Bearing Capacity Factor Dependent on Surcharge for Strip Footing Calculator

Bearing Capacity Factor Formula:

\[ N_q = \frac{q_{fc} - (0.5 \times \gamma \times B \times N_\gamma)}{\sigma_s} \]

Ultimate Bearing Capacity (q_fc):

kPa

Unit Weight of Soil (γ):

kN/m³

Width of Footing (B):

Bearing Capacity Factor (N_γ):

Effective Surcharge (σ_s):

kPa

Bearing Capacity Factor (N_q):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This is a dimensionless factor (N_q) that quantifies the contribution of surcharge to the ultimate bearing capacity of a strip footing.

Purpose: It's used in geotechnical engineering to calculate the bearing capacity of shallow foundations.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_q = \frac{q_{fc} - (0.5 \times \gamma \times B \times N_\gamma)}{\sigma_s} \]

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 calculates N_q by isolating it from the general bearing capacity equation.

3. Importance of N_q Calculation

Details: Accurate calculation of N_q is crucial for designing safe and economical foundations that won't fail under load.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. The ±5% indicates typical accuracy ranges for these parameters in practice.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for N_q?
A: For most soils, N_q ranges from 1 to 100, depending on soil type and footing depth.

Q2: How does surcharge affect bearing capacity?
A: Greater surcharge increases bearing capacity by providing additional confining pressure.

Q3: When would I need to calculate N_q?
A: When designing strip footings or when back-calculating soil parameters from bearing capacity tests.

Q4: What's the difference between N_q and N_γ?
A: N_q accounts for surcharge effects while N_γ accounts for soil weight effects.

Q5: How accurate is this calculation?
A: Results are typically within ±5% of actual values, assuming accurate input parameters.