Bearing Capacity Factor Dependent on Surcharge for Rectangular Footing Calculator

Bearing Capacity Factor Formula:

\[ N_q = \frac{q_{fc} - \left( (C \times N_c) \times (1 + 0.3 \times \frac{B}{L}) + (0.4 \times \gamma \times B \times N_\gamma) \right)}{\sigma_s} \]

Ultimate Bearing Capacity (q_fc):

kPa

Cohesion (C):

kPa

Bearing Capacity Factor (N_c):

Width of Footing (B):

Length of Footing (L):

Unit Weight of Soil (γ):

kN/m³

Bearing Capacity Factor (N_γ):

Effective Surcharge (σ_s):

kPa

Bearing Capacity Factor (N_q):

1. What is Bearing Capacity Factor Dependent on Surcharge?

Definition: This calculator determines the bearing capacity factor (N_q) for rectangular footings based on soil properties and footing dimensions.

Purpose: It helps geotechnical engineers and foundation designers evaluate the bearing capacity of shallow foundations.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ N_q = \frac{q_{fc} - \left( (C \times N_c) \times (1 + 0.3 \times \frac{B}{L}) + (0.4 \times \gamma \times B \times N_\gamma) \right)}{\sigma_s} \]

Where:

\( N_q \) — Bearing capacity factor dependent on surcharge
\( q_{fc} \) — Ultimate bearing capacity in soil (kPa)
\( C \) — Cohesion in soil (kPa)
\( N_c \) — Bearing capacity factor dependent on cohesion (±5%)
\( B \) — Width of footing (m)
\( L \) — Length of footing (m)
\( \gamma \) — Unit weight of soil (kN/m³)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight (±5%)
\( \sigma_s \) — Effective surcharge (kPa)

3. Importance of Bearing Capacity Calculation

Details: Proper calculation ensures foundation stability, prevents excessive settlement, and optimizes foundation design.

4. Using the Calculator

Tips: Enter all required parameters. Note that N_c and N_γ have ±5% tolerance. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What does the ±5% on N_c and N_γ mean?
A: It indicates these factors have a 5% margin of error in typical calculations.

Q2: How do I determine the cohesion value (C)?
A: Cohesion is determined through laboratory tests like unconfined compression tests or field vane shear tests.

Q3: What's a typical value for N_c?
A: For cohesive soils, N_c typically ranges from 5 to 37 depending on soil type and conditions.

Q4: When would I need this calculation?
A: When designing shallow foundations for buildings, retaining walls, or other structures.

Q5: How accurate is this calculation?
A: It provides a theoretical estimate; actual field conditions may require adjustments.