related to, and vary with design speed. Thus all of the
geometric design parameters of a road are directly related to the selected design speed.

By considering different guidelines ERA defines the maximum safe design speed for different
terrain section as shown in table. For this project, the design speeds are as shown in the table
below.

Table: Design speed

Terrain Flat Rolling mountainous

INTEGRATED CIVIL ENGINEERING DESIGN II Page 21

 JU, DEPARTMENT OF CIVIL ENGINEERING

Design 85 70 60
speed, Km/hr

However a design speed of 60 Km/hr is used to provide a radius that suits the existing terrain and
avoid the excessive cut and fill.

Minimum Radius

When a vehicle moves in circular path, it is forced radially outward by centrifugal force. The
centrifugal force is counter balanced by super elevation of the roadway and/or the side friction
developed between the tires and the road surfaces. For the calculation of minimum radius, the
following equation is adopted.

VD2
R min =
127 ( e+ f )

Where, VD = Design Speed (Km/hr)

e = Maximum supper elevation (%/100)

f = Side friction coefficient

From ERA Geometric design manual the maximum super elevation for rural road with any
terrain type is 8%. Side friction coefficients are dependent on vehicle speed, type, condition and
texture of road way surface, weather conditions, and type and condition of tires. But based on the
results of several studies ERA Geometric design manual provides the following coefficient of
friction for different design speed.

Table: Coefficient of Friction

Design speed, Km/hr) 60 70

Side friction factor (f) 0.15 0.14
INTEGRATED CIVIL ENGINEERING DESIGN II Page 22
 JU, DEPARTMENT OF CIVIL ENGINEERING

The design speed in DS4 for rolling terrain is 70Km/h. The minimum radius of horizontal curve
in this area

Vd 2
R=
127(e +f )

e=0.08

Vd=70Km/h

f= 0.14

R= 173.6m

Rprovided= 175m

The calculated R value is lower limit that is possible to be provided. So that the safety of the
traffic is not impaired.

For mountainous area the maximum design speed is 60Km/h for DS 4 then the minimum value of
the radius of horizontal curve

Vd 2
R=
127(e +f )

e=0.08

Vd=60Km/h

f= 0.15

R= 123.4m

Rprovided= 125m

For all terrains it is safe to provide R greater than Rminimum

INTEGRATED CIVIL ENGINEERING DESIGN II Page 23

 JU, DEPARTMENT OF CIVIL ENGINEERING

3.3. DESIGN OF HORIZONTAL CURVES

Horizontal curves are provided between tangents to provide smooth transition. In horizontal
alignment the use of compound curve, reverse, broken back and switch back should be avoided
except where very unusual topographic or right-way condition dictates the use of these curves.
Having a design speed, the radius of curves is selected based on a minimum radius that can suit
the existing terrain.

According to ERA Geometric design manual, transition curves are a requirement for trunk and
link road segments having a design speed of equal to or greater than 80 Km/hr. Although the
design speeds are reduced to 60 Km/hr in reverse curve and broken back curve, spiral curves are
provided because the curves are very sharp and providing these curves makes the driver to pass
the curve safely and smoothly.

Spiral curves are also advantageous because they fit the transition length needed to develop the
full design super elevation without the need to develop any transition on the adjacent tangent
sections.

ERA recommends employing Euler spiral, which is also known as the clothoid, for calculation of
horizontal curve with transition. All the curves are designed using the following formulas.

3.4. SPIRAL CURVES

Chainage of point of inter section for the users first curve=6+36.24

Terrain type =rolling

Design speed=70km/hr

Angle of deflection =89⁰

Radius of the curve=175m

INTEGRATED CIVIL ENGINEERING DESIGN II Page 24

 JU, DEPARTMENT OF CIVIL ENGINEERING

Δ
Tangent length=R tan
2

89
=175 tan
2
= 171.97m

Changing of pc1 =chainage of point of intersection-tangent length

=6+36.24-171.97=4+64.27

Design of the first spiral curve

1
“A” can be assumed for and value between R and R
3

1
A is spiral parameter and constant for a given spiral curve= * 175 =58.3 and 175
3

Take A= 80

L*R=A2

L=length of spiral curve

R=radius of spiral curve at length L

A 2 802
L= = = 36.6m
R 175

INTEGRATED CIVIL ENGINEERING DESIGN II Page 25

 JU, DEPARTMENT OF CIVIL ENGINEERING

PI
Δ

T L ΔR

XM PT
PC τs R R
τs
Δ - 2τs

Fig: horizontal curve with transition

Pc=point of curvature

Pi=point of intersection

PT=point of tangency

∆=deflection angle

∆R =a shift of vertical curve due to the introduction of transition curve

R=Radius

T=Tangent length

L= total length of curve

l=Length of transition

INTEGRATED CIVIL ENGINEERING DESIGN II Page 26

 JU, DEPARTMENT OF CIVIL ENGINEERING

τ= spiral angle

L 36.6
For value of l = = = 0.4575
A 50

From table τ = 6.6475

Δr = 0.003975

xM = 0.228417

x = 0.453518

y= 0.015895

tk = 0.152492

tL = 0.304841

then ΔR = Δr* A = 0.318m

R- ΔR = 174.682m

XM = xM * A = 18.27m

X = x * A = 36.28m

Y = y * A = 1.28m

Length of the total curve = spiral curve + curve length

= 36.6 * 2 + 271.34

= 344.54m

Total chainage at the end of the curve = chainage of PI – tangent length – XM + curve length

=6+ 36.24 – 171.97 – 18.27 + 344.54

= 446m + 344.54

= 7+ 90.54

INTEGRATED CIVIL ENGINEERING DESIGN II Page 27

 JU, DEPARTMENT OF CIVIL ENGINEERING

chainage

Start of transition curve 4+46

Start of simple curve 4+82.6

End of simple curve 7+53.94

End of spiral curve 7+90.51

Second curve

Chainage of point of intersection of the second curve = 9+ 19.74 m

Radius of the curve = 125m

Deflection angle =910

Terrain type = mountainous

Velocity = 60Km/h

Δ
Tangent length= R tan =127.2m
2

chainage

Point of curvature 7+92.54

Point of tangency 9+91.07

For third curve

INTEGRATED CIVIL ENGINEERING DESIGN II Page 28

 JU, DEPARTMENT OF CIVIL ENGINEERING

Chainage of point of intersection of the second curve = 10+ 62.88m m

Radius of the curve = 200m

Deflection angle 520

Terrain type = rolling

Velocity = 70Km/h

Δ
Tangent length= R tan =97.55m
2

Design of spiral curve

Assume A=120

R= 200m

L=72 l=L/A =0.6

From the table

τ = 11.459

Δr = 0.00899

Xm =0.299676

X=0.5980589

Y=0.0359168

Tk =0.200619

TL =0.40068

ΔR = Δr *A =120*0.008899 = 1.0788m

Length of the total curve = 2 *72 + 180.535 = 324.535m

INTEGRATED CIVIL ENGINEERING DESIGN II Page 29

 JU, DEPARTMENT OF CIVIL ENGINEERING

Chainage at the end of the spiral curve= Chainage of PI – tangent length – XM + curve length

=1002.88 – 97.55 – 35.96 = 324.535

=1253.905m =12 + 53.91m

Chainage

Start of spiral curve 10+27.07

Start of simple curve 10+99.07

End of simple curve 12+79.61

End of spiral curve 13+51.61

3.5. SUPER ELEVATION TRANSISITION AND SUPER

ELEVATION RUNOUT AND RUNOFF

Super elevation is a requirement for all standards of roads. However, low maximum rate of super
elevation or no super elevation is employed within important intersection areas or where there is
a tendency to drive slowly because of turning and crossing movements, warning devices and
signals.

The use of 8% super elevation is recommended for DS4 with flat, rolling and mountainous
terrain. Normally circular curves used are followed and preceded by transition lengths which
help make smoother the alignment. The user’s driving comfort is enhanced by the transition
lengths provided suitably for a given radius and design speed.

In alignment design with spirals the super elevation runoff is affected over the whole of the
transition curve. The length of runoff is the spiral length with the tangent to spiral at the
beginning and the spiral to curve at the end. The change in cross slope begins by removing the
adverse cross slope from the lane or lanes on the outside of the curve on the tangent run out.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 30

 JU, DEPARTMENT OF CIVIL ENGINEERING

Between the tangent to spiral and the spiral to curve, the traveled way is rotated about the crown
to reach the full super elevation at the curve. This procedure is reversed on leaving the curve.

In design of horizontal curves without spirals the super elevation runoff is considered to be that
length beyond the tangent run out.

The usual design practice is to place approximately two-thirds of the runoff on the tangent
approach and one-third on the curve. If length of horizontal curve can’t accommodate two-third
of the runoff length, the full super elevation starts from point of curvature.

Calculations on super elevation

For the first curve

As per ERA’s recommendation a minimum length of runoff=52m is used

INTEGRATED CIVIL ENGINEERING DESIGN II Page 31

 JU, DEPARTMENT OF CIVIL ENGINEERING

Length of run out=52*eNc/e

=52*2.5/8
=16.25m
Total length of transition=length of run out + length of runoff
=68.25m
For the second curve
Length of runoff=48m
Length of run out=48*2.5/8=15m
Total length of transition=length of run out + length of runoff
=63m
For the third curve
Length of runoff=52m
Length of run out=52*2.5/8=16.25m
Total length of transition=length of run out + length of runoff
=68.25m

3.6. WIDENING

Widening on Curves
The use of long curves of short radius should be avoided where possible, as drivers
following the design speed will find it difficult to remain in the traffic lane. If not possible
to avoid short radius curves widening is used.

