Diameter of Circular Footing given Bearing Capacity Calculator

Diameter of Section Formula:

\[ d_{section} = \frac{q_{fc} - (\sigma_s \times N_q)}{0.3 \times N_\gamma \times \gamma} \]

Ultimate Bearing Capacity in Soil:

Effective Surcharge:

kPa

Bearing Capacity Factor (Surcharge):

Bearing Capacity Factor (Unit Weight):

Unit Weight of Soil:

N/m³

Diameter of Section:

1. What is Diameter of Circular Footing Calculator?

Definition: This calculator determines the required diameter of a circular footing based on soil bearing capacity, surcharge, and soil properties.

Purpose: It helps civil engineers and construction professionals design appropriate foundation sizes for structures.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ d_{section} = \frac{q_{fc} - (\sigma_s \times N_q)}{0.3 \times N_\gamma \times \gamma} \]

Where:

\( d_{section} \) — Diameter of circular footing (meters)
\( q_{fc} \) — Ultimate bearing capacity in soil (Pascals)
\( \sigma_s \) — Effective surcharge (kPa)
\( N_q \) — Bearing capacity factor dependent on surcharge (±5%)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight (±5%)
\( \gamma \) — Unit weight of soil (N/m³)

Explanation: The formula calculates the minimum diameter needed to support the load based on soil properties.

3. Importance of Footing Diameter Calculation

Details: Proper footing diameter ensures structural stability, prevents excessive settlement, and maintains safety margins.

4. Using the Calculator

Tips: Enter all required parameters. The bearing capacity factors typically have ±5% variability. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What is effective surcharge?
A: It's the additional vertical pressure at the foundation level from nearby structures or soil layers.

Q2: Why ±5% for bearing capacity factors?
A: These factors are empirically derived and typically have about 5% variability in practical applications.

Q3: How do I determine ultimate bearing capacity?
A: It's typically determined through soil testing or using standard values for different soil types.

Q4: What if my soil has cohesion?
A: This formula is for cohesionless soils. For cohesive soils, additional terms would be needed in the equation.

Q5: Should I add a safety factor?
A: Yes, typical engineering practice applies safety factors of 2-3 to the calculated diameter.