Cohesion of Soil given Ultimate Bearing Capacity for Rectangular Footing Calculator

Cohesion Formula:

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

Ultimate Bearing Capacity (kPa):

kPa

Effective Surcharge (kPa):

kPa

Bearing Capacity Factor (Surcharge):

Unit Weight of Soil (kN/m³):

kN/m³

Width of Footing (m):

Bearing Capacity Factor (Unit Weight):

Bearing Capacity Factor (Cohesion):

Length of Footing (m):

Cohesion in Soil (kPa):

1. What is Cohesion of Soil Calculator?

Definition: This calculator determines the cohesion of soil based on ultimate bearing capacity and other soil parameters for rectangular footings.

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

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

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

3. Importance of Soil Cohesion Calculation

Details: Cohesion is crucial for determining soil shear strength, which affects foundation stability and bearing capacity.

4. Using the Calculator

Tips: Enter all required parameters. Bearing capacity factors typically have ±5% variability. Ensure all values are positive.

5. Frequently Asked Questions (FAQ)

Q1: What is typical cohesion value for clay?
A: Soft clay: 10-25 kPa, Medium clay: 25-50 kPa, Stiff clay: 50-100 kPa, Hard clay: 100-200 kPa.

Q2: How does footing shape affect cohesion calculation?
A: The formula includes length/width ratio (B/L) to account for rectangular footing effects.

Q3: What if I have a square footing?
A: For square footings (B=L), the formula simplifies as B/L becomes 1.

Q4: Where can I find bearing capacity factors?
A: These are typically obtained from geotechnical tables based on soil friction angle.

Q5: How accurate is this calculation?
A: Results are theoretical estimates. For critical projects, always verify with laboratory tests.