Widening on curves shall be provided to make operating conditions comparable to those on

tangents. This is necessary as the wheel tracking width is increased. Curve widening is
required on all standards of roads and should be sufficient to cater for the design vehicle.
Table below gives the values to be adopted in the design. Curve Widening shall generally
be applied to both sides of the roadway. It should start at the beginning of the transition
curve and be fully widened at the start of the circular curve.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 32

 JU, DEPARTMENT OF CIVIL ENGINEERING

Widening is also required for Design Standards DS1 through DS5 at high fills for the
psychological comfort of the driver.

Radius of Curve Widening: Curve

Table: Widening Single Lane (m) Widening: Two on Curves
Curve (m)
Lanes (m)

Extra widening of >250 0.0 0.0 pavements on curves

and embankments is provided for the
120- 250 0.0 0.6
following reasons.
60-120 0.0 0.9
 Rear 40-60 0.6 1.2 wheels follow front
wheels in shorter radius.
20-40 0.6 1.5
 Trailers fitted on trucks,
don’t follow path of trucks wheels.
 In build up areas in order to have adequate sight distances.
 Psychologically drivers tend to keep greater clearances with vehicles coming from the
opposite direction and might thus move out of a lane when traversing a curve.

Extra widening is provided for two cases.

1. Widening for vehicle operation

2. Extra widening needed for Psychological reason.

For the first curve

Radius(R)=175m
For R≥ 80 m i=n∗( R−√ R ¿ ¿ 2−D2 )¿
Where D=9m(the maximum taken for truck)

INTEGRATED CIVIL ENGINEERING DESIGN II Page 33

 JU, DEPARTMENT OF CIVIL ENGINEERING

n=2
i=2*(175-√1752-92)
=0.463m
Since B=7m>6m
i=o.463<0.5m thus avoid widening

For the second curve

Radius(R)=125m
For R≥ 80 m i=n∗( R−√ R ¿ ¿ 2−D2 )¿
Where D=9m
n=2
i=2*(125-√1252-92)
=0.6488m
Since B=7m>6m
i=o.6488>0.5m thus provide widening
provide widening equal to 0.7m
Using length of widening 40m
in=(i/30L)*Ln2

For Ln<15m

L 0 3 6 9 12 15

in 0 0.0084 0.0336 0.096 0.1344 0.21

For Ln>15m &<25m

in=(i/25)*(Ln-7.5)

INTEGRATED CIVIL ENGINEERING DESIGN II Page 34

 JU, DEPARTMENT OF CIVIL ENGINEERING

Ln 15 20 25

In 0.21 0.35 0.49

For L>25
in=i-(i/30L)*(40-Ln)2
L 30 35 40

In 0.61 0.68 0.7

For the third curve

Radius(R)=200m
For R≥ 80 m i=n∗( R−√ R ¿ ¿ 2−D2 )¿
Where D=9m(the maximum taken for truck)
n=2
i=2*(200-√2002-92)
=0.4m
Since B=7m>6m

i=o.4<0.5m thus avoid widening

CHAPTER FOUR

VERTICAL ALIGNMENT
Vertical alignment defines the geometry of the highway in elevation or profile. The two major
aspects of vertical alignment are vertical curvature, which is governed by sight distance criteria
and gradient, which is related to vehicle performance and level of service.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 35

 JU, DEPARTMENT OF CIVIL ENGINEERING

Whenever there is a change of grade in the vertical plane, a vertical curve is required to
smoothen the change created. It is usually parabolic as parabolic curves provide a constant rate
of change of grade.

The vertical alignment of the road has a strong influence on the construction cost, operation cost
of vehicles using the road and the number of accidents. The vertical alignment should provide
adequate sight distances over crests and sags and should not present any sudden hidden changes
in alignment to the driver. Gradients need to be considered from the stand point of both length
and steepness and the speed at which heavy vehicles enter the gradient. They should be chosen
such that any increase in construction cost is more than offset by savings in operating costs.

A vertical curve consists of straight parts of highway (grades) with vertical curves and the design
involves:

Selection of grades
Inserting of vertical curves
Determination of maximum gradient
Determination of length of maximum gradient
Minimum stopping sight distance.
Length of vertical curves etc

During vertical alignment the following should be considered

Gradient of the route should be between the allowable maximum & minimum.
The maximum must be kept for vehicle operation and the minimum for drainage
purpose.
Critical length should be within limits.
Vertical & horizontal curves should not overlap if not possible provide the two at
the same point so as its impact on the psychology of the driver is not pronounced.
Cut & fill should be balanced. Balancing by itself is not enough as much as
possible cut and fill are reduced to a minimum.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 36

 JU, DEPARTMENT OF CIVIL ENGINEERING

Provision of adequate sight distance over all crests

Avoidance of very short sag vertical curve, i.e. minimum of 120m for new roads
Avoidance of short grade between two vertical curves
Avoidance short drop immediately before a long up grade
No mis-placing of vertical and horizontal alignment to avoid creation of hazards
and visual defects
Avoidance of combination two vertical curves in the same direction, i.e. they
should be replaced by single vertical curve.

Sight distance in vertical curves

The principal concern in designing vertical curves (mainly crest curves) is to ensure that at least
the minimum stopping sight distance is provided. Two factors affect the availability of sight
distance

1. Algebraic difference between gradients of intersecting tangents

2. Length of vertical curve

With a small algebraic difference in grades, the length of the vertical curve may be relatively
short. To obtain the same sight distance with a large algebraic difference in grades a much longer
vertical curve must be used.

For crest vertical curves

L=∆ GS 2/658--------------------for S≤L

L=2S-658/∆G-------------------for S>L

For sag vertical curves

L=∆ GS 2/(120+3.5S)--------------------for S≤L

L=2S-(120+3.5S)/∆G-------------------for S>L

Where S=Sight distance

INTEGRATED CIVIL ENGINEERING DESIGN II Page 37

 JU, DEPARTMENT OF CIVIL ENGINEERING

L=Length of vertical curve

∆G= difference between grades

In our case the first curve is crest curve having G1=-2.13%

G2=-5.54%

G3=-5.02%

L1=120m

L2=200m

Then solving for S gives the value of sight distance greater than the required for both cases.

4.1. Vertical Curve

The vertical alignment of a highway consists of straight sections of highway, grades or tangents,
connected by vertical curves. Thus, the design of vertical alignment involves the selection of
suitable grades for the tangent sections and the design of vertical curves. The vertical curvature is
governed by sight distance criteria whereas the gradient is related to vehicle performance and
level of service. In addition to the topography of the area through which the road traverses has a
significant impact on the design of the vertical alignment.

The two major aspects of vertical alignment are vertical curvature, which is governed by sight
distance criteria, and gradient, which is related to vehicle performance and level of service.
There are two types of vertical curves- summit or crest and sag or valley curves, which are
introduced at vertical grade changes.

4.2. Vertical Gradients

Gradient is the rate of rise or fall along the length of the road with respect to the horizontal and
connects two successive vertical curves. Vehicle operations on gradients are dependent on a
number of factors: severity and length of gradient, level and length of traffic and the number of
overtaking opportunities on the gradient and its vicinity.
INTEGRATED CIVIL ENGINEERING DESIGN II Page 38
 JU, DEPARTMENT OF CIVIL ENGINEERING

The grades are selected based on:

The amount of earthwork (cut/fill) should be as minimum as possible to reduce

cost.
Design speed and topographic factors.
Vehicle operating cost.
Minimum grade of 0.05% should be provided for drainage purpose.
Grades are selected as much as possible not to cause high fill.

ERA Manual stipulates desirable and absolute gradient for various terrains separately. The
maximum absolute gradient for DS4 road in the mountain and escarpment zones is 9%, whereas
desirable is 7%. For flat the desirable is 4 and 6% and for rolling terrain the desirable is 5 and
7% and accordingly the same have been followed in such sections in the course of the design
works.

Topography Maximum Gradient (%), for Design Standard

DS1 to DS3 DS4 & DS5 DS6 to DS8 DS9 DS10

D A D A D A D A D A

Flat 3 5 4 6 6 8 6 8 6 8
Rolling 4 6 5 7 7 9 7 9 7 9
Mountainous 6 8 7 9 10 12 13 15 14 16
Escarpment 6 8 7 9 10 12 13 15 14 16
Urban 6 8 7 9 7 9 7 9 7 9

Table: maximum gradient Vs design standards

INTEGRATED CIVIL ENGINEERING DESIGN II Page 39

 JU, DEPARTMENT OF CIVIL ENGINEERING

Crest curves

Crest curves are provided where a rising-falling gradient encountered or falling more falling
gradient occurs. The minimum length of vertical curves can be calculated using a formula based
on comfort and stopping sight distance requirement and the governing one can be used.
According to ERA 2002 manuals, for lower standard roads (DS6-DS10), no minimum length
should be specified.

