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- 1. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli INTRODUCTION Differences Between Concrete and Asphalt Pavement Historically, pavements have been divided into two broad categories, rigid and flexible. These classical definitions, in some cases, are an over-simplification. However, the terms rigid and flexible provide a good description of how the pavements react to loads and the environment. The flexible pavement is an asphalt pavement. It generally consists of a relatively thin wearing surface of asphalt built over a base course and subbase course. Base and subbase courses are usually gravel or stone. These layers rest upon a compacted subgrade (compacted soil). In contrast, rigid pavements are made up of portland cement concrete and may or may not have a base course between the pavement and subgrade. The essential difference between the two types of pavements, flexible and rigid, is the manner in which they distribute the load over the subgrade. Rigid pavement, because of concrete’s rigidity and stiffness, tends to distribute the load over a relatively wide area of subgrade. The concrete slab itself supplies a major portion of a rigid pavement's structural capacity. Flexible pavement, inherently built with weaker and less stiff material, does not spread loads as well as concrete. Therefore flexible pavements usually require more layers and greater thickness for optimally transmitting load to the subgrade. The major factor considered in the design of rigid pavements is the structural strength of the concrete. For this reason, minor variations in subgrade strength have little influence upon the structural capacity of the pavement. The major factor considered in the design of flexible pavements is the combined strength of the layers. One further practical distinction between concrete pavement and asphalt pavement is that concrete pavement provides opportunities to reinforce, texture, color and otherwise enhance a pavement, that is not possible with asphalt. These opportunities allow concrete to be made exceedingly strong, long lasting, safe, quiet, and architecturally beautiful. Concrete pavements on average outlast asphalt pavements by 10-15 years before needing rehabilitation. 1
- 2. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli 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. 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 A typical flexible-pavement structure is shown in Figure bellow. It illustrates the terms used in this manual that refer to the various layers. All the layers shown in Figure bellow are not present in every flexible pavement. 2
- 3. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli A new 6-lane expressway is proposed to be built from Bandar A to Bandar B. The length of the expressway is approximately 25 km. AASHTO Flexible Design Procedure : The design basis presented in this document is based upon the 1993 American Association of State Highway and Transportation Officials (AASHTO) Design Guide. The objective is to provide design parameters for local materials and conditions, and to provide guidance on the use of AASHTO equations. For estimating the thickness base on the AASHTO design method procedure we need to determine the SN ( structural number ) from the design chart for flexible pavement or using the equation as the above indicate : In this project we have decided use the chart instead of equation so before using the chart we need to have some parameters for using it : 3
- 4. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli 1.reliability that be given in the project , Reliability= 85% 2.Standard Deviation that be given , Standard Deviation= 0.45 3.ESAL 4.The resilient Modulus for the different roadbed layers 5.Design Serviceability Loss, ∆PSI = PSI terminal – PSI initial = 4.2 – 2.0 = 2.2 By the above information at first we require to have the ESAL ( equivalent Single Axle Load) Traffic analysis : Overview Pavement is designed based on the traffic loadings expected in the highway’s design lane, the lane expected to experience the greatest number of 18,000 pound equivalent single axle loads (18K ESALs) over the design period (usually 20 years). The traffic data required to calculate the ESALS include: base year ADT ADT traffic growth rate for the design year percentage trucks, including dual-rear-tire pickups and buses, for each classification category directional distribution for the design period lane distribution factor for the design period. Traffic Data Provided ADT traffic growth rate for the design year percentage trucks, including dual-rear-tire pickups and buses, for each classification category directional distribution for the design period. 4
