Effective Surcharge given Bearing Capacity of Non Cohesive Soil for Circular Footing Calculator

Effective Surcharge Formula:

\[ \sigma_s = \frac{q_{fc} - (0.3 \times \gamma \times d_{section} \times N_{\gamma})}{N_q} \]

Ultimate Bearing Capacity in Soil:

kPa

Unit Weight of Soil:

kN/m³

Diameter of Section:

Bearing Capacity Factor (Unit Weight):

Bearing Capacity Factor (Surcharge):

Effective Surcharge (kPa):

1. What is Effective Surcharge?

Definition: Effective Surcharge in KiloPascal also called as surcharge load refers to the vertical pressure or any load that acts over the ground surface additional to basic earth pressure.

Purpose: It helps geotechnical engineers determine the additional load on soil for foundation design.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \sigma_s = \frac{q_{fc} - (0.3 \times \gamma \times d_{section} \times N_{\gamma})}{N_q} \]

Where:

\( \sigma_s \) — Effective Surcharge (kPa)
\( q_{fc} \) — Ultimate Bearing Capacity in Soil (kPa)
\( \gamma \) — Unit Weight of Soil (kN/m³)
\( d_{section} \) — Diameter of Section (m)
\( N_{\gamma} \) — Bearing Capacity Factor dependent on Unit Weight
\( N_q \) — Bearing Capacity Factor dependent on Surcharge

Explanation: The formula calculates the effective surcharge by accounting for soil weight and bearing capacity factors.

3. Importance of Effective Surcharge Calculation

Details: Proper calculation ensures safe foundation design by considering all vertical pressures acting on the soil.

4. Using the Calculator

Tips: Enter all required values with ±5% accuracy. Default values are provided for common soil conditions.

5. Frequently Asked Questions (FAQ)

Q1: What is typical unit weight for soil?
A: Most soils range between 16-20 kN/m³, with 18 kN/m³ being a common default value.

Q2: How do I determine bearing capacity factors?
A: These depend on soil friction angle - use standard geotechnical tables or soil testing.

Q3: Why is diameter important?
A: Larger foundations distribute load differently, affecting the surcharge calculation.

Q4: Can this be used for rectangular footings?
A: This specific formula is for circular footings - different factors apply for rectangular ones.

Q5: What's the practical significance of ±5%?
A: Soil properties naturally vary - this accounts for reasonable measurement uncertainty.