(Source: ERA Geometric Design Manual-2002)

Table: Minimum Values for Crest Vertical Curves

In determining the length of the curve the following points are taken in to account

sight distance (both stopping and passing )

class of highway (DS4)
topography (mountainous in our case)
Curvature
general appurtenance

Sag curves

INTEGRATED CIVIL ENGINEERING DESIGN II Page 40

 JU, DEPARTMENT OF CIVIL ENGINEERING

Sag curves are provided where a rising-falling grades encounters or raising a more rising
gradient. The minimum values for sag vertical curves are determined by the required head light
sight distances, drainage requirements and the level of driver’s comfort expected.

Short sag vertical curves and short grades between two vertical curves have been avoided.

(Source: ERA Geometric Design Manual-2002)

Table: Minimum Values for Sag Vertical Curves

The length of the curve is determined by taking the following criteria’s in to account

headlight sight distance

passengers comfort
drainage control
general appearance

INTEGRATED CIVIL ENGINEERING DESIGN II Page 41

 JU, DEPARTMENT OF CIVIL ENGINEERING

When the computed curve length for the above requirements is less than the minimum curve
length recommended by ERA 2001, this recommended value is taken. I.e. L is the max. Of the
two (computed or recommended)

VERTICAL CURVE DESIGN

Minimum length of vertical curves

The minimum lengths of crest and sag curves have been designed to provide sufficient
stopping sight distance. The design is based on minimum allowable "K" values, as defined
by the formula:
K = L/A
Where

K = limiting value, horizontal distance required to achieve a 1% change in grade

L = length of vertical curve (m)

A = Algebraic difference in approach and exit grades (%)

Minimum lengths of crest and sag vertical curves have been recommended based on design
speeds and stopping sight distance requirements. They provide for ride comfort, appearance,
and most importantly, safety. These are shown in Tables9-1 and 9-2, respectively, in terms of
“K” values.

Design of vertical curves

The design of vertical curves includes two tasks---determining the curve length and calculating
the heights of sufficient number of offsets to adequately define or locate the final grade line.

Length determination--- it is possible to design vertical curves to belong and to be gentle(flat) or

short and abrupt. This is done by varying the curve length. Depending on the facility to be
constructed and the standards of construction desired, there are certain limitations on curve
length. Minimum lengths are usually specified.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 42

 JU, DEPARTMENT OF CIVIL ENGINEERING

The curve installed between to grade lines with a large gradient, which might occur at the top of
a steep hill, is longer than the curve required between two grades with a smaller gradient.

Sight distance—when an overt curve is traversed, the ability of the driver to see down the road is
curtailed. If the vertical curve is quite short the distance that can be seen ahead becomes
critically short. Reduced speed is required to reduce the safety hazard. Sight distance depends
upon a design speed permitted

Vertical curve length factor (k); this is used when determining vertical curve length. It is equal to
the horizontal distance required to effect a 1% change in gradient while providing the minimum
stopping distance.

Calculations for vertical curves

 Determination of the vertical curve length by using the vertical curve length factor.

L = k ∆G
Where: - L = length of vertical curve
k = vertical length factor
∆G = difference in gradient

 locating PVI ,PVT and PVC

PVC = PVI – L/2
PVT = PVI + L/2
 Offset determination. For the curve to be defined the offsets must be determined at
various locations along the curve
∆G 2
Offset (Φ) = d
2L

Where: - d= offset distance from PVC or PVT

 The maximum offset will always be located at PVI and it can be calculated using

INTEGRATED CIVIL ENGINEERING DESIGN II Page 43

 JU, DEPARTMENT OF CIVIL ENGINEERING

L ∆G
Maximum offset =
8
 Elevation along vertical curves---vertical curves have the shape of a parabola and their
elevation can be calculated using the following formula.
For overt curve
Y = elev. PVC + change in elevation – offset
∆G 2
Y = elev. PVC + G1d - d
2L
Or
Y = elev. PVT ± change in elevation – offset
∆G 2
Y = elev. PVT ± G2d - d
2L
For invert curve
Y = elev. PVC - change in elevation + offset
∆G 2
Y = elev. PVC - G1d + d
2L

Y = elev. PVT ± change in elevation + offset

∆G 2
Y = elev. PVT ± G2d + d
2L

where:- Y = elevation of points on the curve

d = horizontal distance of pints on a curve from PVC or PVT
G1 = percent slop of first grade line
G2 = percent slop of second grade line

For the first curve

It is crest curve having design speed of 70km/hr
Minimum length required = k*change in gradient

INTEGRATED CIVIL ENGINEERING DESIGN II Page 44

 JU, DEPARTMENT OF CIVIL ENGINEERING

For crest curve k=31 for stopping sight distance

Minimum length of vertical curve =31*(5.54-2.13)
= 105.71m
Provide 120m vertical curve.
Chainage of point of intersection for the vertical curve =5+40
Chainage of point of start of the vertical curve =4+80
Chainage of point of tangency for the vertical curve =6+00
The elevation of the final road sub-grade surface is calculated by using offsets.

4+80 1765.278
4+90 1765.051

5+00 1764.795

5+10 1764.511

5+20 1764.199

5+30 1763.858
5+40 1763.489

5+50 1763.091
5+60 1762.665
5+70 1762.211
5+80 1761.728

5+90 1761.217
6+00 1760.677

For the second curve

It is sag curve having design speed of 60km/hr
Minimum length required = k*change in gradient
For sag curve k=18 for stopping sight distance

INTEGRATED CIVIL ENGINEERING DESIGN II Page 45

 JU, DEPARTMENT OF CIVIL ENGINEERING

Minimum length of vertical curve =18*(5.54-5.02)

= 10m
Provide 200m vertical curve.
Chainage of point of intersection for the vertical curve =8+90
Chainage of point of start of the vertical curve =7+90
Chainage of point of tangency for the vertical curve =9+90
The elevation of the final road sub-grade surface is calculated by using offsets.

7+90 1750.8
8+00 1749.59
8+10 1749.04
8+20 1748.49
8+30 1747.95
8+40 1747.4
8+50 1746.86
8+60 1746.33
8+70 1745.79
8+80 1745.26
8+90 1744.73
9+00 1744.2
9+10 1743.68
9+20 1743.16
9+30 1742.64
9+40 1742.12
9+50 1741.61
9+60 1741.1
9+70 1740.59
9+80 1740.08
9+90 1739.58

CHAPTER FIVE
EARTH WORK AND QUANTITY

INTEGRATED CIVIL ENGINEERING DESIGN II Page 46

 JU, DEPARTMENT OF CIVIL ENGINEERING

Earthwork operations are one of the most important construction aspects in road construction. It

is conversion of natural condition to required section and grade. The most common item of work

encountered in high way project is earth work. The quantity and cost of earthwork are calculated

in terms of cubic meters of excavation in its original position on the basis of cross section notes

from field measurement. According to ERA specification the rate of earth work in it such as

 Excavation in borrow area

 Transporting to the site of embankment including all lifting and loads not greater than 50

meter.

The quantity of work in embankment and cuts are computed by the cross sectional end area

method. The area of earth work in each cross section is computed by the help Microsoft Excel

program.

5.1. EARTHWORK ESTIMATION

Earthwork computations involve the calculation of earthwork volumes, the determination of

final grades, the balancing of cuts and fills, and the planning of the most economical haul of
material. The exactness with which earthwork computations are made depends upon the extent
and accuracy of field measurements, which in turn are controlled by the time available and the
type of construction involved.

For the determination of the earthwork volume the area is determined using the following
methods
 methods of End-Area determination

INTEGRATED CIVIL ENGINEERING DESIGN II Page 47

 JU, DEPARTMENT OF CIVIL ENGINEERING

 trapezoidal method
 stripper method
From the above methods we used the trapezoidal method. In using this method the area of any
cross-section is obtained by dividing the cross section into triangles and trapezoids. And the
assumption is that the ground is perfectly straight between the selected points on the ground line,
while this is not usually correct, the assumption is within the accuracy normally required.

The necessary earthwork computations are determined using the following methods
 Average-end-area
 Prismoidal formula
 Average-depth-of-cut-or-fill
 Grid, or contour method
Average-end-area method is used to calculate the volume of cut or fill between consecutive
points.
To compute the earthwork quantities cross-sections are taken at 20m interval for tangents and at
10m interval for curves.

