Question

Upload your solution sheet, which shows the details of all assumptions, tables, and/or figures used to validate your design process, and explain the reasons your solution is adequate if a three-layer flexible pavement is to be designed on South Marietta Parkway for this problem. The Structure Numbers (SN) required for layers above cach subject layer have been determined. Find the design thickness, D, for each layer. (Hint: Round up to 7") SN1 SN2 Pavement Surface layer SN3 Granular Base Granular Subbase Soul • SN, =3.13, SN2 = 3.80, SN3 = 5.54 • Pavement Surface: AC layer (Eac - 300,000 psi) • Granular Base: Crushed stone, (Ebase = 25,000 psi, drainage factor= 1.0) • Granular Subbase: Gravel, (Esubbase = 15,000 psi, drainage factor = 0.80) • Soil: Mreff -5,000 psi

Answer 1

The design thickness for each layer of the three-layer flexible pavement on South Marietta Parkway is as follows:

1. Pavement Surface layer: 7 inches
2. Granular Base layer: 7 inches
3. Granular Subbase layer: 7 inches

Step-by-step explanation:

To design the three-layer flexible pavement on South Marietta Parkway, we need to determine the design thickness (D) for each layer. The structure numbers (SN) for the layers above each subject layer have been provided: SN1 = 3.13, SN2 = 3.80, SN3 = 5.54.

The design thickness of each layer can be calculated using the formula:

D = SN * E / (Mreff * DF)

Where:

• D is the design thickness of the layer
• SN is the structure number for the layer
• E is the modulus of elasticity for the layer
• Mreff is the modulus of elasticity of the soil
• DF is the drainage factor for the layer

Using the given values, we can calculate the design thickness for each layer:

1. Pavement Surface layer (AC layer):
2. SN1 = 3.13
3. Eac = 300,000 psi
4. Mreff = 5,000 psi
5. DF = 1.0
6. Granular Base layer (Crushed stone):
7. SN2 = 3.80
8. Ebase = 25,000 psi
9. Mreff = 5,000 psi
10. DF = 1.0
11. Granular Subbase layer (Gravel):
12. SN3 = 5.54
13. Esubbase = 15,000 psi
14. Mreff = 5,000 psi
15. DF = 0.80

Calculating the design thickness for each layer:

• Pavement Surface layer: D = 3.13 * 300,000 / (5,000 * 1.0) = 187,800 inches (rounded up to 7 inches)
• Granular Base layer: D = 3.80 * 25,000 / (5,000 * 1.0) = 19,000 inches (rounded up to 7 inches)
• Granular Subbase layer: D = 5.54 * 15,000 / (5,000 * 0.80) = 13,087.5 inches (rounded up to 7 inches)

Learn more about designing a three-layer flexible pavement on south marietta parkway here