Bearing Capacity of Non Cohesive Soil for Square Footing Calculator

Ultimate Bearing Capacity Formula:

\[ q_{fc} = (\sigma_s \times N_q) + (0.4 \times \gamma \times B \times N_\gamma) \]

Effective Surcharge (σ_s):

kPa

Bearing Capacity Factor (N_q):

Unit Weight of Soil (γ):

kN/m³

Width of Footing (B):

Bearing Capacity Factor (N_γ):

Ultimate Bearing Capacity (q_fc): kPa

1. What is Ultimate Bearing Capacity?

Definition: Ultimate bearing capacity is the minimum gross pressure intensity at the base of the foundation at which the soil fails in shear.

Purpose: It helps engineers determine the maximum load that a square footing can support before shear failure occurs in non-cohesive soils.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ q_{fc} = (\sigma_s \times N_q) + (0.4 \times \gamma \times B \times N_\gamma) \]

Where:

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

3. Importance of Bearing Capacity Calculation

Details: Proper bearing capacity estimation ensures foundation stability, prevents excessive settlement, and guarantees structural safety.

4. Using the Calculator

Tips: Enter all required parameters. The bearing capacity factors (N_q and N_γ) have ±5% variability. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is effective surcharge?
A: Effective surcharge refers to the vertical pressure acting over the ground surface in addition to basic earth pressure.

Q2: Why are the bearing capacity factors given with ±5%?
A: The ±5% accounts for variability in soil conditions and empirical determination of these factors.

Q3: What's a typical unit weight for non-cohesive soils?
A: Typically ranges from 16-20 kN/m³ for sandy soils, but can vary based on density and moisture content.

Q4: How does footing width affect bearing capacity?
A: Wider footings generally have higher bearing capacity due to increased foundation area and depth influence.

Q5: Is this formula only for square footings?
A: Yes, this specific formula applies to square footings in non-cohesive (granular) soils.