MS GEOTECHNICAL ENGINEERING SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING Term Paper Report On Course Code

MS GEOTECHNICAL ENGINEERING

SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING

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Term Paper Report
On

Course Code:

Course Title:

Date:

Submitted By:
Zahra Bashir Malik
00000171792
Nabeela Maheen
00000118852
Submitted To:
Dr. Kamran Ahmed

Design of Flexible Pavement Using Asphalt Institute Method and AASHTO
Empirical Method
CE860
Pavement Design & Analysis
16 -Jan -2017

i

TABLE OF CONTENTS
Table of Contents ………………………….. ………………………….. ………………………….. ……………………….. i
List of Tables ………………………….. ………………………….. ………………………….. ………………………….. .. ii
List of Figures ………………………….. ………………………….. ………………………….. ………………………….. . ii
1. INTRODUCTION ………………………….. ………………………….. ………………………….. ……………… 1
2. OBJECTIVES ………………………….. ………………………….. ………………………….. ……………………. 1
3. CALCULATION OF EASL ………………………….. ………………………….. ………………………….. … 1
3.1. Average Annual Daily Traffic (AADT) ………………………….. ………………………….. ……. 2
3.2. % Truck (T) ………………………….. ………………………….. ………………………….. ……………… 2
3.3. Truck Factor (TF) ………………………….. ………………………….. ………………………….. ……… 3
3.4. Growth Factor (GY) ………………………….. ………………………….. ………………………….. ….. 3
3.5. Directional Distributio n Factor (D) ………………………….. ………………………….. ………….. 4
3.6. Lane Distribution Factor (L) ………………………….. ………………………….. ……………………. 4
3.7. Calculation of EASL ………………………….. ………………………….. ………………………….. …. 4
4. PAVEMENT DESIGN ………………………….. ………………………….. ………………………….. ……….. 5
4.1. Pavement Design by Asphalt Institute Method ………………………….. ………………………….. 5
4.1.1. Traffic Characteristics ………………………….. ………………………….. ………………………….. .. 5
4.1.2. Subgrade engineering properties ………………………….. ………………………….. …………… 5
4.1.3. Subbase and base engineering properties ………………………….. ………………………….. ….. 5
4.1.4. Determine Min. Thickness Requirements ………………………….. ………………………….. . 6
4.1.5 . Thickness of HMA layer ………………………….. ………………………….. ……………………… 6
4.1.6. Planned Stage Construction ………………………….. ………………………….. …………………. 7
4.2. Pavement Design by AASHTO Method ………………………….. ………………………….. ………. 8
4.2.1. Pavement Performance ………………………….. ………………………….. ……………………….. 8
4.2.2. Traffic ………………………….. ………………………….. ………………………….. ………………….. 8
4.2.3. Roadbed Soils (subgrade material) ………………………….. ………………………….. ……….. 8
4.2.4. Materials of Construction ………………………….. ………………………….. ……………………. 8
4.2.5. Drainage ………………………….. ………………………….. ………………………….. ……………… 10
4.2.6. Reliability ………………………….. ………………………….. ………………………….. ……………. 11
4.2.7. Calculation of Thicknesses of layers ………………………….. ………………………….. …… 11
5. COMPA RISON ………………………….. ………………………….. ………………………….. ……………….. 13
6. CONCLUSION ………………………….. ………………………….. ………………………….. ………………… 13
7. REFRENCES ………………………….. ………………………….. ………………………….. …………………… 13

