Safe Bearing Capacity given Net Ultimate Bearing Capacity Calculator

Safe Bearing Capacity Formula:

\[ q_{sa} = \frac{q_{net}'}{FOS} + (\gamma \times D_{footing}) \]

Net Ultimate Bearing Capacity:

Factor of Safety:

Unit Weight of Soil:

N/m³

Depth of Footing:

Safe Bearing Capacity (Pa):

1. What is Safe Bearing Capacity?

Definition: Safe Bearing Capacity is the maximum pressure which the soil can carry safely without risk of shear failure.

Purpose: It helps engineers determine the appropriate foundation size and type for structures.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ q_{sa} = \frac{q_{net}'}{FOS} + (\gamma \times D_{footing}) \]

Where:

\( q_{sa} \) — Safe bearing capacity (Pa)
\( q_{net}' \) — Net ultimate bearing capacity (Pa)
\( FOS \) — Factor of safety (typically 2.5-3.0)
\( \gamma \) — Unit weight of soil (N/m³)
\( D_{footing} \) — Depth of footing in soil (m)

Explanation: The net bearing capacity is divided by a safety factor, then the overburden pressure is added.

3. Importance of Safe Bearing Capacity

Details: Proper calculation ensures structural stability, prevents foundation failure, and optimizes construction costs.

4. Using the Calculator

Tips: Enter the net ultimate bearing capacity, factor of safety (default 2.8), unit weight of soil (default 18000 N/m³), and footing depth (default 2.54 m). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical factor of safety?
A: For foundations, FOS typically ranges from 2.5 to 3.0 depending on soil conditions and importance of structure.

Q2: How do I determine net ultimate bearing capacity?
A: It's determined through soil testing or empirical relationships based on soil properties.

Q3: Why include depth of footing?
A: Deeper footings benefit from overburden pressure which increases bearing capacity.

Q4: What affects unit weight of soil?
A: Soil composition, moisture content, and compaction all influence unit weight.

Q5: How accurate are these calculations?
A: Results are estimates ±5% - always verify with geotechnical analysis for critical projects.