EARTHWORK OPERATION
Chainage Area cut Area fill Cut vol Fill vol Adj cut vol Net vol Cumulative vol
  (m2) (m2) (m3) (m3) (factor=0.84) (m3) (m3)
0+00 9.33625   115.7875 -117.983 97.2615 -20.721 -20.721
0+20 2.2425 -11.79825 28.65 -261.21 24.066 -237.144 -257.865
0+40 0.6225 -14.32275 6.225 -355.8 5.229 -350.571 -608.436

INTEGRATED CIVIL ENGINEERING DESIGN II Page 48

 JU, DEPARTMENT OF CIVIL ENGINEERING

0+60   -21.25725   -466.465 -466.465 -1074.901

0+80   -25.38925   -461.105 -461.105 -1536.006
1+00   -20.72125 8.925 -355.795 7.497 -348.298 -1884.304
1+20 0.8925 -14.85825 11.1625 -324.173 9.3765 -314.796 -2199.1
1+40 0.22375 -17.559 11.625 -314.4 9.765 -304.635 -2503.735
1+60 0.93875 -13.881 55.33375 -227.749 46.48035 -181.268 -2685.0034
1+80 4.594625 -8.893875 136.9275 -143.233 115.0191 -28.2134 -2713.2168
2+00 9.098125 -5.429375 229.5075 -74.9525 192.7863 117.8338 -2595.383
2+20 13.852625 -2.065875 329.3237 -20.6588 276.63195 255.9732 -2339.4098
2+40 19.07975   464.775   390.411 390.411 -1948.9988
2+60 27.39775   610.635   512.9334 512.9334 -1436.0654
2+80 33.66575   751.495   631.2558 631.2558 -804.8096
3+00 41.48375   882.23   741.0732 741.0732 -63.7364
3+20 46.73925   941.215   790.6206 790.6206 726.8842
3+40 47.38225   990.45   831.978 831.978 1558.8622

3+60 51.66275   1014.435   852.1254 852.1254 2410.9876

3+80 49.78075   1033.295   867.9678 867.9678 3278.9554
4+00 53.54875   921.2098   773.8162325 773.8162 4052.771633
4+20 38.57223   679.6821   570.932965 570.933 4623.704598
4+40 29.39598   587.1749   493.226958 493.227 5116.931556
4+60 29.32151   619.2993   520.211410 520.211 5637.142967
4+80 32.60841   323.1576   271.452362 271.452 5908.595329
4+90 32.0231   317.4225   266.6349 266.634 6175.230229
5+00 31.4614   321.4865   270.04866 270.048 6445.278889
5+10 32.8359   325.35   273.294 273.294 6718.572889
5+20 32.2341   336.8255   282.93342 282.933 7001.506309
5+30 35.131   353.3505   296.81442 296.814 7298.320729
5+40 35.5391   360.3625   302.7045 302.704 7601.025229

INTEGRATED CIVIL ENGINEERING DESIGN II Page 49

 JU, DEPARTMENT OF CIVIL ENGINEERING

5+50 36.5334   365.799   307.27116 307.271 7908.296389

5+60 36.6264   382.285   321.1194 321.119 8229.415789

5+70 39.8306   418.383   351.44172 351.441 8580.857509

5+80 43.846   423.468   355.71312 355.7131 8936.570629
5+90 40.8476   401.665   337.3986 337.3986 9273.969229
6+00 39.4854   420.677   353.36868 353.3687 9627.337909
6+10 44.65   455   382.2 382.2 10009.53791
6+20 46.35   447   375.48 375.48 10385.01791
6+30 43.05   435.75   366.03 366.03 10751.04791
6+40 44.1   440.8125   370.2825 370.2825 11121.33041
6+50 44.0625   481.375   404.355 404.355 11525.68541
6+60 52.2125   532.8125   447.5625 447.5625 11973.24791
6+70 54.35   543.375   456.435 456.435 12429.68291
6+80 54.325   522.5   438.9 438.9 12868.58291

6+90 50.175   476.75   400.47 400.47 13269.05291

7+00 45.175   431.4   362.376 362.376 13631.42891
7+10 41.105   367.6 -1.7 308.784 307.084 13938.51291
7+20 32.415 -0.34 294.825 -1.7 247.653 245.953 14184.46591
7+30 26.55   245.375   206.115 206.115 14390.58091
7+40 22.525   204.875 -8 172.095 164.095 14554.67591
7+50 18.45 -1.6 162.3158 -9.339 136.3452825 127.0063 14681.68219
7+60 14.013162 -0.2678 266.1383 -6.08656 223.55613 217.4696 14899.15176
7+80 12.600663 -0.949512 89.81581 -17.9295 75.4452825 57.51578 14956.66754
7+90 5.3625 -2.636387 68.39925 -13.1819 57.45537 44.27343 15000.94097
8+00 8.31735   78.83888 -8.15638 66.224655 58.06828 15059.00925
8+10 7.450425 -1.631275 39.84962 -32.2581 33.473685 1.21556 15060.22481
8+20 0.5195 -4.82035 2.5975 -158.44 2.1819 -156.258 14903.96671
8+30   -26.86765   -414.12   -414.12 14489.84721

INTEGRATED CIVIL ENGINEERING DESIGN II Page 50

 JU, DEPARTMENT OF CIVIL ENGINEERING

8+40   -55.95625   -653.99   -653.99 13835.85771

8+50   -74.84165   -802.253   -802.253 13033.60521
8+60   -85.60885   -955.184   -955.184 12078.42171
8+70   -105.4279   -1134.53   -1134.53 10943.88921
8+80   -121.4786   -1330.52   -1330.52 9613.364714
8+90   -144.6263   -1451.98   -1451.98 8161.380214

9+00   -145.7707   -1414.91   -1414.91 6746.467714

9+10   -137.2119   -1227.87   -1227.87 5518.596714
9+20   -108.3624   -1056.86   -1056.86 4461.736714
9+30   -103.0096   -867.317   -867.317 3594.419714
9+40   -70.45375 0.48375 -481.476 0.40635 -481.069 3113.350314
9+50 0.09675 -25.8414 12.98125 -286.679 10.90425 -275.775 2837.575814
9+60 2.4995 -31.49435 31.35125 -200.16 26.33505 -173.825 2663.751114
9+70 3.77075 -8.5376 79.32825 -43.0908 66.63573 23.54498 2687.296094
9+80 12.0949 -0.08055 187.7183 -0.40275 157.68333 157.2806 2844.576674
9+90 25.44875   347.7925   292.1457 292.1457 3136.722374
10+00 44.10975   1032.665   867.4386 867.4386 4004.160974
10+20 59.15675   1212.355   1018.3782 1018.378 5022.539174
10+40 62.07875   1398.045   1174.3578 1174.358 6196.896974
10+60 77.72575   1631.985   1370.8674 1370.867 7567.764374
10+80 85.47275   1724.425   1448.517 1448.517 9016.281374
11+00 86.96975   878.0025   737.5221 737.5221 9753.803474
11+10 88.63075   885.6125   743.9145 743.9145 10497.71797
11+20 88.49175   787.5975   661.5819 661.5819 11159.29987
11+30 69.02775   723.5825   607.8093 607.8093 11767.10917

INTEGRATED CIVIL ENGINEERING DESIGN II Page 51

 JU, DEPARTMENT OF CIVIL ENGINEERING

11+40 75.68875   710.5675   596.8767 596.8767 12363.98587

11+50 66.42475   594.6775   499.5291 499.5291 12863.51497
11+60 52.51075   488.9125   410.6865 410.6865 13274.20147
11+70 45.27175   391.5225   328.8789 328.8789 13603.08037
11+80 33.03275   557.375   468.195 468.195 14071.27537
12+00 22.70475   158.7094 5.518125 133.315875 138.834 14210.10937

12+10 9.037125 1.103625 61.7731 -34.9356 51.889425 16.9538 14227.06317

12+20 3.3175 -8.09075 16.5875 -144.015 13.9335 -130.081 14096.98167
12+30   -20.71225   -261.192   -261.192 13835.78917
12+40   -31.52625   -349.207   -349.207 13486.58167
12+50   -38.31525   -430.347   -430.347 13056.23417
12+60   -47.75425   -534.862   -534.862 12521.37167
12+70   -59.21825   -668.252   -668.252 11853.11917
12+80   -74.43225   -1790.55   -1790.55 10062.56917
13+00   -104.6228   -2108.48   -2108.48 7954.084174
13+20   -106.2257   -2190.67   -2190.67 5763.414174
13+40   -112.8412   -2238.48   -2238.48 3524.934174
13+60   -111.0067   -2234.66   -2234.66 1290.269174

13+80   -112.4597   -1124.6   -1124.6 165.6716743

4.2. MASS HAUL DIAGRAM

The mass haul diagram is one method of analyzing earthwork operations. And it is one of the
most effective engineer tools and is easily and rapidly prepared. It is a continuous curve showing
the accumulated algebraic sum of cuts (+ve) and fills (-ve) from some initial station to any
succeeding station.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 52

 JU, DEPARTMENT OF CIVIL ENGINEERING

The curve (diagram) is plotted using the chainage in the x-axis (abscissa) and the cumulative
total earth mass in the y-axis (ordinate).

