1. What is the Structural Number for Base Course?

The Structural Number for Base Course (SN2) represents the ability of the base course to withstand axle loads in pavement design. It's a key parameter in flexible pavement design that quantifies the structural capacity of the base layer.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( a_n \) — Layer coefficient (represents material strength)
• \( T_a \) — Actual thickness of base course payment (mm)
• \( M_n \) — Drainage coefficient (accounts for drainage characteristics)

Explanation: The structural number is calculated by multiplying the layer coefficient, actual thickness, and drainage coefficient to determine the overall structural capacity of the base course.

3. Importance of Structural Number Calculation

Details: Accurate structural number calculation is crucial for pavement design as it helps determine the required thickness and material properties for base courses to withstand anticipated traffic loads and environmental conditions.

4. Using the Calculator

Tips: Enter the layer coefficient (typically between 0.05-0.5), actual thickness in millimeters, and drainage coefficient (typically between 0.4-1.4). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for layer coefficients?
A: Layer coefficients typically range from 0.05 for weaker materials to 0.5 for high-quality crushed stone or stabilized materials.

Q2: How does drainage coefficient affect the structural number?
A: The drainage coefficient accounts for the relative loss of strength due to drainage characteristics, with lower values indicating poorer drainage conditions.

Q3: What units should be used for thickness measurement?
A: Thickness should be measured in millimeters (mm) for consistent calculation results.

Q4: How is the structural number used in pavement design?
A: The structural number is used to determine the overall structural capacity of pavement layers and ensure they can withstand anticipated traffic loads over the design life.

Q5: Are there standard values for drainage coefficients?
A: Yes, drainage coefficients are typically standardized based on drainage quality and moisture exposure, ranging from 0.4 (poor drainage) to 1.4 (excellent drainage).