Shear Strength of Cohesive Soil Calculator

Shear Strength Formula:

\[ \tau_s = c + (\sigma_{nm} \times \tan(\phi)) \]

Cohesion of Soil:

MPa

Normal Stress:

MPa

Angle of Internal Friction:

Tolerance:

Shear Strength (MPa):

Tolerance Range (MPa):

1. What is Shear Strength of Cohesive Soil?

Definition: Shear strength is the maximum resistance of soil to shearing stresses, a critical parameter in geotechnical engineering for slope stability and foundation design.

Purpose: This calculator determines the shear strength of cohesive soils using Mohr-Coulomb failure criterion.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \tau_s = c + (\sigma_{nm} \times \tan(\phi)) \]

Where:

\( \tau_s \) — Shear strength (MPa)
\( c \) — Cohesion of soil (MPa)
\( \sigma_{nm} \) — Normal stress (MPa)
\( \phi \) — Angle of internal friction (degrees)

Explanation: The shear strength is calculated as the sum of cohesion and the product of normal stress with the tangent of friction angle.

3. Importance of Shear Strength Calculation

Details: Accurate shear strength estimation is crucial for designing stable earth structures, assessing slope stability, and preventing geotechnical failures.

4. Using the Calculator

Tips: Enter cohesion (MPa), normal stress (MPa), friction angle (degrees), and tolerance percentage. All values must be ≥ 0.

5. Frequently Asked Questions (FAQ)

Q1: What is cohesion in soil mechanics?
A: Cohesion is the component of shear strength that is independent of normal stress, representing the "stickiness" of soil particles.

Q2: What's a typical angle of internal friction for clay?
A: For cohesive soils like clay, it typically ranges from 0° to 30°, while sandy soils may have 30°-45°.

Q3: Why include a tolerance percentage?
A: The tolerance accounts for material variability and measurement uncertainties in real-world applications.

Q4: How is normal stress determined?
A: Normal stress is calculated from the overburden pressure at the depth of interest in the soil mass.

Q5: What units should I use?
A: This calculator uses MPa (megapascals) for stress/strength units and degrees for angles.