462460293-Design-of-flexible-pavement-pptx.pptx

Pavements

1. DESIGN OF FLEXIBLE PAVEMENT

2. Elements of flexile pavement structure

3. Design of flexible pavement Malaysian Design Methods (JKR)

4. Arahan Teknik Jalan 5/85 Arahan teknik jalan 5/85 manual introduced in 1985. This manual is suitable for the design of major roads where the traffic is medium or heavy. Date required in the design are Design period, n (JKR suggest to use 10 years) Class of road ( e.g R5, R4) Initial average daily traffic, ADT Percentage of commercial vehicles, Pc Average annual traffic growth, r Subgrade CBR Terrain condition

5. Design process Calculate the initial annual commercial vehicle for one direction ( from the expected year of completion of construction, onwards) Vo = ADT x 0.5 x 365 PC/100 where ADT = Average Daily Traffic PC= Percentage of commercial vehicles

6. Calculate the total number for commercial vehicles for the design period in one direction Where; V o = initial yearly commercial traffic r = rate of annual traffic growth x = design life  

7. Calculate the total cumulative equivalent standard axle load application for the design period ESA = V c x e ;

8. Check daily capacity at the end of the design period Total one way traffic at the end of x years V x = V 1 (1+r) x Maximum one way hourly flow c = I x R x T Where; c is the maximum one way hourly capacity I is the ideal hourly capacity as in Table 3.6 R is the roadway factor as in Table 3.7 T is the traffic reduction factor in Table 3.8 Assuming hourly capacity, c as 10% of the 24 hrs;thus daily capacity is C = 10 x c Where; C is the 24 hrs. one way traffic capacity c is the maximum one way hourly capacity

9. Check C > V x If C > V x  OK (capacity will not be exceed at the end of design period) If C < V x  Not OK (capacity will be exceed by the end of design period) When C < V x happens, need to reduce design period. Years required to reach capacity,  

10. Determine the subgrade CBR In the case of varying CBR within a meter depth of subgrade, the mean CBR is determined as follows: CBR m = [(h 1 CBR 1 1/3 + h 2 CBR 2 1/3 +….+h n CBR n 1/3 )/(1000)] 3 Where CBRm =mean CBR value for that location CBR1, CBR2, CBRn = CBR value of each layer h1,h2,hn = thickness of each layer h1+h2+hn = 1000 mm

11. Obtain the equivalent thickness , TA’ from the nomograph Calculate The thickness for each layers; TA = a1 D1 + a2 D2 +...+ anDn where al,a2 ... an are the structural coefficients of each layer as shown in Table 3.9 D1 D2 ... Dn are the thickness of each layer as shown in Table 3.10, 3.11 and 3.12

12. Nomograph

13. Example Determine the required thickness for a JKR 05 road base on these data: Carriageway width = 7.5 m Shoulder width = 2.0 m ADT, both way = 6,600 Percentage of commercial vehicles = 15% Traffic growth rate = 7% Subgrade CBR = 5% Terrain = rolling Surfacing =asphaltic concrete Road base = wet mix macadam Subbase = sand

14. Solution Initial annual commercial traffic for one way Vo = ADT x 0.5 x 365 PC/100 Vo = 6600 x 0.5 x 365 x 0.15 =181,000 Cumulative commercial traffic for the design period = [181,000 (1+0.07) 10 -1]/0.07 = 2.5 x 10 6   Determine the required thickness for a JKR 05 road base on these data: Carriageway width = 7.5 m Shoulder width = 2.0 m ADT, both way = 6,600 Percentage of commercial vehicles = 15% Traffic growth rate = 7% Subgrade CBR = 5% Terrain = rolling Design period = 10 years Surfacing =asphaltic concrete Road base = wet mix macadam Subbase = sand

15. Since Pc = 15% and JKR 05 road, therefore e = 2 Cumulative equivalent standard axles for the design life ESA = V c x e ESA = 2.5 x 10 6 x 2 = 5.0 x 10 6 Determine the required thickness for a JKR 05 road base on these data: Carriageway width = 7.5 m Shoulder width = 2.0 m ADT, both way = 6,600 Percentage of commercial vehicles = 15% Traffic growth rate = 7% Subgrade CBR = 5% Terrain = rolling Design period = 10 years Surfacing =asphaltic concrete Road base = wet mix macadam Subbase = sand

16. Estimated daily traffic per direction per lane after 10 years; V x = V 1 (1+r) x = 6600/2 (1+0.07) 10 = 6492

17. Maximum hourly one way traffic flow c = I x R x T = 1000 x 1.0 x 0.77 = 770veh/hour/lane

18. Maximum daily capacity per lane per direction is C= 10 x 770 = 7700 veh /day/lane Since 6492<7700, hnce capacity have not been reached after 10 years Estimated daily traffic per direction per lane after 10 years; V x = V 1 (1+r) x = 6600/2 (1+0.07) 10 = 6492

19. From the nomograph , with ESA = 5 x 10 6 and CBR = 5%, the required TA’ is 26 cm

20. Layer coefficient and minimum thickness Layer Material Coefficient Minimum Thickness (cm) a1 Asphaltic concrete 1.00 9 a2 Mechanically stabilized crushed aggregate 0.32 10 a3 sand 0.23 10