- 5. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Traffic Data ADT % Trucks 1ffic growth factor Design period Directional distribution Lane distribution Slow lane Middle lane Fast lane Lane width = 25, 500 vehicles (both direction) = 15* = 12.58 = 10 years = 60/40 = 65% = 25% = 10% = 3.70 m ( 12 ft) *Detailed information on trucks Cars, pickups, light vans Single-unit truck Tractor semi-trailer truck = two 2000-lb (8.9-kN) single axles ( 40%) = 8000-lb (35.6 kN) steering, single axle ( 15%) = 22,000-lb (97.9-kN) drive, single axle ( 15%) = 10,000-lb (44.5-kN) steering, single axle (10%) = 16,000-lb (71.2-kN) drive, tandem axle (10%) = 44, 000-lb (195.7-kN) trailer, triple axle (10%) Tandem drive axle on a tractor frame during manufacturing 5 Saeed Badeli
- 6. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN Determine ESAL : ESAL initial = ADT * %T * Gi * N * 365 * Y ESAL final = ESAL ini * Dd * Ld Determine N : In terms of the table 6.4 the EALF can be found so : Cars, pickups, light vans 2 * 0.00018 = 0.00036 0.00036 * 0.4 = 0.000144 Single-unit truck 0.0343*0.15=0.00514 2.18*0.15=0.327 Tractor semi-trailer truck 0.0877*0.1=0.00877 0.0472*0.1*2 =0.00944 0.723*0.1*3 = 0.2169 N = 0.000144 + 0.00514+0.327+0.00877+0.00944+0.2169 N= 0.567 ESAL initial = 25500 * 0.15 * 12.58 * 0.567 * 365 ESAL initial = 9958364.168 ESAL final = 9958364.168 * 0.6 * 0.65 ESAL final = 3883762.025 psi ESAL final = 3.9 * 10^6 psi 6 ECV 5606 Saeed Badeli
- 7. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli Determine MR : Resilient Modulus (Mr) is a fundamental material property used to characterize unbound pavement materials. It is a measure of material stiffness and provides a mean to analyze stiffness of materials under different conditions, such as moisture, density and stress level. It is also a required input parameter to mechanistic-empirical pavement design method. Mr is typically determined through laboratory tests by measuring stiffness of a cylinder specimen subject to a cyclic axle load. Mr is defined as a ratio of applied axle deviator stress and axle recoverable strain. Reslient Modulus Experimental Setup Resilient modulus is determined using the triaxial test. The test applies a repeated axial cyclic stress of fixed magnitude, load duration and cycle duration to a cylindrical test specimen. While the specimen is subjected to this dynamic cyclic stress, it is also subjected to a static confining stress provided by a triaxial pressure chamber. It is essentially a cyclic version of a triaxial compression test; the cyclic load application is thought to more accurately simulate actual traffic loading. In this project we have resilient modulus for 3 different layers this means that we do not need to find the resilient modulus base on AASHTO design method. Resilient modulus properties : SMA, MR=3104 Mpa (450,000 psi) SMA (Stone Matrix Asphalt) Base, MR= 241 Mpa (35,000 psi) Subbase, MR= 93 Mpa (13,500 psi) Subgrade, MR ( Subgrade Resilient Modulus Varies throughout the project length) Subgrade, MR= 48 Mpa (7,000 psi) The Subgrade resilient modulus is the effective resilient modulus. So we have enough information for determining the Structural Number by using the chart. 7
- 8. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli As the above chart indicates we have 3 different Structural Number by 3 different roadbed Resilient modulus, Base resilient modulus = 35000 psi SN 1 = 2.30 Subbase resilient modulus = 13500 SN 2 = 3.30 Subgrade resilient modulus = 7000 SN 3 = 4.00 8
