Cohesion of Soil given Saturated Unit Weight Calculator

Cohesion Formula:

\[ C = (F_s \times \gamma_{sat} \times z \times \cos(i) \times \sin(i)) - (\gamma' \times z \times \tan(\phi) \times \cos^2(i)) \]

Factor of Safety (F_s):

Saturated Unit Weight (γ_sat):

kN/m³

Depth of Prism (z):

Angle of Inclination (i):

Submerged Unit Weight (γ'):

kN/m³

Angle of Internal Friction (φ):

Cohesion in Soil (kPa):

1. What is Cohesion of Soil Calculator?

Definition: This calculator determines the cohesion of soil based on saturated unit weight, depth, angle of inclination, and internal friction angle.

Purpose: It helps geotechnical engineers evaluate soil stability for construction projects.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ C = (F_s \times \gamma_{sat} \times z \times \cos(i) \times \sin(i)) - (\gamma' \times z \times \tan(\phi) \times \cos^2(i)) \]

Where:

\( C \) — Cohesion in soil (kPa)
\( F_s \) — Factor of safety
\( \gamma_{sat} \) — Saturated unit weight of soil (kN/m³)
\( z \) — Depth of prism (m)
\( i \) — Angle of inclination to horizontal (°)
\( \gamma' \) — Submerged unit weight (kN/m³)
\( \phi \) — Angle of internal friction (°)

3. Importance of Soil Cohesion Calculation

Details: Cohesion is critical for determining slope stability, bearing capacity, and designing retaining structures.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for reference. All values must be ≥ 0. Angles must be in degrees.

5. Frequently Asked Questions (FAQ)

Q1: What is typical cohesion value for clay?
A: Soft clay: 5-25 kPa, Medium clay: 25-50 kPa, Stiff clay: 50-100 kPa.

Q2: How does angle of inclination affect cohesion?
A: Higher inclination angles generally require greater cohesion for stability.

Q3: What's a typical factor of safety for slopes?
A: Usually 1.3-1.5 for temporary works, 1.5-2.0 for permanent works.

Q4: How to measure saturated unit weight?
A: It's determined by laboratory tests on saturated soil samples.

Q5: What if I get negative cohesion?
A: Negative values suggest the soil may not be stable under given conditions.