ii

LIST OF TABLES
Table -1 Estimated Section Wise AADT (Year 2019) ………………………….. ………………………….. …. 2
Table -2 Calculat ion of Percentage Truck (T) ………………………….. ………………………….. …………….. 2
Table – 3 Axle Load Study on National Highway, NTRC, 1995 and NHA ………………………….. …. 3
Table – 4 Calculation of Growth Factor from Expected Growth Rates ………………………….. ……….. 3
Table – 5 Percentage of Total truck Traffic in Design Lane ………………………….. ………………………. 4
Table – 6 Lane Distribution Factor ………………………….. ………………………….. ………………………….. … 4
Table – 7 Calculation of EASL for 2019 -2024 ………………………….. ………………………….. ……………. 4
Table – 8 Calculation of EASL for 2024 -2039 ………………………….. ………………………….. ……………. 5
Table – 9 Quality Requirements for Untreated Aggregate Base and Sub -bases ………………………… 6
Table – 10 Minimum Thickness of Asphalt C oncrete or Untreated Base ………………………….. …….. 6
Table – 11 Definition of Drainage Quality ………………………….. ………………………….. ………………… 10
Table – 12 Recommended m i Values ………………………….. ………………………….. ……………………….. 10
Table – 13 Suggested Levels of Reliability for Various Functional Classifications …………………. 11
Table – 14 AASHTO Recommended Minimum Thickness of Highway Layers ……………………… 12
LIST OF FIGURES
Figure 1: Flow Chart for Calculation of EASL ………………………….. ………………………….. ………….. 1
Figure 2: Flow Chart of Design Procedure for Aspha lt Institute Method ………………………….. …… 5
Figure 3: Design charts for HMA with 8 inches Untreated Aggregate Base ………………………….. .. 6
Figure 4: Determination of thickness of Asphalt layer for Planned Stage Construction ……………. 7
Figure 5: Flow Chart for AASHTO Empirical Method ………………………….. ………………………….. .. 8
Figure 6: Variation in Granular Subbase Layer Coefficient, a 3, with various Subbase Strength
Parameters ………………………….. ………………………….. ………………………….. ………………………….. ……. 9
Figure 7: Variation in Granular Base Layer Coefficient, a 2, with various Base Strength
Parameters. ………………………….. ………………………….. ………………………….. ………………………….. …… 9
Figure 8: Charts for Estimating Structural Layer Coefficient of Dense -Graded/Asphalt Concrete
Based on the Elastic (Resilient) Modulus ………………………….. ………………………….. ………………… 10
Figure 9: Determination of Structural Number from R, S O, W 18, M R and ?PSI …………………….. 11

1

1. INTRODUCTION
On a proposed highway, a flexible pavement is designed by using estimated traffic data from two
methods, i.e. Asphalt Institute Method (AI) and AASHTO Empirical Method . An estimated
traffic and growth rate s were provided.
2. OBJECTIVES
The objectives of this report are:
? Calculation of EASLs
? Design of Flexible Pavement by AI Method
? Design of Flexible Pavement by AASHTO Empirical Method
? Comparison of results obtained from AI and AASHTO methods.
3. CALCULATION OF EASL
For Calculation of EASLs the following formula is used;

Figure 1: Flow Chart for Calculation of EASL

Caculation of EASL
Average
Daily Traffic
ADT

% Truck

T
Truck Factor
TF
Growth
Factor
G
Design Period
Y
Directional
Distribution
Factor
D
Lane
Distribution
Factor
L 365? ? ? ? ? ? ? ? L D Y G TF T ADT ESAL

2

3.1. Average Annual Daily Traffic (A ADT)
Average annual daily traffic was given and provided in Table -1.
Table -1 Estimated Section Wise AADT (Year 2019)

3.2. % Truck (T)
Percentage of Trucks for each section is calculated and shown in Table -2
Table -2 Calculation of Percentage Truck (T)

Se ction Car Hiace Large
Buse s
2-Axle
Truck
3-Axle
Truck
4-Axle
Truck
>5-Axle
Truck
1 23,129 975 266 2,277 895 404 1,033
2 16,876 1,041 217 2,208 708 386 944
3 12,765 978 200 1,550 902 386 858
4 10,937 1,165 163 1,893 858 394 620
5 18,325 1,085 157 1,927 728 518 726
6 20,431 1,015 223 2,608 973 449 944
7 16,254 1,443 255 2,470 1,367 459 923
sum= 1481 14,933 6431 2996 6,048 Se ction Car Hiace Large
Buse s
2-Axle
Truck
3-Axle
Truck
4-Axle
Truck
>5-Axle
Truck
1 23,129 975 266 2,277 895 404 1,033
2 16,876 1,041 217 2,208 708 386 944
3 12,765 978 200 1,550 902 386 858
4 10,937 1,165 163 1,893 858 394 620
5 18,325 1,085 157 1,927 728 518 726
6 20,431 1,015 223 2,608 973 449 944
7 16,254 1,443 255 2,470 1,367 459 923
sum= 1481 14,933 6431 2996 6,048
Total Sum of passes = 31,889
% Truck = 4.644 46.828 20.167 9.395 18.966

3

3.3. Truck Factor (TF)
TF are determined from Table -3 NTRC , 1995.
Table – 3 Axle Load Study on National Highway, NTRC, 1995 and NHA

3.4. Growth Factor (GY)
The estimated growth rate s were provided and are mentioned in Table -4. Growth factors against
each vehicle typ e is calculated and shown as under.
Table – 4 Calculation of Growth Factor from Expected Growth Rates

Growth rates of first 10 design years will be used for calculating EASLs.