21. First trial Nominate D1 =12.5 cm, D2 = 18 cm, D3 = 20 cm Then, SN = (1.00 x 12.5) + (0.32 x 18) + (0.23 x 20) = 22.86 < TA’…..Not ok Second trial Nominate D1 =15 cm, D2 = 20 cm, D3 = 20 cm Then, SN = (1.00 x 15 ) + (0.32 x 20) + (0.23 x 20) = 26 =TA’…..O k

22. Taking into consideration the minimum thickness requirements, the pavement structure then consists of the following thickness Wearing course = 5 cm Binder course = 10 cm Road base = 20 cm Subbase = 20 cm

23. Design of flexible pavement AASHTO

24. AASHTO- Design Consideration

25. Pavement Performance = Structural performance is related to the physical condition of the pavement with respect to factors that have a negative impact on the capability of the pavement to carry the traffic load. Traffic load = different types of vehicles such as cars, buses, single-unit trucks, and multiple-unit trucks expected to use the facility during its lifetime This is usually referred to as the equivalent single-axle load (ESAL). Roadbed soil = The 1993 AASHTO guide also uses the resilient modulus (Mr) of the soil to define its property . Material of construction = subbase , base, surface materials Environment = Temperature and rainfall are the two main environmental factors used in evaluating pavement performance in the AASHTO method Drainage = The effect of drainage on the performance of flexible pavements is considered in the 1993 guide with respect to the effect water has on the strength of the base material and roadbed soil Reliability = Reliability design levels ( R%), which determine assurance levels that the pavement section designed using the procedure will survive for its design period, have been developed for different types of highways.

26. AASHTO Method 1. Traffic in ESAL Calculation ESAL i = fd x Grn x AADT x 365 x Ni x F Ei Where ESAL = equivalent single axle load f d = Design lane factor Grn = growth factor AADT = annual average daily traffic Ni = number of axle Fei = load equivalency factor for axle category

27. 2. Roadbed Soils (subgrade materials) AASHTO used the subgrade Mr to define its property. 3. Materials of construction Layer of coefficient Asphalt concrete surface course (a1) Bituminous treated base (a2) Granular base (a2) Granular subbase (a3) Cement treated bases (a2).

28. 4 . Overall So Overall standard deviation that accounts for standard deviation (or variation) in materials & construction, chance variation in traffic prediction , and normal variation in pavement performance . So = 0.45 for flexible pavement (0.40 - 0.50) So = 0.35 for rigid pavements (0.30 -0.40).

29. 5. Drainage Quality of drainage: measured by the length of time it takes water to be removed from base or subbase up to (50% of saturation ).

30. 6. Pavement Thickness Design, SN Once SN is determined, it is necessary to determine the thickness of various Layers. SN = a1 D1 + a2 D2 m2 + a3 D3 m3 ai : Coefficient of layer i Di : Thickness of layer i mi : Drainage Modifying Factor for layer i.

31. Example 1

32. Solution

33. Example 2 A flexible pavement for an urban interstate highway is to be designed using the 1993 AASHTO guide procedure to carry a design ESAL of 1 x 10 6 . It is estimated that it takes about a week for water to be drained from within the pavement and the pavement structure will be exposed to moisture levels approaching saturation for 26% of the time. The initial serviceability index, pi = 4.5 and terminal serviceability index, pt = 2.5. The following additional information is available: Resilient modulus of asphalt concrete = 400,000 lb /in2 CBR value of base course material = 70, Mr = 30,000 lb /in2 CBR value of sub base course material = 40, Mr = 13,000 lb /in2 CBR value of subgrade material = 6, Mr = 5,500lb/in2 Determine a suitable pavement structure. Make assumption if any.

34. Solution 1. Assumption: Reliability level (R) = 99% Standard deviation, So = 0.49 Design serviceability loss = 4.5-2.5 = 2

35. 2. Determine the design Structural Number ,

36. Subgrade,Mr = 5500, SN3 = 4.5 Repeat step to get values of SN1 and SN2 Ans : SN1 = 2.5, SN2 = 3.5

37. 3. Determine the structural layer coefficient a1, a2, a3 a1 = 0.42

38. a2=0.13

39. a3 = 0.12

40. 4. Determine appropriate drainage coefficient

41. SN = a1 D1 + a2 D2 m2 + a3 D3 m3 SN1 = 2.5 a1= 0.42 m = 0.8 SN2 = 3.5 a2= 0.13 SN3 = 4.5 a3= 0.12 SN1 = a1D1 D1 = SN1/a1 = 2.5/0.42 = 5.9 (use 6) SN1* = 0.42 x 6 = 2.52 D2 = [(SN2-SN1*)/(a2 x m2)] =[(3.5 – 2.52)/(0.13 x 0.8)] = 9.42 (use 10) SN2* = 0.13 X 10 + 2.52 = 3.82 D3 = [( SN3-SN2*)/(a3 x m3)] =[(4.5 – 3.82 )/( 0.12 x 0.8)] = 7.08 (use 8) SN3* = 0.12 X 8 +3.82 = 4.78 Therefore the pavement will consist of 6 in of asphalt concrete surface, 10 in granular base and 8 in subbase .