Effective Surcharge given Round Footing and Bearing Capacity Calculator

Formula Used:

\[ \sigma_{round} = \frac{q_f - (1.3 \times C \times N_c + 0.5 \times \gamma \times B \times N_\gamma \times 0.6)}{N_q} \]

Ultimate Bearing Capacity (qf):

Cohesion (C):

Bearing Capacity Factor (Nc):

Unit Weight of Soil (γ):

N/m³

Width of Footing (B):

Bearing Capacity Factor (Nγ):

Bearing Capacity Factor (Nq):

Effective Surcharge (σ_round): Pa

1. What is Effective Surcharge given Round Footing?

Definition: This calculator determines the effective surcharge pressure on soil when considering a round footing and bearing capacity factors.

Purpose: It helps geotechnical engineers and foundation designers calculate the additional pressure exerted on soil due to external loads distributed over a round footing.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \sigma_{round} = \frac{q_f - (1.3 \times C \times N_c + 0.5 \times \gamma \times B \times N_\gamma \times 0.6)}{N_q} \]

Where:

\( \sigma_{round} \) — Effective surcharge (Pa)
\( q_f \) — Ultimate bearing capacity (Pa)
\( C \) — Cohesion of soil (Pa)
\( N_c \) — Bearing capacity factor dependent on cohesion
\( \gamma \) — Unit weight of soil (N/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( N_q \) — Bearing capacity factor dependent on surcharge

3. Importance of Effective Surcharge Calculation

Details: Accurate calculation of effective surcharge is crucial for designing stable foundations that can support structural loads without excessive settlement or failure.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided but should be adjusted based on your specific soil conditions and project requirements. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is typical cohesion value for clay soils?
A: Soft clay might have 10-25 kPa, medium clay 25-50 kPa, and stiff clay 50-100 kPa cohesion values.

Q2: Why do we multiply Nγ by 0.6?
A: The 0.6 factor accounts for the shape correction for round footings in the bearing capacity equation.

Q3: How do I determine bearing capacity factors?
A: These are typically determined based on soil friction angle using established tables or equations in geotechnical literature.

Q4: What's the difference between square and round footing calculations?
A: Round footings use shape factors (like the 0.6 for Nγ) that differ from square or rectangular footings.

Q5: Should I add a safety factor to the result?
A: Yes, typical practice is to apply a safety factor (often 2-3) to the calculated value for design purposes.