EARTHWORK DATA

cumulative Chainag cumulative chaina cumulative

chainage vol e vol ge vol chainage cumulative vol

(m3) 5+00 6445.27888 7+80 14956.66754 11+00 9753.803474

0+00 -20.721 5+10 6718.57288 7+90 15000.94097 11+10 10497.71797

0+20 -257.865 5+20 7001.50630 8+00 15059.00925 11+20 11159.29987

0+40 -608.436 5+30 7298.32072 8+10 15060.22481 11+30 11767.10917

0+60 -1074.901 5+40 7601.02522 8+20 14903.96671 11+40 12363.98587

0+80 -1536.006 5+50 7908.29638 8+30 14489.84721 11+50 12863.51497

1+00 -1884.304 5+60 8229.41578 8+40 13835.85771 11+60 13274.20147

1+20 -2199.1 5+70 8580.85750 8+50 13033.60521 11+70 13603.08037

1+40 -2503.735 5+80 8936.57062 8+60 12078.42171 11+80 14071.27537

1+60 -2685.0034 5+90 9273.96922 8+70 10943.88921 12+00 14210.10937

1+80 -2713.2168 6+00 9627.33790 8+80 9613.364714 12+10 14227.06317

2+00 -2595.383 6+10 10009.5379 8+90 8161.380214 12+20 14096.98167

2+20 -2339.4098 6+20 10385.0179 9+00 6746.467714 12+30 13835.78917

2+40 -1948.9988 6+30 10751.0479 9+10 5518.596714 12+40 13486.58167

2+60 -1436.0654 6+40 11121.3304 9+20 4461.73671 12+50 13056.23417

2+80 -804.8096 6+50 11525.6854 9+30 3594.41971 12+60 12521.37167

3+00 -63.7364 6+60 11973.2479 9+40 3113.35031 12+70 11853.11917

INTEGRATED CIVIL ENGINEERING DESIGN II Page 53

 JU, DEPARTMENT OF CIVIL ENGINEERING

3+20 726.8842 6+70 12429.6829 9+50 2837.57581 12+80 10062.56917

3+40 1558.8622 6+80 12868.5829 9+60 2663.751114 13+00 7954.084174

3+60 2410.9876 6+90 13269.0529 9+70 2687.296094 13+20 5763.414174

3+80 3278.9554 7+00 13631.4289 9+80 2844.576674 13+40 3524.934174

4+00 4052.7716 7+10 13938.5129 9+90 3136.722374 13+60 1290.269174

4+20 4623.7045 7+20 14184.4659 10+00 4004.160974 13+80 165.6716743

4+40 5116.9315 7+30 14390.5809 10+20 5022.539174

4+60 5637.1429 7+40 14554.6759 10+40 6196.896974

4+80 5908.5953 7+50 14681.6821 10+60 7567.764374

4+90 6175.2302 7+60 14899.1517 10+80 9016.281374

20000
mass haul
15000
volume in(m3)

10000

5000

-5000

PART TWO: STRUCTURAL DESIGN OF PAVEMENT

INTEGRATED CIVIL ENGINEERING DESIGN II Page 54

 JU, DEPARTMENT OF CIVIL ENGINEERING

CHAPTER SIX

PAVEMENT DESIGN

INTRODUCTION TO THE PAVEMENT DESIGN PROCESS

Effective pavement design is one of the more important aspects of project design. The pavement is the
portion of the highway which is most obvious to the motorist. The condition and adequacy of the highway
is often judged by the smoothness or roughness of the pavement. Deficient pavement conditions can
result in increased user costs and travel delays, braking and fuel consumption, vehicle maintenance
repairs and probability of increased crashes.

Pavement design is an integral part of the project decision process. The Project Team should discuss,
consider, and document the pavement design as it relates to the overall project. The pavement is typically
one of the major costs of a project. The pavement design affects maintenance of traffic, constructability,
the environment, as well as other aspects of the project.

Pavement Design Engineer (PDE), and Research & Materials. The Designer must also apply sound
engineering judgment. Steps in the design process include:

 Review Pavement Management Data to determine the appropriate scope of work and treatment
type (i.e. new pavement, reconstruction, reclamation, resurfacing, or pavement preservation);
 Evaluate existing pavement to confirm the scope of work and determine preliminary design and
appropriate construction strategy. Research roadway history and traffic data, verify existing
pavement materials and structure. Perform field trips to make site inspections, prepare a
pavement condition checklist, communicate with engineering and maintenance forces for history
of roadway performance, groundwater problems and other background information;
 Evaluate sub-base and sub-grade for drainage characteristics and bearing capacity;
 Make structural calculations. The traffic, soils, and existing pavement data is used to calculate
specific pavement course requirements;
 Set specifications. The pavement materials, construction methods, and finished project
requirements must be both practical to attain and clearly defined. The Designer must ensure that
the plans, specifications, and estimate clearly and unambiguously define the requirements.

For HMA structural resurfacing on Interstate and other controlled access highways, the design procedures
contained in the 1993 AASHTO Guide features the following:

INTEGRATED CIVIL ENGINEERING DESIGN II Page 55

 JU, DEPARTMENT OF CIVIL ENGINEERING

 Use of statistical reliability instead of the factor of safety design;

 Use of resilient modulus tests for soil support (a dynamic test) vs. CBR (a static test); and
 Introduction of environmental factors to evaluate the effects of spring thaw and frost heave.
PAVEMENT TYPES, DEFINITIONS, AND ABBREVIATIONS

Different types of pavement are commonly used in the construction of roadways. There are three different
types of pavement. These are:

 Flexible Pavement
 Rigid Pavement
 Composite Pavement

Each of these pavement types is presented below.

FLEXIBLE PAVEMENT

A flexible pavement structure consists of the following layers – the sub-base, base course, intermediate
course, surface course, and where determined necessary, a friction course.

 The sub-base consists of granular material - gravel, crushed stone, reclaimed material or a
combination of these materials.
 The base course is an HMA or concrete pavement layer placed upon the compacted sub-base. A
gravel base course can be designed and specified for low volume roadways (<2,000 vehicles per
day) depending upon loading and other design considerations.
 The intermediate course is an HMA pavement layer placed upon the base course.
 The surface course is the top HMA pavement layer and is placed upon the intermediate course.
 A friction course is a specialized thin-lift wearing course which, when specified, is placed over
the surface course. Friction courses provide improved vehicle skid resistance, but do not provide
any structural value to the pavement. Typically friction courses are placed on high volume
limited access roadways.
RIGID PAVEMENT

A rigid pavement is constructed of Portland cement concrete (PCC) placed on a granular sub-base. PCC
pavements are either plain and jointed or continuously reinforced. All newly constructed or rehabilitated
rigid pavements shall be designed as directed and approved by the PDE.

Composite Pavement

INTEGRATED CIVIL ENGINEERING DESIGN II Page 56

 JU, DEPARTMENT OF CIVIL ENGINEERING

A composite pavement consists of one or more HMA pavement courses over a PCC base. All newly
constructed or rehabilitated composite pavements shall be designed as directed and approved by the PDE.

PAVEMENT DESIGN TERMS AND DEFINITIONS

The following terms and abbreviations are commonly used in pavement design.

 Binder – The liquid asphalt material in an HMA mixture that bonds the aggregate together.
 Equivalent Single Axel Load (ESAL) – The conversion of mixed vehicular traffic into its
equivalent single-axle, 18-Kip Load. The equivalence is based on the relative amount of
pavement damage.
 Daily ESAL (T18) – The average number of equivalent 18-Kip loads which will be applied to
the pavement structure in one day. Normally, a 20-year design period is used to determine the
daily load.
 ESAL Applications per 1000 Trucks and Combinations – A factor which reflects the relative mix
of sizes (see Exhibit 9-2) and weights of trucks on various classes of highways (e.g., freeways,
arterials, collectors, and local streets). Truck percentages typically exclude two-axle, four-tire
pickup trucks, the effect of which may be ignored.
 Pavement Serviceability Index (PSI) – A measure of a pavement's ability to serve traffic on a
scale of 0 to 5. It reflects the extent of pavement condition.
 Terminal Serviceability Index (Pt) – A pavement design factor which indicates the acceptable
pavement serviceability index at the end of the selected design period (usually 20 years).
 Sub-grade – The undisturbed virgin substrate or embankment material which the pavement
structure is placed upon.
 Bearing Ratio – The load required to produce a certain penetration using a standard piston in a
soil, expressed as a percentage of the load required to force the piston the same depth in a
selected crushed stone. Bearing Ration values are normally determined using the California
Bearing Ratio (CBR) text method.
 Design Bearing Ratio (DBR) – The selected bearing ratio used to design the pavement. It is based
on a statistical evaluation of the CBR test results on the soil samples.
 Soil Support Value (SSV) – An index of the relative ability of a soil or stone to support the
applied traffic loads. It is specifically used for the pavement design method in the AASHTO
Interim Guide for Design of Pavement Structures. The soil support value of the sub-grade is
related to its CBR (DBR).

INTEGRATED CIVIL ENGINEERING DESIGN II Page 57

 JU, DEPARTMENT OF CIVIL ENGINEERING

 Structural Number (SN) – A measure of the structural strength of the pavement section based on
the type and thickness of each layer within the pavement structure.
 Layer Coefficient – The relative structural value of each pavement layer per inch of thickness. It
is multiplied by the layer thickness to provide the contributing SN for each pavement layer.
 Skid Resistance – A measure of the coefficient of friction between an automobile tire and the
roadway surface.
 Pavement Design Engineer (PDE) – Mass Highway Pavement Design Engineer.
 Designer – The consultant under contract to Mass Highway or the municipality, or the Designer
within Mass Highway.

Factors affecting pavement design

Traffic and loading

Traffic is the most important factor in the pavement design. The key factors include contact pressure,
wheel load, axle configuration, moving loads, load, and load repetitions.

Contact pressure: The tire pressure is an important factor, as it determines the contact area and the contact
pressure between the wheel and the pavement surface. Even though the shape of the contact area is
elliptical, for sake of simplicity in analysis, a circular area is often considered.

Wheel load: The next important factor is the wheel load which determines the depth of the pavement
required to ensure that the sub grade soil is not failed. Wheel configuration affects the stress distribution
and deflection within a pavement. Many commercial vehicles have dual rear wheels which ensure that the
contact pressure is within the limits. The normal practice is to convert dual wheel into an equivalent
single wheel load so that the analysis is made simpler.

Axle configuration: The load carrying capacity of the commercial vehicle is further enhanced by the
introduction of multiple axles.

Moving loads: The damage to the pavement is much higher if the vehicle is moving at creep speed. Many
studies show that when the speed is increased from 2 km/hr to 24 km/hr, the stresses and deflection
reduced by 40 per cent.

