PAVEMENT DESIGN: Flexible Pavement Design (JKR Method)

Transcription

1 CHAPTER 3 PAVEMENT DESIGN: Flexible Pavement Design (JKR Method) FACTORS THAT INFLUENCE PAVEMENT DESIGN () Traffic Loading Magnitude of axle load Wheel configuration Volume and composition of axle loads Tyre pressure and contact area (2) Material Characteristics (3) Climate or Environment

2 Single Axle Tandem Axle Tridem Axle Traffic Loading L L x S L = S = 80kN, 8.6 tonne, 8,000 lb = 0.00 Car.5 tonne Lorry 9 tonnes = = Bus 8 tonnes Trailer 26 tonnes =

3 Climatic / Environmental Effect Seepage from highlands / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / Water ponding Seepage through shoulder Water content rises in subgrade Subgrade looses strength and stability Seepage through pavement If subgrade is too weak, pavement will fail JKR ARAHAN TEKNIK (JALAN) 5/85 DESIGN METHOD PROCEDURE:. Design life is usually taken as 0 years. 2. Traffic Estimation: Initial Annual Commercial Vehicle Traffic per direction, V o P V ADT c o = 365 D L 00 where ADT = average daily traffic P c = percentage of commercial vehicles D = directional distribution (usually 0.50) L = lane distribution (usually.00) 3

4 Total Number of Commercial Vehicles per direction, V c V c Vo[( + r) ] = r where r = traffic growth rate x = design life x Total Equivalent Standard Axles, ESA ESA = V c x e where e = equivalent factor (Table 3.5) Daily Traffic Flow at the end of the design period, V x V x = V ( + r) x where V = ADT / 2 (per direction) 3. Capacity Estimation Maximum Hourly Capacity, c c = I x R x T where I = ideal hourly capacity (Table 3.6) R = roadway reduction factor (Table 3.7) T = traffic reduction factor (Table 3.8) Daily Capacity, C C = 0 x c (assume c is 0% of C) Check C > V x If C > V x capacity will not be exceeded at the end of the design period (OK) If C < V x capacity will be exceeded by the end of the design period (not OK) When C < V x happens, need to reduce design period. Years required to reach capacity, log C V n = x log + r ( )

5 . Calculate thickness, T A. T A = a D + a 2 D 2 + a 3 D 3 where a, a 2, a 3 = structural coefficients (Table 3.9) d, d 2, d 3 = layer depth (based on Tables 3.0, 3., 3.2) 5. Determine the equivalent thickness, T A using Thickness Nomograph Based on subgrade CBR, ESA and T A values (Figure 3.5). If CBR varies within the m depth of the subgrade, the mean CBR is calculated: CBR = h CBR h CBR n n + h CBR Make sure T A > T A Let s try Example Calculation 6 Yeah! 5

6 Table 3.5: Guide for Equivalence Factor Percentage of selected heavy goods vehicles 0 5% 6 50% 5 00% Type of road Equivalence Factor Local.2 Trunk Table 3.6: Maximum Hourly Capacity under ideal conditions Road Type Multilane Two Lanes (bothways) Three Lanes (bothways) Passenger Vehicle Unit per hour 2000 per lane 2000 total for bothways 000 total for bothways Table 3.7: Carriageway Roadway Reduction Factor Carriageway Width 7.5 m 7.0 m 6.0 m 5.0 m 2.00 m Shoulder Width.50 m m m Table 3.8: Traffic Reduction Factor Type of Terrain Flat Rolling Mountainous Factor T = 00/(00+P c ) T = 00/(00+2P c ) T = 00/(00+5P c ) 6

7 Table 3.9: Structural Layer Coefficient Component Type of Layer Property Coefficient Wearing and Binder Course Asphalt Concrete.00 Base Course Subbase Dense Bituminous Macadam Cement Stabilized Mechanically Stabilized crushed aggregate Sand, Laterite etc Crushed aggregate Cement Stabilized Type : Stability > 00 kg Type 2: Stability > 300 kg Unconfined compressive strength (7 days) 30-0 kg/m 2 80% 20% 30% 60% Table 3.0: Structural Layer Coefficient Type of Layer Wearing Course Binder Course Bituminous Base Course Wet Mix Cement Treated Granular Subbase Cement Treated Minimum Thickness cm 5 cm 5 cm 0 cm 0 cm 0 cm 5 cm 7

8 Table 3-: Standard and Construction Layer Thickness Type of Layer Wearing Course Binder Course Bituminous Base Course Wet Mix Cement Treated Granular Subbase Cement Treated Standard Thickness -5 cm 5-0 cm 5-20 cm 0-20 cm 0-20 cm 0-30 cm 5-20 cm One layer lift -5 cm 5-0 cm 5-5 cm 0-5 cm 0-20 cm 0-20 cm 5-20 cm Table 3.2: Minimum Thickness of Bituminous Layer T A < 7.5 cm cm cm > 30.0 cm Total thick of bituminous layer 5.0 cm 0.0 cm 5.0 cm 7.5 cm 8