Width of Footing given Square Footing and Bearing Capacity Calculator

Width of Footing Formula:

\[ B_{square} = \frac{q_f - ((1.3 \times C \times N_c) + (\sigma' \times N_q))}{0.5 \times N_\gamma \times \gamma \times 0.8} \]

Ultimate Bearing Capacity:

Cohesion:

Bearing Capacity Factor (Cohesion):

Effective Surcharge:

Bearing Capacity Factor (Surcharge):

Bearing Capacity Factor (Unit Weight):

Unit Weight of Soil:

N/m³

Width of Footing (m):

1. What is Width of Footing given Square Footing and Bearing Capacity?

Definition: This calculator determines the required width of a square footing based on soil bearing capacity and other geotechnical parameters.

Purpose: It helps civil engineers and construction professionals design proper foundation dimensions to ensure structural stability.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ B_{square} = \frac{q_f - ((1.3 \times C \times N_c) + (\sigma' \times N_q))}{0.5 \times N_\gamma \times \gamma \times 0.8} \]

Where:

\( B_{square} \) — Width of Footing (meters)
\( q_f \) — Ultimate Bearing Capacity (Pascals)
\( C \) — Cohesion of soil (Pascals)
\( N_c \) — Bearing capacity factor dependent on cohesion
\( \sigma' \) — Effective surcharge (Pascals)
\( N_q \) — Bearing capacity factor dependent on surcharge
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( \gamma \) — Unit weight of soil (N/m³)

Explanation: The formula calculates the minimum footing width needed to distribute structural loads without exceeding the soil's bearing capacity.

3. Importance of Footing Width Calculation

Details: Proper footing width ensures structural stability, prevents excessive settlement, and maintains safety factors against bearing capacity failure.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is ultimate bearing capacity?
A: It's the maximum pressure the soil can withstand before shear failure occurs.

Q2: How do I determine soil cohesion?
A: Cohesion is determined through geotechnical laboratory tests like unconfined compression or triaxial tests.

Q3: What's a typical value for Nc, Nq, Ny?
A: These depend on soil friction angle. For φ=0° (clay), Nc=5.14, Nq=1, Ny=0. The calculator provides typical defaults.

Q4: Why the 0.8 factor in the denominator?
A: This is a safety factor to account for uncertainties in soil properties and loading conditions.

Q5: Can this be used for rectangular footings?
A: No, this formula is specifically for square footings. Different formulas apply for rectangular or circular footings.