1. What is the Actual Thickness Calculation?

The Actual Thickness calculation determines the required thickness of subbase course materials in flexible pavement design using the structural number approach. This calculation ensures adequate pavement strength to withstand anticipated traffic loads.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( T_a \) — Actual Thickness Base Course Payment (mm)
• \( SN_3 \) — Structural Number for Subbase Course (mm)
• \( a_n \) — Layer Coefficient (dimensionless)
• \( M_n \) — Drainage Coefficient (dimensionless)

Explanation: The formula calculates the required thickness of the subbase course by dividing the structural number (which represents load-bearing capacity) by the product of layer coefficient (material strength) and drainage coefficient (moisture resistance).

3. Importance of Actual Thickness Calculation

Details: Accurate thickness calculation is crucial for designing durable and cost-effective pavement structures. It ensures the pavement can withstand traffic loads while considering material properties and environmental conditions.

4. Using the Calculator

Tips: Enter the structural number for subbase course, layer coefficient, and drainage coefficient. All values must be positive numbers. The calculator will compute the required actual thickness in millimeters.

5. Frequently Asked Questions (FAQ)

Q1: What is the Structural Number (SN₃)?
A: The Structural Number represents the overall structural capacity required from the subbase course to support anticipated traffic loads over the design life of the pavement.

Q2: How is the Layer Coefficient determined?
A: The Layer Coefficient is determined through laboratory testing and represents the relative strength of the material compared to a standard crushed stone base course.

Q3: What factors affect the Drainage Coefficient?
A: The Drainage Coefficient depends on the quality of drainage, the percentage of time the pavement structure is exposed to moisture levels approaching saturation, and the material's sensitivity to moisture.

Q4: What are typical values for Layer Coefficient?
A: Typical values range from 0.05 for marginal materials to 0.15 for high-quality crushed stone, with 0.10-0.14 being common for good quality base courses.

Q5: How does drainage affect pavement design?
A: Poor drainage reduces pavement strength and service life. The drainage coefficient accounts for this reduction, with values typically ranging from 0.4 (very poor drainage) to 1.2 (excellent drainage).