S. No Ve hicle Type Growth
Rate (1+r)^n Growth Factor
(1+r)^n-1/r
Growth
Rate (1+r)^n Growth Factor
(1+r)^n-1/r
1 Passenger Cars, Jeep/ 4WD 5 1.277 5.54 4.5 1.936 20.8
2 Hiace/Mini Bus 4 1.217 5.425 3.5 1.676 19.315
3 Large Buses 4 1.217 5.425 3.5 1.676 19.315
4 2 – Axle Rigid Truck 4.5 1.247 5.489 4 1.801 20.025
5 3 – Axle Rigid Truck 4.5 1.247 5.489 4 1.801 20.025
6 4 – Axle Articulated Truck 4.5 1.247 5.489 4 1.801 20.025
7 5 – Axle Articulated Truck 4.5 1.247 5.489 4 1.801 20.025
8 6 – Axle Articulated Truck 4.5 1.247 5.489 4 1.801 20.025
2019 – 2024 2024 – 2039

4

3.5. Directional Distribution Factor (D)
Assuming 3 lanes in each direction. The number of traffic l anes in two directions will be 6 and
directional distribution factor will be 0. 40. Table -5 provides directional distribution.
Table – 5 Percentage of Total truck Traffic in Design Lane

3.6. Lane Distribution Factor (L )
Assuming 3 lanes in each direction. The lane distribution factor will be 0. 6. Table -6 provides
Lane distribution factor against no. of lanes in each direction.
Table – 6 Lane Distribution Factor

3.7. Calculation of EASL
Following Tables 7, and 8 shows calculations of EASLs for 5 and 15 years of design life.
Table – 7 Calculation of EASL for 2019 -2024

Ve hicle Type AADT T
(%age ) TF GY D L EASL
Large Buse s 1481 4.644 0.939 5.425 0.4 0.6 30691.4
2-Axle Truck 14,933 46.828 4.67 5.489 0.4 0.6 1.6E+07
3-Axle Truck 6431 20.167 8.84 5.489 0.4 0.6 5512764
4-Axle Truck 2996 9.395 10.35 5.489 0.4 0.6 1400800
>5-Axle Truck 6,048 18.966 10.9 5.489 0.4 0.6 6011895
2.9E+07

5

Table – 8 Calculation of EASL for 2024 -2039

Design EASL s are 2.9 x 10 7.
4. PAVEMENT DESIGN

4.1. Pavement Design by Asphalt Institute Method
A flow chart of the design procedure for AI method is shown is Figure 2 as under

Figure 2: Flow Chart of Design Procedure for Asphalt Institute Method
4.1.1. Traffic Characteristics
Calculated EASLs = 29 x10 6
4.1.2. Subgrade engineering properties
Assuming CBR of Sub grade = 6
M r = 1500 x 6 = 9,0 00 psi
4.1.3. Subbase and base engineering properties
Certain requirements are needed for subbase and base materials , which are given in Table -14 .
AI Method
Traffic characteristics
EASL
Subgrade engineering
properties
Mr
Subbase and base
engineering
properties
Determine Min.
Thickness
Requirements
Feasibility of
Planning stage
construction Ve hicle Type AADT T
(%age ) TF GY D L EASL
Large Buse s 1481 4.644 0.939 19.315 0.4 0.6 109272.7
2-Axle Truck 14,933 46.828 4.67 20.025 0.4 0.6 57285695
3-Axle Truck 6431 20.167 8.84 20.025 0.4 0.6 20111696
4-Axle Truck 2996 9.395 10.35 20.025 0.4 0.6 5110408
>5-Axle Truck 6,048 18.966 10.9 20.025 0.4 0.6 21932627
1.05E+08

6

Table – 9 Quality Requirements for Untreated Aggregate Base and Sub -bases

4.1.4. Determine Min. Thickness Requirements
From Table -15, minimum thickness of Asphalt Concrete over untreated aggregate base is
determined its value is 5 inches which is satisfied .
Table – 10 Minimum Thickness of Asphalt Concrete or Untreated Base

4.1.5. Thickness of HMA layer
From Figure 3, the thickness of HMA with 8 inches untreated aggregate base is = 1 4 inches

Figure 3: Design charts for HMA with 8 inches Untreated Aggregate Base
Total thickness of pavement by AI method = 1 4 + 8 = 22 inches

7

4.1.6. Planned Stage Construction
Planned Stage Construction involves successive application of HMA layers according to a
predetermined time schedule. Assuming Damage ratio of 60%;
n1= 2.9×10 7 & D r = 0.6
N1 = n 1/D r = 2.9×10 7/ 0.6 = 4.8×10 7
From design Chart with N 1 & M r; h1=15.8 i n. (use 16 in.)
n2 = 1.05×10 7 & 1 -Dr = 0.40
N2 = n 2/ (1 -Dr) = 1.05×10 7 / 0.4 = 2.61×10 7
From design chart with N 2 & M r; h2 =1 4 in.
Overlay thickness h s = h 2 –h1 = 1 6 – 14 = 2.0 in.