Repetition of Loads: The influences of traffic on pavement not only depend on the magnitude of the
wheel load, but also on the frequency of the load applications. Each load application causes some
deformation and the total deformation is the summation of all these. Although the pavement deformation

INTEGRATED CIVIL ENGINEERING DESIGN II Page 58

 JU, DEPARTMENT OF CIVIL ENGINEERING

due to single axle load is very small, the cumulative effect of number of load repetition is significant.
Therefore, modern design is based on total number of standard axle load (usually 80 kN single axle).

The deterioration of paved roads caused by traffic results from both the magnitude of the
individual wheel loads and the number of times these loads are applied. It is necessary to
consider not only the total number of vehicles that will use the road but also the wheel loads (or,
for convenience, the axle loads) of these vehicles. Equivalency factors are used to convert traffic
volumes into cumulative standard axle loads and are discussed in this section. Traffic classes are
defined for paved roads, for pavement design purposes, by ranges of cumulative number of
equivalent standard axles (ESAs).

The pavement life is substantially affected by the number of heavy load repetitions applied, such as
single, tandem, tridem and quad axle trucks, buses, tractor trailers and equipment. A properly designed
pavement structure will take into account the applied loading.

DESIGN PERIOD
Determining an appropriate design period is the first step towards pavement design. Many
factors may influence this decision, including budget constraints. However, the designer should
follow certain guidelines in choosing an appropriate design period, taking into account the
conditions governing the project. Some of the points to consider include:

Functional importance of the road

Traffic volume
Location and terrain of the project
Financial constraints
Difficulty in forecasting traffic

It generally appears economical to construct roads with longer design periods, especially for
important roads and for roads with high traffic volume. Where rehabilitation would cause major
inconvenience to road users, a longer period may be recommended. For roads in difficult
locations and terrain where regular maintenance proves to be costly and time consuming because

INTEGRATED CIVIL ENGINEERING DESIGN II Page 59

 JU, DEPARTMENT OF CIVIL ENGINEERING

of poor access and non-availability of nearby construction material sources, a longer design
period is also appropriate.

Based on ERA manual the allowable design periods are given below

Road Classification Design Period (years)

Trunk Road 20

Link Road 20

Main Access Road 15

Other Roads 10

Considering all the above limitations in this project the design period is taken as 20 years.

TRAFFIC
As mentioned before pavement design relies heavily on the expected level of traffic. The
deterioration of paved roads cause by traffic results both the magnitude of the individual wheel
loads and the number of times these loads are applied. It is necessary to consider not only the
total number of vehicles that will use the road but also the wheel loads (or, for convenience, the
axle loads) of these vehicles. Equivalency factors are used to convert traffic volumes into
cumulative standard axle loads.

VEHICLE CLASSIFICATION

Vehicle classification is an essential aspect of traffic volume evaluation (as well as evaluation of

equivalent axle loads). The types of vehicles are defined according to the breakdown adopted by

ERA for traffic counts: cars; pick-ups and 4-wheel drive vehicles such as Land Rovers and Land

Cruisers; small buses; medium and large size buses; small trucks; medium trucks; heavy trucks;

and trucks and trailers. This breakdown is further simplified, for reporting purposes, and

expressed in the five classes of vehicles (with vehicle codes 1 to 5) listed in table below.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 60

 JU, DEPARTMENT OF CIVIL ENGINEERING

Vehicle Type of Vehicle Description

Code
1 Small car Passenger cars, minibuses (up to 24-passenger seats), taxis, pick-
ups, and Land Cruisers, Land Rovers, etc.

Medium and large size buses above 24 passenger seats

2 Bus

Small and medium sized trucks including tankers up to 7 tons

3 Medium Truck
load

Trucks above 7 tons load

4 Heavy Truck

Trucks with trailer or semi-trailer and Tanker Trailers

5 Articulated
Truck

Select Design Period

Estimate Initial Traffic

Volume (Initial AADT) per

Class of Vehicle

Estimate Traffic Growth

Determine Cumulative
INTEGRATED CIVIL ENGINEERING DESIGN II Page 61
Traffic Volumes over the
Design Period
 JU, DEPARTMENT OF CIVIL ENGINEERING

Estimate Mean Equivalent

Axle Load (ESA) per

Class of Vehicle

DETERMINATION OF CUMULATIVE TRAFFIC VOLUMES

In order to determine the cumulative number of vehicles over the design period of the road, the
following procedure should be followed:

INTEGRATED CIVIL ENGINEERING DESIGN II Page 62

 JU, DEPARTMENT OF CIVIL ENGINEERING

1. Determine the initial traffic volume (AADT0) using the results of the traffic survey and any
other recent traffic count information that is available. For paved roads, detail the AADT in
terms of car, bus, truck, and truck-trailer.

2. Estimate the annual growth rate “i” expressed as a decimal fraction, and the anticipated
number of years “x” between the traffic survey and the opening of the road.
3. Determine AADT1 the traffic volume in both directions on the year of the road opening by:

AADT1 = AADT0 (1+i)x

For paved roads, also determine the corresponding daily one-directional traffic volume for
each type of vehicle.

For this project, according to the survey data conducted on 2004 undertaken in 2005:

no Vehicle classification 2004 AADT

1 Car 1
2 4 W/D 64
3 Small bus 48
4 Large bus 31
5 Small truck 77
6 Medium truck 99
7 Heavy truck 88
8 Truck and trailer 17

Opening year is the beginning of 2011

Two sets of growth rate have been estimated at 10% and 8% for the period 2005 to2020 and 2021 to 2030
respectively in projecting future growth of normal traffic.

Generated traffic is expected at about 28% of normal traffic for Jimma to Bonga.

10 %∗15+8 %∗10
Normal traffic growth rate = = 9.2%
25

INTEGRATED CIVIL ENGINEERING DESIGN II Page 63

 JU, DEPARTMENT OF CIVIL ENGINEERING

Generated traffic rate = 2.8% of normal traffic growth rate

=2.8% * 9.2%

=2.576%

Total growth rate = Normal traffic growth rate + Generated traffic rate

=9.2% + 2.576% = 11.776%

So to forecast the future traffic we use a total growth rate of about 12% and the years between
the starting of the project and the year the road became open to the traffic is 6 years.

Based on these data’s and following the above procedures’, the AADT of 2011 is presented by
the table below.

No Vehicle classification AADTo2005) AADT(2011) One way AADT

Car 1 1.973823 0.986911
2 4 W/D 64 126.3247 63.16233
3 Small bus 48 94.74349 47.37174
4 Large bus 31 61.1885 30.59425
5 Small truck 77 151.9843 75.99217
6 Medium truck 99 195.4084 97.70422
7 Heavy truck 88 173.6964 86.8482
8 Truck and trailer 17 33.55499 16.77749

4. The cumulative number of vehicles, T over the chosen design period N ( in years) is obtained
by:

T = 365 AADT1 [ (1+i)N – 1] / ( i )

In this step by using design year 0f 20 and average growth rate of 12% we calculate cummulative number
of vehicles over 20 years.

No Vehicle classification One way AADT T

Car 0.986911 25954.92

INTEGRATED CIVIL ENGINEERING DESIGN II Page 64

 JU, DEPARTMENT OF CIVIL ENGINEERING

2 4 W/D 63.16233 1661115

3 Small bus 47.37174 124583

6
4 Large bus 30.59425 804602.6
5 Small truck 75.99217 1998529
6 Medium truck 97.70422 2569537
7 Heavy truck 86.8482 228403

3
8 Truck and trailer 16.77749 441233.

AXLE LOADS

The following method of analysis is recommended by ERA:

a. Determine the equivalency factors for each of the wheel loads measured during the axle
load survey, using Table or the accompanying equation, in order to obtain the
equivalency factors for vehicle axles. The factors for the axles are totaled to give the
equivalency factor for each of the vehicles. For vehicles with multiple axles i.e. tandems,
triples etc., each axle in the multiple group is considered separately.

b. Determine the mean equivalency factor for each class of heavy vehicle (i.e. bus, truck and
truck-trailer) travelling in each direction. It is customary to assume that the axle load
distribution of the heavy vehicles will remain unchanged for the design period of the
pavement.

Finally, the cumulative ESAs over the design period (N) are calculated as the products of the

cumulative one-directional traffic volume (T) for each class of vehicle by the mean equivalency

factor for that class and added together for each direction. The higher of the two directional

values should be used for design.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 65

 JU, DEPARTMENT OF CIVIL ENGINEERING

The relationship between a vehicle’s EF and its axle loading is normally considered in terms of
the axle mass measured in kilograms. The relationship takes the form:

axle load i ) n
Equivalency factor = (
8160

Where

Axle loadi = mass of axle i

n= a power factor that varies depending on the pavement construction

type and subgrade but which can be assumed to have a value of 4.5 and the

standard axle load is taken as 8160kg with the summation taken over the number of

axles on the vehicle in question.

