This assignment deals with the mechanistic design of a full depth asphalt pavement for a 2 way 2 lane rural road somewhe

[answerhappygod]

This Assignment Deals With The Mechanistic Design Of A Full Depth Asphalt Pavement For A 2 Way 2 Lane Rural Road Somewhe 1 (156.28 KiB) Viewed 14 times

This assignment deals with the mechanistic design of a full depth asphalt pavement for a 2 way 2 lane rural road somewhere in rural New South Wales. In particular, a specific section having a design speed of 80 km/hr is considered. The data relative to the project are: • 5% of Heavy Vehicles are expected There is no site-specific data about NHVAG and ESA/HVAG (i.e use presumptive values). • Annual average daily traffic is 5,200 vehicles per day • Directional split of traffic: DF=0.5 • Constant annual growth rate of 3.3%. • Design period: 20 years. • Consider a WMAPT of 20 degrees. • SARS/ESA=1.2, SAR7/ESA=2.3. Subgrade compaction data are given in Figure 1. Recommendation is to compact the subgrade at optimum moisture content and 93% of maximum dry density. Asphalt properties: Test modulus = 2000 MPa, binder volume = 11%, target void ratio after compaction = 5% Figure 2 provide the correlation between the critical horizontal strain at the bottom of the asphalt layer as function of asphalt thickness (in mm), asphalt modulus and subgrade modulus. These were established using CIRCLY under specific conditions, defined for this assignment. Figure 2 can here be used as an alternative to elastic calculations with CIRCLY. • The section of road under consideration passes through a residential area. Consequently, the pavement should be designed in order to limit noise emitted by the pavement. Reliability of the project: 95% (see table 6.15 of AGPT02-12). . . 19 Figure 1: Compaction data of subgrade on which pavement will be built. 18 CBR=9 16.8 X x X ięwny) Kisuap na X 15 CBR=7 X XA CBR-5 14 CBR=3 13 16 28 20 24 Moisture content [%]
650 650 Ex=1000 MPa Subgrade Modulus 30 MPa E=1000 MPa 600 600 Subgrade Modulus 50 MPa 550 550 500 500 450 450 E=3000 MPa E=3000 MPa 400 $400 Micro Strain 350 Micro Strain 350 300 300 250 250 200 200 150 150 100 E-5000 MPa 100 50 E =5000 MPa 50 100 150 400 450 200 250 300 350 Asphalt thickness [mm] 100 150 1 1 1 200 250 300 350 Asphalt thickness (mm) 400 450 650 E,=1000 MPa 600 Subgrade Modulus 70 MPa 550 Figure 2: correlation between critical horizontal micro- strain at the bottom of the asphalt layer as a function of asphalt thickness for different asphalt modulus (Ea). 500 450 E=3000 MPa 400 Micro Strain (a) Subgrade modulus = 30 MPa. (b) Subgrade modulus = 50 MPa. © Subgrade modulus = 70 MPa. 350 300 250 200 Predominant failure mode: asphalt fatigue. WMAPT of 20 degrees. 150 100 Note: figures to be used only for this assignment. E =5000 MPa 50 50 100 400 450 150 200 250 300 350 Asphalt thickness [mm]
1. List the criteria to be addressed to satisfy serviceability and stability requirements. Based on these criteria and the project information given to you, select a suitable type of asphalt for the pavement (i.e. DGA, SMA, OGA, etc...). 2. Identify the relevant fatigue model(s) to use for this pavement design (see slide 38 of lecture 8) 3. Calculate the relevant design traffic, the maximum allowable micro strain for the asphalt layer and the corresponding thickness of asphalt (using Figure 2).
4. Determine the maximum allowable vertical strain of the subgrade in order to avoid excessive subgrade deformation. Note that, not having CIRCLY, you cannot fully design the pavement and check that the asphalt layer is thick enough for the subgrade not to deform excessively. However, you can tell which value the vertical strain should not exceed. 5. Determine the life expectancy of the pavement if the subgrade was actually only compacted to 83% of maximum dry density and do not support the asphalt layer as initially designed. Indeed, some verification tests conducted on site to check subgrade compaction showed that, at some location, 93% of MDD was not achieved.