Figure 4: Determination of thickness of Asphalt layer for Planned Stage Construction

8

4.2. Pavement Design by AASHTO Method

Figure 5: Flow Chart for AASHTO Empirical Method
4.2.1. Pavement Performance
Serviceabili ty Performance: Measured by PSI ( Present Serviceability Index ) with scale 0 to 5.
The PSI initial value that was measured at AASHTO test road about 4.2 for flexible pavement
while 2.5 is taken as terminal value.
Pi = 4.2 , Pt = 2.5
?PSI = 4. 2 – 2.5 = 1.7
4.2.2. Traffic
Calculated EASLs = 29 x10 6
4.2.3. Roadbed Soils (subgrade material)
During struc tural design, only M r values are used. The f ollowing conversion formula is used f or
CBR .
M r = 1500 x 6 = 9 ,000 psi
4.2.4. Materials of Construction
M r of AC at 68 oF = 450,000 psi
CBR value of base = 100, M r = 31 ,000 psi (25,000 psi – 75,000 psi )
CBR value of sub base = 22, M r = 13,500 psi (5,000 psi – 50,000 psi )

AASHTO Method
Pavement
performance
Serviceability
?PSI
Traffic
EASL
Roadbed soils
(subgrade
material)
Mr
Materials of
construction
a3, a2, a1
Drainage
mi
Reliability
ZR x S o

9

4.2.4.1. For Subbase, a 3

Figure 6: Variation in Granular Subbase Layer Coefficient, a 3, with various Subbase Strength Parameters
From Figure 6 , a3 = 0.1 (CBR = 22, sub base)
4.2.4.2. Base course, a 2

Figure 7: Variation in Granular Base Layer Coefficient, a 2, with various Base Strength Parameters .
From figure 7, a2 = 0.14 (CBR = 100, Base)

10

4.2.4.3. AC surface, a 1

Figure 8: Charts for Estimating Structural Layer Coefficient of Dense -Graded/Asphalt Concrete Based
on the Elastic (Resilient) Modulus
From figure 8, a1 = 0.44 ( Mr = 450 ,000 psi, AC )
4.2.5. Drainage
A week for water to be drain with in moisture level = 30%
Table – 11 Definition of Drainage Quality

From Table -11 the drainage quality is assumed as „Fair?.
Table – 12 Recommended m i Values

For “Fair” and 30% exposure, then mi is 0.80.

11

4.2.6. Reliability
Table – 13 Suggested Levels of Reliability for Various Functional Classifications

From Table -13, for urban highway interstate and other freeways have reliability of 80 -99%.
Reliability level (R ) = 99%
So for flexible pavement i s 0.4 -0.5. Taking S o = 0.4 9
4.2.7. Calculation of Thicknesses of layers

Figure 9: Determination of Structural Number from R, S O, W 18, M R and ?PSI
a1 = 0.44, a2 = 0.14 , a3 = 0.1
By using Figure 9, SN 3 = 7.3 (M r= 9 ,000 psi)
SN 2 = 6.2 (M r = 13 ,500 psi)
SN 1 = 4 .8 (M r = 31 ,000 psi)

12

a

SN 1*= a1 D1* =0.44 x 11 = 4.84
2

0. 4 x 0. x 4 . 2

0. x 0. x 4 . 2
Asphalt concrete surface = 11 ”
Granular base = 1 2.5 ”
Su b base = 1 7″
Total Thickness of Pavement = 40.5 ”
Table – 14 AASHTO Recommended Minimum Thickness of Highway Layers

13

5. COMPARISON
AI Method AASHTO Method
Structural Design
Total thickness of Pavement 22 inch 40.5 inch
Thickness of Asphalt Wearing course 14 inch 11 inch
Thickness of Aggregate Base course 8 inch 12.5 inch
Thickness of Subbase 17 inch
CBR and M r
Asphalt Concrete at 68 OF M r = 450,000 psi
Base Course Min CBR = 20 CBR = 100, M r = 31,000 psi
Subbase Min CBR = 80 CBR = 22, M r = 13,500 psi
Subgrade CBR = 6, M r = 9,000 psi CBR = 6, M r = 9,000 psi
Cost (depends on Asphalt layer)
Higher than other Lower than other
6. CONCLUSION
It is concluded that AASHTO Empirical method is more realistic than AI method, because it
comprises of variety of parameters for pavement designing.
7. REFRENCES
i. TRC tudy, “Axle Load tudies on ational Highways”, ational Transport Research
Centre, Government of Pakistan, 1995.
ii. Pavement Analysis and Design, Second Edition, Yang H . Huang, University of Kentucky .