Bearing Capacity Factor Dependent on Surcharge for Circular Footing Calculator

Bearing Capacity Factor Formula:

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

Ultimate Bearing Capacity in Soil:

kPa

Unit Weight of Soil:

N/m³

Diameter of Section:

Bearing Capacity Factor dependent on Unit Weight:

Effective Surcharge:

kPa

Bearing Capacity Factor dependent on Surcharge (Nq):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This factor (Nq) is a dimensionless parameter used in geotechnical engineering to calculate the ultimate bearing capacity of shallow foundations.

Purpose: It quantifies the effect of surcharge (overburden pressure) on the bearing capacity of circular footings.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_{fc} \) — Ultimate bearing capacity in soil (kPa)
\( \gamma \) — Unit weight of soil (N/m³)
\( d_{section} \) — Diameter of circular footing section (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight (±5%)
\( \sigma_s \) — Effective surcharge (kPa)

Explanation: The formula calculates Nq by considering the ultimate bearing capacity, soil properties, footing size, and surcharge pressure.

3. Importance of Bearing Capacity Factor

Details: Accurate calculation of Nq is crucial for designing safe and economical foundations that can support structural loads without excessive settlement.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. The bearing capacity factor dependent on unit weight (Nγ) has a default value of 1.6 with ±5% variation.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for Nq values?
A: Nq typically ranges from 1 to 60, depending on soil friction angle and foundation type.

Q2: Why is there a ±5% variation for Nγ?
A: The ±5% accounts for uncertainties in soil properties and empirical relationships used to determine Nγ.

Q3: How does footing shape affect Nq?
A: This calculator is specifically for circular footings. Different shape factors apply for strip or rectangular footings.

Q4: What if my soil has cohesion?
A: This calculator assumes cohesionless soil. For cohesive soils, additional terms would be needed in the bearing capacity equation.

Q5: How accurate are these calculations?
A: Results are theoretical estimates. Field tests and professional judgment should always supplement calculations.