Bearing Capacity Factor Dependent on Cohesion Calculator

Bearing Capacity Factor Formula:

\[ N_c = \frac{q_f - (\sigma' \times N_q + 0.5 \times \gamma \times B \times N_\gamma \times s_\gamma)}{s_c \times C} \]

Ultimate Bearing Capacity (qf):

Effective Surcharge (σ'):

Bearing Capacity Factor (Nq):

Unit Weight of Soil (γ):

N/m³

Width of Footing (B):

Bearing Capacity Factor (Nγ):

Shape Factor (sγ):

Shape Factor (sc):

Cohesion (C):

Bearing Capacity Factor (Nc):

1. What is Bearing Capacity Factor Dependent on Cohesion?

Definition: The Bearing Capacity Factor dependent on Cohesion (Nc) is a dimensionless factor used in geotechnical engineering to calculate the ultimate bearing capacity of shallow foundations.

Purpose: It quantifies the contribution of soil cohesion to the foundation's bearing capacity in the Terzaghi's bearing capacity equation.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_c = \frac{q_f - (\sigma' \times N_q + 0.5 \times \gamma \times B \times N_\gamma \times s_\gamma)}{s_c \times C} \]

Where:

\( N_c \) — Bearing capacity factor dependent on cohesion
\( q_f \) — Ultimate bearing capacity (Pa)
\( \sigma' \) — Effective surcharge (Pa)
\( N_q \) — Bearing capacity factor dependent on surcharge (±5%)
\( \gamma \) — Unit weight of soil (N/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight (±5%)
\( s_\gamma \) — Shape factor dependent on unit weight (±5%)
\( s_c \) — Shape factor dependent on cohesion (±5%)
\( C \) — Cohesion of soil (Pa)

3. Importance of Bearing Capacity Factor Calculation

Details: Accurate calculation of Nc is crucial for designing safe and economical foundations that can support structural loads without shear failure.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for common factors. Note that factors marked with ±5% have typical variation ranges.

5. Frequently Asked Questions (FAQ)

Q1: Why do some factors have ±5% variation?
A: These factors are empirically derived and can vary slightly based on soil conditions and testing methods.

Q2: What's a typical value for Nc?
A: For cohesive soils, Nc typically ranges from 5.14 (for pure clay) to higher values for mixed soils.

Q3: How do I determine soil cohesion?
A: Cohesion is determined through laboratory tests like unconfined compression tests or field vane shear tests.

Q4: What if I get a negative Nc value?
A: Negative values indicate invalid input parameters as Nc must always be positive. Check your input values.

Q5: How does footing shape affect Nc?
A: Shape factors (sc, sγ) account for how rectangular or circular footings differ from strip footings.