Bearing Capacity for Purely Cohesive Soil given Depth of Footing Calculator

Ultimate Bearing Capacity Formula:

\[ qf = (Cs \times Nc) + ((\gamma \times D) \times Nq) \]

Cohesion of Soil (Cs):

Bearing Capacity Factor (Nc):

Unit Weight of Soil (γ):

N/m³

Depth of Footing (D):

Bearing Capacity Factor (Nq):

Ultimate Bearing Capacity (qf): Pa

1. What is Ultimate Bearing Capacity?

Definition: The Ultimate Bearing Capacity is defined as the minimum gross pressure intensity at the base of the foundation at which the soil fails in shear.

Purpose: It helps civil engineers determine the maximum load that can be applied to the soil without causing shear failure.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ qf = (Cs \times Nc) + ((\gamma \times D) \times Nq) \]

Where:

\( qf \) — Ultimate Bearing Capacity (Pa)
\( Cs \) — Cohesion of Soil (Pa)
\( Nc \) — Bearing Capacity Factor dependent on Cohesion
\( \gamma \) — Unit Weight of Soil (N/m³)
\( D \) — Depth of Footing (m)
\( Nq \) — Bearing Capacity Factor dependent on Surcharge

Explanation: The formula combines the cohesive strength of soil with the surcharge effect from soil above the footing depth.

3. Importance of Bearing Capacity Calculation

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

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for bearing capacity factors (Nc=9, Nq=2.01). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is typical cohesion value for clay soils?
A: Soft clay: 10-20 kPa, Medium clay: 20-40 kPa, Stiff clay: 40-75 kPa, Hard clay: 75-150 kPa.

Q2: Why are there ±5% tolerances?
A: Soil properties can vary naturally, and these tolerances account for typical measurement uncertainties.

Q3: How does footing depth affect bearing capacity?
A: Deeper footings generally have higher bearing capacity due to increased surcharge and confining pressure.

Q4: What units should be used?
A: Cohesion in Pascals (Pa), Unit Weight in N/m³, Depth in meters. Results are in Pascals.

Q5: Is this for cohesive soils only?
A: This calculator is specifically for purely cohesive (clay) soils where cohesion is the primary strength parameter.