Bearing Capacity Factor Dependent on Surcharge given Effective Surcharge Calculator

Formula:

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

Net Ultimate Bearing Capacity (q_nf):

kN/m²

Cohesion of Soil (C_s):

kN/m²

Bearing Capacity Factor (N_c):

Unit Weight of Soil (γ):

kN/m³

Width of Footing (B):

Bearing Capacity Factor (N_γ):

Effective Surcharge (σ_s):

kN/m²

Bearing Capacity Factor (N_q):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This is a dimensionless factor used in geotechnical engineering to calculate the bearing capacity of shallow foundations considering the effect of surcharge.

Purpose: It helps engineers determine the additional bearing capacity provided by the soil's self-weight and any surcharge load above the foundation level.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_{nf} \) — Net ultimate bearing capacity (kN/m²)
\( C_s \) — Cohesion of soil (kN/m²)
\( N_c \) — Bearing capacity factor dependent on cohesion
\( \gamma \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( \sigma_s \) — Effective surcharge (kN/m²)

3. Importance of the Calculation

Details: Accurate calculation of \( N_q \) is crucial for designing safe and economical foundations, ensuring they can support structural loads without excessive settlement or failure.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. The bearing capacity factors \( N_c \) and \( N_\gamma \) typically have ±5% uncertainty.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for \( N_q \)?
A: \( N_q \) typically ranges from 1 to 60, depending on soil friction angle and other factors.

Q2: How does surcharge affect bearing capacity?
A: Surcharge increases the confining pressure around the foundation, thereby increasing its bearing capacity.

Q3: What if my soil has no cohesion?
A: For cohesionless soils, simply enter 0 for cohesion (C_s).

Q4: Why are there ±5% uncertainties on some factors?
A: These factors are empirically derived and may vary slightly depending on soil conditions and testing methods.

Q5: Can this be used for deep foundations?
A: No, this calculator is specifically for shallow foundations. Different methods are used for deep foundations.