Equivalency Factors for Different Axle Loads (Flexible Pavements)

Equiva
Wheel load   Axle load lency
(single & (103
dual) kg) Factor  
3
(10 kg)     (EF)
  1.5 3 0.01
  2 4 0.04
  2.5 5 0.11
  3 6 0.25
  3.5 7 0.5
  4 8 0.91
  4.5 9 1.55
  5 10 2.5
  5.5 11 3.93
  6 12 5.67

INTEGRATED CIVIL ENGINEERING DESIGN II Page 66

 JU, DEPARTMENT OF CIVIL ENGINEERING

  6.5 13 8.13
  7 14 11.3
  7.5 15 15.5
  8 16 20.7
  8.5 17 27.2
  9 18 35.2
  9.5 19 44.9
  10 20 56.5

The above table is provided for all vehicles. But for this particular project, the equivalent factor
from table provided on ERA PDM is used.

no Vehicle classification Equivalent factor

1 Car 0
2 4 W/D 0
3 Small bus 0.41
4 Large bus 1.52
5 Small truck 0.7
6 Medium truck 1.7
7 Heavy truck 1.5
8 Truck and trailer 2.2

Finally the équivalent standard axle load is calculated by multiplyinng cumulative

number of vehicles in the design year by the equivalent factor for each type of vehicle
and summed together to determine in which class the traffic falls.

No Vehicle classification T Equivalent factor ESA ESA*106

Car 25954.92 0 0 0
2 4 W/D 1661115 0 0 0
3 Small bus 124583 0.41 510792.8 0.5107290

6
4 Large bus 804602.6 1.52 1222996 1.222996
5 Small truck 1998529 0.7 1398970 1.398970
6 Medium truck 2569537 1.7 4.368213
7 Heavy truck 228403 1.5 3426050 3.426050

3
8 Truck and trailer 441233. 2.2 970714 0.970714

7
total 11897736 11.897736

INTEGRATED CIVIL ENGINEERING DESIGN II Page 67

 JU, DEPARTMENT OF CIVIL ENGINEERING

After calculating the cumulative traffic we normally classify this number to traffic classes of
flexible pavement design.

Table: Traffic Classes for Flexible Pavement Design

Traffic classes Range (106 ESAs)

T1 < 0.3
T2 0.3-0.7
T3 0.7-1.5
T4 1.5-3
T5 3-6
T6 6-10
T7 10-17
T8 17-30

Based on the above Table, ERA manual, the traffic class is T7, [10-17] ESAS

SUBGRADE MATERIALS
Clearly all structures including pavements lie on the soil. That is the sub grade is the
foundation that eventually support all the loads coming from the pavement. In the fundamental
concept of the flexible pavements, the combined thickness of the pavement layers above the sub
grade must be sufficiently thick to reduce the stresses coming to the sub grade in order to not
cause the considerable distortion or the displacement of the sub grade soil.

SUBGRADE

The type of sub grade soil is largely determined by the location of the road. However,
where the soils within the possible corridor for the road vary significantly in strength from place
to place, it is clearly desirable to locate the pavement on the stronger soils if this does not
conflict with other constraints. For this reason, the pavement engineer should be involved in the

INTEGRATED CIVIL ENGINEERING DESIGN II Page 68

 JU, DEPARTMENT OF CIVIL ENGINEERING

route corridor selection process when choices made in this regard influence the pavement
structure and the construction costs.

The strength of the road sub grade for flexible pavements is commonly assessed in terms of
the California Bearing Ratio (CBR) and this is dependent on the type of soil, its density, and its
moisture content. Direct assessment of the likely strength or CBR of the sub grade soil under the
completed road pavement is often difficult to make. Its value, however, can be inferred from an
estimate of the density and equilibrium (or ultimate) moisture content of the sub grade together
with knowledge of the relationship between strength, density and moisture content for the soil in
question. This relationship must be determined in the laboratory. The density of the sub grade
soil can be controlled within limits by compaction at suitable moisture content at the time of
construction. The moisture content of the sub grade soil is governed by the local climate and the
depth of the water table below the road surface.

SURFACING

This is the uppermost layer of the pavement and will normally consist of a bituminous
surface dressing or a layer of premixed bituminous material.

Where premixed materials are laid in two layers, these are known as the wearing course and
the base course (or binder course).

The wearing surface may range in thickness from less than 25 mm in the case of a bituminous
surface treatment used for low-cost, light-traffic roads to 150 mm or more of asphalt concrete
used for heavily traveled routes.

The wearing surface must be capable of withstanding the wear and abrasive effects of moving
vehicles and must possess sufficient stability to prevent it from shoving and rutting under traffic
loads.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 69

 JU, DEPARTMENT OF CIVIL ENGINEERING

In addition, it serves a useful purpose in preventing the entrance of excessive quantities of

surface water into the base and sub grade from directly above.

For some heavily traveled highways, a 13 mm to 18 mm thickness of highly drainable open-

graded friction course is placed on top of the wearing course for the purpose of improving skid
resistance, and improving wet night visibility.

To determine the pavement structure fully it is compulsory to know the strengths of the subgrade
which can be articulated by CBR (California Bearing Ratio).

For this project the CBR values are given as below.

0.6 2.5 4.8 6.2 10.0 16.0

0.9 2.9 5.0 6.3 10.5 17.0
1.0 3 5.1 6.4 10.8 17.7
1.1 3.2 5.2 6.5 10.9 18.0
1.2 3.4 5.3 6.9 11.0 18.9
1.3 3.5 5.4 7.0 11.5 21.8
1.4 3.7 5.5 7.8 11.8 24.0
1.5 4.0 5.7 8.0 12.0 27.0
1.8 4.2 5.8 8.2 12.5 29.0
2 4.5 5.9 9.0 13.0 32.0
2.4 4.7 6.0 9.4 15.0 62.1

Fig:-CBR valued collected on the site

INTEGRATED CIVIL ENGINEERING DESIGN II Page 70

 JU, DEPARTMENT OF CIVIL ENGINEERING

As we can see from the table there are different types of CBR value for different sections of the
road .The representative design CBR value is determined using chart below measuring a distance
‘d’ from the smallest test and reading the value of CBR at that specific location.

Where the graph is plotted using number of tests on the x-axis and CBR (in ascending order) on
the y-axis.

d=0.1*(n-1); where n= no of test

d – Is measured along the X-axis from the first test and the design CBR is from the y-axis

d = 0.1 * (66 – 1) = 6.5(which gives CBR value of about 1.75)

70
60 CBR
50
40
30
20 CBR
10
0
1
4
7
10
13
16
19
22
25
28
31
34
37
40
43
46
49
52
55
58
61
64

INTEGRATED CIVIL ENGINEERING DESIGN II Page 71

 JU, DEPARTMENT OF CIVIL ENGINEERING

The structural catalog given in ERA manual requires that the subgrade strength for design

be assigned to one of six strength classes reflecting the sensitivity of thickness design to

subgrade strength. The classes are defined in table above. For subgrade with CBRs less than 2,

special treatment is required, but for this projects a minimum CBR value = 2 is used.

Finally using traffic class of T7 and subgrade class of S1 and based on the Summary of
Material Requirements for the design charts on ERA manual selected charts are chart number
2,4,5,6 and 7.

The provisions of different layer thickness given on these charts are presented as below.

Chart 2 chart 4 chart 5 chart 6 chart 7

Alternative 1 alternative 2 alternative 3 alternative 4 alternative 5

Determination of economical pavement structure

INTEGRATED CIVIL ENGINEERING DESIGN II Page 72

 JU, DEPARTMENT OF CIVIL ENGINEERING

To differentiate the most economical pavement structure, it is crucial to calculate the relative unit

cost of each possible pavement structure. The unit cost (relative) can be found out from table 10-

3 of ERA manual. To select the appropriate pavement type/treatment and properly design a pavement

structure, the Designer must obtain information and input from the Pavement Management System

(PMS).

MATERIALS THICKNESS RELATIVE UNIT

COST

ASPHALT CONCRETE SURFACE 5cm thick 0.33

DRESSING 15cm thick 0.87

BITUMINOUS STABILIZED ROAD

BASE 20cm thick 1.0

CRUSHED STONE ROAD 15 cm thick 0.56

BASE 25 cm thick 0.9

CEMENT STABILIZED ROAD

BASE(4 Mpa) 15 cm thick 0.81

CEMENT STABILIZED ROAD 12.5 cm thick 0.73

BASE(2.5 Mpa) 22.5 cm thick 0.9

INTEGRATED CIVIL ENGINEERING DESIGN II Page 73

 JU, DEPARTMENT OF CIVIL ENGINEERING

20 cm thick 0.29

GRANULAR SUB BASE 15 cm thick 0.39

10 cm thick 0.13

SELECTED FILL MATERIALS 15 cm thick 0.19

The selected chart number and its thickness tabulated as follows

2 4 5 6 7

PAVEMENT POSSIBLE ALTER ALTE ALTER ALTE ALTER

COMP ALTERNATIVE R R
NATE NATE NATE
ONENT AND PAVEMENT NATE NATE
NO 1 NO 3 NO 5
SELE
STURUCTURES NO 2 NO 4
CTED FILL

SURFACING ASPHALT CONCRETE( AC) 5cm 5cm 12.5cm 12.5cm 5cm

ROAD BASE

 Crushed stone 15cm 15cm 27.5cm 15cm -

 Cement stabilized (4 Mp)
12.5cm 12.5cm - - -
 Cement stabilized (2.5 Mp)
 Bituminous stabilized 17.5cm 15cm - 25cm -

