Width of Footing given Bearing Capacity Factor and Depth of Footing Calculator

Width of Footing Formula:

\[ B = \frac{q_{nf} - (C_s \times N_c + (\gamma \times D) \times (N_q - 1))}{0.5 \times \gamma \times N_\gamma} \]

Net Ultimate Bearing Capacity:

Cohesion of Soil:

Bearing Capacity Factor (Cohesion):

Unit Weight of Soil:

N/m³

Depth of Footing:

Bearing Capacity Factor (Surcharge):

Bearing Capacity Factor (Unit Weight):

Width of Footing (m):

1. What is Width of Footing Calculator?

Definition: This calculator determines the required width of a footing based on soil bearing capacity factors and depth of footing.

Purpose: It helps civil engineers and construction professionals design stable foundations that can support structural loads.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ B = \frac{q_{nf} - (C_s \times N_c + (\gamma \times D) \times (N_q - 1))}{0.5 \times \gamma \times N_\gamma} \]

Where:

\( B \) — Width of footing (meters)
\( q_{nf} \) — Net ultimate bearing capacity (Pascals)
\( C_s \) — Cohesion of soil (Pascals)
\( N_c \) — Bearing capacity factor dependent on cohesion (±5%)
\( \gamma \) — Unit weight of soil (N/m³)
\( D \) — Depth of footing (meters)
\( N_q \) — Bearing capacity factor dependent on surcharge (±5%)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight (±5%)

Explanation: The formula accounts for soil cohesion, surcharge effects, and soil weight to determine the minimum footing width needed.

3. Importance of Footing Width Calculation

Details: Proper footing width ensures structural stability, prevents excessive settlement, and distributes loads effectively to the soil.

4. Using the Calculator

Tips: Enter all required parameters. Bearing capacity factors typically have ±5% variability. All values must be > 0 (except cohesion which can be 0 for cohesionless soils).

5. Frequently Asked Questions (FAQ)

Q1: Why are bearing capacity factors given with ±5%?
A: These factors are empirically derived and can vary slightly depending on soil conditions and testing methods.

Q2: What if my soil has no cohesion?
A: For cohesionless soils (sand, gravel), set cohesion (Cs) to 0.

Q3: How do I determine the bearing capacity factors?
A: These are typically found in geotechnical engineering references based on soil friction angle.

Q4: What units should I use?
A: Use consistent SI units: Pascals for pressure, Newtons per cubic meter for unit weight, and meters for dimensions.

Q5: Does this consider safety factors?
A: No, the result is the theoretical width. Apply appropriate safety factors per your design code.