- 9. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli Determine the Thickness : For determining the thickness by AASHTO ,it gives the equation SN = a1D1 + a2D2m2 + a3D3m3 In which a1 , a2 and a3 are the layer coefficients of the asphalt, base and subbase layers which be given in this project D1 , D2 and D3 are the thicknesses of the different layers ,m2 is the drainage coefficient for the base layer and m3 for the subbase layer. Design of layer thickness : D1 = SN1 / a1*m1 D1=2.30/0.44*1 D1=5.227 ≈ 5.50 inch = 13.97 cm SN* = D1*a1*m1 SN* = 5.50*0.44*1 SN*=2.42 ≥ 2.30 OK√ -----------------------------------------------------------------------------------------------------D2 = (SN2-SN1*)/(a2*m2) D2=(3.30-2.42)/(0.15*0.75) D2=7.82 inch ≈ 8.00 inch = 20.32 cm SN*2 = 8.00*0.75*0.15 SN*2 = 0.90 SN*1 + SN* 2 ≥ SN2 0.90 + 2.42 = 3.32 3.32 ≥ 3.30 OK√ -----------------------------------------------------------------------------------------------------D3 = (SN3 – ( SN* 2 + SN*1 )) / (a3*m3) D3 = (4.00 – (0.90+2.264)) / (0.75*0.10) 9
- 10. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN D3 = 11.147 D3 = 11.50 inch = 29.21 cm SN* 3 = 11.50*0.75*0.10 SN* 3 = 0.8625 SN*3 + SN*2 + SN*1 ≥ SN3 0.8625+0.90+2.42=4.183 4.00 OK√ So the layer thickness for the asphalt , base and subbase are : D1=5.50 inch = 13.97 cm D2=8.00 inch = 20.32 cm D3=11.50 inch = 29.21 cm 10 ECV 5606 Saeed Badeli
- 11. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN 11 ECV 5606 Saeed Badeli
- 12. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli JKR method based on CBR California Bearing Ratio (CBR) The California Bearing Ratio (CBR) test is a simple strength test that compares the bearing capacity of a material with that of a well-graded crushed stone (thus, a high ,quality crushed stone material should have a CBR @ 100%). It is primarily intended for but not limited to, evaluating the strength of cohesive materials having maximum particle sizes less than 19 mm (0.75 in.) (AASHTO, 2000). It was developed by the California Division of Highways around 1930 and was subsequently adopted by numerous states, counties, U.S. federal agencies and internationally. As a result, most agency and commercial geotechnical laboratories in the U.S. are equipped to perform CBR tests. JKR Method This method is a combination of two methods using a formula and figures from the result of the testing. A complete guideline for pavement design can be found in “ Arahan Teknik (Jalan) 5/85”. The thickness of the pavement depends on the CBR value and the Total Cumulative of Standard Axle ( JBGP ).Some data need to be collected before starting any design. They are; i. Design life. ii. Road hierarchy base of JKR classification. iii. Average daily traffic volume. iv. Percentage of commercial vehicle. v. Yearly rate of traffic growth. vi. CBR value for sub-grade. vii. Topography condition. Design Life The design life on JKR Design Method is suggested for 10 years. The design life begins from the road starts in use for traffic until the maintenance is required. 12
- 13. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli This manual is to be used for the design of flexible pavements for roads. It comprises of details for the thickness design,materials specification and the mix design requirements. For determining the thickness JKR recommend to use the bellow nomograph So in terms of the above nomograph we require to find the CBR of the subgrade and also Equivalent Axle Load. 13
- 14. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli FHWA Class 9 five-axle tractor semi trailer (18 tires total). A typical tire load is 18.9 kN (4,250 lbs) with an inflation pressure of 689 kPa 100 psi Traffic Estimation Vo = ADTT*Dd*Ld*365*Pc/100 ADTT = ADT * T% ADTT = 25500*0.15 ADTT = 3'825.00 Determine Pc : In terms of the table 6.4 the EALF can be found so : Cars, pickups, light vans 2 * 0.00018 = 0.00036 0.00036 * 0.4 = 0.000144 Single-unit truck 0.0343*0.15=0.00514 2.18*0.15=0.327 Tractor semi-trailer truck 0.0877*0.1=0.00877 0.0472*0.1*2 =0.00944 0.723*0.1*3 = 0.2169 14
- 15. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli Pc = 0.000144 + 0.00514+0.327+0.00877+0.00944+0.2169 Pc= 0.567 Vo=3825*0.60*0.65*365*0.567 Vo = 308'725.1213 In which Vo is the initial annual commercial traffic for one direction . The total number of commercial vehicles for one direction Vc is obtained by : Vc = (Vo*(((1+r)^x) – 1 )) / r Vc = Vo * Gi Vc= 308725.1213 * 12.58 Vc = 3883762.026 psi Vc = 3.9 * 10^6 In this case we have : The total equivalent standard axles (ESA) can determine as : ESA = Vc ESA = 3.90 * 10^6 The maximum hourly traffic volume is calculated as follows : C=I*R*T For determining the above equation we should use the table 3.2 , 3.3 and 3.4 on the JKR Road type = Multilane I = 2000*3 = 6000 R= 1.00 T= 100 / (100+pc) 15