- - - - 17.5cm

INTEGRATED CIVIL ENGINEERING DESIGN II Page 74

 JU, DEPARTMENT OF CIVIL ENGINEERING

Granular sub base - - 22.5cm - 22.5cm

Selected fill 30cm 30cm 27.34cm 35cm 24.34cm

Alternate pavet. Description Relative unit cost

Str. No.
1 5cm SURFACING ASPHALT CONCRETE( AC) 2.75
15cm granular road base
12.5cm cement stabilized road base
17.5cm cement stabilized road base
30cm granular capping layer
2 5cm flexible bituminous surface 2.075
15cm granular road base
12.5cm cement/lime stabilized road base 1
15cm cement/lime stabilized road base 2
30cm granular capping layer
3 12.5cm bituminous surface 2.298
27.5cm granular road base
22.5cm granular sub base
27.34cm selected fill
4 12.5cm bituminous surface 2.6675
15cm granular road base
25cm cement/lime stabilized road base
35cm granular capping layer
5 5cm flexible bituminous surface 1.983
17.5cm bituminous road base
22.5cm granular sub base
27.34cm selected fill

Therefore the most economical pavement structure is from Chart – 7 with 5cm asphalt concrete,
17.5cm bituminous stabilized road base, 22.5cm Granular Road base, and 27.34cm selected fill,
which has a relative cost unit of 1.983.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 75

 JU, DEPARTMENT OF CIVIL ENGINEERING

PART THREE
CHAPTER SEVEN
DRAINAGE DESIGN
Highway drainage structures are an essential component in the design development of highway. Drainage
design manual is prepared to establish basic design techniques for economical design of surface drainage
structure including side ditches, culverts and bridges.

The drainage design of roads is aimed at the protection of the road through the prevention of damage
due to water to achieve a chosen level of service, without major rehabilitation, at the end of selected
design period, as economically as possible. The design procedures take into account factors such as
rainfall intensity, catchment areas, ground cover, and run-off. The main objective of drainage design is to
allow the runoff of any water with limited damages and disturbances to the road and to the surrounding
areas.

Design storm/flood
Drainage works shall be designed for storm having a recurrence interval of at least that shown
in table below.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 76

 JU, DEPARTMENT OF CIVIL ENGINEERING

Design storm frequency (yrs) by Geometric Design criteria

Flow Velocity
The introduction of a culvert is to convey the stream flow beneath a highway can cause an increase in
flow velocity downstream of the structure. The increased in flow velocity downstream of the structure is
sufficient to cause erosion.

In addition to the above consideration, there are also different parameters required to get the design
discharge of the culvert.

 Catchment area
 Average slope of the catchment
 Length of the main stream
 Soil groups and land use, etc.

The above parameters can be easily determined from the topographic map of the project area.

Hydraulic procedures
Stream flow measurements for determining a flood frequency relationship at a site are usually
unavailable in such cases. It is an accepted practice to estimate peak runoff rates and hydrographs using
statistical or empirical methods. In general, applicable for Ethiopia

INTEGRATED CIVIL ENGINEERING DESIGN II Page 77

 JU, DEPARTMENT OF CIVIL ENGINEERING

Methods used for discharge calculation

Based on the size of the catchment area, the following methods were used for computation at discharge
for the design of culverts.

Rational method: - For small catchment wild area less than 50 hectare.
SCS method: - For catchment area greater than 50 hectares.

Determination of Design discharge

It is the amount of water passing through the structure per second. To calculate the amount discharge we
used the equation shown below:

Q= 0.00278 C I A

Where:

Q = maximum rate of runoff, m 3/sec

C = Run off coefficient representing ratio of run off to rain fall

I = Average rainfall intensity for a duration equal to the time of concentration, for
selected return period, mm/hr

A = catchment area tributary to the design location, ha

But for us we haven’t IDF curve for the given region and we haven’t information about land use for the
surrounding.

Due to this we have enforced to assume any data required for drainage design.

 The road is located in south east Ethiopia.

 The surrounding covered by natural vegetation and the runoff will not be much exaggerated
because infiltration will be more.
 The terrain ranges from flat to mountainous hence the discharge in mountainous area will be

From manning’s formula

1
Q= *A*R2/3*S1/2
n

S is taken to be equal with slope of the road.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 78

 JU, DEPARTMENT OF CIVIL ENGINEERING

At points of sag curve culverts are provided. The size (diameter) of culverts depends on the discharge that
will flow through it. The thickness of the culvert is designed based on the dead load and live load that will
apply on it.

In our project we have provided one sag curve at that point it needs culvert. And the culvert must be
provided at a chainage of 9+00.

PART FOUR
CHAPTER EIGHT
ROAD SIGNS AND MARKINGS
Introduction
Road furniture and marking are a very important of the communication system for road users along our
national highway roads. This help the users to correctly position their vehicle, guide them through the
many different situations that encountered; indicate where passing and turning is allowed, and warn them
the upcoming conditions.

Elements addressed in the terrain include road marking and marker post.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 79

 JU, DEPARTMENT OF CIVIL ENGINEERING

Traffic sign
Traffic signs provide essential information to drive safely and efficient maneuvering on the road. The
safety and efficiency of a road depends to a considerable degree on its geometric design. In this project,
while designing a vertical alignment, mis-phasing’s that are difficult or uneconomical to correct due to
small width of corridor. So that this dictates to use traffic sign that gives sign to the divers and make
necessary preparation for the potential hazardous.

Traffic signs are of three of general types.

Regulatory signs: indicate legal requirement of traffic movement this include stop signs,

Warning signs: indicate conditions that may be hazardous to highway users.

Should be provided at a distance of minimum stopping sight

Should be provided at a distance of minimum stopping sight distance

before entrance of curve.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 80

 JU, DEPARTMENT OF CIVIL ENGINEERING

- Should be provided to warn us for watching school children. Whenever there is a school in the vicinity
of the road.

Slippery When Wet.

These signs should be provided on relatively steep vertical curves

Informatory signs: convey information of use to the driver.

Road markings
The road marking delineates the pavement edges and there by clarity the paths that vehicles are to follow.
The function of road markings is to encourage safe and expeditious operation. In many case road marking
supplement and enhance the massages of other traffic control devices such as traffic signs and signals.

Generally three types of road marking is in use

Pavement marking
Object marking
Road studs

Pavement marking
Pavement marking can be divided in to four

Longitudinal
Transversal line

INTEGRATED CIVIL ENGINEERING DESIGN II Page 81

 JU, DEPARTMENT OF CIVIL ENGINEERING

Arrows, words, symbol markings

Special markings

The longitudinal pavement marking consists of center line, lane lines, no overtaking lines, etc…

By their pattern center lines regulate whether passing or overtaking is allowed or prohibited.

In our project at the second and third curve since the available sight distance is less than the required
passing sight distance no over taking lines must be provided.

Object markings
Physical obstructions in or near the carriage way should be removed to provide the appropriate clear zone.
Where removal is impractical, such objects should be adequately marked by painting or by use of other
high visibility materials.

For this project, since the data given does not have any information about the physical feature of the
project, it is better to mark at the time of construction rather than at this time.

Marker posts
Marker posts assist in a timely perception of the alignment ahead and, when equipped with reflections,
provide good guidance at night.

There are two types of marking posts.

Guide posts
Kilometer posts

1. Guide posts are intended to make driver aware of potential hazards such as abrupt changes in shoulder
width, abrupt changes in the alignment and appropriate to structural etc….

ERA GDM recommend that spacing of the guide posts to indicate shoulder width is 50 m interval.

Spacing of guideposts at curves

INTEGRATED CIVIL ENGINEERING DESIGN II Page 82

 JU, DEPARTMENT OF CIVIL ENGINEERING

The spacing of guideposts at curves depends with their radius, as indicated in the table below.

2. Kilometer post since our road is main access road it is not compulsory to have kilometer posts.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 83

 JU, DEPARTMENT OF CIVIL ENGINEERING

CONCLUSION

In general transportation plays a vital role for economical growth of a country. A good

engineering design is the one which is both economical and safe. In this project we have tried our

best so that the project will give the expected service with minimum construction operation cost.

In countries like Ethiopia development process will be achieved if the roads are constructed well.

Also road construction will help a complete communication between different towns in the

country. The road from Jimma to Bonga is a main access road and. Finally this particular project

helped us to know more about Highway engineering and to be aware about field work.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 84

 JU, DEPARTMENT OF CIVIL ENGINEERING

LIMITATION

Some of the constraints we faced while working this project are:

Provision of incomplete data- we are not provided with sufficient data for the

drainage conditions thus we are forced to use data’s recommended by ERA design

manual to design the drainage.

Computer and Internet access- since our lab is not equipped with appropriate

materials thus we are forced to do many of the project work manually.

Lack of adequate space for the drawing- we have done all the project drawings in our

dormitories and class rooms due to the fact that the drawing room is not available in

the break time.

INTEGRATED CIVIL ENGINEERING DESIGN II Page 85

 JU, DEPARTMENT OF CIVIL ENGINEERING

RECOMMENDATION

REFERENCES

INTEGRATED CIVIL ENGINEERING DESIGN II Page 86

 JU, DEPARTMENT OF CIVIL ENGINEERING

ERA design manual 2002

Highway engineering-I teaching material by Prof.
Dr. Eng. Alemayehu Gebissa
Highway engineering-II teaching material by Ins-
Yifru Kebede
Previous year projects
Internet

INTEGRATED CIVIL ENGINEERING DESIGN II Page 87