Bearing Capacity Factor Dependent on Surcharge for Square Footing Calculator

Bearing Capacity Factor Formula:

\[ N_q = \frac{q_{fc} - (0.4 \times \gamma \times B \times N_\gamma)}{\sigma_s} \]

Ultimate Bearing Capacity in Soil:

kPa

Unit Weight of Soil:

kN/m³

Width of Footing:

Bearing Capacity Factor (Unit Weight):

Effective Surcharge:

kPa

Bearing Capacity Factor (N_q):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This calculator determines the bearing capacity factor (N_q) for square footings based on soil properties and loading conditions.

Purpose: It helps geotechnical engineers and foundation designers evaluate the surcharge-dependent component of soil bearing capacity.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_q = \frac{q_{fc} - (0.4 \times \gamma \times B \times N_\gamma)}{\sigma_s} \]

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_{fc} \) — Ultimate bearing capacity in soil (kPa)
\( \gamma \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( \sigma_s \) — Effective surcharge (kPa)

Explanation: The formula separates the surcharge-dependent component from the total bearing capacity.

3. Importance of Bearing Capacity Factor

Details: Accurate determination of N_q is crucial for designing safe and economical foundations that consider both soil strength and surcharge effects.

4. Using the Calculator

Tips: Enter all required parameters. Note that all values have ±5% tolerance to account for typical soil variability.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a ±5% tolerance on inputs?
A: Soil properties naturally vary, and this tolerance accounts for typical measurement uncertainties.

Q2: What's a typical value for N_γ?
A: For many soils, N_γ ≈ 1.6, but this can vary based on soil type and conditions.

Q3: How does footing width affect N_q?
A: Wider footings generally have higher bearing capacity, but N_q primarily depends on surcharge effects.

Q4: What if my N_q result is negative?
A: Check your inputs - this suggests either incorrect values or soil conditions where the formula doesn't apply.

Q5: How accurate is this calculation?
A: It provides a theoretical estimate - always verify with site-specific testing and engineering judgment.