- 16. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 T= 100/(100+15) T= 0.87 C= 6000 * 1 * 0.87 C= 5220 veh/hour/lane C reflects 10% of the 24 hours , then the one way daily capacity is as follows: C= 10 * c C = 52200 veh/day/lane V = ( ADT * (1+r)^x) / 2 Gi=12.58 For finding r ,we can use the 6.13, r=0.05 V= ( 25500 * (1+0.05)^10 ) / 2 V = 20768.41 veh/day/lane Hence capacity has not been reached after 10 years . Determine the subgrade CBR: The CBR can be found by the resilient modulus of subgrade soil which is : Subgrade, MR= 48 Mpa (7,000 psi) In terms of the subgrade resilient modulus we have : CBR = 48 / 10 CBR = 4.80 16 Saeed Badeli
- 17. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN From the above nomograph, the chart shows that for ESA of 8.30*10^6 ,the required TA is 24.70 cm Determine the Structural Layer Coefficient : For estimating this number for each layers we can use the Table 3.5 17 ECV 5606 Saeed Badeli
- 18. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN a1=1.00 a2=0.32 a3=0.23 18 ECV 5606 Saeed Badeli
- 19. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli Design of Layer Thickness : In terms of the table 3.8 ,the minimum thickness of bituminous layer in this case will be 15.0 cm. TA = a1D1 + a2D2 + a3D3 1st Trial : Nominate D1=15.00 cm D2=16.00 cm D3=18.00 cm Then TA = 1.00*15.00 + 0.32*16 + 0.23*18 TA = 24.26 ≤ T Second Trial D1=15 cm D2=18 cm D3=18 cm T 24. ≈T So the Final thickness of Asphalt, Base and Subbase layers are : D1 = 15 cm D2 = 18 cm D3 = 18 cm 19
- 20. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN Cost considerations : Cost of Materials and construction (includes transportation cost) Crusher-run Base Sand Subbase Stone Mastic Asphalt Cost of construction cubic meters * density = tonnes 20 = RM 22.00 tonne = RM 15.00 per tonne = RM 330.00 per tonne RM 15.50 per sq meter ECV 5606 Saeed Badeli
- 21. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli Determining the total cost by using the AASHTO thickness : Layer Cost of Material (RM/ton) Required Density (ton/m³) No. of Lane Lane Width (m) Road Length (m) Thickness (m) Construction cost (m²) Project Cost (RM) SMA 330.00 2.35 6 3.7 25000 0.1397 15.50 68'729'729 Base 22.00 2.25 6 3.7 25000 0.2032 15.50 14'184'912 Subbase 15.00 2.3 6 3.7 25000 0.2921 15.50 14'195'485 Total = 97'110'126 RM The above table is indicated that the sum of cost will be more than 97 million RM which is effected from the Stone Matric Asphalt layer which is more than 68 million RM. 21
- 22. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli Determining the total cost by using the JKR method and thickness : Layer Cost of Material (RM/ton) Required Density (ton/m³) No. of Lane Lane Width (m) Road Length (m) Thickness (m) Construction cost (m²) Project Cost (RM) SMA 330.00 2.35 6 3.7 25000 0.15 15.50 73'162'875 Base 22.00 2.25 6 3.7 25000 0.18 15.50 13'547'550 Subbase 15.00 2.3 6 3.7 25000 0.18 15.50 12'049'050 Total = 98'759'475 RM The above table is indicated that the sum of cost will be more than 98 million RM which is affected from the Stone Matric Asphalt layer which is more than 73million RM. 22
- 23. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN ECV 5606 Saeed Badeli RECOMMENDATIONS : The above tables is indicated the different cost for constructing the roadway. The first table shows that the cost of AASHTO method is more than 108 million RM with 0.1651 m asphalt layer thickness. The second table shows that the cost of using the JKR method of design is more than 101 million RM with 0.158 m asphalt layer thickness. The JKR method gives a higher cost than the AASHTO . The layer thickness of AASHTO method is thinner compare to the JKR method. So the AASHTO method in this case is cost-effectiveness than the JKR method so the authorities should use the AASHTO method . Many project in the U.S.A and many other countries design by AASHTO method. The most important factor that effects the cost is the asphalt thickness We require to have a minimum thickness of asphalt layer for have a cost-effective design so try to use the minimum thickness and finding the base and subbase based on the minimum thickness of asphalt layer. Maximize crushed stone thickness and sand subbase thickness – minimize AC thickness Can also stabilize base to use less HMA Use gravel only for fill or frost 23

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