Cohesion of Soil given Safe Bearing Capacity Calculator

Cohesion of Soil Formula:

\[ C_s = \frac{(q_{sa} \times F_s) - (F_s \times \sigma') - [\sigma_s \times (N_q - 1) + (0.5 \times \gamma \times B \times N_\gamma)]}{N_c} \]

Safe Bearing Capacity (q_sa):

kPa

Factor of Safety (F_s):

Effective Surcharge (σ'):

kPa

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):

Bearing Capacity Factor (N_c):

Cohesion of Soil (C_s):

1. What is Cohesion of Soil given Safe Bearing Capacity?

Definition: This calculator determines the cohesion of soil based on the safe bearing capacity and other soil parameters.

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:

\[ C_s = \frac{(q_{sa} \times F_s) - (F_s \times \sigma') - [\sigma_s \times (N_q - 1) + (0.5 \times \gamma \times B \times N_\gamma)]}{N_c} \]

Where:

\( C_s \) — Cohesion of soil (kPa)
\( q_{sa} \) — Safe bearing capacity (kPa)
\( F_s \) — Factor of safety
\( \sigma' \) — Effective surcharge (kPa)
\( \sigma_s \) — Effective surcharge in kPa
\( N_q \) — Bearing capacity factor dependent on surcharge
\( \gamma \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight
\( N_c \) — Bearing capacity factor dependent on cohesion

3. Importance of Soil Cohesion Calculation

Details: Soil cohesion is critical for determining foundation stability, slope stability, and earth pressure calculations.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for reference. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is typical cohesion for different soil types?
A: Clay: 10-100 kPa, Silt: 5-20 kPa, Sand: 0 kPa (cohesionless).

Q2: How does factor of safety affect the calculation?
A: Higher F_s values result in lower calculated cohesion for the same bearing capacity.

Q3: What if my soil has no cohesion?
A: For cohesionless soils (sand), use other bearing capacity formulas that don't include the N_c term.

Q4: How accurate is this calculation?
A: Results are theoretical estimates. Always verify with field tests (±5% margin).

Q5: Where can I find bearing capacity factors?
A: These are available in geotechnical references like Terzaghi's or Meyerhof's bearing capacity theories.