Cohesion of Soil given Bearing Capacity for Circular Footing Calculator

Cohesion Formula:

\[ C = \frac{q_f - \sigma_s}{1.3 \times N_c} \]

Cohesion in Soil (kPa):

1. What is Cohesion of Soil Calculator for Circular Footing?

Definition: This calculator determines the cohesion of soil based on the ultimate bearing capacity, effective surcharge, and bearing capacity factor for circular footings.

Purpose: It helps geotechnical engineers and construction professionals evaluate soil strength parameters for foundation design.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ C = \frac{q_f - \sigma_s}{1.3 \times N_c} \]

Where:

\( C \) — Cohesion of soil (kPa)
\( q_f \) — Ultimate bearing capacity (kPa)
\( \sigma_s \) — Effective surcharge (kPa)
\( N_c \) — Bearing capacity factor (dimensionless, typically 9 for circular footings)

Explanation: The formula calculates soil cohesion by considering the net bearing pressure (after subtracting surcharge) divided by a factor that accounts for footing shape and soil properties.

3. Importance of Soil Cohesion Calculation

Details: Cohesion is a critical parameter in determining soil shear strength, which affects foundation stability, slope stability, and earth pressure calculations.

4. Using the Calculator

Tips: Enter the ultimate bearing capacity in kPa, effective surcharge in kPa, and bearing capacity factor (default 9 for circular footings). The bearing capacity factor has ±5% tolerance.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for soil cohesion?
A: Cohesion values vary widely: 0-10 kPa for loose sands, 10-50 kPa for stiff clays, and up to 200 kPa for very stiff clays.

Q2: Why is the factor 1.3 used in the formula?
A: The 1.3 factor accounts for the shape effect of circular footings compared to strip footings.

Q3: How is effective surcharge determined?
A: Effective surcharge is the vertical stress at foundation level from any overburden or surface loads.

Q4: When would Nc differ from 9?
A: Nc varies with soil type and footing shape (e.g., 5.14 for strip footings in cohesive soil).

Q5: How accurate is this calculation?
A: Results are theoretical estimates; actual field conditions may vary by ±5% or more depending on soil heterogeneity.